Genetic architecture of wheat (Triticum aestivum L.) phenology to maximize yield in water limited environments

Water deficiency during the critical growth stages is one major concern affecting successful wheat production in the rainfed agriculture systems used in Australia and other semi-arid regions of the world. Bypassing the sensitive growth phases from a water stress period can result in higher grain yields in water limited environments. Therefore, this study was concentrated on the adjustment of phenology genes to synchronize the critical growth phases with the rainfall pattern or water availability of target environments. Vernalization (Vrn), photoperiod (Ppd) and earliness per se are the three major components of flowering pathway in wheat. A series of experiments were conducted to determine the role of allelic variations of vernalization and photoperiod genes in heading and subsequent grain production. The first experiment with double haploid (DH) lines differing for winter/spring alleles of Vrn-1 loci (vrn-A1, vrn-B1 and vrn-D1) revealed that combination of all three spring alleles confers the earliest flowering while the combination of all three winter alleles results in the latest flowering. On the other hand a combination of any one winter allele with two spring alleles results in intermediate heading but performed better in terms of a higher number of grain per spike, thousands kernels weight and test weight. Inclusion of a photoperiod insensitive allele with any combination of Vrn-1 loci reduces the heading time further by at least 20 days except for the combination with all winter alleles. The results also revealed that allelic variation in the Vrn and Ppd genes also alters the water requirement rate and total water consumption by modifying the duration of the growth phases. Investigation of the role of photoperiod sensitive/insensitive alleles of Ppd-D1 on heading and spike development revealed the relationship of photoperiod insensitive alleles Ppd-D1a with the gibberellin regulated pathway in addition to the effects of day length on flowering. Field experim