Control of bacterial wilt of bean (Curtobacterium flaccumfaciens pv. flaccumfaciens) by seed treatment with Rhizobium leguminosarum

Experiments were conducted in a growth chamber to determine the effectiveness of seed treatment with Rhizobium leguminosarum bv. viceae R12 or R21, R. leguminosarum bv. phaseoli BR, or Pantoea agglomerans PA for control of bacterial wilt of bean caused by a yellow variant "YSB-2" of Curtobacterium flaccumfaciens pv. flaccumfaciens. In the first experiment, seeds of navy bean cv. Morden003 artificially inoculated with C. flaccumfaciens pv. flaccumfaciens and treated with any of the biocontrol agents resulted in a significant reduction in incidence and severity of bacterial wilt and an increase in seedling emergence and height. Among the biocontrol agents tested, R. leguminosarum bv. viceae R21 was the most effective agent and thus, was used for the second experiment on treatment of bean seeds naturally infected with C. flaccumfaciens pv. flaccumfaciens. In the second experiment, seeds of great northern bean cv. US1140 collected from a commercial field were divided into five categories based on the degree of yellow discoloration of the seed coat caused by natural infection of the yellow variant of C. flaccumfaciens pv. flaccumfaciens. Results showed that seed treatment with R. leguminosarum bv. viceae R21 was effective in reducing incidence and severity of wilt and increasing seedling emergence and height only for the seeds without visible symptoms (0% discoloration) or with light symptoms (1-25% of yellow discoloration), but not for seeds with moderate symptoms (26-50% discoloration), severe symptoms (51-75% discoloration), or very severe symptoms (76-100% discoloration). The potential of using R. leguminosarum bv. viceae R21 for management of bacterial wilt of bean is discussed. Crown Copyright © 2006.