Morphogenetic characterization of Stenotrophomonas maltophilia infecting white stripe disease of rice (Oryza sativa L.)

Rice is a major cereal crop which ensure food security to more than half of the global population. Several biotic factors impact rice grain quality and its final production. White stripe disease, caused by pathogen Stenotrophomonas maltophilia is considered among the major limiting factor for reducing rice yields and quality. Present study was performed to understand the white stripe disease, which has been frequently misdiagnosed as bacterial leaf blight (BLB) due to similar symptoms. A survey was carried out based on accessibility and farmer participation to monitor incidence and sample collection. The survey was conducted in districts Faisalabad, Gujranwala, Sialkot, Sheikhupura, and Hafizabad, these districts were selected for their importance for rice cultivation in Pakistan. The total sample size was around 500 leaves distributed evenly throughout each study area. The results of study indicated presence of new pathogen of rice. These isolates were biochemically identified and confirmed by gram staining negative, 3% KOH positive, 5% salt tolerance positive, oxidase test negative, catalase test positive, starch hydrolysis test negative, nitrate reductase test positive, indole test negative, lactose test positive, maltose test positive, methyl red test negative, Voges-prokauer test negative and urea hydrolysis test negative. The pathogenicity test was confirmed that pathogen and the Sialkot isolate were the most aggressive isolate among the five isolates collected form the studied areas. The molecular characterization was accomplished by PCR and sequencing. The results of the phylogenetic study indicate that this pathogen belongs to a distinct group, as it is distantly related to Xanthomonas oryzae pv. oryzae (Xoo). This study provides important findings into a novel clade of pathogen causing white stripe disease in rice.