Masters Degrees (Genetics)

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Breeding for improved biomass yield in triticale
(Stellenbosch : Stellenbosch University, 2020-03) Mohamed, Mohammed Naweed; Botes, Willem; Strauss, Johann; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.
ENGLISH ABSTRACT: Triticale (x Triticosecale Wittmack ex. A. Camus, AABBRR, 2n=6x=42) is the first manmade wheat developed through distant hybridization between rye [Secale cereale, RR, 2n=2x=14] and bread wheat (Triticum aestivum, AABBDD, 2n=6x=42). Triticale combines the qualities of its parents such as high degree of pest and disease resistance and potential to produce high yield gains when cultivated under drought and acid soil conditions. These and other characteristics sparked the attention paid to the crop. Triticale is being largely studied for its dual functionality, which includes its ability to serve as a grazing crop by producing biomass yields which are highly competitive with other forages and its ability to be used for grain production. Believed to be rich in fibre, producing large quantities of biomass material and requiring reduced amounts of management, this crop has the potential to be regarded as a high potential alternative to be included into crop rotations to supplement feedstocks. A multilocation research study was conducted over two years of which selected triticale entries were evaluated with a selection of barley, oats and rye crops as well as evaluated against advanced breeding triticale entries. A two-stage biomass sampling approach was utilised, sampling at 30 cm plant height (GS29-31) or milk stage and during the soft dough growth stage (GS69-71). Statistical analyses were conducted via Agrobase software, in which a General linear model approach was done with a randomised complete block design. A Nearest Neighbour Analysis (NNA) was conducted as well for increased accuracy. Triticale entries that were ranked among the best producers in terms of biomass yield during 2016 were included in 2017, whilst entries that were ranked the best during 2017 were further evaluated. Triticale on average produced a 1 000 kg ha-1 of biomass yield during the first cutting, indicative of its potential to offer grazing material and being superior to its other competitors in most cases. Within the soft dough stage biomass yields exceeded 12 000 kg ha-1. Heritability was measured among the trials for the trait of dry matter yield, with heritability values ranging from 0.14 to 0.88 across the trials during soft dough. The CV reported for the trials ranged from 7.95% to 24.8%. Among the top performing entries in terms of biomass yield at the end of the second year of the study, five oats, one barley and eight triticale entries were selected and analysed for nutritional value. The nutritional parameters analysed included ash, crude protein, fibre, fat, moisture and dry matter content. Certain triticale entries were among the top ranked entries in terms of both biomass yield as well as nutritional value. Through this study the hypothesis which considered triticale having high potential for consideration as an alternative crop to be included on rotations, is accepted. The entries "AgBeacon", "Snel", "US2017", "US2018" and "17USTRITEL020" have been selected potential crossing parents to be included into a formal breeding programme aimed at improving biomass yield. The need for further research to be conducted for further improvement of triticale is clear from this study. Further research aimed at increasing biomass yield of triticale as well as nutritional value will aid a greater uptake and utilization of the crop in the industry.
Continuation of a pre-breeding program for improving wheat yield
(Stellenbosch : Stellenbosch University, 2020-03) Slabbert, Johannes Diederick; Botes, Willem; Visser, Marike; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.
ENGLISH ABSTRACT: Wheat is a crop that has been cultivated around the globe for centuries and forms a substantial portion of the population’s diet, particularly in third world countries. Food security is under major stress with the human population increasing, thus it is important to increase the amount of wheat produced to meet the demand. Higher yields along with better quality can be reached by an increased breeding efficiency through research and development of breeding techniques. The aim of this study was to identify increased yield-related traits and introducing them into the marker-assisted recurrent selection (MS-MARS) facilitated pre-breeding program of the Stellenbosch University Plant Breeding Lab (SU-PBL) to breed wheat lines higher yields. Germplasm was identified through literature that could benefit the breeding program by having traits related to increased yield. The standard set of the SU-PBLs molecular markers were used to make informed decisions during the selection process. Remote sensing by a Remote Pilot Aircraft System (RPAS) was used to perform detailed observations of wheat and was compared to traditional instruments. Field- and post-harvest phenotyping was done to aid in the selection of lines with high-yielding traits. Lines with high yield-related traits were identified by using the different techniques and were introduced into the MS-MARS scheme. R-squared values of linear regression models displayed that the RPAS data could not predict the phenotypic data in the field, except for yield. Scatter plot matrices shown that there was no correlation between the data captured by the traditional instruments and the RPAS. The field and post-harvest data indicated that a nearest neighbour analysis (NNA) was the best option during this study as there were field trends and the data was used in the selection process. Future studies should include the addition of molecular markers that correlate with increased yield-related traits to make more informed decisions during selection. The development of cameras and software for remote sensing will definitely benefit the tool. Additional vegetative indices can be explored and the model can be improved over time by the addition of data.
Determining the phenotypic and molecular diversity within a collection of wheat wild relatives
(Stellenbosch : Stellenbosch University, 2023-03) Bester, Cecile; Botes, Willem; Le Maitre, Nicholas; Stellenbosch University. Faculty of Agrisciences. Dept. of Genetics.
ENGLISH ABSTRACT: Common bread wheat, Triticum aestivum L., is the third most important staple crop, after rice and maize. Wheat provides 20% of the globally consumed calories, and is cultivated on 242 389 108 ha globally. In South Africa, wheat was planted on 523 500 ha with a total production of 2 285 000 tonnes in the 2021/2022 season. The continuous improvement of wheat is important for global and local food security. Crop wild relatives are rich sources of genetic diversity that have been used in 4 157 documented cases of plant improvement by 2022. Wheat wild relatives, like Triticum and Aegilops spp. have been employed 333 times for wheat improvement by 2022. The Stellenbosch University Plant Breeding Laboratory has a collection of 1246 different wheat wild relatives belonging to the genera Triticum and Aegilops. There is limited information on the accessions from this collection, and the diversity present within, restricting the use of these plant genetic resources in wheat improvement. Obtaining more information that can assist when planning introductions, selections, renewal, description, and characterisation of the material is therefore vital. The development of digital phenotyping and characterisation methods can aid in the determination of morphological diversity and species identification. Chloroplast DNA is universal in plants and allows for the assessment of molecular diversity between species with different genomic combinations. From the Stellenbosch University Plant Breeding Laboratory crop wild relative collection, 92 entries were renewed, identified, characterised, and described. The collection showed a high level of morphological diversity in grain yield, flag leaf area and awn types. To improve phenotyping, a digital method of spike length estimation, using ImageJ, was compared to actual physical measurements. There was no significant difference between values obtained by these two methods, verifying the technique. Transfer Learning was applied to train pre-trained MobileNet Convolutional Neural Network models to distinguish between genus, species, subspecies and variety, with accuracies of 0.8750, 0.923, 0.742 and 0.600, respectively. These models can be applied to increase the accuracy of plant identification. Twelve chloroplast simple sequence repeats in four multiplex reactions were used to determine the genetic diversity within the wheat wild relative collection. Polymorphic information content ranged from 0.615 to 0.972 and gene diversity from 0.663 to 0.9724. These values indicate that there is a high level of diversity present within the wheat wild relative collection. Due to the high morphological, and molecular diversity within the ex situ species material collection, the plant genetic resources have a good potential for use in wheat breeding for crop improvement. The information can assist breeders to select the best wild relatives to be used in interspecies crosses to improve common bread wheat.
