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 whose combining ability has not yet been studied for utilization in hybrid development programme. 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×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., 2002; Sharma et al., 1982).

Results and Discussion

Variance due to females, males and female×male interaction in respect to 13 quantitative traits are presented in Table 1. The variance due to female was highly significant for most of the traits under study indicating sufficient variability and variances due to male were highly significant for days to 50% silking and non significant for remaining traits. This indicates that the male and female lines would contribute to the final yield trait indirectly through the yield contributing traits. The female×male interaction variance was highly significant for plant height, ear height, ear length, no of kernels per row, grain yield per hectare and shelling percentage. This implies that the divergence of testers from lines with respect to these characters.

Table 1 Analysis of variance for combining ability for 13 different characters

Among the ten parents studied, the parental lines L1 was best general combiner for plant height, ear height, ear girth, 100-grain weight, grain yield per hectare and fodder yield per hectare. L2 was best general combiner for plant height, ear height, ear length, 100-grain weight, grain yield per hectare and fodder yield per hectare. L7 was found to be best general combiner for ear length, 100-grain weight, grain yield per hectare and shelling percentage. Days to 50 per cent silking, plant height, ear height, days to 50% brown husk maturity and shelling percentage for these characters L8 showed significant general combining ability effects and parent L10 can be given the status of best general combiner for majority of the characters like ear height, no. of kernel rows per ear, shelling percentage and fodder yield per hectare. Hence these parents can be better utilized for the improvement of the characters for which the parents showed significant gca effects (Table 2).

Table 2 General combining ability (gca) effects of parents in respect of 13 characters

Out of thirty hybrids/crosses, six hybrids have shown significant sca effects for the grain yield per hectare viz., L2×T1, L4×T1, L6×T3, L7×T1,L8×T3 and L9×T2 (Table 3). The crosses, L1×T2, L3×T1 and L8×T3 for plant height and ear height (Paul and Debnath., 1999; Zelleke., 2000), and for ear length (Kumar., 1971) the crosses like, L1×T3 and L8×T1 and for no. of kernel rows per ear (Premalata et al., 2011) L10×T1 were the best specific combinations. It was clear that these hybrids were the combinations of either both the parents as good general combiners or one of the parents as good general combiner for grain yield character.

Table 3 Specific combining ability (sca) effects of single cross experimental hybrids in respect of 13 characters

The variances (s²GCA,s ² SCA, s²A and s²D) and ratios (s²GCA/s² SCA, s²A/s²D) are presented in Table 4. The analysis of variance revealed highest magnitude of SCA than GCA for all characters except for days to 50% tasseling, days to 50% silking and ear girth and the ratio of GCA to the SCA variance for all the traits was less than unity except for days to 50 per cent tasseling and ear girth. The analysis of variance revealed highest magnitude of dominance for all traits except for days to 50% tasseling and ear girth, they exhibited highest magnitude of additive gene action. The ratio of additive to dominance was lesser than unity for all characters except 50 per cent tasseling and ear girth. 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), Sedhom (1994), Mohammad (1993) and Satyanarayana et al (1994).

Table 4 Estimates of variance components as reference to the prevailing gene action for 13 characters

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 5). 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 heterobeltiosis, 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% over EH434042 and 8.07 per cent over 900M), L1×T2 (6.86% over EH434042 and 7.64% over 900M) and L×T3 (3.16% over EH434042 and 3.92% over 900M). Such results were also reported by Jha and Khehra (1992) and Larish and Brewbaker (1999), which supports our investigation.

Table 5 Per cent relative heterosis (RH), heterobeltiosis (HB) and standard heterosis (SH) for grain yield/ha characters

In brief overall results from present investigation revealed that the parents, L1, L2, L7, L8 and L10 were considered to be an best general combiners and of the 30 hybrids L2×T1, L1×T2 and L8×T3 were found to be good specific combination for grain yield and its contributing traits like plan height, ear height, ear length and no. of kernel rows per cob. Same hybrids also showed significant heterosis over checks.

Material 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 2011-12 (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.

References

Zelleke H., 2000, Combining ability for grain yield and other agronomic characters in inbred lines of maize (Zea mays L.), Indian J. Genet. Plant Breed., 60: 63-7