HETEROSIS, COMBINING ABILITY AND GENETIC ARCHITECTURE IN SUMMER GROUNDNUT [Arachis hypogaea L.]
Abstract
An experiment was conducted in a randomized block design with three replications at Instructional Farm, Junagadh Agricultural University, Junagadh during summer, 2010 with a view to estimate heterosis, inbreeding depression, combining ability and nature of gene action involved in the inheritance of pod yield, its components and quality traits in groundnut (Arachis hypogaea L.) using diallel mating design (excluding reciprocals) involving eight different Spanish bunch and one Virginia bunch genotypes in F1 and F2 generations. The analysis of variance revealed highly significant differences among parents, F1’s and F2’s for all the traits studied except for days to number of primary branches per plant in parents vs. F1 and days to 50 per cent flowering and sound mature kernel per
cent in F1’s vs. F2’s, indicating considerable amount of genetic variability present in the material studied.
Low to medium magnitude of heterobeltiosis, high magnitude of standard heterosis and low to moderate inbreeding depression were observed in case of pod yield per plant (g), kernel yield per plant (g), 100-kernel weight (g), number of mature pods per plant, shelling outturn (%), total soluble sugar and harvest index (%). The highest heterobeltiosis and standard heterosis for pod yield per plant was recorded in the cross, TPG 41 x AK 303.
The estimate of variance components due to general and specific combining ability indicated that both additive as well as non-additive gene action played an important role in the expression of all the characters. However, additive gene action was predominant in the expression of most of the traits.
The combining ability analysis revealed that the parents, TPG 41, JB HPS K 08-1 and AK 303 were observed to be the best general combiners for pod yield per plant, kernel yield per plant and 100-kernel weight (g) in both generations. While the parents, NRCG 10389 was also a good general combiner for days to 50 per cent flowering, days to maturity, number of mature pods, sound mature kernel, shelling outturn, protein content, harvest index and biological yield in both F1 and F2 generations. The parent, J 11 was a good general combiner for days to 50 per cent flowering, days to maturity, plant height, number of immature and mature pods, shelling outturn, total soluble sugar content, and biological yield. These parents could be used in the hybridization programme to isolate superior segregants. The per se performance of the parents and hybrids could be a good indicator for predicting general
combining ability (gca) and specific combining ability (sca) effects, respectively.
The cross, TPG 41 x AK 303 was found to be best specific combiner for pod yield per plant, kernel yield per plant, number of mature pods per plant and total soluble sugar content with best per se performance for pod and kernel yield per plant which could be expected to throw good transgressive segregants in later generations.
The cross, NRCG 10389 x TPG 41 was found to be the best specific combiner for pod yield and kernel yield per plant in both generations followed by two cross combinations, J 11 x AK 303 and NRCG 115 x JB HPS K 08-1.
Estimation of variance due to additive and dominance components revealed that additive as well as dominance gene actions were involved in the inheritance of most of the traits studied with preponderance of additive gene action for most of the traits. These findings were also confirmed by estimates of GCA/SCA variance ratios.
Average degree of dominance was found in the range of over dominance for all the characters in both the generations except for the traits like, days to 50 per cent flowering, days to maturity, 100- kernel weight, sound mature kernels, pod and kernel yield per plant and biological yield in which partial dominance was observed. Asymmetrical distribution of positive and negative genes and unequal frequency of dominant and recessive genes in the parents were observed for all the traits except for sound mature kernels in both the generations.
Heritability estimates in narrow sense in both the generations, was high for days to 50 per cent flowering, days to maturity, 100-kernel weight, sound mature kernel, pod yield per plant, kernel yield per plant, and biological yield; moderate for number of mature pods per plant, oil content, protein content, total soluble sugar content and harvest index and low for plant height, number of primary branches per plant and number of immature pods per plant. On other hand, shelling outturn (%) exhibited high heritability in F1 and moderate heritability in F2 generation.
The results of present investigation suggested that reciprocal recurrent selection procedure would mop up the additive gene effects and would also allow dissipation of non-additive gene effects. Biparental mating may also be used in the segregating generations to break the undesirable linkages and to exploit both additive and non-additive gene effects simultaneously for isolating superior transgressive segregants in later segregating generations.
Description
Keywords
SUMMER GROUNDNUT, BOTANY