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.
Highlights
Rice is increasingly becoming an important staple food in most parts of the world with hundreds of millions of people worldwide depending on it (International Rice Research Institute [IRRI], 2013; TeBeest, Guerber, & Ditmore, 2007, 2016; Oerke & Dehne, 2004) for food and household income
Twelve (12) of the districts surveyed were from the eastern region that constituted the largest number of small-scale rice farmlands (165) followed by the northern, central, and mid-western regions in descending order
The districts of Amuru, Nwoya, and Oyam in the northern region had blast-affected fields with isolated plants or groups of plants that displayed blast-like symptoms, unlike the districts in the eastern region where most parts of the rice farmlands were symptomized
Summary
The production of the crop among smallholder farmers has increased steadily over the years (Food and Agriculture Organization Statistics [FAOSTAT], 2014) as more swamps and arable lands are opened-up for cultivation. The low and stagnated yield of the crop despite efforts made by rice breeders to develop high-yielding varieties is due to the increasing challenges of abiotic and biotic stresses (Onaga & Asea, 2016). These include a high prevalence of pests and diseases as major constrains as well as increasing cases of drought, soil infertility, and increased urbanization (Skamnioti & Gurr, 2009). According to Séré et al (2013), rice in Sub Saharan Africa, Uganda inclusive, succumb to three major diseases, namely: Bacterial Leaf Blight caused by Xanthomonas oryzae pv. oryzae, Rice Yellow Mottle Virus Disease caused by Rice yellow mottle sobemovirus and Rice Blast caused by jas.ccsenet.org
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