Floret development and grain setting characteristics in winter wheat in response to pre-anthesis applications of 6-benzylaminopurine and boron

• Dynamics of floret development and grain set were studied in Chinese winter wheat.
• We examined the effects of 6-BA and boron on wheat floret development and grain set.
• 6-BA and boron foliar spray treatments reduced floret degeneration and abortion.
• Exogenous 6-BA treatment was more effective at promoting grain set in distal florets.

The number of grains per unit land area is the most important component to determine grain yield in wheat. Survival of floret primordia seems to be critical for the determination of grain number, which is related to the number of fertile florets at anthesis and the growth of the florets have been frequently considered the determinant key to establish grain number. The objective of this study was to explore the dynamics pattern of floret generation/degeneration/abortion and the grain setting characteristics in winter wheat under contrasting conditions of foliar spraying. Field experiments were carried out during the 2011–2012 and 2012–2013 growing seasons at the Experiment Station of Henan Agricultural University. The experiment involved the wheat cultivar Yumai 49-198 and three foliar applications; water, 6-benzylaminopurine (6-BA), and boron, which were applied 25 days after the jointing stage. This study analysed in detail floret development in wheat as affected by resource availability (mainly foliar spraying), and found that the degeneration rates of the basal spikelet florets decreased by 24% and 6%, respectively, following application of 6-BA and boron. Similarly, the floret abortion rates were reduced by 73% (6-BA) and 22% (boron) when compared to the water control. The degeneration rates of florets from central spikelets decreased by 15% and 8%, after treatment with 6-BA and boron, respectively, while the abortion rates were reduced by 76% and 44%, respectively, when compared to the control. Spraying 6-BA significantly enhances the process by which florets became grains at different floret and spikelet positions, and especially promoted the grain setting of distal florets, respect to the rachis, into the spikelets (i.e., Florets 3 and 4).