GENETICS OF SALT TOLERANCE IN RICE (Oryza sativa L.)
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Date
2015
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Acharya N.G. Ranga Agricultural University, Guntur
Abstract
The present investigation on “Genetics of salt tolerance in rice (Oryza sativa L.)” was undertaken at Agricultural Research Station, Machilipatnam during 2010-12. The experimental material for genetic divergence and variability studies comprised of fifty elite rice genotypes obtained from different locations, while 10 divergent and elite rice genotypes identified from genetic divergence studies along with their 45 hybrids obtained from 10 x 10 diallel mating excluding reciprocals constituted the experimental material for studies on combining ability and stability studies with regards to yield, yield attributes and salinity traits under saline conditions.
In general, shoot length, shoot dry weight, shoot potassium content, productive tillers hill-1 and grain yield plant-1 had recorded high variability (PCV and GCV) and heritability coupled with high genetic advance as per cent mean. Fifty genotypes studied in the present investigation were grouped into eight clusters. Among the eight clusters, cluster II was the largest comprising of 14 genotypes while V, VI and VII clusters had single genotype. The results on intra-cluster D2 values revealed maximum genetic divergence among the genotypes in cluster IV, compared to those in other clusters. Further, the inter-cluster D2 values of eight clusters revealed highest divergence between clusters VII and VIII, followed by cluster I and VIII indicating that genotypes from these clusters were highly divergent. Minimum inter-cluster distance was observed between clusters IV and VIII indicating their close relationship and similarity with regards to the characters studied.
A perusal of these results revealed that there was no cluster with at least one genotype with all the desirable traits, which ruled out the possibility of selecting directly one genotype for immediate use. The results revealed high grain yield, productive tillers, spikelet fertility percent and shoot potassium content for cluster VII; shoot length, shoot dry weight, number of days to 50 percent flowering and 1000 seed weight for cluster V; plant height, root length and root dry weight for cluster VI; and shoot sodium content for cluster VIII indicating the importance of selection of genotypes from these clusters in hybridization programmes for improvement of the respective traits.
Further, shoot sodium content contributed maximum (59.67%) followed by shoot potassium content (15.51%) and shoot dry weight (9.80%). Grain yield per plant (4.33%), plant height (3.59%), days to 50 per cent flowering (3.51%), 1000 seed weight (2.86%), productive tillers hill-1 (0.49%), root length (0.16%) and spikelet fertility per cent (0.08%) each were noticed to contribute less than 5 per cent towards the total divergence.
The results on mean performance for parents and hybrids in general, revealed higher grain yield, spikelet fertility per cent, productive tillers hill-1 and shoot length were recorded during normal rabi. The mean squares due to gca and sca indicated the importance of both additive and non-additive gene actions for different traits studied. However, pre dominant role of non-additive gene action was observed for all characters studied in the present investigation. The analysis of variance for stability revealed mean squares due to seasons and genotypes x seasons interaction to be significant for all the traits. Studies on environmental index revealed the suitability of normal kharif season to be favourable for shoot dry weight and plant height, while late kharif season was noticed to be congenial for 1000 seed weight. Normal rabi, however, was noticed to be suitable for shoot length, shoot potassium content, root length, root dry weight, productive tillers hill-1, spikelet fertility percentage and grain yield plant-1, whereas late rabi was favourable for shoot sodium content and days to 50 percent flowering.
The results on AMMI analysis revealed IPCA II and IPCA III axis to be nonsignificant for most of the characters studied. However, IPCA I was significant for all characters studied, except spikelet fertility percentage. The interaction of 55 genotypes in four seasons was therefore inferred to be best predicted by the first interaction principal component. AMMI analysis of variance for grain yield plant-1 indicated that the genotype main effect and environment additive effect were significant and accounted 61.08% and 3.62% of the total variation. G x E interaction (35.30% of total variation) was partitioned into three interaction principal component axes (IPCAs), out of which IPCA 1 was significant and accounted for 55.27 per cent of the total G x E interaction sum of squares percentage.
In general, MTU 1061 and MTU 1001 recorded greater means and were good general combiners in addition to being stable and widely adaptable over seasons reflecting their potential in development of stable and adaptable high yielding varieties with resistance to salinity. Further, BPT 2231 during normal kharif and NLR 40024 during late kharif and normal rabi seasons, were identified as promising parents for season specific breeding programmes. NLR 33359 X MTU 1001, NLR 40024 X MTU 1061 and NLR 40024 X MTU 1001 were identified as high yielding, stable and widely adaptable hybrids for saline soils. The hybrids, NLR 33057 X NLR 3041, NLR 33057 X MTU 1061 and MTU 1001 X BPT 2231 were found promising for normal and late kharif seasons, while NLR 40024 X PUSA 1121 was noticed to be superior for normal kharif and rabi in addition to late rabi. The hybrids, NLR 33358 X MTU 1061, NLR 33358 X MTU 1001 and NLR 33359 X MTU 1061 were noticed to be potential for both normal and late rabi under saline conditions.
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D5095
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