Genetic and environmental control of yellow pigment in durum wheat (Triticum turgidum Durum) in Australia.

Abstract

Environmental and genetic control of grain yellow pigment (YP) content of Australian durum cultivars has been investigated using large genotype x environment (including controlled environments) data sets and 2 large bi-parental recombinant inbred line durum wheat populations respectively. Non-genetic variation in YP concentration was shown to be highly complex. This complexity was simplified by showing that final YP concentration is a function of the negative relationship between YP concentration and thousand grain weight (TGW), possibly due to starch dilution, and the total YP content synthesised per grain (YP/grain). Non-genetic variation in YP/grain was, not surprisingly, shown to be dependent on final TGW; however, it was also shown to be independent of TGW. Limited plant available water during grain filling resulted in both lower YP/grain and lower TGW; the net result was a modestly higher grain YP concentration. An hypothesis based on endosperm cell number that attempts to explain the observations is proposed and the implications of non-genetic control of YP for breeding programs discussed. YP concentration and YP/grain were shown to be multi-genic traits and in both populations examined there was evidence of transgressive segregation. QTL on chromosomes 7AL, 7BL, 7BS, 6B, 1A and 3B in Wollaroi/Tamaroi and 7AL, 7BL, 7BS, 6BL, 6BS, 1A and 3B in WID22221/Tamaroi were additive and together explained >50% and >40% of the phenotypic variation respectively with 7AL and 7BS being the most important. Allelic variation at Psy1-A1, encoding phytoene synthase, was identified in both populations but contrary to expectation was not associated with significant differences in YP phenotype. Rather the effect of chromosome arm 7AL appeared to be contributed by a QLT located proximal to Psy1-A1. In contrast, association between YP concentration and allelic variation at Psy1-B1, which has been identified in international germplasm, was confirmed in Australian durum wheat.