The development, validation and implementation of a drought stress index for the evaluation of the drought tolerance potential of South African sugarcane
(Stellenbosch : Stellenbosch University, 2013-03) Sewpersad, Chandani; Botes, Willem; Van Heerden, Riekert; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.
ENGLISH ABSTRACT: In the rainfed areas of the South African sugar industry the unpredictability of rainfall is of major concern for producers. Currently, research into the drought tolerance of South African sugarcane varieties is very limited. Knowledge of varietal drought tolerance potential would allow for more informed decision making when it comes to planting a crop that stays in the ground for between five and fifteen years. The aim of this study was to ascertain the drought tolerance potential of commercial sugarcane varieties using historical field trial data by employing statistical modelling. The first step was to establish a reliable methodology of quantifying the level of drought stress, defined through a drought stress index (DSI), employing the sugarcane growth modelling software Canesim. The second step was to use the selected DSI to evaluate and rate the drought tolerance potential of commercial varieties. Of the six DSI’s calculated, the index comprising a ratio of Canesim simulated rainfed yield (representative of a water stressed environment) to Canesim simulated irrigated yield (representative of a water unstressed environment) was the best at quantifyingthe level of trial drought stress. Using three varieties with previously identified drought potential, two intermediate susceptible (IS) and one intermediate (I) variety, this was the only DSI that was able to quantify all the differences between the varieties. Using the selected DSI, two different methodologies were used to evaluate varietal drought tolerance potential: General linear regression and Residual maximum likelihood meta-analysis. The regression method proved to be a better method of varietal rating when using historical field data. The two rainfed regions, coastal and midlands were analyzed separately due to the difference in climatic conditions. Using the regression analysis, with N12 as the observed intermediate reference variety, coastal varieties were rated as being susceptible (N16, N19, N39 and NCO376) or intermediate (N27, N29, N33, N36, N41, N45, N47). Rating of the midlands varieties, with both statistical methods, were unsuccessful.
A diallel study of Secale cereale
(Stellenbosch : Stellenbosch University, 2016-12) Moller, Ernst Lodewicus; Botes, Willem; Stellenbosch University. Faculty of AgriScience. Dept. of Genetics.
ENGLISH ABSTRACT: Rye (Secale cereale) originated and was domesticated in the fertile cresent in the Middel East. It has been part of the human staple diet for thousands of years in those areas as well as Eastern Europe. It is known for its ability to grow and produce grain and animal feed in harsh environments. Therefore, as a result of its hardiness, rye is cultivated in many countries across the globe. In a rapid changing environment, due to climate change and human population growth, the importance of food security cannot be over emphasised. Therefore, this study aimed to select superior parent lines for the following characteristics: days to heading, plant length, spike number, thousand kernel weight and yield to be used in the Stellenbosch University’s Plant Breeding programme. In the first part of the study seed, from eight randomly selected plants from a synthetic population, were planted in planting pots. Due to it’s outbreeding nature and high degree of inbreeding depression, the first filial from each individual plant are half-siblings. DNA from three half-siblings from each parent line was extracted to determine variance at molecular level. Eight clones were made from the half-sibling showing the greatest variance for each line. In the second part of the study these clones were planted according to a Griffing full diallel mating design in all possible combinations. The progeny of these crosses was planted in a random block design with three repititions and the results were measured and compared to determine the general as well as specific combining ability of the diverent lines. Althouth no significant differences were observed, promising general combiners were identified for days to heading, plant length, spike number, thousand kernel weight and yield. One line may also be considered as a potential parent line for use in a synthetic population to improve qualities for animal fodder and yield. It was also found that one cross performed better than the means for four of the five traits and may therefore be considered for use in a hybrid production program.
Evaluation and implementation of DNA-based diagnostic methodology to distinguish wheat genotypes
(Stellenbosch : Stellenbosch University, 2007-12) Honing, Jennifer; Marais, G. F.; Botes, Willem; University of Stellenbosch. Faculty of Agrisciences. Dept. of Genetics.
