Maize (Zea mays L.) is the third most important crop among the cereal crops grown in India. Maize grain is gaining popularity in our country due to huge demand, particularly for poultry feed industry. Besides, maize has diversified uses as food and industrial raw materials. Maize acreage and production have an increasing tendency with the introduction of hybrids due to its high yield potential. The nature and magnitude of gene action is an important factor in developing an effective breeding programme. Combining ability analysis is useful to assess the potential inbred lines and also helps in identifying the nature of gene action involved in various quantitative characters. This information is helpful to plant breeders for formulating hybrid breeding programmes. Efforts are therefore required to be made to develop hybrids with high yield potential in order to increase production of maize. A good number of inbreds developed recently is available at the All India Coordinated Research Project on Maize, ARS, Arabhavi. Most efficient use of such materials would be possible only when adequate information on the amount and type of genetic variation and combining ability effects in the materials is available. A wide array of biometrical tools is available to breeders for characterizing genetic control of economically important traits as a guide to decide upon an appropriate breeding methodology to involve in hybrid breeding. The present investigation was carried out to determine breeding value of genotypes, nature and magnitude of gene action and heterosis for various yield and other important traits in maize (Zea mays L.). Line x tester mating design developed by Kempthorne (1957), which provides reliable information on the general and specific combining ability effects of parents and their hybrid combinations was used to generate the information. The design has been widely used in maize by several workers and continues to be applied in quantitative genetic studies in maize (Joshi et al., 1998).

Table 1 Estimates of variance components as reference to the prevailing gene action for 13 characters

Heterosis Estimates of the promising hybrids for Grain yield per hectare

The extent of heterosis for grain yield per hectare was observed from -28.57 (L6×T1) to 7.28 (L2×T1) per cent over EH-434042, -28.04 (L6×T1) to 8.07 (L2×T1) per cent over 900M and -30.14 (L6 ×T1) to 4.92 (L2×T1) per cent over Pinnacle, respectively (Table 2). All the experimental hybrids exhibited significant positive heterosis over mid parent and the hybrid L2×T1 (152.65%) had highest mid parent positive heterosis followed by L4×T1 (148.20%). Twenty six hybrids expressed significant positive heterosis over better parent, out of which the hybrid, L2×T1 (149.81%) had exhibited highest positive hetero- beltiosis, followed by L7×T1 hybrid (136.24%). Among 30 hybrids, three hybrids showed significant positive standard heterosis over both EH434042 and 900M and they were, L2×T1 (7.28 per cent over EH434042 and 8.07 per cent over 900M), L1×T2 (6.86 per cent over EH434042 and 7.64 per cent over 900M) and L×T3 (3.16% EH434042 and 3.92% over 900M).

Table 2 Per cent relative heterosis (RH), heterobeltiosis (HB) and standard heterosis (SH) for grain yield/ha characters

Discussion

The studies revealed higher SCA variance than GCA variance and thus the GCA/SCA variance ratio was lower than one, indicating the importance of SCA variance than GCA variance. These results are in line with findings of Paul and Duara (1991) and Sedhom (1994), Mohammad (1993) and Satyanarayanaet al (1994). For grain yield per hectare (t/ha) among 30 hybrids, two crosses, L1×T2 and L2×T1 showed significant highest positive heterosis over all the three checks, EH434042, 900M and Pinnacle (best check). Such results were also reported by Jha and Khehra (1992) and Larish and Brewbaker (1999), which supports our investigation.

Materials and Methods

The present investigation was carried out at All India Co-ordinated Maize Improvement Project, Agricultural Research Station, Arabhavi during the year 2011 (kharif) and 2011-2012 (rabi). The parents used in the experiment comprised of ten lines selected from newly derived 79 inbred lines of tropical origin which were available in All India Co-ordinated Maize Improvement Project, based on their per se performance. These lines were used as female lines and crossed with three tester’s viz., KDMI-10, KDMI-16 and CI-5. All the thirty F1 hybrids along with their parental lines were grown in the following growing season. Trials were irrigated throughout the growing season and cultural operations, fertilization, and weed control were accomplished according to normal field practices. The experiment was replicated twice in a randomized complete block design. The experimental unit was two rows for each entry, 4 m long and 75 cm apart, with plant to plant distance of 20 cm. The observations were recorded from five plants randomly selected from each plot for 13 quantitative traits viz., days to 50% tasseling, days to 50% silking, plant height, ear height, days to 75% brown husk maturity, ear length, ear girth, number of kernel rows per cob, number of kernels per row, 100-grain weight, grain yield per hectare, shelling percentage and fodder yield per hectare.

Sedhom S.A., 1994, Estimation of general and specific combining ability in maize under different planting dates, Ann. Agri. Sci., 28(1): 25-30