Transgenic IR72 lines resistant to nine Philippine races of Xanthomonas oryzae pv. oryzae
2003
Aldemita, R.R. | Gueco, L.S. | Ilar, G.Y. | Avellanoza, E.S. | Shiping, Z. | Fauquet, C.
Transgenic IR72 (T4) containing the Xa21 gene for bacterial blight resistance was evaluated in the screenhouse for reaction of nine races of Xanthomonas oryzae pv. oryzae and one local Maligaya isolate in the dry and wet season. Inoculation was done at the maximum tillering stage following the clipping method and the percent diseased leaf area (% DLA) was measured 14 and 21 days after inoculation. The results revealed that IR24 obtained the highest mean % DLA. The untransformed IR72, which contains some genes for resistance to Xoo, showed an intermediate response, IRBB21 showed a moderately resistant response, and most of the transgenic lines were resistant to moderately resistant across the lines and races. The differences among transgenic lines, however, were not significant, which may imply that the integration events might have been the same. Race 6 is the most virulent, while the Maligaya isolate is the weakest. The transgenic plants showing a resistant phenotype contain the expected 1.4-kb band corresponding to the Xa21 DNA fragment as analyzed through polymerase chain reaction. Yield component determination revealed that some of the transgenic lines were comparable to the untransformed IR72 such as in days to flowering and maturity, percent productive tillers, panicle length, grain weight, and harvest index. However, the untransformed IR72 produced significantly taller plants and a higher percentage of filled grains vis-a-vis the transgenic plants. The transgenic lines IR72-82-3-13-1-19, IR72-82-3-4-1-2, and IR72-82-3-4-1-26 were resistant and possess good agronomic characteristics.
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