Heterosis and Segregation Distortion for Grain Quality Traits Using Diverse Genotypes in Rice (Oryza sativa L.)

ABSTRACT

Heterosis and segregation distortion have been estimated in a 7 × 7 half-diallel genetic design utilizing seven diverse genotypes for four rice grain quality traits, viz., kernel size, shape, weight and protein content. Majority of crosses manifested significant heterosis and/or segregation distortion for the selected grain quality traits. Heterosis was found to be manifested with much greater extent for major quality components like grain weight (W) than other grain quality traits. The data revealed that rice grain quality could be markedly improved by direct selection of kernel length and shape index (Length/Width ratio) traits. Significant values of correlation coefficient between heterobeltiosis (improved heterozygotes with hybrid vigor) and inbreeding depression (heterozygotes with transgressive vigor) for the targeted ecomorphotypes have been observed. These large correlations may have practical implications in prognosis of heterosis for grain quality traits. The occurrence of segregation distortion or transgressive segregants has been attributed partly due to unconscious selection favoring quality traits in cultivated high yielding varieties. Involving parents of diverse ecosystems (or ecologies) sharing common primary genepools both within and amongst ecomprphotypes/landraces may generate maximum heterozygosity vis-à-vis heterosis. The assemblage of gene pools with desirable genes or gene blocks as originated through ecomorphotypes and/or landraces has been considered desirable for maintaining useful varietal diversification and spatial population structure for grain yield and quality traits interactions.

KEYWORDS:

• Crop improvement
• grain quality traits
• gene pool
• genetic diversity
• genotypes
• heterobeltiosis
• heterozygosity
• landraces
• rice (Oryza sativa L.)
• standard heterosis
• segregation distortion
• transgressive segregant