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In order to identify the morphological and physiological basis for yield variation
and to determine the most important traits affecting yield in grain corn hybrids, an
experiment was conducted in Agricultural Research Farm, Isfahan University of
Technology in 1996. Thirteen corn hybrids were studied in a randomized complete
block design with three replications. High genotypic variation was observed for all different traits in the studied hybrids. Grain yield had positive significant correlation
with plant height and leaf area, dry matter accumulation, growth period, days to
silking, grain filling period duration, grain filling rate, kernel number per ear, and
kernel weight. The increase in average growth and grain filling rates increased grain
yield. The coefficient of correlation between harvest index and grain yield was negative and significant. Stepwise regression and path analysis indicated that the maximum grain yield differences observed among hybrids, can be attributed to
average grain filling rate. Also, path analysis revealed that the number of kernel per ear was the most important yield component. Kernel weight was affected by grain
filling period and important rate, as well as the number of kernels per ear, but grain filling rate was the most important determining factor in kernel weight. In general, it seems that average grain filling rate, because of it's relationship with all of the yield components and it's determinant effect on grain yield, is a suitable criterion for evaluating the productivity of corn genotypes.