No abstract

Validamycin A (VM-A), the active ingredient of Validacin(R), inhibits fungal growth by inhibiting trehalase activity. Therefore, VM-A was tested against Pseudomonas solanacearum for its efficacy in

A taxonomic study of Streptomyces strain T-36496, which produces an antibiotic effective against rice blast, revealed that it represented a new taxon and it was named Streptomyces novoguineensis sp. nov. The antibiotic, which was named amipurimycin, showed antifungal activity in vitro and considerable curative effect on leaf blast both in green house and field tests at concentrations ranging from 10 to 20 ppm. It was also effective against neck and panicle blast at the same concentration range.

Foliar sprays of validamycin A (VMA) controlled cabbage black rot effectively in pot and field trials. In a pot test, VMA reduced the number of Xanthomonas campestris pv. campestris (Xcc) in leaves. VMA inhibited the production of extracellular polysaccharide (EPS) on yeast-peptone (YP) agar containing carbohydrates. Injection of EPS from Xcc on medium containing VMA produced fewer lesions than that without VMA. These results suggested that VMA might inhibit the multiplication of Xcc in plants and affect the quantity and quality of EPS.