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Title: Influence of Rice Development on the Function of Bacterial Blight Resistance Genes

Author
item Webb, Kimberly
item GARCIA, EPIFANIA - International Rice Research Institute
item VERA CRUZ, CASIANA - International Rice Research Institute
item LEACH, JAN - Colorado State University

Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2010
Publication Date: 8/27/2010
Citation: Webb, K.M., Garcia, E., Vera Cruz, C.M., Leach, J.E. 2010. Influence of Rice Development on the Function of Bacterial Blight Resistance Genes. European Journal of Plant Pathology. 128:399-407 DOI 10.1007/s10658-010-9668-z.

Interpretive Summary: Not all plant resistance genes are effective at all plant growth stages. In rice, several resistance genes have been shown to not be effective at the seedling stage. Effectiveness of three rice resistance genes, Xa4, xa5, and Xa7, were tested to determine if they were effective during all growth stages. Based on lesion lengths (on leaves) and bacterial numbers, Xa4 and xa5, were effective at all growth stages tested. Xa7 was not effective at very young seedlings (11das), however, resistance was effective by 21das, which corresponds to approximate growth stage of plants when they are at most risk to wounding during transplanting.

Technical Abstract: Disease resistance genes most commonly used in breeding programs are single, dominant, resistance (R) genes with relative effectiveness influenced by plant developmental stage. Knowing the developmental stages at which an R gene is functional is important for disease management. In rice, resistance at the seedling stage is crucial, as wounding during transplanting increases the potential for bacterial blight (BB) disease, and not all BB R genes are effective in seedlings. Effectiveness of the BB R genes Xa7, xa5, and Xa4 at different developmental ages was evaluated by measuring lesion length and bacterial numbers after inoculation with the bacterial pathogen, Xanthomonas oryzae pv. oryzae (Xoo). The xa5 or Xa4 genes controlled disease at all growth stages. In contrast, Xa7 was not fully functional in very young seedlings, but was completely effective by 21 days after sowing (das). Thus, Xa4, xa5, and Xa7 will be effective at the transplant stage (>21das).