engleski

Validation of KASP markers associated with pre- harvest sprouting tolerance in a panel of European winter wheat cultivars

Pre-harvest sprouting (PHS) can reduce grain yield as well as bread-making quality of wheat resulting in economic losses for farmers and millers. Tolerance to PHS is therefore a desirable trait of a cultivar when prolonged rainy periods occur before harvest. Although the tolerance to PHS is known to be associated with various physiological, morphological and developmental characteristics of the seed and the spike, seed dormancy has been considered most critical factor for PHS tolerance. The level of seed dormancy as well as other components of PHS tolerance are controlled by genotype (G), environment (E) as well as G × E interaction. A number of studies reported various types of DNA markers to be significantly associated with quantitative trait loci (QTL) controlling PHS resistance, offering the possibility of their use in marker- assisted selection (MAS). In the present study, we validated 40 kompetitive allele-specific PCR (KASP) markers in a panel of 178 European winter wheat cultivars. All KASP markers have been previously reported to be significantly associated with the PHS tolerance in the cultivar panels or mapping populations, thus revealing potential application in wheat breeding programs. The PHS tolerance of 178 wheat genotypes, which was grown in a replicated field trial at location Zagreb, Croatia in 2016/2017 and 2017/2018 growing seasons was assessed using germination tests with hand threshed grains at harvest maturity and was expressed as weighted germination index (WGI) as described by Reddy et al. (1985). Forty KASP assays were selected from published reports and leaf samples from 178 genotypes were collected using LGC’s Plant Sample Collection KitTM and sent to LGC Genomics for genotyping. Single-marker linear regression analysis was used to determine the association between KASP marker and genotype mean WGI across years. The magnitude of the marker-associated phenotypic effect was described by the coefficient of determination (r2), which is a fraction of the total phenotypic variance accounted by the marker genotype. Combined analysis of variance across years revealed significant effect of genotype (G), year (Y) and G×Y for WGI. Out of 40 used KASP markers, 12 markers were included in the regression analysis, while other 28 markers were discarded because of being monomorphic, heterozygous on too many loci or they gave no signals. The regression of WGI on KASP markers was significant only for three markers, TaPHS1-646, TaPHS-666 (chromosome 3A) and TamKK3-A (chromosome 4A) with coefficients of determination (r2) being 0.0238, 0.0412 and 0.0825, respectively. Regression of WGI on the combinations of alleles (haplotypes) with the above mentioned three markers resulted in a considerably larger determination coefficient (r2 = 0.098) suggesting a greater efficiency of the marker combination than individual markers in MAS implementation.

Pre-harvest sprouting, molecular markers, wheat, dormancy

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