The aim of this study was to develop a DNA-based diagnostic system that can be used to distinguish between genotypes in the wheat breeding program at the University of Stellenbosch. Known marker systems were investigated and the chosen marker system would then be implemented to determine its utility in the breeding program. Three marker systems were considered, i.e. microsatellites, Amplified Fragment Length Polymorphisms (AFLPs) and various retrotransposon-based markers. Each system is based on polymerase chain reaction (PCR) amplification from specific primer pairs. The multitude of primer options was narrowed down during a review of published literature regarding wheat molecular markers. Thirty nine microsatellite primer pairs and nine AFLP primer combinations were chosen for the initial genotype evaluation. Four different retrotransposonbased techniques were investigated; namely Inter-Retrotransposon Amplified Polymorphism (IRAP), REtrotransposon-Microsatellite Amplified Polymorphism (REMAP), Sequence- Specific Amplified Polymorphism (SSAP) and, a derivative of these developed in this study, Wis-2 Retrotransposon Amplification. The study started with twenty genotypes which included varieties/breeding lines from five breeding programmes. The genotypes were chosen as representative of the respective breeding populations and were used in the initial testing of the marker systems. Eighteen microsatellites were evaluated using the panel of twenty genotypes. From this, six primer pairs (Xgwm190, Xgwm437, Xgwm539, Xwmc11, Xwmc59 and Xwmc177) were chosen to test the semi-automated DNA sequencer detection system. A single band/peak in each microsatellite profile was used for genotyping. Four of the primer pairs were labelled with different fluorochromes which enabled them to be multiplexed. The differences in amplification products of the six microsatellites meant that all six could be detected in one electrophoresis run. The banding pattern produced by microsatellite Xwmc177 was complex and highly polymorphic and was therefore also analysed in the same way as the AFLP patterns. When analyzed in this manner it proved to be more informative than the combination of six microsatellites (with a single prominent band scored in each). Three AFLP primer combinations could also be multiplexed and visualised together. The three EcoRI selective primers were labelled with different dyes and used with one MseI selective primer. The SSAP system also used fluorescently labelled primers and proved to be the most useful of the retrotransposon-based methods. However, this system produced such a large amount of data that it made analysis too time consuming. Therefore the six microsatellites and three AFLP primer combinations (MseI-CTC and EcoRI-ACA, -AAC, - AGG) were selected for routine genotyping. Due to the numerous highly polymorphic bands produced by the SSAP system it could be very useful to differentiate very closely related genotypes that cannot be distinguished with the markers proposed for routine use. A panel of 119 breeding lines were then used to implement the two chosen marker systems. The results obtained for these markers were used to produce a dendrogram of the lines using the SAS cluster analysis function. The clusters showed that most of the lines could be distinguished from each other. The MseI-CTC and EcoRI-AGG primer combination was the most informative. It produced the largest number of clusters (53) and could therefore discriminate between more of the lines than any other method. The dendrograms and clusters allowed sixteen of the breeding lines to be selected to test the optimal number of seeds to represent an entire population (variety/breeding line) as one seed was not sufficient. It was decided that eight seeds could provide a good representation of the intra-line variability.
Evaluation of the crossability between small grains
(Stellenbosch : Stellenbosch University, 2011-12) Coetzee, Kim; Botes, Willem; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.
ENGLISH ABSTRACT: The greatest concern associated with genetically engineered crops is the possibility of GM crops contaminating other non-GM crops as a result of cross-pollination. Pollen drift is the primary mechanism in which GM crops contaminate traditional crops. However, genes can only be transferred between species if a certain degree of crossability exists. The aim of this study was to determine the potential risks associated with the release of transgenic crops and how to minimize these risks. Therefore, in this study crossability between three small grains was evaluated as well as pollen mediated gene flow from blue aleurone wheat. The potential frequency of cross pollination as well as the distance at which gene flow takes place was determined. When crossing triticale and rye the outcrossing was low in both directions. When rye was used as the female the F1 hybrid emergence was equal to zero and when triticale was used as the female parent the F1 hybrids were sterile. Therefore the potential for gene flow between triticale and rye is highly unlikely. The crossability between triticale and wheat was higher when triticale was used as the male parent, however these crosses did not produce many viable hybrid plants. When wheat was used as the male parent the F1 hybrid emergence was much higher and the F1 generation produced viable seed. In crosses between wheat and rye, gene flow is only possible when wheat acts as the female parent. The F1 generation is also capable of producing seed. In the pollen dispersal study an average OC of 0.4% was observed. A maximum OC of 2.4% was observed at a distance of 2.5 meters from the pollinator. There were samples with outcrossing percentages of 1% and 1.3% at distances of 50 meters and 60 meters respectively. Therefore, results indicated that prevailing wind direction is not necessarily associated with higher OC rates. Therefore, to reduce gene flow as much as possible an isolating distance of at least 65m should be used.
Genome editing in bread wheat using CRISPR/Cas9
(Stellenbosch : Stellenbosch University, 2022-04) Dijkerman, Alexander; Burger, Johan; Campa, Manuela; Botes, Willem; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics. Institute for Plant Biotechnology.
ENGLISH ABSTRACT: Bread wheat (Triticum aestivum) is one of the most important food crops consumed by humans, providing approximately 20% of the world’s total caloric intake. However, wheat yields must be increased to supply the growing demand of an increasing global population. Traditional breeding techniques will not be sufficient to confront this challenge and improved genetic engineering and molecular-based techniques will be a necessity. The CRISPR/Cas (clustered regularly interspaced short palindromic repeats/CRISPR associated) technology has emerged as a promising genetic engineering tool for the purposes of plant breeding. The CRISPR/Cas9 system has recently been developed as a DNA-free genome editing technique allowing for a precise and efficient method to genetically improve bread wheat while mitigating regulatory concerns. This study, therefore, aimed to establish CRISPR/Cas9 system in bread wheat and investigate the feasibility of this system in a DNA-free format. To achieve this, ribonucleoproteins (RNPs) were assembled by complexing single guide RNA (sgRNA) sequences targeting regions of a gene involved in the carotenoid pathway to the Cas9 protein. The RNPs were subsequently introduced to immature embryos through biolistic bombardment. Immature embryos were assessed to confirm successful editing of the target genes. No editing was detected in the experimental target. Evidence is provided for successful editing in embryos bombarded with RNPs mediated by a previously validated sgRNA. To establish an efficient method of achieving CRISPR/Cas9 edited wheat plants, a multiplex CRISPR/Cas9 DNA construct was assembled and introduced into wheat tissues through Agrobacterium-mediated transformation and particle bombardment. No edits were detected in plantlets that were regenerated on selective media from embryos transformed with Agrobacterium carrying the CRISPR/Cas9 construct. However, indels were detected in pre-initiated calli bombarded with the multiplex CRISPR/Cas9 DNA construct when analysed with the ICE v2 online software. Furthermore, various wheat transformation and regeneration protocols are assessed. Overall, the results provide insights into methods to deliver CRISPR/Cas9 components into bread wheat explant tissue for genome editing. A rapid and accessible method of screening for edits in pooled samples through PCR/RE assays followed by ICE v2 software analyses is demonstrated. Further, a vector delivery method that could circumvent challenging tissue culture procedures through the bombardment of mature embryos is explored. Possible optimisations of CRISPR/Cas delivery systems and experimental design are highlighted for future studies.
Implementation of marker assisted breeding in triticale
(Stellenbosch : Stellenbosch University, 2011-12) Ntladi, Solomon Magwadi; Botes, Willem; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.
