Acharya N. G. Ranga Agricultural University, India
M Sudharani is presently working as Scientist (Pl. Br.), Seed Research and Technology Center, ANGR Agricultural University, Hyderabad. She joined as Scientist (Pl. Br.) at ARS, Machilipatnam during 1999 and involved in developing rice varieties with salt tolerance. Later, she involved in development of gall midge tolerant varieties (2 Nos) at RARS, Warangal. Presently her work is involved in Seed Research of different crops particularly in the area of safer storage of seed, development of seed testing strategies in various crops and DUS testing of maize, Greengram and blackgram varieties for protecting them under PPV&FR Act. Also actively involved in guiding P.G. students and so far she had guided two students. And she has 15 research publication and 15 popular articles at her credit s as on date.
The present investigation was carried out at Directorate of Rice Research, Rajendranagar, Hyderabad and Agricultural Research Station, Machilipatnam during rabi, 2009-10 and Kharif, 2010 with an aim to evaluate 24 rice genotypes for salinity tolerance, to estimate heterosis and combining ability involving eight parents and 28 F1s (Crossed in diallel manner) for 16 (including yield and salt tolerance related physiological) traits. Further, the variability and genetic parameters were estimated for physiological, yield and its component traits under coastal saline soil conditions.
Through screening at various levels of salt stress at seedling stage, the 24 rice genotypes were categorized into three classes based on Na+/K+ ratio and salt injury score. The cultivars viz., RPBio-226, Swarna, Krishna Hamsa, Sampada, NLR-3042, NLR-145, BPT-5204, Varadan, BPT-2231, BPT-2270 and Dhanarasi were graded as susceptible to salinity, while the genotypes CSR-27, CSR-30, CST7-1, CSRC(S)2-1-7,Santhi,NLR-33359,NLR-3041, NLR-33892 and NLR-34449 were found to be moderately tolerant and the cultivars SR26B, CSRC(S)5-2-2-5, CSR-4 and SCRC(S) 7-1-4 were identified to be tolerant to salt stress.
The mean value of the parents indicated that the cultivar SR26B excelled others by expressing significantly superior mean values for nine traits The next best parent was CSRC(S)7-1-4 for eight traits. The genotypes CSRC(S)5-2-2-5 was also adjudged as desirable for development of salt tolerant varieties coupled with high yield. Among the 28 hybrids studied, SR26B x CST7-1 and Swarna x CSRC(S)7-1-4 were superior as they exhibited high mean performance for majority of the characters studied. Estimation of genetic parameters revealed the moderate opportunities to improve grain yield plant-1 and panicle weight in the material studied. Further, the high heritability estimates for number of total tillers plant-1, number of productive tillers plant-1, panicle length, panicle weight, number of filled grains panicle-1, spikelet fertility per cent, 1000- grain weight, grain yield plant-1, SES for visual salt injury and Na+/K+ ratio coupled with high genetic advance as per cent of indicated the scope for rapid improvement these traits through selection under saline soil conditions.
The examination of the heterotic trends revealed that the hybrid, Swarna x CSRC(S)7-1-4 manifested significant heterotic expression over mid and better-parents for number of filled grains panicle-1, grain yield plant-1, root / shoot ratio, harvest index, SPAD chlorophyll meter values and desirable negative heterosis for Na+/K+ ratio.
The GCA and SCA variances revealed the preponderance of non-additive gene action for all the characters under both the environments, except for SPAD chlorophyll meter readings under normal situation under saline conditions, indicating the option of population improvement methods rather the direct selection to breed for salinity tolerance. Based on gca effects, the genotypes viz., CSRC(S)5-2-2-5, SR26B and CSRC(S)7-1-4 were found to be good combiners for yield attributing as well as salt tolerance related traits (number of tillers plant-1, number of productive tillers plant-1, panicle length, number of filled grains panicle-1, 1000-grain weight, SES for visual salt injury, harvest index, Na+/K+ ratio and yield reduction per cent) including yield. Based on sca effects, the hybrids namely, SR26B x CST-7-1, RPBio-226 x CSR-30 and CSR-27 x CSRC(S)5-2-2-5 were adjudged as the best hybrids for yield attributes as well as salt for tolerance related physiological traits. Based on per se performance, sca effects and heterobeltiosis, the hybrids viz., Swarna x CSRC(S)7-1-4, RPBio-226 x CSR-30 and CST-7-1 x CSRC(S)5-2-2-5 were identified to be promising.
From the overall investigation it is inferred that there is a greater scope to develop high yielding varieties tolerant to salinity by monitoring parents with genetic diversity and selecting the elite lines based on the traits viz., more number of filled grains panicle-1, higher spikelet fertility per cent, longer panicle with more test weight and low visual salt injury symptoms as well as Na+/K+ ratio and pursuing the cross combination Swarna x CSRC(S)7-1-4 considering to the logical end.
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