Early generation selection based on genetic parameters and molecular diversity in parental lines of soybean [Glycine max (L.) Merrill]
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Date
2018-01
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
The present investigation was carried out with the objectives to study the efficiency of early generation selection, residual heterosis, transgressive segregation, inter-character association and their direct and indirect effects on yield and molecular marker analysis using seventeen different SSR primers for effective selection of genotypes and improvement of soybean. For field experiment, 36 genotypes of soybean comprising 14 crosses, 20 parents and two checks (PS 19 and SL 688) were evaluated in F2 generation using randomized block design with two replications in kharif 2015 and 14 crosses along with their 21 progenies (10 high value group, 10 low value group and 10 bulk) were evaluated in compact family block design with two replications in kharif 2016 at the Norman E Borlaug Crop Research Centre, G.B. Pant University of Agriculture and Technology, Pantnagar. The Analysis of variance was found highly significant for all the characters undertaken in both the generations. The study on early generation selection with various genetic parameters revealed that characters days to 50% flowering, plant height, number of pods per plant and seed yield per plant exhibited positive and significant value for intergeneration correlation coefficient. The estimate of intergeneration regression coefficient revealed that days to 50% flowering, plant height and seed yield per plant were positive and significant. The number of pods per plant and seed yield per plant displayed significant and positive value for response to selection. High heritability coupled with high genetic advance was observed for seed yield per plant in both the generations. The value of realized heritability was found higher for days to 50% flowering, number of pods per plant and seed yield per plant. High performance of F3 bulk than F2 generation and F3 high group proved bulk method to be more effective than the pedigree method The per se performance of F2 generation for seed yield per plant was highest for three crosses, PS 1584 X JS 20-69 (20.7g), PS 1583 X JS 20-29 (20.08g) and PS 1225 X PS 1347 (19.58 g), for F3 high yielding group it was highest in PS 1584 X JS 20-69 (42.63g), PS 1583 X JS 20-29 (33.40g) and PS 1584 X JS 20-41 (29.79g), similarly the per se performance in F3 bulk was highest in PS 1584 X JS 20-69 (50.12g), JS 20-29 X JS 20-55 (39.76g) and JS 20-69 X JS 20-59 (35.63g). On overall basis, seed yield per plant was found to be effective for early generation selection. The study of nature and magnitude of residual heterosis revealed that PS 1584 X JS 20-41. PS 1583 X Bragg, PS 1584 X JS 20-69 and PS 1583 X JS 20-29 showed significant and positive residual heterosis over mid-parents. Over better parent, PS 1584 X JS 20-41 and PS 1583 X Bragg showed significant and positive residual heterosis over better parent, while PS 1584 X JS 20-69 showed positive and significant residual heterosis over both the checks, in F3 generation while none of the crosses showed significant residual heterosis in F2 generation. All the F2 crosses showed positive transgressive segregants for seed yield per plant but moderate frequency was observed. Highest positive transgressive segregant for seed yield per plant was recorded in the cross, PS 1042 X PS 1347. Occurrence of transgressive segregants in segregating generation is helpful for development of homozygous lines by continued selfing in crops like soybean. The present study revealed that in F2 and F3, dry matter weight per plant, plant height, number of primary branches per plant, number of pods per plant, number of seeds per pod and harvest index exhibited significant and positive correlation with seed yield per plant. The component characters which showed highest direct effect on seed yield per plant were harvest index and dry matter weight per plant in F2 generation and number of pods per plant in F3 generation indicating selection of these characters will bring direct improvement in seed yield The molecular diversity analysis of twenty two soybean genotypes revealed that the Jaccard’s similarity coefficient estimates varied from 0.29 (JS 20-59 and Pb1, JS 20-54 and Pb1, PS 1584 and PS 1347, JS 20-41 and PS 1347) to 0.82 (JS 97-52 and JS 20-29, PS 1583 and RVS 200-1, PS 1583 and JS 20-29 and PS 1042 and Pb1) genetic similarity. The average number of alleles per marker was 1.88, while percentage of all bands showed the polymorphism was 100%. The dendrogram constructed from SSR marker data divided twenty two genotypes into two main groups A and group B which consisted of seven clusters: Cluster I, II, III, IV, V, VI and VII. On the basis of dendrogram, genotypes PS 1225 and JS 20-59 was found to be most distant.
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