GENETIC-ANALYSIS OF GRAIN DIMENSIONS AND WEIGHT AND THEIR ASSOCIATIONWITH GRAIN-YIELD IN RAIN-FED RICE (ORYZA-SATIVA)

An experiment was conducted during rainy season of 1991 to study the i nheritance of grain size, shape and weight and their interrelationship s with grain yield in rainfed rice (Oryza sativa L.). Grain length, br eadth and shape were found quantitatively inherited and thier expressi on was influenced by modifiers in 5 intervarietal crosses, viz 'RR51-1 ' x 'Kalinga 3', 'BG 367-4' x 'RR 149-177'. 'BG 367-4' x 'RR 203-2', ' Annada' x 'Kalinga 3' and 'Annada' x 'Prasanna'. The frequency distrib ution for grain weight in the F2 generation of 'BG 367-4' x 'RR 149-17 7' and 'Annada' x 'Kalinga 3' indicated the segregation of genes of ma jor effect, whereas in the rest of the 3 crosses the expression of gra in weight was under polygenic control. High heritability (broad sense) along with high to moderate expected genetic advance for grain weight , grain length, breadth and shape indicated that selection in the segr egating generation might be very useful in the improvement of these ch aracters. There was no consistent trend of interrelationship among gra in size, shape, weight and yield.