Foliar Diseases and the Associated Fungi in Rice Cultivated in Kenya

Abstract

We conducted a survey to assess the occurrence and severity of rice blast and brown spot disease on popular cultivars in paddies in the Busia, Kirinyaga, and Kisumu counties of Kenya during 2019. Working with agricultural extension workers within rice production areas, we interviewed farmers (n = 89) regarding their preferred cultivars and their awareness of blast disease, as this was the major focus of our research. We scored the symptoms of blast and brown spot and assessed the lodging, plant height, and maturity of the crops (days after planting). Furthermore, we collected leaf and neck tissues for the assessment of the prevailing fungal populations. We used specific DNA primers to screen for the prevalence of the causal pathogens of blast, Magnaporthe oryzae, and brown spot, Cochliobolus miyabeanus, on asymptomatic and symptomatic leaf samples. We also conducted fungal isolations and PCR-sequencing to identify the fungal species in these tissues. Busia and Kisumu had a higher diversity of cultivars compared to Kirinyaga. The aromatic Pishori (NIBAM 11) was preferred and widely grown for commercial purposes in Kirinyaga, where 86% of Kenyan rice is produced. NIBAM108 (IR2793-80-1) and BW196 (NIBAM 109) were moderately resistant to blast, while NIBAM110 (ITA310) and Vietnam were susceptible. All the cultivars were susceptible to brown spot except for KEH10005 (Arize Tej Gold), a commercial hybrid cultivar. We also identified diverse pathogenic and non-pathogenic fungi, with a high incidence of Nigrospora oryzae, in the rice fields of Kirinyaga. There was a marginal correlation between disease severity/incidence and the occurrence of causal pathogens. This study provides evidence of the need to strengthen pathogen surveillance through retraining agricultural extension agents and to breed for blast and brown spot resistance in popular rice cultivars in Kenya.

Seed-Borne Fungi Associated with Diverse Rice Varieties Cultivated in the Western North Region of Ghana

“…Mucor spp. identifed in this study, was recently isolated from rice seeds in Kenya [27]. In another study, Nustugah et al [15] identifed Bipolaris oryzae, Pyricularia spp.…”

“…Tose who did not treat their seeds before planting relied on the sun as a treatment to control seed-borne diseases [13]. Rice farmers in Bangladesh, treated their seeds with hot water, as well as selected fungicides (Bavistin 50 WP, Dithane M 45 and neem extract) [27].…”

“…Bipolaris spp. has been found to be the most important pathogen of rice and the most frequently identifed pathogen on rice seeds [27]. Tis organism has been reported to be the cause of brown spot and seedling blight diseases of rice.…”