Genotyping South African wheat germplasm for hardness alleles

De Groot, Gerida (2019-04)

Thesis (PhDFoodSc)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: Wheat grain kernel hardness (GKH) is one of the most important quality properties of wheat (Triticum aestivum). The molecular basis of GKH is determined by the combination of Puroindoline a (Pina- D1) and b (Pinb-D1) alleles in a wheat cultivar. The current study investigated the Pin alleles present in commercial South African (SA) wheat cultivars. Wheat production regions in South Africa are diverse; and divided into the summer rainfall irrigation (SRI) and winter rainfall dryland (WRD) regions where spring wheat is planted, as well as the summer rainfall dryland (SRD) region where facultative and winter wheat are planted. Nine commercial wheat cultivars, differing in GKH, were planted at four locations per region, with three replications, over three production seasons (2012 – 2014). After each season, the wheat grain was harvested followed by determination of kernel characteristic, milling yield, flour and dough quality properties. The Pin allele identities, of the 27 cultivars, were determined using polymerase chain reaction and allele sequencing. Four Pin allelic genotypes were identified. Wheat cultivars produced in the WRD region showed no diversity in Pin genotypes. GKH prediction models, based on the Pin allele identities of the samples, were thus developed for only the SRI and SRD production regions. Following analysis of variance (ANOVA) and Pearson’s correlations of the WRD region, where the cultivars had identical Pin genotypes, it was shown that genotype (G) primarily contributed to variation in GKH in the Swartland region. GKH correlated negatively with break flour yield (BFY), total flour yield (TFY) and α-amylase activity. Environment (E) primarily contributed to variation in GKH in the Rûens region, where GKH had negative correlations with BFY and TFY. In addition, negative GKH correlations were observed with kernel weight and diameter, and positive correlations with flour ash content, water absorption, dough strength, -stability, and -tenacity. Wheat cultivars of the SRI and SRD regions were subjected to ANOVA, with cultivars nested within Pin genotypes. Wheat containing the Pina-D1b/Pinb-D1a genotype had increased GKH, flour water absorption (FWA), dough tenacity and alveograph P/L ratio; however, decreased kernel weight, diameter, BFY, TFY, dough extensibility, -strength, -stability, and tolerance to overmixing, compared to the Pina-D1a/Pinb-D1b genotype. The Pinb-D1p mutation had decreased kernel weight, diameter, dough extensibility, and swelling index; with increased BFY and TFY, FWA, dough development time, -strength and -tenacity compared to the Pinb-D1b and Pinb-D1ab mutations. The molecular weight distribution of proteins within wheat cultivars of different Pin genotypes were determined with size exclusion high performance liquid chromatography. ANOVA with nested design and Pearson’s correlations showed environmental influence, and G x E interaction, primarily contributed to the variation in all protein fractions. The Pina-D1b/Pinb-D1a and Pina-D1a/Pinb-D1b genotypes showed decreased sodium dodecyl sulphate (SDS) -soluble monomeric protein with increased kernel hardness. In contrast the Pina-D1a/Pinb-D1b genotype showed decreased SDSsoluble polymeric protein and increased SDS-insoluble monomeric protein. This study contributed valuable knowledge on the Pin alleles present in SA wheat cultivars as well as the influence of Pin genotype combinations and Pinb-D1 allele mutations on the GKH and processing quality. The influence of Pin genotype and GKH on the molecular weight distribution of proteins were also demonstrated. This will enable SA wheat breeders to select specific Pin allele combinations to more rapidly breed wheat for specific end-use purposes.

