Effects of Major Fungal Pathogens on Growth and Yield of Improved and Local Sorghum Genotypes under Field Trials in Lower Eastern Kenya

Sorghum is a climate resilient cereal that offers food and nutrition security for the arid and semi-arid lands (ASALs). Its production potential is however limited by fungal diseases. A study on the effects of major fungal diseases on sorghum growth and yield and identification of tolerant genotypes is critical for sustainable sorghum production. A total of 14 germplasms were analyzed under a two-seasonal field trial laid out in Randomized Complete Block Design with four replications at two different agro-ecological zones within Kenya’s ASALs. A spreader row technique using a highly susceptible variety and natural infections was used for fungal inoculation. Ten plants randomly sampled and tagged from two inner rows in each plot, were used to asses plant growth, yield, and diseases. Diseases were identified using identification keys, visual symptoms, and signs and effects scored through disease severity (DS) and disease incidence (DI). Identified diseases included anthracnose, leaf blight, rust, gray leaf spot, ladder leaf spot, oval leaf spot, downy mildew, and covered kernel smut. Higher DS (>7.0) and DI (>50%) were recorded in anthracnose, leaf blight, and leaf rust across most genotypes. The significant (P≤0.01) negative correlations between DS and days to 50% flowering, number of green leaves, leaf area and panicle width indicated potential disease inhibition of sorghum growth. Correlations between DS and dry biomass, grain yield and grain weight were also negative but insignificant (P>0.05) implying no disease effects on sorghum yield. Improved genotypes had the least foliar and panicle infections and produced significantly higher grain yield (>2.0 t/ha) compared to local varieties with lower yield (<1.5t/ha) and higher foliar and panicle symptoms. The improved genotypes were thus classified as tolerant to fungal diseases and could be used to support resistance breeding programs as a sustainable management strategy for improved sorghum production in ASALs of Kenya.