Field performance of Xa21 transgenic indica rice (Oryza sativa L.), IR72

Based on the characterization of the resistance phenotype and molecular analysis, several homozygous lines carrying Xa21 against the bacterial blight (BB) pathogen were obtained from previously transformed indica rice, IR72. The homozygous line, T103-10, with the best phenotype and seed-setting, was repeatedly tested under normal field conditions to evaluate its levels of resistance to the BE pathogen in Wuhan, China, in 1998 and 1999. The isolates of Xanthomonas oryzae pv oryzae (Xoo) used in this experiments were PXO61, PXO79, PXO99 and PXO112 isolated from the Philippines, T2 isolated from Japan, and Zhe173 isolated from China. The results demonstrated that the transgenic homozygous line expressed the same resistance spectrum, but with a shorter lesion length to each inoculated isolates as the lesion length of the Xa21 donor line IRBB21. The non-transformed control IR72 carrying Xa4 was resistant to PXO61, PXO112, Zhe173 and T2, but susceptible to PXO99 and PXO79. The negative control variety IR24 was susceptible to all isolates under field conditions. The results demonstrated clearly that the Xa21 transgene led to an excellent field performance of the introduced bacterial blight resistance trait on the recipient plants. The yield performance of this transgenic homozygous line, T103-10, is comparable with that of the control under field conditions.