Analysis of the Growth of Individual Grains in Different Bread Wheat Genotypes

The objective of this study was to evaluate dry matter accumulation and grain growth rates of individual grains at different positions within a spike of aestivum wheat genotypes including PBW–154, PBW–343 and PBW–138. Dry matter accumulation were determined in ten labelled mother shoots which sampled nine times through the grain filling period on 7, 11, 15, 19, 23, 27, 31 and 35 days after anthesis as well as at harvest maturity. The spikes were divided into three grain positions included proximal, middle, and distal regions, and further into two grain types within each spikelet included basal (bold) and apical (small). Comparisons amongst the bold grains, growing in different segments of the spike, distinctively projected that there were insignificant variations in their net dry matter collection amongst themselves. However, variations among small grains were significant especially in distal segments of ear, as compared to proximal or middle segments. The grain filling duration taken by grains in distal or proximal segments of spike were relatively less than the grains dwelling in middle segment of a spike. The variations, in the growth rate amongst different grains were more prominent during the early stages of growth in all the varieties. Somehow, at the later stages of grain filling there were insignificant variations in growth rate between the two types of grains with a higher growth rate in small grains as compared to bold grains especially in proximal and middle segments of the varieties PBW–154 and PBW–343. The analysis on relative growth rates showed a similar trend of a brisk growth rate in both the types of grains in first 15 days with a relatively bigger impetus in smaller grains in three different segments of a spike in all the varieties. Later on, the two types of grains grew with equal potency in relative growth rates till maturity. A comparison amongst the different grains in same spike depicted that the pattern of relative growth rate, in totality was same and no significant differences were detected amongst various grains. However, at varietal level PBW–154 grew at relatively faster rate than PBW–343 or PBW–138.