Abstract
Lepto-leaf spot caused by Leptosphaerulina briosiana, foliar disease, is prevalent in Konsen district with the cool and humid weather in the summer. The resistance to Lepto-leaf spot is very important for the establishment and persistence of alfalfa plant. Two tests were carried out to determine the difference among cultivars in Lepto-leaf spot under the field condition. (1) Differences among cultivars in Lepto-leaf spot were extremely large and stable among growing seasons or among years under the natural infection. Broad sense heritability of resistance to Lepto-leaf spot was high (0.8), suggesting that the selection of resistance to Lepto-leaf spot may be effective under the field condition in Konsen district. (2) Cultivars originated from Flemish origin with the growth type III were more resistant to Lepto-leaf spot than cultivars from other germplasms. Exceptionaly, a few cultivars of M. varia origin belonging to growth type IV had relatively high resistance to Lepto-leaf spot. They would become sources of resisttance to Lepto-leaf spot.