ENGLISH ABSTRACT: Research into markers for the detection of genetic diversity and cultivar identification has become an important component of the genetic improvement of crops. However, the incorporation of marker assisted selection (MAS) as a tool for the identification and characterization of breeding material has not been fully implemented in the breeding of spring triticale at Stellenbosch University’s Plant Breeding laboratory (SU-PBL). The present study served as a case study in order to achieve this. The first part of the study concerned the detection of genetic diversity in 101 newly sourced triticale cultivars, from a USDA germplasm bank, together with five local control cultivars, in order to identify possible crossing parents. Eight SSR markers, including five derived from rye and three from wheat, and five agronomic characteristics were used to assess diversity. In seedling screening the foreign cultivars showed resistance towards the stem rust isolate used, but were mostly susceptible to the leaf rust isolate. Out of the 8 SSR markers tested, 7 markers were polymorphic and revealed 140 alleles varying from 12 to 26 with an average of 17.5 alleles per locus. The observed polymorphic information content (PIC) value ranged from 0.39 to 0.88 with an average of 0.70, indicative of the good discriminatory ability of the SSR markers. The data revealed that the South African cultivars were genetically closely related to cultivars from the USA and Canada. The second part of the study focused on the introgression of a blue aleurone layer gene (Ba), carried by a wheat cultivar, ‘Cltr1202STR’, and purple pericarp genes (Pp1; Pp3) also carried by a wheat cultivar, ‘Amethyst’, into a triticale background. Unfortunately the introgression of the purple pericarp genes failed. Two lines containing the blue aleurone layer, 11T023 and 11T028, were however successfully created. Molecular typing of these lines with SSR markers were able to show that BC4F1 line 11T023 (Ba) B was genetically similar to the recurrent parent ‘Agbeacon’; and that the BC4F1 11T028 line (Ba) A was closest to the ‘US2007’ recurrent parent. The study illustrated that MAS was a reliable tool for detecting genetic diversity in newly sourced germplasm, and assisted in making a backcross breeding effort more effective. The data generated from MAS could therefore clearly assist in making the SU-PBL breeding program more effective by moving, better informed, decision making toward data based partly on the genotype, thereby minimizing the risks associated with purely phenotypic based decisions.
Implementation of molecular markers for triticale cultivar identification and marker-assisted selection
(Stellenbosch : Stellenbosch University, 2012-12) Bitalo, Daphne Nyachaki; Botes, Willem; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.
Triticale is an amphidiploid that consists of wheat (A and B) and rye (R) genomes. This cereal is fast becoming important on a commercial basis and warrants further assessment for the better management and breeding of the hybrid. The assessment of the genetic diversity among the wheat and rye genomes within triticale can be obtained by using molecular markers developed in both donor genomes. Simple sequence repeats markers (SSRs) and amplified fragment length markers (AFLPs) have been previously used to assess the genetic diversity among triticale lines. SSRs are highly polymorphic markers that are abundant and which have been shown to be highly transferable between species in previous studies while AFLP markers are known to generate plenty of data as they cover so many loci. Thus, the aim of this study was to develop a marker system suitable to assess the genetic diversity and relationships of advanced breeding material (and cultivars) of the Stellenbosch University’s Plant Breeding Laboratory (SU-PBL). Therefore, both AFLP and SSR markers were initially analysed using eight triticale cultivars (with known pedigrees) to facilitate cultivar identification. Fourty-two AFLP primer combinations and 86 SSR markers were used to assess the genetic diversity among the Elite triticale cultivars. The AFLP primer combinations generated under average polymorphism information content (PIC) values. Furthermore, these markers generated neighbour-joining (NJ) and unweighted pair group method with arithmetic average (UPGMA) dendograms that displayed relationships that did not correspond with the available pedigree information. Therefore, this marker system was found not to be suitable. A set of 86 SSRs previously identified in both wheat and rye, was used to test the genetic diversity among the eight cultivars. The markers developed in wheat achieved 84% transferability while those developed in rye achieved 79.3% transferability. A subset of SSR markers was able to distinguish the cultivars, and correctly identify them by generating NJ and UPGMA dendograms that exhibited relationships that corroborated the available pedigree data. This panel of markers was therefore chosen as the most suitable for the assessment of the advanced breeding material. The panel of seven SSR markers was optimised for semi-automated analysis and was used to screen and detect the genetic diversity among 306 triticale entries in the F6, Senior and Elite phases of the SU-PBL triticale breeding programme. An average PIC value of 0.65 was detected and moderate genetic variation was observed. NJ and UPGMA dendograms generated showed no clear groupings. However, the panel of markers managed to accurately identify all cultivars within the breeding program. The marker panel developed in this study is being used to routinely distinguish among the advanced breeding material within the SU-PBL triticale breeding programme and as a tool in molecular-assisted backcross.
Improvement of rust resistance and FHB resistance QTL in wheat through the application of an integrated biotechnology approach
(Stellenbosch : Stellenbosch University, 2017-03) Meintjes, Schalk Willem; Botes, Willem; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.
