Journal of Taiwan Agricultural Research

Author:Lih-Jiuan Hsieh, Yih-Chang Chang and Ting-Fang Hsieh*

Abstract:

    The ability of 212 Taiwanese isolates of Xanthomonas oryzae pv. oryzae (Xoo) to induce pale-yellow-leaf (PYL) symptom on the rice cultivar Taichung sen 10 and the susceptibility of 53 rice cultivars to express PYL symptom after inoculation with Xoo were studied in the experimental field of Taiwan Agricultural Research Institute (TARI). The results from experiments conducted in three crop seasons of 1999 and 2000 showed that the PYL symptom was observed on the plants inoculated with 72 out of 212 tested isolates. Among the 72 isolates, 14 were isolated before 1997 when the first incidence of PYL symptom was observed on rice in Taiwan, indicating strains that are able to cause PYL symptom have already existed. Three isolates of Xoo from plants showing leaf-blight symptoms and three isolates from plants showing PYL symptoms were used to inoculate 53 rice cultivars in 4 continuous crop seasons of 2000 and 2001. The results revealed that the occurrence of PYL symptoms was associated with the virulence of Xoo isolates and the susceptibility of rice cultivars. The differential interaction between rice varieties and isolates of the pathogen was also observed. The isolates from PYL plants caused more severe PYL symptoms than those from leaf blight plants. In addition, the cultivars with high disease index of PYL symptoms also showed high disease severity of leaf-blight symptoms, but not vis versa. The severity of PYL symptoms in the 1^st crop was higher than that in the 2^nd crop. Among 53 cultivars tested, 27 did not show PYL symptoms and were considered as highly resistant to pale-yellow-leaf disease, but 10 cultivars were most susceptible to express PYL symptoms.

Key words:Pale-yellow-leaf of rice bacterial blight, Rice varieties, Disease resistance

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