Some problems on the breeding leafspot resistant varieties of sugar beets.

Abstract

In order to obtain some useful information about the breeding of a resistant variety of sugar beet to leaf-spot disease (Cercospora beticola), the authors have been carring out several experiments since 1958. The results obtained, up to 1962, are summarized as follows. 1) The resistance of sugar beet plants to leafspot disease usually varied according to the respective plant age, viz., plants in the early half of the growing stage were tnore resistant to leaf-spot disease than older ones in latter half growing stage. 2) It was experimentally observed in the field that climatic conditions played an important roll in the prevalence of leaf-spot disease. Resistance to leaf-spot disease generally declined when sugar beets are grown at higher temperatures (above 27°C) and high humidity (above 90%).3) Significant pathogenetic differences were observed among the isolates from various locations in Japan. However, no consistent relationships could be ascertained between pathogenicities and charac teristics of development on artificial medium.