ENGLISH ABSTRACT: The international demand for wheat production is placing pressure on breeders to increase and develop elite cultivars which are adapted to meet specific criteria such as high grain quality and high yield potential (Francki and Appels, 2002). Unfortunately these cultivation and agronomical demands are not the only factor for breeders to think about when it comes to food security. More specifically, abiotic and biotic stressor influence food security significantly. Each year 10-16 % of global harvest is lost due to plant diseases (Oerke, 2006). Based on a Molecular Plant Pathology survey taken in 2012, the top 10 fungal pathogens affecting crop production was taken and Puccinia species where listed third, followed by Fusarium graminearum (FHB) in fourth place (Dean et al., 2012). The wheat rust fungi (leaf, stem and stripe rust) have become economical important diseases worldwide. Puccinia have the ability to mutate, migrate and recombinate, these abilities are predominantly the reason why wheat rust epidemics are a serious concern in wheat growing areas around the world (Sing et al., 2002). FHB occurs in a number of wheat growing regions (Asia, Australia, Canada, Kenya, Europe, North and South America and South Africa) (Waalwjik et al., 2003; Guo et al., 2008; Karugia et al. 2009). The first FHB report on wheat in South Africa was in 1980 in the North-West Province (Scott et al., 1988). FHB produces mycotoxins that contaminate grain, causing lower yield and quality (Leonard and Bushnell, 2003). The challenge however is to pyramid FHB QTL and rust genes into one cultivar for durable resistance. The aim of the study was to pyramid rust genes and FHB QTL in to one genotype by performing the male sterility mediated marker assisted recurrent selection scheme (MS-MARS). A segregating F1 population was provided for the MS-MARS cycle 1 from an existing pre-breeding nursery. Molecular markers were successfully implemented to determine the gene frequenciesof rust genes (Sr2, Sr31, Sr24, Sr26, Lr34,Lr37 and Lr19) in the segregating F1 population. The cross was between a rust male donor and a FHB male donor population to produce two independent subpopulations in MS-MARS cycle 1. The gene frequencies of the rust male donors were known. The gene frequencies of the FHB male donor population were successfully determined through molecular characterization. The FHB QTL of interest was (Qfhs.ifa-5A, 7AQTL and Qfhs.ndsu-3BS). The gene frequencies of 40 %, 92 %, 0.8 %, 48 %, 1.68 %, 69 % and 9.45 % were observed for Sr2, Sr24, Sr26, Sr31, Lr19, Lr34 and Lr37 respectively in the segregating F1 base population of cycle 1. The gene frequencies of 83.30 %, 17 % and 66.67 % were observed for Qfhs.ndsu-3BS, 7A QTL and Qfhs.ndsu-5A-1 respectively in the FHB male donor population. Future studies will include the development of a double haploid population with pyramided rust genes and FHB resistant QTL. Determine the effect FHB resistance have on the bread baking properties. Phenotyping the presence of rust and FHB QTL through inoculating the population with rust and fusarium isolates.
Improving water stress tolerance of triticum aestivum by means of male sterility marker assisted recurrent selection
(Stellenbosch : Stellenbosch University, 2022-12) Khambule, Mhlengi Sboniso; Botes, Willem; Hess, Lezaan; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.
ENGLISH ABSTRACT: Wheat is the most widely grown cereal. More than 90% of the crop is grown for direct human consumption with increasing alternative potential for starch, glutens and biofuels. Wheat agronomic and genetic improvements will increasingly play key roles in meeting current and future food security needs and/or demands, particularly in the face of climate change. With the crop’s genetic complexity, the use and potential of molecular markers in the breeding process cannot be overlooked. The aim of this study was to select crossing parents for wheat vegetative water stress improvement under low water retention. The 4th Wheat Yield Consortium Yield Trial nursery (4-WYCYT) from CIMMYT was used as a prospective donor and evaluated for vegetative water stress tolerance at different vegetative growth stages before selection and crossing with an existing MS-MARS base population. The initial evaluation was undertaken in a growth chamber setting, selection trials were undertaken in in glasshouse conditions while crossing events used a combination of these environments. Seeds resulting from the crossing events were evaluated for early vegetative vigour under glasshouse conditions. Water retention and water availability regimes facilitated various stress combinations in both the evaluation and selection trials. Water availability was a strong factor under growth chamber (GC) conditions. Early vegetative water stress survival ranged from 16-30 plants and varying across the four retention regimes under growth chamber conditions. Survival was comparable under glasshouse conditions despite growth stage of water stress onset. Evaluated entry (EE) 005 (particularly accessions 005A and 005D) performed consistently in both growth chamber trials despite stage of stress onset, and when stress occurred during early vegetative stages despite growth environment. The said entry recorded the highest evaluated average entry yield for early vegetative stress (average of yield or total seed mass performance of available accessions for a given entry) although a single accession from EE - 006 recorded the highest individual yields (significant from two other accessions of the same genotype) when stress occurred during mid-vegetative growth under glasshouse (GH) conditions. All evaluated local checks (5 in GC and 10 in GH) performed significantly below the best performing accession and/or entry for yields in both the respective glasshouse trials, with an above average performance only when stress occurred later in the vegetative growth stages. Mid-vegetative stressed trials however recorded the least yields comparatively. The 4-WYCYT was however robust and displayed varying tolerances to water stress. This informed the selection of entries of this nursery which resulted to a male fertility segregating population produced through male sterility mediated introgression. Low retention evaluated F1 male fertile seedlings were taller on average compared to their infertile counterparts. Future studies should aim to improve wheat vegetative resilience and growth in varied and relevant water stress combinations.
Improving wheat grain yield by employing an integrated biotechnology approach
(Stellenbosch : Stellenbosch University, 2018-03) Rhoda, Rayganah; Botes, Willem; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.
ENGLISH ABSTRACT: Wheat is a widely cultivated crop as it forms a significant part of the world’s diet, especially within developing countries. However, food insecurity is increasing at a rapid rate and to meet this demand, wheat yields need to increase by 50%, by the year 2050. To gain higher wheat yields, breeding efficiency needs to increase which can be done through employing biotechnological approaches that can aid in achieving increased yields. Yield, however, is quantitatively inherited and strongly influenced by the genotype x environment interaction. Therefore, yield-determining traits that have less genotype x environment interaction should be investigated to identify underlying inheritance of high yield, along with good husbandry practises that can result in increased wheat yield. The aim of this study was to assess high-yielding genotypes through validating yielddetermining traits using genotypic and phenotypic screening as well as the use of these highyielding genotypes as male crossing parents within the male-sterility marker-assisted mediated recurrent selection breeding (MS-MARS) scheme for the improvement of grain yield. The yield-determining traits as well as molecular markers associated to some of the yielddetermining traits were identified through literature. The molecular markers were validated through genotypic screening and each yield-determining trait was phenotypically screened for each genotype and statistically analysed. The validation of two mobile applications, SeedCounter and 1KK, that measures grain morphology was also executed. All molecular markers were validated as reliable diagnostic markers to be used in markerassisted selection (MAS) for identifying its specific yield-determining trait, except for one marker. The statistical analysis for the yield-determining traits displayed that three genotypes were better performing among this set of genotypes and therefore can be used as the male crossing parents within the next MS-MARS cycle. The association of the molecular marker with the yield-determining traits displayed negative correlations that suggests that the function of the high-yielding genes are different within this set of genotypes. Only the SeedCounter application was validated to be used as a future phenotyping tool for grain morphology and the MS-MARS cycles were successfully executed. Future studies should include the validation of more mobile applications, the identification of the relationship between yield and these molecular markers identified and QTL mapping to contribute to the understanding of the underlying genetic control of the desired phenotypes that contribute to higher grain yield.
