First Report of Bacterial Wilt Caused by Ralstonia solanacearum on Chard in Taiwan

Abstract

Saposhnikovia divaricata (Turcz) Schischk, a perennial plant in the Umbelliferae, is widely cultivated in north China. As a traditional Chinese medicine, it can be used to cure colds and rheumatism (1). During disease surveys on medicinal plants in August 2010, a bacterial leaf blight was discovered with a general incidence of 40 to 60% on S. divaricata farms in Longxi, Weiyuan County in Gansu China. In young plants, tiny yellowwhite points were visible on the backs of the leaves. They then expanded to 2-to 3-mm oil-soaked lesions; leaves appeared crimped and deformed. Later the leaves shriveled; black-brown oil-soaked lesions appeared on the vein and the tissue around it; and black streaks appeared on the stems. Ten diseased leaf and stem tissues were cut into 4-to 5-mm squares, surfacesterilized in 1% sodium hypochlorite for 1 min, rinsed three times, and macerated for 5 min in sterilized distilled water. They were then streaked onto nutrient agar (NA) medium and incubated at 28°C for 3 days. Colo nies on NA were round, smooth, translucent, and yellowish green. They were Gram negative and induced a hypersensitive response on tobacco {Nicotiana tabacum L.) leaves. The strain was positive for gelatin, cata lase, oxidase, and utilization of glucose and saccharose. Pathogenicity tests were performed by spraying bacterial suspension containing 107 CFU/ml on six leaves of three healthy potted S. divaricata plants and injecting it into another six leaves on three plants. Plants inoculated with sterile distilled water alone served as controls. They were placed in a growth chamber at 25°C and bagged for 24 h to maintain >95% humidity. Thirty-six hours after inoculation, the inoculated leaves appeared watersoaked; 10 days later, the symptoms were apparent on leaves and the plant wilted. The negative control appeared normal. Finally, Koch's postulates were verified by re-isolating P. viridiflava from the leaves with typical blight. The genomic DNA of the isolate was extracted, and the partial 16S rDNA sequence was amplified with a universal bacterial primer set (27f and 1492r) (2). The sequence was deposited in GenBank as KM030291. BLAST search yielded 99% identity with P. viridiflava strains, including the strains KNOX209 (AY604847), RMX3.1b (AY574911), ME3.1b (AY574909), and UASWS0038 (AY919300). Based on the symptoms, colony morphology, biochemical tests, and 16S rDNA sequence identity, the pathogen was identified as P. viridiflava. To our knowledge, this is the first report of leaf blight of S. divaricata by P. viridiflava in Gansu prov ince of China. In Jilin province, the same disease was reported in 2008 (3). The impact of P. viridiflava on S. divaricata production is not yet known.

Assessing the Pathogenic Ability of Ralstonia pseudosolanacearum (Ralstonia solanacearum Phylotype I) from Ornamental Rosa spp. Plants

“…Although, traditionally the most predominantly represented plant families harboring hosts of R. pseudosolanacearum and R . solanacearum are the Solanaceae and Musaceae (Buddenhagen, 1961 ; Hayward, 1994b ; Elphinstone, 2005 ; Alvarez et al, 2010 ; Albuquerque et al, 2014 ), still new host species have been recently reported belonging to different plant families (Chandrashekara and Prasannakumar, 2010 ; Prieto Romo et al, 2012 ; Lin et al, 2015 ; Jiang et al, 2016 ). Recently, we reported, for the first time worldwide, the finding of R. pseudosolanacearum (phylotype I, race 1, biovar 3), causing bacterial wilt in Rosa spp.…”

“…Although the RSSC has been studied intensively for decades, still new host species have been recently reported (Chandrashekara and Prasannakumar, 2010 ; Prieto Romo et al, 2012 ; Lin et al, 2015 ; Jiang et al, 2016 ; Tjou-Tam-Sin et al, 2017 ). The potential movement of RSSC representatives via propagative material between countries has probably been underestimated.…”

Bacterial Wilt in China: History, Current Status, and Future Perspectives

“…in China encompasses more than 90 plant species belonging to 39 botanical families with the largest number of hosts in Solanaceae ( Figure 2 ). New hosts are still being reported including roselle and chard in Taiwan ( Wu et al, 2013 ; Lin et al, 2015 ) and fig in Fujian ( Jiang et al, 2016 ). Around 20 of these host plants have not been reported to become infected by Ralstonia spp.…”

Selection, Formulation, and Field Evaluation of Bacillus amyloliquefaciens PMB01 for Its Application to Manage Tomato Bacterial Wilt Disease

“…The yield loss of tomato varies up to 91%, and the losses vary from about 10% to 30% in tobacco and from 33% to 90% in potato [5]. Tomato plants infected by R. solanacearum often show stunting, leaf wilting and chlorosis, vascular discoloration, and death [6]. Bacteria constantly oozed from the cut end of diseased stems when placed in water.…”