MOLECULAR CHARACTERIZATION OF ELITE LINES FOR BACTERIAL LEAF BLIGHT (BLB) RESISTANCE IN RICE (Oryza sativa L.)
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Date
2023-12-04
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Acharya N G Ranga Agricultural University
Abstract
The present investigation was carried out during Kharif, 2021 at Regional Agricultural Research Station (RARS), Maruteru, with an objective to identify the elite lines resistant for BLB, to study the genetic parameters, magnitude of variability, correlation and path coefficient analysis for yield enhancement. The experimental material comprised of 88 elite lines including checks namely, Maruteru Samba (MTU 1224), Sravani (MTU 1239), Maruteru Mahsuri (MTU 1262), Improved Samba Mahsuri, Swarna, TN1 and Krishnaveni which were evaluated in alpha lattice design with two replications. Observations on days to 50 % flowering, plant height (cm), ear bearing tillers per m2, panicle length (cm), number of grains per panicle, spikelet fertility (%), grain yield per plant (g), test weight (g), grain type and phenotypic scores for BLB resistance were recorded. Molecular screening was performed using 50 SSR markers simultaneously.
A total of 88 elite lines including national resistant check Improved Samba Mahsuri, local resistant check Swarna, national susceptible check TN1 and local susceptible check Krishnaveni were screened against BLB under field conditions by adopting leaf clipping method of artificial inoculation. Phenotypic screening categorized five lines viz., AM853, AM857, AM863, AM867 and Improved Samba Mahsuri as resistant, 7 lines viz., AM855, AM858, AM865, AM866, AM869, AM873 and AM874 as moderately resistant, 24 lines as moderately susceptible, 50 lines as susceptible and 2 lines as highly susceptible.
The analysis of variance among 88 elite lines revealed the presence of significant differences for all 8 characters indicating existence of variability in the material. The mean performance of the elite lines studied for yield and yield components revealed that the lines, AM885, AM891 and AM913, significantly outperformed the superior yield check, Sravani, for panicle length, ear bearing tillers per m2, number of grains per panicle, test weight and grain yield per plant. The genetic parameters revealed that high heritability coupled with high genetic advance
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as per cent of mean for the traits days to 50% flowering, plant height, panicle length, test weight, spikelet fertility and grain yield per plant.
The correlation studies revealed that the traits, plant height, ear bearing tillers per m2, panicle length and number of grains per panicle had significant positive genotypic correlation with grain yield per plant. This indicates that, the enhancement of grain yield is possible by giving emphasis on selection of these characters in breeding programmes. Direct positive association towards grain yield was contributed by the traits, ear bearing tillers per m2, panicle length, number of grains per panicle, test weight and spikelet fertility indicating the importance of these traits as selection criteria for enhancing the yield potential.
Out of 50 markers analyzed, a total of 25 markers were used to identify the elite lines resistant to BLB. Among the lines with resistant and moderately resistant reaction at field conditions, AM865 was detected with four gene combination (Xa4+xa5+xa13+Xa21). The lines, AM853 (Xa4+xa13+Xa21), AM857 (Xa4+xa5+xa13), AM867 (Xa4+xa5+Xa21) and AM855 (Xa4+xa13+Xa21) were detected with three gene combination. The lines, AM863 (Xa4+Xa21), AM858 (Xa4+Xa21), AM866 (Xa4+Xa21), AM873 (Xa4+Xa5) and AM874 (Xa4+Xa21) were detected with two gene combination. The genotype, AM869 (Xa4), was detected with only one resistant gene.
The markers, RM206, RM400, RM21 and RM6100, were considered to be more informative and effective for differentiating the elite lines as they had higher PIC values, more number of effective alleles, higher Nei's genetic diversity index and higher Shannon's informative index. Molecular diversity analysis grouped all the elite lines into 3 major clusters, which were further divided into sub clusters. All the resistant and moderately resistant elite lines were grouped under cluster I.
The elite line, AM865, was detected with the multiple resistance genes (Xa4+xa5+xa13+Xa21) along with the phenotypic score of 3, could confer broad spectrum resistance. Additionally, the elite lines, AM857 (Xa4+xa5+xa13) and AM873 (Xa4+xa5), exhibited resistance and moderately resistance reaction under field screening also had multiple gene combinations along with the high yield potential when compared to the superior yield check Sravani.