Morpho-physiological traits associated with variable field performance of different types maize germplasm across multiple environments

Abstract

Field performance of maize varies substantially among various types of germplasm, such as- hybrids, inbred lines, and often with open pollinated varieties (OPVs). Variations in per se performance is better realized under optimal growing conditions, and further widened with increase in level of stresses. We examined sub-tropical/mid-altitude germplasm, including promising hybrids, OPVs and inbred lines under different growing conditions, including optimal conditions, mild-stress (double population density) and severe drought stress. At vegetative growth stage, dry mater partitioning between vegetative and reproductive plant parts, proportion of dry matter allocated to leaf growth in relation to stem, and within reproductive parts the amount of dry matter available for ear development varied significantly among the types of germplasm, across the growing conditions. The best performing genotypes, both within a germplasm type and across the germplasm, showed relatively more biomass allocation to leaf at the cost of stem dry weight, and more dry matter accumulation for ear development at the cost of both tassel and stem biomass. Apart from relatively more leaf area, the longevity of active leaf area duration was one of the important characteristics of superior germplasm, across the types of germplasm and growing conditions. Comparatively more cob weight at anthesis was positively correlated with grain yield under drought stress. However, under unstressed or mild stress conditions the relationship was significant only with inbred lines. Across the environments, striking difference was observed for percent kernel abortion during early stage of grain filling (lag phase), both among the germplasm, and also between the best and worst entries within a germplasm type. Rate of kernel growth clay -1 and length of grain filling period were comparatively higher with hybrids than with inbred lines and OPVs. Our findings indicate that these variations in constitutive traits might be the factors responsible for distinct differences in field performance of different types of germplasm. Emphasis on these constitutive traits during selection and improvement of germplasm may prove to be beneficial in improving the performance of genotypes across the unstressed and less-favorable environments.