Abstract
Bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) is a major limiting factor to rice productivity worldwide. Genetic control through the identification of novel sources of bacterial blight resistance and their utilization in resistance breeding remains the most effective and economical strategy to manage the disease. Here we report the identification of a novel locus from the wild Oryza species, Oryza latifolia, conferring a race-specific resistance to Philippine Xoo race 9A (PXO339). The locus was identified from two introgression lines i.e. WH12-2252 and WH12-2256 that segregated from O. latifolia monosomic alien addition lines (MAALs). The discrete segregation ratio of susceptible and resistant phenotypes in the F2 (χ2[3:1] = 0.22 at p>0.05) and F3 (χ2[3:1] = 0.36 at p>0.05) populations indicates that PXO339 resistance in the MAAL-derived introgression lines (MDILs) is controlled by a single, recessive gene. Genotyping of a total of 216 F2, 1130 F3 and 288 F4 plants derived from crossing either of the MDILs with the recurrent parent used to generate the MAALs narrowed the candidate region to a 1,817 kb locus that extends from 10,425 to 12,266 kb in chromosome 12. Putative candidate genes that were identified by data mining and comparative sequence analysis can provide targets for further studies on mapping and cloning of the causal gene for PXO339 resistance in the MDILs. To our knowledge, this is the first report of a genetic locus from the allotetraploid wild rice, O. latifolia conferring race-specific resistance to bacterial blight.
Highlights
Bacterial blight of rice (Oryza sativa L.) caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most destructive diseases that negatively impacts the major rice growing regions worldwide
We identified two introgression lines i.e. WH12-2255 and WH12-2256 that were derived from monosomic alien addition lines (MAALs) of O. latifolia with resistance to Philippine Xoo races 5 (PXO112), 7 (PXO145), 8 (PXO280) and 9A (PXO339)
Two introgression lines i.e. WH12-2255 and WH12-2256 that segregated from O. latifolia (IRGC 100914) MAALs in the background of the elite rice breeding line IR31917-42-3 were used in the study
Summary
Bacterial blight of rice (Oryza sativa L.) caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most destructive diseases that negatively impacts the major rice growing regions worldwide. Bacterial blight of rice (Oryza sativa L.) caused by Xanthomonas oryzae pv. Oryzae (Xoo) is one of the most destructive diseases that negatively impacts the major rice growing regions worldwide. Novel bacterial blight resistance locus from Oryza latifolia planted cultivar, the virulence of the pathogen and the environmental conditions, the disease can cause significant yield losses of up to 20–81% [1,2,3]. Application of copper compounds or antibiotics has been sufficient in providing rice plants with a degree of protection against the causal pathogen [4, 5]. A more efficient, economical and ecologically friendly alternative to control the disease is to provide plants with innate resistance mechanisms that can overcome pathogenic infection. Critical to the success of this approach is the screening of various germplasm to identify sources of novel genetic loci regulating host plant resistance, as well as the development of an efficient strategy to transfer target loci across genomes
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