Molecular Identification of <em>Xanthomonas oryzae pv. oryzae</em> and Bacterial Leaf Blight Resistance Genes Xa5, and Xa21 in Cultivated Rice Accessions Benin

Abstract

In Benin, Xanthomonas oryzae pv. oryzae (Xoo) causing bacterial blight (BLB) was first described in 2013 on wild rice Oryza longistaminata. No studies have been conducted on Beninese Xoo strains and resistant rice varieties. The aim of this study is to check whether Xoo has already spread to cultivated varieties and to screen some rice accessions for the main resistance genes detection. To achieve this aim, rice leaves showing typical BLB symptoms were collected from various rice fields in Benin and analyzed by PCR to identify Xoo-specific sequences. In addition, seventy-five rice accessions were examined to identify Xoo resistance genes. The results showed that Xanthomonas oryzae (Xo) had been identified in Banikouara and Malanville. In addition, Sphingomonas sp was detected in several rice fields. A Xo-Sphingomonas Sp co-infection was also noted. 47 of 75 rice accessions examined (62.66%) carried Xoo resistance genes with 3 (4%) and 40 (53.33%) of xa5 and Xa21 respectively. None of the accessions had neither Xa7 nor Xa13 resistance genes. Three accessions had both xa5 and Xa21 genes. In addition, the rice isogenic lines IRBB60 and IRBB21used as positive controls, were found to be susceptible. These results indicate that Xo has evolved from a wild rice to cultivated varieties in northern Benin. Consequently, a varietal improvement program must be implemented with varieties having resistance genes to prevent a BLB pandemic in Benin.