Rice blast prevalence in smallholder rice farmlands in Uganda.

Abstract

Rice blast disease remains the most important contributor to low and stagnated rice yields in Uganda. However, the role of the smallholder farming system in shaping the prevalence of the disease in the country is not known. In 2015B and 2016A, we surveyed smallholder rice farmlands in 27 districts of Uganda and recorded blast incidence, severity, and symptoms expression. Infected rice samples taken from the infected plants were sub-cultured on PDA media to confirm the pathogen and obtain isolates for the establishment of a core collection for breeding work. Rice blast prevalence in the districts varied from 50-100% and the national average stood at 72.61%, higher than that recorded five years ago. Mean incidence and severity varied significantly (< 0.001) with the highest incidence (96.8%) recorded in Luwero district and the least (21.3%) was recorded in the Amuru district. However, the eastern region recorded the highest average incidence (74.5%) followed by the central, the northern, and Mid-western regions. In the rice ecologies, the highest blast incidence was recorded in the rain-fed lowland rice (72.18%) followed by irrigated lowland (59.53%) and rain-fed upland rice (47.27%). This is the first report on the prevalence of blast in smallholder rice farmlands in Uganda and showed a higher prevalence of the disease. Keywords: Incidence, Rice blast, Rice farmlands, Severity, Symptom expression