Effects of Rht-B1 and Ppd-D1 loci on pollinator traits in wheat.

Elite wheat pollinators are critical for successful hybrid breeding. We identified Rht-B1 and Ppd-D1 loci affecting multiple pollinator traits and therefore represent major targets for improving hybrid seed production. Hybrid breeding has a great potential to significantly boost wheat yields. Ideal male pollinators would be taller in stature, contain many spikelets well-spaced along the spike and exhibit high extrusion of large anthers. Most importantly, flowering time would match with that of the female parent. Available genetic resources for developing an elite wheat pollinator are limited, and the genetic basis for many of these traits is largely unknown. Here, we report on the genetic analysis of pollinator traits using biparental mapping populations. We identified two anther extrusion QTLs of medium effect, one on chromosome 1BL and the other on 4BS coinciding with the semi-dwarfing Rht-B1 locus. The effect of Rht-B1 alleles on anther extrusion is genotype dependent, while tall plant Rht-B1a allele is consistently associated with large anthers. Multiple QTLs were identified at the Ppd-D1 locus for anther length, spikelet number and spike length, with the photoperiod-sensitive Ppd-D1b allele associated with favourable pollinator traits in the populations studied. We also demonstrated that homeoloci, Rht-D1 and Ppd-B1, influence anther length among other traits. These results suggest that combinations of Rht-B1 and Ppd-D1 alleles control multiple pollinator traits and should be major targets of hybrid wheat breeding programs.