Durum wheat adaptation and yield formation as affected by Ppd-1 photoperiod sensitivity genes

Understanding the effect of genetic factors controlling flowering time is crucial to fine-tune crop adaptation to each target environment and maximize yield.
A set of spring durum wheat inbred lines carrying all but one of the possible allelic combinations at Ppd-A1 and Ppd-B1 genes was developed through a collaboration between IRTA and CIMMYT. The collection was grown during several years at four sites at latitudes ranging from 19?N to 41?N in order to assess the effect of Ppd-1 genes on development, biomass production and allocation, as well as grain yield formation.
Environmental constraints were responsible for most of the observed variation for flowering time and yield components. Latitude was a main driver of flowering time, which was later in northern sites and associated with lower minimum temperatures before flowering. Data on environmental constraints explaining a large proportion of grains m-2 and kernel weight variation will be presented. The effect on flowering time of Ppd-A1 alleles conferring photoperiod insensitivity was enhanced at sites with average daylength before flowering lower than 12h. Ppd-A1 caused a stronger effect on flowering time than Ppd-B1, which was found responsible for differences in grains m-2, associated with longer photoperiods from double-ridge to terminal spikelet stages. These differences in grains m-2, however, did not result in higher yields due to kernel weight compensation. Late flowering genotypes carrying alleles conferring photoperiod sensitivity had greater biomass at anthesis but it did not confer superior yields. Early flowering times were associated with higher yields in autumn-sowing sites due to a large contribution to yield of current photosynthesis during grain filling. Early flowering genotypes tended to yield more due to higher kernel weights, and the interaction of allele combination x environment will be discussed in the context of using allelic information as environment-specific guideline in breeding efforts.