Occurrence of Turnip Scab Caused by Phytotoxin-Producing Streptomyces spp.

Turnips (Brassica rapa L var. rapifera) purchased from a New Brunswick supermarket in the winter of 2003 contained discernable corky scab-like lesions on their surfaces. The turnips were surface-disinfested with a warm-water rinse, and microorganisms from excised lesions were isolated with methodologies developed for the specific isolation of Streptomyces spp.

More chemistry of the thaxtomin phytotoxins.

Chemical and biochemical studies indicated the possible involvement of N-acetyltryptophan and 4-nitrotryptophan as intermediates in biosynthesis of the thaxtomin phytotoxins. A search for other potential pathways indirectly resulted in the identification of three unusual thaxtomin analogues derived from the o-thaxtomin A isomer. Investigations to resolve the identity of a previously described thaxtomin A di-glucoside were not supportive of the proposed structure.