First Report of Potato Blackleg Disease Caused by Pectobacterium atrosepticum in Guangdong China

摘要

Sunn hemp (Crotalaria juncea) is widely grown in tropical and subtropical regions. In Brazil, this species is commonly used for green manure, since this legume is an efficient nitrogen fixer that produces organic residues for soil improvement. In July of 2012, C. juncea exhibiting intense shoot proliferation, leaf malformation, shortened internodes, and generalized yellowing were found in an experimental field located in Piracicaba, State of S?o Paulo, Brazil. The incidence was about 1 to 2% and the diseased plants were distributed at random. Since these symptoms are indicative of infection by phytoplasmas, the present study aimed to detect and identify the phytoplasma. Four symptomatic and two asymptomatic plants were sampled. Small segments of leaf veins were prepared for microscopy, as previously reported (1), and observations were made using a Jeol (Akishima/Japan) model Jem-1011 transmission electron microscope. Total DNA was extracted from leaves using a commercial kit (DNeasy Plant Mini, Qiagen Inc.), and nested PCR assays were performed with primers, P1/Tint followed by R16F2n/R16R2 (2).