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 deter mined 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.) tha t differed in time to maturity. Glenlea, Katepwa, PT516, Roblin, and W ildcat were sown in replicated trials on four seeding dates in 1988 an d 1989 at Winnipeg, Manitoba. Mean grain dry weight was measured at va rious intervals from anthesis to maturity. A logistic equation was use d to characterize grain filling and estimate final grain dry weight, a nd the duration and maximum rate of grain filling. Stepwise multivaria te analysis indicated that final grain dry weight was the most importa nt variable characterizing the grain filling curves, followed by durat ion and then maximum rate of grain filling. The highest grain dry weig hts 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 h ighest grain dry weights had shorter durations and higher maximum Fate s of grain filling.