Genetics of Morpho-Physiological Traits in Segregating Populations of Interspecific Hybrid Rice Under Stress and Non-Stress Conditions

Abstract

Drought is one of the major constraints for rice (Oryza sativa L.) production in the rainfed ecologies in Sub-Saharan Africa. The objectives of this study were to investigate the genetic effects of morpho-physiological traits controlling drought-stress tolerance. Five Oryza glaberrima genotypes, four interspecific inbred lines, two interspecific hybrids, and two O. sativa lines and their progenies from a North Carolina II mating design were evaluated at ICRISAT in Mali under drought and fully irrigated conditions in 8 × 8 lattice designs. Data were collected on morpho-physiological traits, such as plant height, leaf rolling and stress recovery ability. General combining ability (GCA) effects for females and males were significant for all traits. Female GCA and specific combining ability (SCA) effects were significant for tiller number, plant height, and specific leaf dry weight. Heritability estimates based on variance ratios ranged from 47% to 67% for plant height, leaf area, specific leaf dry weight, and SPAD (chlorophyll); these were not significant for tiller number, which was controlled by overdominance. Heritability estimates based on regression were significant and ranged from 22% to 72% for drought-tolerance scores and leaf rolling scores. Highly significant positive relationships were observed between F₃ and F₄ generations for drought tolerance and leaf-rolling scores in all the populations examined. Both additive and non-additive genetic affects were important in controlling morpho-physiological traits; hence breeding procedures that exploit both GCA and SCA should be considered to improve drought tolerance in this rice germplasm.

KEYWORDS:

• drought tolerance
• heritability
• combining ability
• interspecific hybrid
• morpho-physiological traits

This study was supported by a grant from the Rockefeller Foundation, New York. The authors acknowledge Africa Rice Centre (WARDA) and ICRISAT, Bamako, Mali, for their logistical supports.