Dynamics of floret development determining differences in spike fertility in an elite population of wheat

Further increases in wheat yield potential could be achieved through a better understanding of the dynamics of floret primordia generation/degeneration, a process which has received little attention. We quantified genotypic variation among elite genotypes of the CIMCOG panel assembled by CIMMYT for its usefulness for wheat breeding. Ten genotypes, representing the range of variation for yield and its components of the whole panel, were grown under high-yielding conditions in NW Mexico for two growing seasons. The stage of development of floret primordia was determined 2-3 times weekly during stem elongation for apical, central and basal spikelets within the spike. The dynamics of floret initiation/death, and the resulting number of fertile florets, were determined for each spikelet position. We found that the variation in number of fertile florets within this elite germplasm was much more related to the survival of floret primordia than to the maximum number of florets initiated. As the two floret primordia most proximal to the rachis were almost always fertile and most distal florets (florets 6-8) were never fertile, the differences in number of fertile florets were clearly attributed to the differential developmental patterns of intermediate florets (floret primordia 3, 4 and 5, counted from the rachis, depending on the spikelet position). We found significant differences among elite germplasm in dynamics of floret development. Differences in floret survival seemed positively related to those in the length of the period of floret development: the longer the duration of floret development the higher the likelihood of that floret becoming fertile. It is proposed that this type of study may be instrumental for identifying prospective parents for further raising yield potential wheat breeding programmes.