Different Sequevars of Ralstonia pseudosolanacearum Causing Bacterial Wilt of Bidens pilosa in China

Abstract

Bidens pilosa is an invasive weed that threatens the growth of crops and biodiversity in China. In 2017, suspected bacterial wilt of B. pilosa was discovered in Qinzhou and Beihai, Guangxi, China. A variety of weeds are considered as reservoirs harboring bacterial wilt pathogens, but most do not show obvious symptoms in the field. Identifying the classification status of the B. pilosa bacterial wilt pathogen and exploring its geographical origin might be helpful for clarifying the role of weeds in the circulation of the disease. Phylotyping, sequevar analysis, and cross inoculation of pathogens isolated from B. pilosa and nearby peanut (Arachis hypogaea), balsam gourd (Momordica charantia), and eucalyptus (Eucalyptus robusta) plants were carried out. Three isolates of B. pilosa (Bp01, Bp02, and Bp03) were identified as Ralstonia pseudosolanacearum, race 1, biovar 3, and phylotype I, and belonged to sequevars 17 and 44, and an unknown sequevar. The sequevars isolated from B. pilosa were not completely consistent with those of the nearby hosts, and the virulence of these isolates differed when cross inoculated. The Bp03 sequevar was different from peanut isolate sequevars in the same field and was not identical to any previously designated sequevars. The isolates from B. pilosa and other nearby hosts displayed low or no virulence toward their cross hosts (with wilt incidences less than 33.33%). An exception to this was the isolates from B. pilosa, which displayed high virulence toward eucalyptus (with a wilt incidence of 70.00 to 100.00%). This is the first report of different sequevars of R. pseudosolanacearum causing typical bacterial wilt symptoms in B. pilosa in the field.

Genetic diversity of Ralstonia solanacearum species complex strains obtained from Guangxi, China and their pathogenicity on plants in the Cucurbitaceae family and other botanical families

“…Guangxi is located in a subtropical region with a warm climate and abundant rainfall, which is very suitable for the occurrence of bacterial wilt. In addition to tomato, eggplant, tobacco, peanut, ginger, and other common host plants of the RSSC, new RSSC host plants, such as Emilia sonchifolia, Eucalyptus spp., Bidens pilosa, were reported for the first time (Cao, 1982;He et al, 2020;Liao et al, 2008). Understanding the genetic diversity of RSSC strains is a key factor for the development of successful control strategies; however, no relevant systematic research has been undertaken thus far in Guangxi.…”