The influence of zinc content on wheat seed quality and vigour

Shandu, Minenhle (2021-12)

Thesis (MScAgric)--Stellenbosch University, 2021.

Thesis

ENGLISH ABSTRACT: It is the objective of every farmer to obtain high yields and therefore the use of good quality seeds is of importance. Most soils that support wheat cultivation are zinc (Zn) deficient. Biofortification was shown to be a solution to improve mineral content (particularly Zn) of cereals. Improved Zn content has secondary benefits during seedling development under Zn deficient conditions. On the other hand, yields are limited by other factors such as weeds, soil borne diseases and environmental stresses such as extreme drought conditions. All these factors reduce productivity of wheat, which have implications for global food demand to meet a growing population. The use of seeds with high vigour ensure investment returns because these seeds are believed to have better germination and tolerance against biotic and abiotic stresses. This study aims to investigate the influence of seed Zn levels on vigour of wheat accessions with varying quality attributes. Seed Zn has been associated with improving agronomic traits such as germination and optimum field emergence. The influence of seed Zn was investigated through laboratory and field experiments. Vigour was determined using the EC test, standard germination test, according to ISTA and accelerating ageing test (AA). Field experiments were conducted at two different localities, namely Langgewens and Roodebloem, respectively. Proper mineral content is vital for germination and zinc has been reported to improve vigour of seeds. The electrical conductivity (EC) test provided the best estimate of seed vigour, R1H (51.3 mg kg-1) had the least electrolyte leakage as well as, the best germination (>80%). Results indicated that seed vigour is affected by age, seed Zn concentration and locality of the seeds and their weight. Adequate Zn in wheat is an essential micronutrient required during physiological processes like germination. Accessions were one year apart with optimal germination from one-year old accessions. Due to natural ageing or artificial ageing, seeds lose vigour over time. The potential of using Zn-biofortified seeds still need to be investigated further because some of the accessions which had low zinc content managed to perform similarly to high Zn content accessions. Increasing sowing depth had a significant effect (p>0.05) on germination and emergence of wheat. This study revealed that seed Zn is beneficial to a seedling during early development. In field experiments and despite variation in seed Zn concentrations, both experiments at Langgewens and Roodebloem had uniform canopies at harvest. The benefits of high seed Zn content were inconclusive. Zinc biofortified seeds had an advantage of better germination and good establishment under different environmental conditions. However, the benefits of high seed Zn concentrations seemed to be sensitive to the availability of Zn in the soil. Zinc plays a crucial role in early stages from germination to emergence and early growth stages (tillering) but does not seem to influence the growth of wheat at later growth stages.

AFRIKAANSE OPSOMMING: Die doelwit van enige produsent is om hoë opbengste te behaal en daarom is die gebruik van goeie kwaliteit saad belangrik. Die meeste grond waarop koring verbou word het tekorte aan sink (Zn). Biofortifikasie is reeds bewys as ‘n oplossing om die mineraalinhoud (veral Zn) van grane te verbeter. Sekondêre byvoodele van verhoogde Zn inhoud is die beter ontwikkeling van saailinge onder toestande waar Zn beperkend is. Aan die ander kant word opbrengs beperk deur faktore soos onkruid, grondgedraagde siektes en omgewingsstremmings soos uiterste droogtetoestande. Al hierdie faktore verlaag die produktitwiteit van koring, wat gevolge het vir die globale voedselaanvraag om ‘n groeiende populasie te voed. Die gebruik van saad met goeie lewenskragtigheid verseker goeie opbrengs op insetkostes deurdat hierdie saad na bewering beter ontkiem en beter weerstand het teen biotiese an abiotiese stremmings. Die doel van hierdie studie was om die invloed van Zn vlakke op die lewenskragtigheid van koringmonsters met wisselende kwaliteitseienskappe te ondersoek. Sinkinhoud van saad word verbind met verbeterde agronomiese eienskappe soos ontkieming en vestiging in die land. Die invloed van Zn inhoud van saad is ondersoek deur laboratorium- en veldproewe. Lewenskragtigheid is bepaal deur middel van elektriese konduktiwiteitstoetse (EK), standaard ontkiemingstoets (volgens ISTA voorskrifte) en die versnelde verouderingstoets (VV). Veldproewe is uitgevoer op twee lokaliteite, naamlik Langgewens en Roodebloem respektiewelik. Voldoende mineraalinhoud is onontbeerlik vir ontkieming en Zn is bekend daarvoor dat dit lewenskragtigheid van saad verbeter. Die EK toets het die beste beraming van lewenskragtigheid verskaf: R1H (51.3 mg Zn kg-1) het die minste elektroliete gelek en ook die beste ontkiemingspersentasie getoon (>80%). Die resultate het getoon dat lewenskragtigheid van die koringsaad beïnvloed is deur ouderdom, Zn inhoud van die saad, oorsprong van die saad en hulle massa. Voldoende Zn in saad is essensieel vir fisiologiese prosesse soos ontkieming. Saadmonsters het met een jaar verskil in ouderdom en optimale ontkieming is verky van een jaar oue saad. As gevolg van natuurlike en versnelde veroudering het saad met tyd hulle lewenskragtigheid verloor. Die moontlikheid om saad wat met Zn gebiofortifiseer is te gebruik om te plant moet verder ondersoek word omdat sommige saadmonsters met lae Zn inhoud net so goed presteer het as saadmonsters met hoë saad Zn inhoud. Dieper saaidieptes het ‘n betekenisvolle (p<0.05) invloed gehad op die ontkieming en vestiging van koringsaad. Hierdie studie het getoon dat genoegsame Zn inhoud van saad voordelig is vir vroeë ontwikkeling van saailinge. In die veldproewe het beide proewe op Langgewens en Roodebloem uniforme plantstande gehad tydens oes, ongeag variasie in Zn inhoude van die saad. Die voordele van hoë Zn inhoud van die saad was nie opmerklik nie. Saad wat met Zn gebiofortifiseer is het die voordeel van beter ontkieming en vestiging onder verskillend omgewingstoestande. Die voordele van hoë Zn inhoud van saad blyk egter beïnvloed te word deur die beskikbaarheid van Zn in die grond. Sink speel ‘n belangrike rol in vroeë groeistadia van ontkieming tot vestiging en tot stoelvorming, maar blyk nie die groei van koring op latere groeistadia te beïnvloed nie.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/123918
This item appears in the following collections: