GENETIC ANALYSIS OF YIELD, YIELD ATTRIBUTES AND RESISTANCE TO LATE LEAF SPOT AND RUST IN A 8 × 8 DIALLEL IN GROUNDNUT (Arachis hypogaea L.)
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Date
2011
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY
Abstract
The experimental material of the present investigation comprised of 28 crosses generated by 8 × 8 half diallel in F1 and F2 generations and the parents. These were evaluated for sixteen characters i.e., morphological, yield and foliar disease resistance traits over two seasons, kharif 2009 and rabi 2009-10 at Regional Agricultural Research Station, Tirupati to study combining ability, nature of gene action and inter-relationships between yield and resistance parameters which will be useful in planning breeding programmes and selection procedures to evolve high yielding foliar disease resistant genotypes with desirable pod and seed attributes.
Combining ability analysis of kharif 2009, rabi 2009-10 and pooled data indicated that the gene action varied from season to season for a particular trait. During kharif season, the number of primary branches per plant was predominantly governed by additive gene action while all the other characters were influenced by both additive and non-additive gene actions. During rabi season, except LLS severity, all the other characters were under the influence of both additive and non-additive gene actions while LLS severity was profoundly
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under the control of additive genetic variance. The pooled data analysis indicated that the traits, days to maturity, plant height at harvest, number of secondary branches per plant, number of leaves per plant at harvest, percentage of leaves affected by foliar diseases, number of immature pods per plant, kernel weight per plant, sound mature kernel percentage, shelling out-turn, LLS severity and pod yield per plant were largely governed by additive gene action while the remaining traits were predominantly governed by non-additive gene action.
Considering mean and general combining ability effects among parents, ICG (FDRS) 79 was identified as best combiner for days to 50% flowering, days to maturity, number of primary branches per plant, number of secondary branches per plant, number of leaves per plant at harvest, percentage of leaves affected by foliar diseases per plant, number of mature pods per plant, kernel weight per plant, LLS and rust severities, harvest index and pod yield per plant during both kharif and rabi seasons. The parent, GPBD 4 was identified as a best combiner for the traits, percentage of leaves affected by foliar diseases per plant and LLS and rust severities; Tirupati 1, Narayani, Kadiri 6 and TLG 45 were found to be good combiners for early flowering and early maturity during both the seasons and TCGS 876 was found to be best combiner for the number of primary branches per plant during both the seasons. For shelling out-turn, Tirupati 1 and Narayani exhibited good breeding potential while Kadiri 6 was a good combiner for sound mature kernel percentage.
Based on mean and SCA effects, the hybrid, TCGS 876 × ICG (FDRS) 79 in both kharif and rabi seasons, TLG 45 × GPBD 4 and TLG 45 × ICG (FDRS) 79 in kharif 2009 and TPT 25 × GPBD 4, TPT 25 × Kadiri 6 and TCGS 876 × GPBD 4 in rabi 2009-10 were found promising for pod yield, other yield attributes and for foliar disease resistance traits. Variability studies indicated that most of the traits except days to flowering and maturity, shelling out-turn and sound mature kernel percentage are highly influenced by additive genetic variance.
The highest magnitude of heterosis was observed for number of secondary branches per plant followed by percentage of leaves affected by foliar diseases per plant, number of immature pods per plant and kernel weight per plant. The best heterotic crosses identified for pod yield per plant were TPT 25 × GPBD 4, Kadiri 6 × TLG 45 and Narayani × Kadiri 6 during rabi 2009-10 and TPT 25 × ICG (FDRS) 79, TLG 45 × GPBD 4, TLG 45 × ICG (FDRS) 79 and TCGS 876 × ICG (FDRS) 79 during kharif 2009.
Analysis of correlation among pod yield, yield attributes and the traits conferring resistance to foliar diseases in parents, F1s and F2 populations indicated the strong association of days to maturity, number of primary and
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secondary branches per plant, number of mature pods per plant and kernel weight per plant with pod yield and the scope for concurrent improvement of these traits. Significant negative association of foliar disease resistance traits with yield clearly demonstrates the need to go for systems of mating that promote recombination to break these undesirable linkages. Most of the traits that had shown positive correlation exerted high positive direct effects in parents, F1s and F2 populations. In F2 populations, shelling out-turn and sound mature kernel percentage had exerted high direct effect which is a desirable change as these are the traits that most often exhibited negative relationship with yield in foliar disease resistance breeding programmes.
Sixteen polymorphic primer pairs were used for screening eight genotypes that were used as parents among which GPBD 4 and ICG (FDRS) 79 were resistant to LLS and rust while TPT 25, TLG 45 and TCGS 876 were moderately susceptible and Tirupati 1, Narayani and Kadiri 6 are susceptible. The amplification profiles (separated through 9% non-denaturing PAGE) of two SSR primer pairs, pPGPseq 5D05 and pPGPseq 1B09 were found to be different in resistant and susceptible genotypes.
These were further validated in F1s. Bulk segregation analysis in F2 generation further confirmed the association of alleles amplified with these primer pairs with resistance and susceptibility. In susceptible genotypes, the primer pair, pPGPseq 5D05 amplified alleles of size, 250 and 300bp. In resistant genotypes, SSR alleles amplified were of size greater than 300, 275 and 250bp. The SSR primer pair, pPGPseq 1B09 amplified alleles of size greater than 300 and 275bp in susceptible genotypes and alleles of size lower than 300 and 275bp in resistant genotypes.
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Keywords
planting, diseases, developmental stages, yields, crossing over, harvesting, heterosis, biological phenomena, groundnuts, genetics, Arachis hypogaea L.,, planting, diseases, developmental stages, yields, crossing over, harvesting, heterosis, biological phenomena, groundnuts, genetics