Unraveling the influence of kernel row number and cob-related traits on the expression of heterosis in field corn (Zea mays L.)

Kernel row number (KRN) is an important agronomic trait of the female inflorescence and it is a significant breeding target. In the investigation, a set of 280 inbred lines derived from multiple disease-resistant pools was characterized for KRN and other cob-related traits. Out of 280 inbred lines, 45 lines differing for KRN were selected and evaluated at two locations and three environments. The inbred lines showed significant variation in yield and yield contributing traits at both locations and all the environments considered for evaluation. The KRN and other traits showed a high phenotypic coefficient of variation (ranged 6.47-24.39), genotypic coefficient of variation (ranged 6.47-24.39), and heritability (ranged 71.5-99.6), which were consistent across environments, suggesting the stability of performance of inbred lines and the possibility of genetic gain through selection for these traits. Further, the contrast inbred lines for the KRN trait were identified, which ranged from 10–12 rows (AI 504, AI 505, AI 515, AI 516, AI 518, and AI 519 low KRN) to 18–24 rows (AI 545, AI 536, AI 537, AI 542, AI 543, and AI 544 high KRN). These selected lines (six lines each) were crossed in a diallel fashion and generated 144 F₁ combinations. Hybrids so obtained showed significant variation for KRN and other yield component traits, coupled with significant general combining ability (GCA) and specific combining ability (SCA) variances and effects. The ratio of GCA/SCA variance and effect suggested that all the traits, including KRN, are governed by additive gene action. The combinations having low × low KRN have not expressed any significant heterosis, but the cross involving low × high KRN, and high × high KRN showed significant heterosis for grain yield of hybrids viz., AH-4271, AH-4152, AH-4139, AH-4072, and AH-4039. Hence, the parental lines of these selected hybrids have the potential to improve the productivity of field corn and are also sources for future heterosis breeding programs.