Agronomic performance of durum wheat landraces and modern cultivars and its association with genotypic variation in vernalization response (Vrn-1) and photoperiod sensitivity (Ppd-1) genes

This study analyzed the relationship between important agronomic traits and major genes regulating flowering time in a panel of 151 Mediterranean durum wheat landraces and 20 modern cultivars. Field experiments were conducted under rainfed conditions during six crop seasons in northeastern Spain. Multivariate analysis of agronomic traits and genotypic data allowed the modern cultivars to be differentiated from the landraces and germplasm pools to be identified within the landraces associated with their geographic origin. The high frequency of the Vrn-A1c allele and the photoperiod insensitive alleles GS105 and GS100 at Ppd-A1 reduced time to anthesis and enlarged the grain filling period of the modern cultivars compared with the landraces. Ancient durums collected close to the domestication area of wheat showed a high frequency of the winter allele vrn-B1 and the photoperiod sensitivity allele Ppd-B1b. None of the allele variants or allelic combinations accounted significantly for variations in any agronomic trait of modern cultivars. Vernalization and photoperiod genes acted additively in explaining the genotypic variance for the agronomic traits of the landraces. Vrn-A1 alleles and Vrn-A1+Vrn-B1 allelic combinations significantly affected the number of grains per spike (NGS), thousand kernel weight (TKW) and grain filling rate (R), accounting for 9%–12% of the genotypic variance for these traits. Ppd-1 accounted for 6%–21% of the genotypic variance for R, grain filling duration (GFD), plant height (PH), biomass at anthesis (CDW) and harvest index (HI). Vrn-1+Ppd-1 allelic combinations accounted for 21%–26% of the genotypic variance for these traits. Except for NGS, the effect of vernalization and photoperiod genes on the agronomic traits was linked to their effect on anthesis time. The three-day delay in anthesis time caused by the allele Vrn-A1d irrespective of the allele Vrn-A1c resulted in increases of 10 % in R and 7% in TKW. The eight-day delay in anthesis time caused by the allele Ppd-A1(DelCD) compared with Ppd-A1(GS105) increased R by 19 % and PH by 28 %, but reduced GFD and HI by 10 %. None of the allele variants or allelic combinations at the Vrn-1 or Ppd-1 genes accounted significantly for variations in yield or number of spikes m⁻² (NSm²).