Initiation of a pre-breeding effort for water stress resistance traits and yield improvement in wheat
(Stellenbosch : Stellenbosch University, 2018-12) Mthembu, Jabulani Bhekisisa; Botes, Willem; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.
ENGLISH ABSTRACT: Wheat (Triticum aestivum L.) is an important crop produced in South Africa and across the world. Water stress and rust diseases (Puccinia spp.) are common factors hindering wheat growth and development. Leaf lifespan is reduced under water stress conditions from the leaf being infected by rust diseases. High-heritable Mendelianinherited and quantitative traits as well as male sterility mediated marker assisted selection (MS-MARS) technique was utilised for water stress and rust disease resistant wheat characterisation. The aim of the study was initiation of a pre-breeding effort for water stress resistance traits and yield improvement in wheat Sixty high-yielding genotypes and a female F1 1:1 male sterile and male fertile segregating population postulated to carry the leaf and stem rust resistance genes were screened for the presence of Lr34, Sr2, Sr31, Sr24, Lr37, Sr26 and Lr19 markers using a routinely standardised panel of markers used in the Stellenbosch University Plant Breeding Laboratory. Molecular characterisation of wheat lines was followed by cross-pollinations of a selected male sterile female and donor lines in the growth chamber using a reticulated hydroponic system (RHS) for the MS-MARS cycle scheme. Male fertile tillers were allowed to self-pollinate and were used for singleseed dehiscence. Sixty genotypes were phenotypically screened using identified and selected target traits associated with water stress resistance. Five genotypes were selected and further screened for water stress resistance using added traits of interest. An RHS was utilised for screening of the target traits including excised-leaf water loss, leaf relative water content, specific leaf area, number of tillers (NT), number of leaves and lengthrelated parameters such as root length (RL) and shoot length (SL). Fresh weight parameters included roots fresh weight (RFW), shoots fresh weight (SFW), leaves fresh weight (LFW) and total plant fresh weight (TPFW). Dry weight parameters included roots dry weight, shoots dry weight, leaves dry weight (LDW), above-ground dry weight and total plant dry weight (TPDW). Additional traits included chlorophyll content index (CCI), stomatal conductance, photosynthetic active radiation, leaf area index, radiation use efficiency, relative growth rate (RGR) and root-to-shoot ratio. Rust disease resistant genotypes were identified from the studied population. Molecular characterisation of the wheat genotypes for rust resistance genes showed increased allele frequencies in MS-MARS cycles 1 to 2 for both female and male lines, more specifically Lr34 and Sr2. However, the male lines showed lower allele frequencies and absence of the Lr19 marker in the population. Analysis of variance showed that water stress significantly influenced the growth and development of wheat genotypes for all the studied traits except RL and NT. The selected five genotypes showed better water stress resistance for all the traits studied. Genotypes were ranked as follows based on their performance under water stress conditions: 15HYLD-30, 15HYLD-22, 15HYLD-29, 15HYLD-18 and 15HYLD-26. A strong positive association observed under water stress conditions from fresh weight components included LFW and RFW (r = 0,884), followed by TPFW with FW components such as RFW (r = 0,848), SFW (r = 0,922) and LFW (r = 0,920). A strong positive association was also recorded for SFW and SL (r = 0,832), CCI with SL (r = 0,835) and SFW (0,890) and lastly, TPDW with RGR (r = 0,879) and LDW (r = 0,872). A strong positive association was recorded under well-watered conditions namely TPFW showed a strong positive association with SFW (r = 0,872), LFW (r = 0,920), TPDW with SL (r = 0,877) and LDW (r = 0,841).
Initiation of a pre-breeding programme for enhancing genetic resistance against wheat rust
(Stellenbosch : Stellenbosch University, 2012-12) De Groot, Stephan; Botes, Willem; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.
ENGLISH ABSTRACT: Plant diseases are among the major causes of food insecurity. In South Africa the wheat fungal diseases including stem rust caused by Puccinia graminis f. sp. tritici, leaf rust caused by P. triticina and stripe rust caused by P. striiformis f. sp. tritici are the most important. Genetic resistance is a viable way of protecting wheat crops against the wheat rusts, especially cultivars carrying multiple genes that confer durable resistance. In order to breed for multi-gene resistance an effective breeding strategy that allows for selecting multiple resistance genes and other desirable traits needs to be devised. The aim of this study was to identify a number of genotypes with combinations of different rust resistance genes, good grain yield and end-use quality out of an existing pre-breeding population and thereby identify superior parents. In order to achieve the stated aim the following objectives have been identified: identify wheat lines through marker-assisted selection (MAS) carrying the gene complexes, Sr31/Lr26/Yr9, Lr24/Sr24, Lr37/Sr38/Yr17, Lr34/Yr18 and Sr2; to develop inbred lines to evaluate selected lines under field trials. From the initial subset of 64 lines, 60 were chosen and advanced to the doubled haploid (DH) phase and seed multiplication. The 60 lines either carried one or more of the three rust resistance gene complexes. The genes that were the most prominent were Sr31/Lr26/Yr9 and Lr24/Sr24. The selected lines were incorporated into a DH seed multiplication phase. After 4 cycles of seed increases and preliminary field evaluation during multiplication, 15 lines were chosen and subjected to multi-location field trails. The extensive multi-location field trails carried out in this study aided in identifying genotypes from the 15 MS-MARS lines with good adaptability and stability in regards to yield and baking quality. An important observation was that the molecular markers employed to indentify quality loci correlated well with the genes encoding the HMW-GS 5, 10 and 12 as observed with the Agilent© 2100 Bioanalyzer. In future studies the lines which performed the best could be re-introduced into the existing MSMARS pre-breeding programme of the Stellenbosch University’s Plant Breeding Laboratory (SUPBL). The frequencies of desired alleles could be increased in this manner. Since the majority of these characteristics are influenced by quantitatively inherited alleles, using these lines as recurrent parents will increase the frequencies of these alleles in the existing SU-PBL pre-breeding population.
Initiation of a wheat pre-breeding effort aimed at yield improvement using male-sterility marker assisted recurrent selection
(Stellenbosch : Stellenbosch University, 2018-12) Ngcamphalala, Wandile; Botes, Willem; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.
