RATE AND DURATION OF GRAIN FILLING IN 5 SPRING WHEAT (TRITICUM-AESTIVUM L) GENOTYPES

Final grain dry weight, a component of yield in spring wheat, is determined by the rate and duration of grain filling, The objective of this study was to compare grain dry weight and rate and duration of grain filling amongst five spring wheat genotypes (Triticum aestivum L.) that differed in time to maturity. Glenlea, Katepwa, PT516, Roblin, and Wildcat were sown in replicated trials on four seeding dates in 1988 and 1989 at Winnipeg, Manitoba. Mean grain dry weight was measured at various intervals from anthesis to maturity. A logistic equation was used to characterize grain filling and estimate final grain dry weight, and the duration and maximum rate of grain filling. Stepwise multivariate analysis indicated that final grain dry weight was the most important variable characterizing the grain filling curves, followed by duration and then maximum rate of grain filling. The highest grain dry weights were produced by Glenlea (40.4 mg) and Wildcat (36.9 mg). Roblin (34.9 mg) was intermediate in grain dry weight while Katepwa (32.4 mg) and PT516 (30.3 mg) produced the smallest grains. Genotypes with the highest grain dry weights had shorter durations and higher maximum Fates of grain filling.