Changes in Race Frequency of<i>Xanthomonas oryzae</i>pv.<i>oryzae</i>in Response to Rice Cultivars Planted in the Philippines

Abstract

In an extensive survey of rice-growing areas in the Philippines from 1972 to 1988, 960 strains of Xanthomonas oryzae pv. oryzae (the bacterial blight pathogen) were collected. These strains were separated into six races based on their interactions with a distinct set of five differential cultivars carrying different resistance genes. Race 1, which was predominant before improved modern rice cultivars highly responsive to nitrogen fertilizer and management become widely cultivated, was virulent to rice with Xa-10, Xa-11, and Xa-14 genes (.)