RELATIONSHIPS BETWEEN LENGTH OF THE ACTUAL AND EFFECTIVE GRAIN FILLING PERIODS AND THE GRAIN YIELD OF CORN

Abstract

Studies were conducted near Guelph, Ontario in 1970 and 1971 to examine the relationship between grain yield of corn and two measures of the length of the grain filling period, AFPD (actual filling period duration — days from mid-silking to black layer maturity) and EFPD (effective filling period duration — final kernel size divided by mean rate of kernel dry weight accumulation during the middle of the grain filling period). The studies involved 30 adapted commercial hybrids in 1970 and 35 in 1971, with 27 common to both years. Measures of AFPD and EFPD were highly correlated across years. Positive relationships were evident in each year, and over the averages of 2 yr, between AFPD and EFPD, and between both parameters and grain yield; averaged over 2 yr for 27 hybrids, the correlation coefficients between AFPD and yield, and EFPD and yield, were 0.56 and 0.53, respectively (both significant at [Formula: see text]). In general, results provided support for earlier suggestions that selection for an extended grain filling period could result in increased grain yield. However, notable exceptions existed among hybrids to the overall relationship between length of filling period and yield. The existence of these exceptions may indicate that the general relationships observed between length of filling period and yield were only indirect rather than direct, and that exceptional hybrids with high grain yield, high rate of grain dry matter accumulation, and short grain filling period may represent a better breeding objective in short-season corn-growing regions.