High resolution genetic mapping of xa43(t) gene for bacterial blight resistance in rice (oryza sativa l.)
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Date
2020
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Punjab Agricultural University, Ludhiana
Abstract
Bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the epidemic
diseases in rice causes significant yield losses worldwide, especially in Southeast Asia. Due to
the lack of effective chemical control, most effective strategy to combat the BB disease is the
finding of new resistance sources and its deployment in the elite rice cultivars. Since the
durability of resistance is always at stake due to the rapid change in the pathogenicity of the
Xoo pathogen, there is a need to identify and characterize novel BB resistance genes. Tagging
and fine mapping is pre-requisite for transfer and pyramiding of BB resistance genes through
marker-assisted selection (MAS). Therefore, the present investigation was undertaken to
develop high resolution genetic map of novel bacterial blight resistance gene, xa43(t)
identified from Oryza rufipogon acc. CR100098A. The backcross introgressed lines (BILs,
BC1F7) were developed from cross between PR114 and Oryza rufipogon acc. CR100098A.
The genetic studies using BC1F2 population and BC1F3 progenies showed single recessive
locus conditioning resistance to the Xoo pathotype #7 (PbXo-7). The BILs were segregated in
the ratio of 197 resistant : 195 susceptible which is consistent with the expected allelic
frequency of 1:1 ratio for single gene inheritance. The xa43(t) gene was tagged with two SSR
markers viz. RM27154 and RM2136 on long arm of chromosome 11 using bulked segregant
analysis. To fine map the gene, 85 SSR and 86 KASP markers of chromosome 11 were
surveyed for parental polymorphism. A total of 22 SSR and five KASP markers were found
to be polymorphic between parents. The polymorphic markers were analysed on 392 BILs
and genetic analysis placed the xa43(t) BB resistance gene between two flanking SSR
markers, PAU11_39 and PAU11_44 within an approximately 447 kb region. Bioinformatic
analysis revealed a total of 73 genes within that region and seventeen of them were putative
candidate genes involved in biotic stress resistance. The novelty of xa43(t) gene was
confirmed by testing the linked markers on other cultivars as well as by surveying the linked
markers of other BB resistance genes present on chromosome 11 on parents and bulks.
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Citation
Bhatia, Sukhpreet (2020). High resolution genetic mapping of xa43(t) gene for bacterial blight resistance in rice (oryza sativa l.) (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.