Blackleg and soft rot of potato cause economic loss through reduced yield and quality. The causal agents of bacterial blackleg and soft rot of potato were identified based on biological data and sequence analyses of the 16S rDNA gene. Between 2016 and 2018, diseased potato stems and tubers were collected in Chai Prakan District, Chiang Mai Province, and Chiang Khum District, Pa Yao Province. The symptoms included black stem lesions, soft rot on tubers, wilting, break down of the stem vascular ring and foliar yellowing. Of 13 bacterial isolates, five were identified as Pectobacterium carotovorum subsp. brasiliense, four‐Dickeya dadantii, two‐Pseudomonas putida and two‐Bacillus altitudinis. Pathogenicity tests of P. carotovorum subsp. brasiliense and D. dadantii resulted in lower leaves turning yellow and wilting followed by blackleg symptoms on lower stems and maceration of tuber tissue. Symptoms caused by P. putida were yellowing and wilting of leaves. B. altitudinis caused yellowing of the lower leaves and wilting followed by drying of leaf tissue. This is a first report of these bacterial pathogens causing blackleg and soft rot of potato in Thailand.

Phylotype and sequevar of Ralstonia solanacearum were associated with geographic region and geographic distribution. This is the first study to identify phylotype and sequevar of R. solanacearum from Patumma in Chiang Mai, Thailand. This will be useful for study of disease epidemiology and could help management for control of bacterial wilt diseases in this host.

Melon yellow spot virus (MYSV) was previously reported from wax gourd in Thailand. A survey of cantaloupe, cucumber, melon, pumpkin and watermelon plants was carried out to determine if MYSV occurred more widely in cucurbit species. The survey revealed melon was mostly infected with MYSV. In addition, MYSV was detected for the first time in pumpkin in Thailand.

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Bacterial wilt disease caused by the soil-borne bacterium, Ralstonia solanacearum species complex (formerly Pseudomonas solanacearum), causes great yield losses (Elphinstone, 2005). Because of the broad host range of and the limited control measures for R. solanacearum species complex, which attacks more 200 species representing 50 families of plants including the Solanaceae, Musaceae, Zingiberaceae and Cucurbitaceae (Hayward, 1994;She et al., 2017), the disease is difficult to manage. Bacterial wilt is a common disease in tropical, subtropical and warm temperate regions of the world. The disease is known to cause substantial damage to the economic plant production . The initial symptom is a drooping of leaves.Affected leaves later become permanently wilted, as the disease develops, a brown discoloration of xylem vessels in the stem is observed. A creamy or slimy mass of bacteria exudes from cut or broken vascular bundles. Eventually, plants fail to recover and become yellow and then necrotic (Charkowski et al., 2020;Dhital et al., 2000).In traditional classification schemes, R. solanacearum was currently classified into four biovars based on the oxidization of three

Sugarcane, an important agricultural crop, is susceptible to white leaf disease, which can severely damage the crop and income. The disease is caused by phytoplasma, a prokaryote in the class mollicutes. This study investigated the efficacy of treating the disease by sterilization with solution plasma technology, including wire-to-wire, plasma jet, and gliding arc systems. Nested PCR and a scanning electron microscope were used to examine the phytoplasma disease and evaluate the effectiveness of the various solution plasma treatments. The most effective treatments, in terms of balancing plant growth and disease reduction, were the wire-to-wire system, with infected specimens immersed during discharge for 2 min with discharge repeated every 2 min, for 120 min (Exp 13); and the plasma jet system, with infected specimens immersed during discharge for 30 min and then continuously immersed for 180 min (Exp 18). The wire-to-wire treatment yielded 50% disease-free sugarcane specimens with 80% growth; the plasma jet system yielded fewer disease-free sugarcane specimens (40%), but more growth (90%). Additionally, SEM results showed that the solution plasma treatments as a group reduced disease incidence by about one third compared to the controls.

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