PHENOTYPIC AND GENETIC-RELATIONSHIPS BETWEEN YIELD COMPONENTS IN MAIZE

Physiological components of kernel development - LAG [lag period in days], effective filling period duration (EFPD) and grain filling rate (GFR), ear moisture release (.DELTA.U), ear size (row number and kernels per row), days from emergence to silking and number of leaves, were examined on 45 F1 hybrids (10 .times. 10 diallel cross) in order to study their genetic relationships with yield. Combining ability analysis revealed that all trait variability derived mainly from g.c.a. [general combining ability] effects. LAG and EFPD were the traits most affected by genotype-environment interaction. Covariation analysis (path method) based on mean phenotypic values and on g.c.a. effects yielded similar information. GFR and EFPD are both related to plant yield, but GFR made the most important contribution. On the contrary, a significant relationship between yield and LAG was not detected. Ear size components were also positively related to yield and had negative effects on GFR. The dry matter accumulation rate is the main limiting factor of yield. Considering s.c.a. [specific combining ability] effects, kernel number per row made the most important contribution.