ENGLISH ABSTRACT: Continous decline in South Africa’s wheat production over the past few decades has lead to a corresponding rise in reliance on wheat imports to satisfy the local consumption needs. Wheat breeders need to work faster to contribute towards increasing profitability and the attractiveness of the commodity. In response to this, a study was undertaken with the aim of identifying and assessing traits that confer yield in wheat whilst investigating the possibility of a technologically-advanced high throughput phenotyping platform for assessing traits. The first objective was to assess traits by conducting a multilocation field yield trial and a detailed study of yield attributing traits in a controlled environment. The second objective was to initiate a male sterility marker assisted recurrent selection (MS-MARS) population based on the use of wheat quality markers as well as resistance gene markers to wheat rusts and Fusarium head blight while adding high-yield traits via single seed descent breeding. Thirdly, a pilot study was conducted to test if a high-throughput phenotyping platform, based on remote sensing imagery and Remotely Piloted Aircraft Systems (RPAS) technology could be established for automated data collection of agronomic traits. Results of the yield trial showed highly significant (p=0.0000) differences between the three localities where the trial was planted as a result of drought conditions in the season. The top ten yielding entries across the three localities did not yield significantly different from each other (LSD (5%) 1.17 t/ha) and from this set, five entries were selected for the trait study. The top two entries overall were also the best two entries at the locality that was badly affected by drought, indicating yield stability. Grain yield was positively correlated (r>0.75) to biomass, grain number/spike, as well as tiller number and these correlations were highly significant (p<0.0001). The male sterility gene was found to be stable in the population by segregating in the expected 1:1 (sterile: fertile) ratio in the multiple cycles that were conducted. Rust resistance gene frequencies were also successfully maintained during crosses, with no significant differences between cycles (chi-square test, α=5%). Out of the ninety genotypes used in the field trial, forty-four were identified as crossing parents to contribute high-yield alleles in the population, with additional Fusarium resistance gene donor lines. In the resulting progeny of the cross, the Fhb1 gene was found to have been successfully transferred to 10% of the plants. Correlations from the RPAS phenotyping study were not satisfactory, but they were promising enough to warrant further investigation towards establishing a high throughput phenotyping platform.
Investigation into the suitability of spring triticale (×Triticosecale Wittmack) for bio-ethanol production in the Western Cape
(Stellenbosch : University of Stellenbosch, 2009-12) Tsupko, Yuriy Vadimovich; Botes, Willem; University of Stellenbosch. Faculty of Agrisciences. Dept. of Genetics.
ENGLISH ABSTRACT: In the Western Cape small grain cereals, triticale (×Triticosecale Wittmack ex A. Camus) in particular, appear to be among the most promising starch-carrying raw materials for the production of bio-ethanol. A core group of cultivars and lines from the Stellenbosch University Plant Breeding Laboratory spring triticale breeding programme were subjected to initial testing for the purpose of ethanol production. They underwent multi-location field-testing across six (season 2006–2007) and nine (season 2007–2008) locations representing the Western Cape cereal production area. Climatic conditions during the study were characterised as generally favourable, especially in the 2007 season. During the season, trials were visited in order to make in situ observations. Disease susceptibility was given specific attention. After harvesting, grain yield (kg.ha-1), test weight (kg.HL-1), total starch content in whole grain (%), amylose/amylopectin ratio, protein content (%), ethanol output (L.tonne-1) and ethanol yield (L.ha-1) were analysed. Near infra-red reflectance spectroscopy calibration models were developed for moisture and starch contents. The best calibration based on whole grain spectra for moisture content had RPD = 1.691, R2 = 0.657 and SEP = 0.271%, and for starch content RPD = 1.646, R2 = 0.634 and SEP = 1.356%. Calibrations developed from milled grain showed better results for moisture content RPD = 2.526, R2 = 0.843, SEP = 0.182%, and for starch content RPD = 1.741, R2 = 0.673, SEP = 1.277%. These calibrations are suitable for rough screening of samples. In the 2006 season, starch yield was highly positively correlated with grain yield (R2 = 0.988, P <0.001). Both starch yield and grain yield were positively correlated with days to heading (R2 = 0.533 and R2 = 0.556, respectively; P <0.001). The 2007 season was characterised by a generally higher starch yield (2952– 3142kg.ha-1, 95%CI) compared to the 2006 season (2077–2315kg.ha-1, 95%CI). Starch yield was strongly positively correlated with grain yield (R2 = 0.975, P <0.001). Test weight demonstrated weak positive correlation with ethanol yield (R2 = 0.238, P <0.01) and grain yield (R2 = 0.279, P <0.001). Mean ethanol output ranged between 466–477L.tonne-1 at the 95%CI. Ethanol output was demonstrated to be more dependent on starch and other polysaccharides accessibility to enzymatic digestion than on the total starch content as such. The best lines for ethanol output in the 2007 season were G2, D3 and H2 for the Swartland region, and D3, G2 and D1 for the Overberg region. The best triticale lines under investigation showed their potential from a biological point of view to be a suitable crop for ethanol production in the Western Cape, with the achieved ethanol yield ranging between 2446–2625L.ha-1 at the 95%CI. For the Swartland region the best genotypes for ethanol yield were D1, H1 and D2, and for the Overberg H1 and G2. The 23 best lines were selected from the elite and senior blocks, and then used for the establishment of a recurrent massselection pre-breeding block.
Investigation into the suitability of wheat for ethanol production in the Western Cape
(Stellenbosch : Stellenbosch University, 2010-12) Dix, Rodger; Botes, Willem; University of Stellenbosch. Faculty of Agrisciences. Dept. of Genetics.
