INHERITANCE OF GRAIN WEIGHT, SIZE AND SHAPE IN RAIN-FED RICE (ORYZA-SATIVA)

Gene effects for grain weight, grain length, breadth and shape (L : B ratio) were estimated using means of P-1, P-2, F-1, F-2 and F-3 genera tions of a cross, 'Khaolo 33' x 'Kalinga III' of rainfed rice (Oryza s ativa L.). The estimates of scaling tests, C and D along with joint sc aling test indicated the involvement of inter-allelic interactions in the inheritance of these traits. Dominance gene effects (h) and domina nce x dominance (I) interaction were important for grain weight and gr ain shape. However, grain length and breadth were governed predominant ly by additive gene effects (d) and their interaction (I). The number of effective factor pairs controlling these traits varied from 0.13 (g rain shape) to 3.86 (grain weight). The estimates of heritability and genetic advance were fairly consistent for grain length and breadth in F-2 and F-3 generations, whereas there was appreciable reduction for grain weight. These characters showed similar trend of relationship in F-2 and F-3 generations. Selection for grain length could bring forth the correlated improvement in these characters.