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Isolation and characterization of rice mutants compromised in Xa21-mediated resistance to X. oryzae pv. oryzae


The rice gene, Xa21, confers resistance to diverse races of Xanthomonas oryzae pv. oryzae (Xoo) and encodes a receptor-like kinase with leucine-rich repeats in the extra-cellular domain. To identify genes essential for the function of the Xa21 gene, 4,500 IRBB21 (Xa21 isogenic line in IR24 background) mutants, induced by diepoxybutane and fast neutrons, were screened against Philippine race six (PR6) Xoo for a change from resistance to susceptibility. From two greenhouse screens, 23 mutants were identified that had changed from resistant to fully (6) or partially (17) susceptible to PR6. All fully susceptible mutants carried rearrangements at the Xa21 locus as detected by PCR and Southern hybridization. For the partially susceptible mutants, no changes were detected at the Xa21 locus based on Southern and PCR analyses. However, two of these mutants were confirmed via genetic analysis to have mutations at the Xa21 locus. Partially susceptible mutants exhibited variation in level of susceptibility to different Xoo strains, suggesting that they may carry different mutations required for the Xa21-mediated resistance. The mutants identified in this study provide useful materials for dissecting the Xa21-mediated resistance pathway in rice.

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This work was supported, in part, by a grant from the Rice Biotechnology Program of the Rockefeller Foundation to GLW and HL, a seed grant from OARDC to GLW and a grant from the National Natural Science Foundation of China to GLW and CH (#30028016). We thank the initial contribution of Ning Huang and Susan McCouch in propagating the IRBB21 mutant collection.

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Correspondence to G. L. Wang.

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Communicated by D.J. Mackill

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Wang, G.L., Wu, C., Zeng, L. et al. Isolation and characterization of rice mutants compromised in Xa21-mediated resistance to X. oryzae pv. oryzae . Theor Appl Genet 108, 379–384 (2004).

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  • Powdery Mildew
  • Fast Neutron
  • Partial Resistance
  • Lesion Length
  • International Rice Research Institute