National Academy of Agricultural Sciences (NAAS)
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PRINT ISSN : 2319-7692
Online ISSN : 2319-7706 Issues : 12 per year Publisher : Excellent Publishers Email : editorijcmas@gmail.com / submit@ijcmas.com Editor-in-chief: Dr.M.Prakash Index Copernicus ICV 2018: 95.39 NAAS RATING 2020: 5.38 |
Bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is a devastating disease in rice worldwide. The resistance gene Xa7, which provides dominant resistance against the pathogen with avirulence (Avr) gene AvrXa7, has proved to be durably resistant to BB. A set of SSR markers were selected from the ‘‘gramene’’ database based on the Xa7M5 gene initial mapping region on chromosome 6. This marker was used to construct a high-resolution genetic map of the chromosomal region surrounding the Xa7 gene. An F2 mapping population with 1300 highly susceptible individuals derived from a cross between the near isogenic lines (NILs) IRBB65 and Mahamaya were constructed to localize the Xa7 gene. Xa7 was previously located in a region between two markers M1 (2.2 cM) and M3 (0.5 cM) of chromosome 6 (Porter et al., 2003). Recently, Xa7 was further integrated to the region between two proximal markers GDSSR02 and RM20593, an interval of approximate 118.5 kb (Chen et al., 2008). Finally, the Xa7 gene was mapped to a 0.21-cM interval between the markers GDSSR02 and RM20593. The Xa7-linked markers were landed on the reference sequence of cv. Nipponbare through bioinformatics analysis. A contig map corresponding to the Xa7 gene was constructed. Candidate gene analysis of Xa7 revealed that the fourteen genes encode novel domains that have no amino acid sequence similar to other cloned Xa genes.
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