Heterosis breeding for grain yield and other agronomic characters in rice (Oryza sativa L.)

Thirty six hybrids evolved from nine high yielding and widely adapted cultivars were evaluated with parental lines and the standard variety, Jaya, to determine the nature and extent of heterosis for seven characters including grain yield per plant. Most of the crosses manifested significant heterosis for grain yield and panicle number per plant, panicle length, 1000-grain weight, grains per panicle, and days to maturity. Very few hybrids manifested significant heterosis for plant height. The range of heterosis for seed yield per plant was -96.7 to 258.2% over the better parent, -96.1 to 268.2% over midparent and -96.3 to 301.6% over the standard variety. The highest heterotic effects for grain yield were observed in the crosses Prasad x PP 72, Govind x PP 72, Govind x Sita, Prasad x Mahsuri and Govind x Jaya hybrids, which was, respectively, 258.2, 216.8, 177.8, 161.6 and 108.8% over better parent, 268.2, 250.8, 178.1, 204.2 and 119.4% over mid parent, and 301.6, 255.2, 151.6, 285.0 and 108.8% over the best check variety Jaya. A comparison between heterotic and nonheterotic hybrids for yield and its components indicated that heterosis for grain yield was due to two or more direct yield contributing characters. Implications of the nature and magnitude of heterosis for commercial exploitation in rice are discussed.