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Chang, S. W., and Hwang, B. K. 2003. Effects of plant age, leaf position, inoculum density, and wetness period on Bipolaris coicis infection in adlays of differing resistance. Plant Dis. 87:821-826.
The effects of plant age, leaf position, inoculum density, and wetness period on the development of adlay leaf blight caused by Bipolaris coicis were evaluated using six adlay cultivars or lines of differing resistance in field plots and in the greenhouse. Levels of resistance to leaf blight among the six cultivars or lines were consistent between the 1998 and 1999 field experiments. With the aging of adlay plants, leaf blight development gradually increased in all cultivars or lines tested. Leaf blight severity was significantly greater on the lower (older) leaves than on the upper (younger) leaves. As inoculum density increased from 10^sup 3^ to 10^sup 6^ conidia per ml, the development of leaf blight increased. Disease severity also increased as the time of leaf wetness duration increased from 0 to 60 h. Wetness duration above 48 h and a high inoculum density at 10^sup 6^ conidia per ml caused severe leaf blight symptoms in adlay seedlings. The data from the greenhouse experiments consistently revealed the same trends in relative levels of susceptibility of adlay cultivars to leaf blight as those seen at late plant growth stages under field conditions.
Bipolaris coicis (Nisikadoi) Shoem. (teleomorph: Cochliobolus nisikadoi) causes leaf blight of adlay (Coix lacryma-jobi L. var. ma-yuen (Romanet) Stapf.) (10,22). Seeds of adlay perennial grasses are used ornamentally and as a medicinal and cereal food in many countries (11). Leaf blight of adlay plants was first found in 1977 in Korea's Kyeonggi Province. During the past decade, leaf blight has become one of the most destructive diseases throughout most of the adlay-growing regions of Korea. Increased severity of adlay leaf blight has been associated with infested crop residues that remain on the soil surface (2,15).
Leaf blight is extremely severe in adlay plants at the ripening stage (2,3). Brown lesions are linear and delimited by the major veins of leaves. Eventually, the entire leaf becomes blighted (2,22). Significant differences in disease severity among adlay cultivars or lines have been documented in the field (3,10). Reactions of adlay plants to leaf blight appear...