AFRIKAANSE OPSOMMING: Koring graankorrelhardheid (GKH) is een van die belangrikste eienskappe van koring (Triticum aestivum). Die molekulêre basis van GKH word bepaal deur die kombinasie van Puroïndolien a (Pina-D1) en b (Pinb-D1) allele teenwoordig in 'n koringkultivar. Die huidige studie het die Pin-alleel identiteit in kommersiële Suid-Afrikaanse (SA) koringkultivars ondersoek. Koringproduksie-streke in SA is uiteenlopend en word verdeel in die somerreënval besproeiing (SRI) en winterreënval droëland (WRD) streke waar lente koring geplant word, sowel as die somerreënval droëland (SRD) streek waar fakultatiewe- en winterkoring geplant word. Nege kommersiële koringkultivars, wat verskil in GKH, is op vier lokaliteite per streek geplant, met drie herhalings, oor drie produksieseisoene (2012 – 2014). Na elke seisoen is die koringkorrels ge-oes, gevolg deur die bepaling van korreleienskappe, maal opbrengste, meel- en deegkwaliteit eienskappe. Die Pin-alleel identiteite, van die 27 kultivars, is bepaal deur gebruik te maak van polimerase kettingreaksie en alleel nukleotied volgordebepaling. Vier Pin-alleliese genotipes is geïdentifiseer. Koringkultivars wat in die WRD-streek geproduseer is, het geen verskil in Pin-genotipes gehad nie. GKH voorspellingsmodelle, gebaseer op die Pin-alleel identiteite van die monsters, is dus vir slegs die SRI en SRD produksie streke ontwikkel. Na die analise van variansie (ANOVA) en Pearson se korrelasies van die WRD-streek, waar die kultivars identiese Pin-genotipes gehad het, is getoon dat genotipe (G) hoofsaaklik bygedra het tot die variasie in GKH in die Swartland-streek. GKH korreleer negatief met breek-meelopbrengs (BMO), totale meelopbrengs (TMO) en α-amilase aktiwiteit. Omgewing (E) het hoofsaaklik bygedra tot die variasie in GKH in die Rûens-streek, waar GKH negatiewe korrelasies met BMO en TMO gehad het. Daarbenewens is negatiewe GKH-korrelasies waargeneem met korrelgewig en - deursnee, en positiewe GKH-korrelasies met meel asinhoud, -waterabsorpsie (MWA), deegsterkte, -stabiliteit en -elastisiteit. Koringkultivars van die SRI- en SRD-streke is onderwerp aan ANOVA, met kultivar gene binne Pin-genotipes. Koring wat die Pina-D1b/Pinb-D1a genotipe bevat, het in GKH, MWA, deegsterkte en alveograaf P/L-verhouding verhoog. Dit het egter verminderde korrelgewig, -deursnee, BMO, TMO, deegrekbaarheid, -sterkte, -stabiliteit en verdraagsaamheid teenoor oormeng getoon, in vergelyking met die Pina-D1a/Pinb-D1b genotipe. Die Pinb-D1p mutasie het verminderde korrelgewig, -deursnee, deegrekbaarheid en -swellingsindeks gehad; met verhoogde BMO en TMO, MWA, deegontwikkelingstyd, -sterkte en -elastisiteit in vergelyking met die Pinb-D1b- en Pinb-D1abmutasies. Die molekulêre gewigsverdeling van proteïene binne koringkultivars van verskillende Pingenotipes is bepaal met grootte-uitsluiting hoë-verrigting vloeistofchromatografie. ANOVA met ‘n geneste ontwerp en Pearson se korrelasies het omgewingsinvloed getoon, en G x E-interaksie het hoofsaaklik bygedra tot die variasie in alle proteïen fraksies. Die Pina-D1b/Pinb-D1a en Pina- D1a/Pinb-D1b genotipes het afname in natriumdodesielsulfaat (NDS) oplosbare monomeer proteïene met verhoogde korrel hardheid getoon. In teenstelling hiermee, het die Pina-D1a/Pinb- D1b genotipe afgename in NDS-oplosbare polimeriese proteïene en toename in SDS-onoplosbare monomeer proteïene getoon. Hierdie studie het bygedra tot waardevolle kennis oor die Pin-allele teenwoordig in SA koringkultivars, asook die invloed van Pin-genotipe-kombinasies en Pinb-D1-alleelmutasies op die GKH en verwerkingskwaliteit van koring. Die invloed van Pin-genotipe en GKH op die molekulêre gewigsverdeling van proteïene is ook gedemonstreer. Dit sal SA koringtelers in staat stel om spesifieke Pin-alleelkombinasies te selekteer om koring vir spesifieke eindgebruiksdoeleindes te kweek.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/105825
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