Genetic studies on bacterial leaf blight resistance, variance, combining ability, heritability, heterosis and generation mean analysis in rice (Oryza sativa L.)
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Date
2019-05
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
This research included four experiments, genetic studies on bacterial leaf blight resistance, variance study of exotic rice genotypes, estimation of genetic parameters viz. combining ability, heritability, heterosis, and study of gene action through generation mean in rice. To understand the genetics of bacterial leaf blight resistance, F2 population derived from Pant Basmati 2 × BBL-180-5-1-4-1 was screened for bacterial blight reaction after artificial inoculation of Xanthomonas oryzae pv. oryzae at phenotypic level. For molecular study, about 1-2 gram leaf samples were taken from each F2 plants and used for DNA extraction. Only six primers RM13, RM21, RM164, RM206, RM224, and RM230 showed polymorphism during electrophoresis out of 15 simple sequence repeats used. Chi-square tests were found non significant indicating the observed and expected value were the same. The F2 plants segregated by 3:1 at phenotypic and 1:2:1 at genotypic level following Mendelian law of inheritance. Only 11 plants were resistant, 34 moderate resistant, 9 moderate susceptible and 13 susceptible both at phenotypic and genotypic level. Gene linked primers detected Xa4, Xa5, Xa10, Xa13, and Xa21 BLB resistant genes in F2 resistant plants which could be used to develop resistant variety. To characterize and compare rice yields and its attributing traits, two-season trials were conducted in a randomized complete block design with a standard check Pant Dhan 4 in 2016 and 2017. The tested genotypes were statistically significant (p<0.05) based on days to flowering and maturity, effective tillers, panicle length, fertile and sterile grains per panicle and yield. The average grain yield of all genotypes transplanted in 2016 (10, 153.85 kg/ha) was higher than 2017 (5, 598.38 kg/ha). A rise in minimum temperature of 3.41 0C was noticed during the grain filling period in 2017 than 2016 and predicted that the elevated night temperature was detrimental to rice productivity. The yield increment in 2016 might be due to favorable weathers and ideal night temperature during crop growth and development phase. Only four genotypes viz. IRRI 146, TP 29651, TP 29632 and IRRI 104 were found resistant to blight during both the years of experiments. Similarly, combining ability, heritability, heterosis and five generation mean were estimated by taking three susceptible and resistant varieties Pant Basmati-1, Pant Basmati-2, and Pant Sugandh Dhan 17 as lines and BBL-180-5-1-4-1, Oryza perennis and Improved Pusa Basmati 1 as testers to get P1, P2, F1, F2, and F3 populations from 2016 to 2018. Result showed maximum variations among the genotypes and their traits. The gca and sca values for different traits revealed the presence of additive and non additive gene interactions. The gca value suggested that Pant Basmati 1 was best line and BBL-180-5-1- 4-1 was best tester respectively. Pant Basmati 1 × Oryza perennis was best cross based on sca value. Pant Basmati 2 × Oryza perennis showed maximum heterosis followed by Pant Basmati 2 × BBL-180-5-1-4-1. Similarly Pant Basmati 1 × Pant Basmati 2 was considered best cross based on mid and better parents value. Heritability was at top for 100 grain weight in all crosses. Five generation mean analysis showed epistatic non allelic gene interactions like dominance, additive × dominance and dominance × dominance gene interactions.
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