ENGLISH ABSTRACT: This study aimed to investigate the suitability of spring wheat in the Western Cape as a potential feedstock for a future bio-ethanol industry as well as initiate a pre-breeding effort to develop bioethanol -directed improved lines. Determined primarily on grain yield, disease resistance and, direct as well as indirect assaying of important parameters, material was selected from a base-population for use as male parents. These were crossed with female parents sourced from the Stellenbosch University Plant Breeding Laboratory (SU-PBL) male sterility -mediated marker-assisted recurrent selection (MSMARS) programe. This programe is constituted by an agronomically and disease-resistance - improved population, containing a dominant male sterility gene (Ms3). The progeny of these crosses was used to initiate the production of doubled haploids in order to ultimately derive higher ethanol yielding lines. Multi-location field trial (MLFT) data revealed that 00K60-16-3-3 was the best adapted and highest yielding (2160.95 litres ethanol per hectare) advanced breeding line (ABL). Its performance was not statistically significantly less than first-ranked 03H86-8-2 (2184.62 litres per hectare) and both ABLs significantly (P≤0.05) out-performed six controls in the study. ABL 00K60-16-3-3 was also the most adapted in terms of potential yield in litres per ton of grain. ABL 03H86-8-1 was second recommended for the Western Cape, performing above the expected mean for yield in litres per hectare. Further adaptation of specific ABLs to the two major sub-regions of the Western Cape i.e. the Swartland and Southern Cape including the Rûens was also elucidated. Napier was significantly the highest yielding trial site although none of the considered sites were both stable and high yielding. It was also determined that entry X locality interaction (GxE) was indeed significant across the whole production area regarding litres per hectare as well as its two subregions. This is expected considering the environmentally diverse nature of the region as a whole. Using several entries as examples, relationships between starch, ethanol production in litres ethanol per hectare and litres per ton where grain yield is not taken into consideration were illustrated. Overall applicable relationships other than clear grouped entry differences could not be established. What was clearly demonstrated however, is that the maximization of grain yield is paramount. Highlighted thus, is the individuality of a specific genotype where MLFTs will always be required to quantify genotype potential.
Molecular genetic study of wheat rusts affecting cereal production in the Western Cape
(Stellenbosch : Stellenbosch University, 2010-03) Le Maitre, Nicholas Carlyle; Botes, Willem; University of Stellenbosch. Faculty of Agrisciences. Dept. of Genetics.
ENGLISH ABSTRACT: Microsatellites were used to differentiate Leaf (Puccinia triticina Eriks.) and Yellow rust (Puccinia striiformis Westend. f. sp. tritici Eriks.) pathotypes. There was sufficient diversity in the Leaf rust microsatellite markers to differentiate the pathotypes and create a phylogenetic tree of Leaf rust. Three of the microsatellite markers were sufficient to differentiate all the Leaf rust pathotypes. Sufficient diversity in the Yellow rust microsatellite markers was also observed which made it possible to differentiate the pathotypes. Only three pathotypes were used so no phylogenetic inference was made. Two microsatellite markers were sufficient to differentiate all the yellow rust pathotypes. Microsatellite and Amplified Fragment Length Polymorphisms (AFLP) markers were used to differentiate Stem rust (Puccinia graminis f. sp. tritici Eriks. and Henn.) pathotypes, and the data was combined for phylogenetic analysis. AFLP bands unique to each Stem rust pathotype were converted to Sequence Characterised Amplified Region (SCAR) markers. A single specific SCAR marker was created for UVPgt52. A second SCAR marker amplified four of the eight pathotypes. None of the other SCAR markers were specific. A 270 basepair fragment of the ITS1 region of the rDNA gene of all the Puccinia spp. was also sequenced in order to develop pathotype specific primers that could be used in a Real Time-PCR to determine relative levels of pathogen inoculum in a sample. Unfortunately insufficient diversity in the sequences of the ITS1 region of the rDNA gene did not allow unique primers to be designed for each pathotype making it impossible to proceed with the relative quantification using Real Time-PCR. Following marker development ninety one field isolates were collected from eleven sites in the Overberg and Swartland regions during 2008 and 2009. In the field isolates, four different Leaf rust pathotypes were identifiable. UVPgt13 and UVPgt10 were most prevalent. The most prevalent Stem rust pathotypes were UVPgt50, UVPgt52, UVPgt54 and UVPgt57. Only 6E16A- was identifiable in the Yellow rust isolates. There were no apparent patterns in the distribution of Leaf, Stem or Yellow rust. Leaf and Stem rust were widely distributed, while Yellow rust was confined to three sites in the central South Cape, the only sites where climatic conditions were favourable for its development during the sampling period. The low levels of diversity found in the rust population when compared to international populations are probably due to the relatively small population size, the lack of a host for sexual reproduction, the small sample size, the effective monoculture and the strong selective pressure created by artificial control methods.
Ontwikkeling van ’n koringkwekery met gestapelde, spesie-verhaalde roesweerstand
(Stellenbosch : Stellenbosch University, 2010-12) Wessels, Elsabet; Botes, Willem; University of Stellenbosch. Faculty of Agrisciences. Dept. of Genetics.
ENGLISH ABSTRACT: Wheat rust is a significant contributor to the total impact of diseases on sustainable wheat production. Genetic resistance, produced by using resistance genes from wheat and other related wild species, is the simplest and most cost-effective way to guard against these diseases. The pyramiding of resistance genes in a single line is a vital practice in bringing about durable resistance. This study aimed to develop a series of doubled haploid (DH) wheat lines containing combination's of wild species genes for rust resistance. Rust resistance genes Lr19 (7BL), Sr31/Lr26/Yr9/Pm8 (1BS) and Lr54/Yr37 (2DL) were combined by means of crossing. Breeders. lines which have complex resistance including Lr24/Sr24 (3DL), Lr34/Yr18 (7D), Sr36 (2BS) and Sr2 (3BS), were used. Marker assisted selection (MAS) was used to type populations for the above mentioned genes. Using the DH method (maize pollination technique), an inbred population was developed from the selected lines, after which the lines were characterised molecularly for the resistance gene translocations which they contain. The study produced 27 lines with diverse genetic profiles. Seven lines contain four translocations (Lr24/Sr24, Lr34/Yr18, Sr2 and Lr19 or Sr31) each, 11 lines contain three genes each, six lines contain two genes each and only three lines contain a single translocation (Lr24/Sr24). The reality that rust pathogens have already overcome three of the resistance genes in the final population . Lr19, Sr31 and Sr24 . is a clear indication of the value of using non-major gene resistance for bringing about durable resistance. The focus should fall ever more greatly upon the application of quantitative trait loci (QTL) for this purpose, which will result in MAS contributing to the development of more durable resistance. The value of the integration of MAS and DH in combination with conventional breeding practices in breeding programmes has already been illustrated internationally for increasing the rate of cultivar development and this is reaffirmed by this study.

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