GENETIC VARIABILITY AND STABILITY ANALYSIS IN SUMMER GROUNDNUT (Arachis hypogaea L.)

Groundnut (Arachis hypogaea L.) is an autotetraploid (2n=4x=40), self-pollinated crop grown worldwide for superior edible oil (45-54%), protein (22%-32%) and carbohydrates (8-14%). It has high oleic acid content, and crop is valued for both edible oil and confectionery purposes. The average productivity of groundnut in India is about 1000 kg /ha, and stagnated for the last several years. To over come such stagnation in production and productivity, efforts on varietal improvement with emphasis on high yield, stable genotypes and resistance/ tolerance to biotic and abiotic stresses, and development of low cost crop management practices are needed. The objectives of present investigation were to generate information on the extent of genetic variability, characters association and stability of genotypes for pod yield per plant and its components characters. Fifty groundnut genotypes having bunch type growth habit were evaluated during Summer 2008 at Regional Research Station, Anand Agricultural University, Anand in a Randomized Complete Block Design replicated thrice in three environments created by three (E1 = 22nd January, 2008, E2 = 12th February, 2008 and E3 = . Abstract ii 28th February, 2008) dates of sowing. The experiments were conducted under Middle Gujarat Agro-climatic situation (Agro-climatic Zone-III). The observations were recorded for two phenological characters, and other growth and yield contributing characters of pod yield per plant. The collected data were subjected to statistical analysis for estimates of variability parameters, correlation, path analysis and stability parameters. The analysis of variance revealed that the mean square values due to genotypes were significant for all the characters in each individual environment and pooled over the environments. The pooled analysis revealed that mean squares due to G × E interaction were significant for all the characters except oil content. The pooled analysis over environments showed that the mean square values due to environments were significant for all the characters. Mean performance for majority of the characters was high in environment E3 followed by E2 and E1. The estimates of GCV and PCV were high across the environments for number of mature pods per plant, number of immature pods per plant, 100-pod weight, kernel yield per plant, test weight of 100-kernel, harvest index; while, those were moderate for plant height, number of primary branches per plant, total biological yield, pod yield per plant, fodder yield per plant, there by suggesting existence of sufficient variability among these traits. The estimates of heritability in broad sense and genetic advance were high for 100-pod weight and test weight of 100-kernel, which suggested that these characters primely governed by additive gene action, and improvement through direct selection on existing variability would be possible. The characters days to 50% flowering, days to maturity, plant height, . Abstract iii number of mature pods per plant, total biological yield, pod yield per plant, fodder yield per plant and harvest index had high heritability estimates, but estimates of genetic advance were moderate in all the environments, which suggested that the character can be improved, when high selection pressure is applied. The correlation analysis indicated that pods yield per plant exhibited significant and positive correlation with kernel yield per plant and harvest index in all the environments; also 100-pod weight and test weight of 100-kernel in E3. In contrast to this, significant and negative correlation between pod yield and fodder yield per plant was observed in all the environments. Significant and positive/ desirable correlation was also observed for other characters, which suggested that for improvement of pod yield due weightage should be given for improvement of other characters. The path analysis revealed that total biological yield followed by kernel yield per plant had high and positive direct effects on pod yield. While, pod yield had high and negative direct effects of fodder yield per plant followed by shelling percentage in all the environments. Kernel yield per plant showed positive direct effect coupled with significant and positive genotypic correlation; while, fodder yield per plant had negative direct effect along with significant and negative correlation on pod yield in all the environments; therefore, with the minimization of fodder yield improvement in pod yield could be brought. Studies on the genotypes × environments interaction effects revealed that mean square values due to genotypes × environments interaction were significant for all the characters except number of primary branches per plant, fodder yield per plant, harvest index and oil content indicating variable expression of the characters in different . Abstract iv environments. The preponderance of linear component of G × E interaction in comparison to pooled deviation for all the characters except primary branches per plant, harvest index and oil content revealed that performance of genotypes may be predicted in varied environments. Based on stability parameters, genotypes ICGV-00340, ICGV00350, ICGV-00441 and ICGV-99229 were found stable in favourable environment for pod yield per plant; hence these genotypes may be evaluated under favourable environment over years, and the most promising genotypes may be recommended for commercial cultivation. None of the genotypes was found stable for all the characters in any specific environment; however, genotypes AG-2006-6, ICGV-00440, ICGV-00441, GG-7 and GG-20 had well adaptation for seven or above seven characters along with pod yield in different specific environments. On the outcome of present investigation, it can be concluded that the genotypes could not performed consistently across the environments, and those exhibited variable performance due to high proportion of G × E interaction.