COMBINING ABILITY AND HETEROSIS IN MAIZE (Zea mays L.)

A line × tester analysis was conducted in maize involving 12 lines and 3 testers for grain yield and its components to determine the heterosis as well as general combining ability (GCA) and specific combining ability (SCA) effects. Highly significant genotypic differences were observed indicated wide range of variability present among the genotypes. GCA and SCA variance for yield per plant number of kernels per row and 100-kernels weight were observed significant, which indicated importance of additive as type of gene action for these characters. The ratio of SCA and GCA variances were high for the all character studied that revealed the preponderance of non additive type of gene action. Standard heterosis ranged from 28.29 to 28.41%; -12.29 to 24.38%; -1.11 to 24.44%; -14.75 to 6.67%; -17.24 to 11.26% and -10.94 to 20.83% for grain yield per plant, number of grains per row, number of rows per ear, ear length, ear diameter and 100-kernel weight, respectively. The lines IPB 911-16, IPB 911-12, IPB 911-2, IPB 911-18 and IPB 911-47 showed significant positive GCA effect and simultaneously possessed high mean value indicating that the per se performance of the parents could prove as an useful index for combining ability. The crosses exhibited significant SCA effects involved high x high, high x low, low x high, average x low and low x low general combining parents. The cross combinations with significant positive SCA effect having high mean values might be used for obtaining high yielding hybrids. The information on the nature of gene action with respective variety and characters might be used depending on the breeding objectives. Key word: Maize, line, tester, heterosis, combining ability, GCA, SCA INTRODUCTION Maize plays a significant role in human and livestock nutrition worldwide (Bantte and Prasanna, 2004). In Bangladesh, area, production and yield of maize decreased by 2.9%, 3.59% and 0.69% respectively from the year 1967-68 to 1986-87 due to utilization of traditional variety (Mohiuddin, 2003). Introduction of hybrid varieties and appropriate management practices increased area, production and yield increased by 19.83%, 34.40% and 14.56% respectively from the year 1987-88 to 2003-04 (Moniruzzaman et al., 2007). Now maize has become an important cereal in terms of yield (Maize: 5.36; wheat: 2.21; and rice: 2.15 ton ha -1 ., Anonymous, 2003) but in terms of area and production, it could be good source of nutrients for under nourished and mal-nourished populations in Bangladesh. It is 1 Seed Technology Division, Bangladesh Agricultural Research Institute, Gazipur-1701, Bangladesh; Wheat Research Center, Bangladesh Agricultural Research Institute, Dinajpur,