Relationship of Host Genotype to Bipolaris Leaf Blight Severities and Yield Components of Adlay

Leaf blight, caused by Bipolaris coicis, is one of the most destructive and major yield-limiting diseases of adlay (Coix lacryma-jobi var. ma-yuen). Adlay is used as an ornamental, and as a medicinal and cereal food in many countries. Field studies performed from 1997 to 1999 in Korea evaluated the resistance of 30 adlay genotypes to Bipolaris coicis and determined the relationship of cultivar resistance to leaf blight development and yield. Adlay response to leaf blight was quantitative rather than qualitative, varying greatly among cultivars or lines tested. Disease severity was lowest in Tsukuba B7, Tsukuba B15, and Muzu, and highest in Huksuk 1, Limgae, and Huksuk 2. Leaf position significantly affected disease severity, with lower leaves being more severely infected than upper leaves. Yield reductions of up to 52.4% for line Huksuk 2 were observed and were primarily associated with reductions in kernel numbers per plant, thousand kernel weight, and percent kernel ripeness. Loss of yield and yield components by leaf blight were less in resistant line Tsukuba B15 than in susceptible line Huksuk 2.