Molecular Identification of Xa4 Resistance Gene to Xanthomonas oryzae pv. oryzae in Cultivated Rice in Northwest Benin

Abstract

Aims: The aim of this study was to identify the cultivated rice varieties that were resistant to Xanthomonas oryzae pv. oryzae (Xoo) by molecular screening. Xanthomonas oryzae pv. oryzae (Xoo) was the causal agent of bacterial blight, in the department of Atacora in Benin. Place and Duration of Study: Laboratory of Molecular Biology and Bioinformatics Applied to Genomics, between July 2021 and November 2021. Methodology: Thirty-two rice accessions were collected in the department of Atacora and the IRBB4 isogenic line carrying Xa4 resistance gene, as a positive control, were screened using SSR marker. Genomic DNA was extracted from plants leaves. PCR using a pair of MP12 primers linked to the Xa4 gene were performed and amplified products were analyzed by electrophoresis in a 2% agarose gel. Results: Our results showed that a significant number of rice varieties grown in northern Benin were resistant to Xoo. 62.5% were resistant of which 70% were local varieties. Some of these resistant varieties (35%) were heterozygous (Xa4/xa4) and others were homozygous (Xa4/Xa4). 10% had specific genotypes other than those expected, which showed the probability of existence new resistance alleles that need to be characterized. Conclusion: This is the first time that a bacterial blight resistance gene has been identified in Beninese rice cultivation. This result will be very useful to rice breeders for developing elites resistant varieties through markers assisted selection programs.