GENE ACTION AND GENOTYPING OF ELITE RICE LINES FOR LODGING RESISTANCE LOCI USING MOLECULAR MARKERS
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Date
2015
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Acharya N.G. Ranga Agricultural University, Guntur
Abstract
Rice crop continues to suffer with biotic and abiotic stresses. It is often prone to lodging due to unpredicted cyclonic rains. Sometimes heavy precipitation in short period at flowering to harvesting stage causes severe yield loss. Lodging can reduce yield up to 80% and can cause severe knock on-effects, including reduced grain quality, greater drying cost, slower manual as well as mechanical harvest.
The present study was aimed to detect presence of identified lodging resistant QTLs in elite lines, gene action of lodging resistance and to confirm presence of lodging resistance QTL through bulked segregant analysis in F2. Genetic diversity among 51 elite rice lines for lodging resistance was determined using 13 molecular markers linked to SCM2 (strong culm 2) conferring lodging resistance and estimated magnitude of genetic diversity for 14 phenotypic characters viz., days to 50 % flowering, plant height, number of ear bearing tillers plant-1, panicle length, number of filled grains panicle-1, spikelet fertility, test weight, grain yield plant-1, culm diameter, culm thickness, culm strength, 4th internodal length, bending strength and per cent of lodging with D2 analysis. Based on molecular diversity, sixteen hybrids were generated using parents susceptible to lodging as lines (MTU 7029, MTU 1061, MTU 1001 andMTU 1010) and lodging resistant lines as testers (II 110-9-1-1-1-1, PS140-1, MTU 1121 and BPT 2270) in LxT fashion during kharif 2012-13. Choice of parents using molecular diversity is in agreement with genetic diversity studies of phenotypic characters.
Selection of superior hybrid by combining per se performance, sca and heterosis is more desirable for evolving good segregants. Hybrids, MTU 7029/ II 110-9-1-1-1-1 and MTU 7029/MTU 1121 were found to be superior for grain yield per plant and lodging resistance out of 16 hybrids evaluated during Rabi 2012-13.
These hybrids MTU 7029/II 110-9-1-1-1-1 and MTU 7029/MTU 1121 were also studied to unveil gene action for lodging resistance loci and associated markers in identified donors using bulked segregant analysis during kharif 201314.
Lodging resistance related traits such as culm diameter, culm thickness, culm strength, basal inter nodal length, bending strength and per cent of lodging expressed dominance x dominance type of interaction along with duplicate epistasis in both cross combinations.
Results of bulked segregant analysis revealed that two markers RM 20557 and RM 5509, on chromosome 6 were associated with per cent of lodging, culm strength and culm diameter in F2 plants of MTU 7029/II 110-9-1-1-1-1. Identified markers, RM 20557 and RM 5509 linked to lodging resistance from the donor II 110-9-1-1-1-1 and found to be associated with previously reported QTL region of strong culm 2 (SCM2 ) on chromosome 6.
` In F2 derived population of MTU 7029/MTU 1121, SSR marker RM 6933 was found to be linked with culm strength and culm diameter and RM 216 was associated with culm diameter. RM 6933 is in the vicinity of reported QTL SCM4 on chromosome 2 which confers culm strength. Identified lodging resistant loci were confirmed by genotyping and phenotyping of F3 families of two crosses during Rabi 2013-14.
Studies on genetics of lodging resistance revealed modified epistatic dihybrid ratio of 10:6 for lodging susceptibility and resistant families in MTU 7029/II 110-9-1-1-1-1. While in cross combination MTU 7029/MTU 1121, modified dihybrid ratio of 1:15 for lodging susceptible and resistant families indicated duplicate dominance epistatic interaction of lodging resistant loci.
Analysis of variance of F3 families of both crosses revealed there is significant difference for all the 14 characters studied. Clustering pattern of lodging resistant F3 lines was assessed using Mahalonobis D2. Lodging resistant F3 lines with high yield, strong and wider culms were grouped in clusters 14 and 4 in cross combination of MTU 7029/II 110-9-1-1-1-1. Eight lodging resistant F3 lines of MTU 7029/ MTU 1121with higher yield were grouped in cluster 4. These lodging resistant lines can be advanced to next generation for development of high yielding non lodging varieties.
In both the crosses, per cent of lodging positively correlated with plant height among F3 families. Culm diameter also positively correlated with panicle length among F3 families of MTU 7029/II 110-9-1-1-1 and identified markers RM 20557 and RM 5509 associated with QTL SCM2 had pleiotropic effect on panicle organization. In MTU 7029/MTU1121 derived F3 families, bending strength expressed negative significant association with number of productive tillers plant-1.
Genetic basis of lodging resistance loci was identified as epistatic interaction involving two genes. Expression of lodging resistance is specific with donor parent. Identification of lodging resistant loci associated with molecular markers will help in precise selection of lodging resistant lines in breeding programmes which can with stand cyclones and give assured yields.
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D5192
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