Molecular analysis of rice (Oryza sativa L.) for bacterial blight resistance genes
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Date
2016
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CCSHAU
Abstract
Rice (Oryzasativa) is an important cereal food crop that servesas amajor carbohydrate source for half
of the world’s population. Bacterialblight (BB),caused by the bacterium, Xanthomonasoryzaepv.
oryzae(Xoo) is one of the most serious threatto the rice production.
The present work was undertaken to analyse the major BB resistance genes (Xa21, xa13 and xa5) in the
backcrossed populations derived from the crosses between HKR-47 x IRBB-60 and HKR-127 x IRBB-
60 using STS markers. Foreground selection was carried out in theBC3F2plants of both the crossesusing
specific STS markers pTA248, RG136 and RG556 linked to Xa21, xa13 and xa5 genes, respectively.
A total of sixand nine BC3F2 plantswere found to have all the three resistance genesin the crosses HKR-47 x IRBB-60 and HKR-127 x IRBB-60, respectively. Theseedsfrom these positive plants from
both the crosses were harvested separately. Foreground selection of BC3F3 plants of both the crosses
was carried out to confirm the presence of three BB resistant genes using the same STS markers.Plants
having all the three resistance genes were selected for background selection.Three hundred and sixty
SSR markers representing whole of the genome wereused to identify polymorphism between parental
genotypes. A total of 77/360 and 79/360 SSR markers produced polymorphism between the parents
HKR-47 and IRBB-60 and between, HKR-127and IRBB-60, respectively. Finally, the maximum
genome recoveryfor positivegenotypeswas analyzedby NTSYS andGGT softwares. The percentage
recovery of recurrent parent genome in three-gene positiveBC3F3 genotypes of the crosses HKR-47 x
IRBB-60 and HKR-127 x IRBB-60 ranged from 82.8% to 91.0% and78.6% to 92.1%, respectively.
Based on agronomic evaluation, BB reaction, percentage recovery of recurrent parent genome and
grain quality evaluation,genotypes G1-8, G1-12 and G1-13from the cross HKR-47 x IRBB-60and
genotypes, H1-17and H1-18from the cross HKR-127 x IRBB-60were found promising. The present
work successfully analysedthegenotypes from both the crosses forthethree BB resistant genes(Xa21,
xa13 and xa5) and recovery of the positive genotypes with maximum recurrent parent genome and
other agronomic traits.
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