Morphological, Biochemical and Molecular Characterization of the Causal Agent of Bacterial Panicle Blight Disease of Rice (BPB) In Selected Rice Production Zones of Zamfara State

Abstract

Bacterial panicle blight (BPB) is an emerging rice disease in Nigeria, causing up to 75% yield loss and widespread globally. In the 2019 season, rice farmers in Zamfara State's Gusau, Talata Mafara, Maradun, and Bakura communities reported significant yield declines due to an unidentified disease. Infected samples suggested BPB as the cause, yet the pathogen had not been identified in Nigeria. A trial was conducted to identify and characterize BPB pathogens in Zamfara State, aiming to screen rice germplasm and find resistant sources. Infected rice grains from the region were collected and cultured on King's B medium at 37°C for 48 hours in the microbiology lab of Federal University Gusau. The bacteria were purified to single colonies and analyzed morphologically and via polymerase chain reaction (PCR), identifying the strain as Burkholderia glumae. This strain produced toxoflavin, a compound linked to its pathogenicity. PCR amplification of a 1079-bp fragment using gyrB-specific primers confirmed B. glumae as the BPB agent in Nigeria. A pathogenicity test was performed on three commercial rice varieties (Faro 44, FARO 56, and FARO 59) using the syringe inoculation method at the Biological Garden, Department of Biological Sciences, Federal University Gusau. All inoculated rice varieties exhibited typical BPB symptoms within three days, similar to those seen in naturally infected rice panicles. This confirmed B. glumae as the causative pathogen and highlighted the urgent need for resistant rice varieties.