Bacterial wilt of bellflower caused by Ralstonia solanacearum in Japan

A sudden wilt of bellflower (Campanula lactiflora) was observed in Japan in 1997. A bacterium that formed white fluidal and mucoid colonies resembling those of Ralstonia solanacearum was isolated from the infected plants. The bacterium was bacteriologically identified as biovar 3 of R. solanacearum. This is the first report of R. solanacearum affecting a plant species of the Campanulaceae family.     

茄青枯病菌引起的新病害-罗汉果青枯病

 罗汉果为葫芦科(Cucurbitaceae)罗汉果属[Siraitia grosvenorii(Swingle) C.Jeffrey]植物。罗汉果中含有0.8%~1.0%的罗汉果甜甙,其甜度为蔗糖的300倍,是肥胖症、高血压、高血脂、糖尿病等患者最理想的甜味剂与保健品。罗汉果甜贰远销美国、日本等国外市场,产品供不应求。     

Plant growth inhibitors in turmeric (Curcuma longa) and their effects on Bidens pilosa

Turmeric (Curcuma spp.) has numerous biological activities, including anticancer, antibacterial, antifungal and insecticidal properties. Here, we evaluated the plant growth‐inhibitory activities of two cultivars of Curcuma longa (C. longa ; Ryudai gold and Okinawa ukon) against radish, cress, lettuce and Bidens pilosa (B. pilosa ). The methanol extracts of both turmeric varieties inhibited the seed germination and seedling growth of all the tested plants. Ryudai gold had a significantly higher inhibitory effect on the seed germination and root and shoot growth of the plants than Okinawa ukon. Therefore, Ryudai gold was chosen for the isolation of plant growth‐inhibitory compounds using a silica gel column and high‐performance liquid chromatography. The structural identification of the compounds was carried out using ¹H NMR, ¹³C NMR and liquid chromatography–tandem mass spectrometry. The growth inhibitors were identified as four curcuminoids; dihydrobisdemethoxycurcumin ( 1 ), bisdemethoxycurcumin ( 2 ), demethoxycurcumin ( 3 ) and curcumin ( 4 ). The IC₅₀ of the curcuminoids against the root and shoot growth of B. pilosa ranged from 8.7 ± 1.7 to 12.9 ± 1.8 and from 15.5 ± 1.8 to 38.9 ± 2.8 μmol L^?1, respectively. Compound 1 showed the lowest IC₅₀ against the root and shoot growth of B. pilosa . These results suggested that Ryudai gold has a potential growth‐inhibitory effect against B. pilosa .     

Potato bacterial wilt in India caused by strains of phylotype I, II and IV of Ralstonia solanacearum

Bacterial wilt or brown rot is one of the most devastating diseases of potato caused by a bacterium Ralstonia solanacearum (Smith 1986) Yabuuchi et al. (Microbiol Immunol 39:897–904 1995). Traditionally, R. solanacearum is classified into five races (r) on the basis of differences in host range and six biovars (bvs) on the basis of biochemical properties. Recently using molecular methods, R.?solanacearum has been classified into phylotypes based on the intergenic transcribed sequence of the ribosomal RNA genes 16S and 23S and into sequevars based on the endoglucanase gene (egl) sequence. In the present study, 75 bacterial strains, isolated from wilt infected potatoes from various potato growing regions of India, were classified by traditional and molecular methods. The identity of all the strains was confirmed as R. solanacearum as expected single 280-bp fragment resulted in all the strains following PCR amplification using R. solanacearum specific universal primer pair 759/760. Biovar (bv) analysis, based on utilization of disaccharide sugars and hexose alcohols, categorised the 75 strains into bv2 (78.7 %), 2 T (5.3 %), 3 (5.3 %) and 4 (10.7 %). The phylotype specific multiplex PCR assigned 78.7 % strains to phylotype II, 16.0 % to phylotype I and 5.3 % to phylotype IV. Phylogenetic analysis of egl gene sequences clustered all fifty nine phylotype II (bv2) strains with reference strain IPO1609 (IIB-1), all four phylotype IV (bv2T) strains with reference strain MAFF301558 (IV-8), three phylotype I (bv3) strains with reference strain MAFF211479 (I-30) and all eight phylotype I (bv4) and one phylotype I (bv3) strain with reference strain CIP365 (I-45). The study concluded that the Indian potato strains of R. solanacearum belong to three out of four phylotypes namely: the Asian phylotype I, the American phylotype II, and the Indonesian phylotype IV. This is the first study to address the diversity of R. solanacearum from potato in India using phylotype and sequevar scheme. We also report here for the first time the occurrence of phylotype IV sequevar 8 (bv2T) strain of R. solanacearum causing potato bacterial wilt in mid hills of Meghalaya in India.     

PM 7/21 (2) Ralstonia solanacearum,R. pseudosolanacearum and R. syzygii (Ralstonia solanacearum species complex)

Specific scope

This Standard describes a diagnostic protocol for Ralstonia solanacearum, Ralstonia pseudosolanacearum and Ralstonia syzygii, i.e. phylotype/sequevar strain in the Ralstonia solanacearum Species Complex (RSSC). 1 It should be used in conjunction with PM 7/76 Use of EPPO diagnostic protocols.

Specific approval and amendment

Approved in 2003‐09. First revised in 2018‐02.     

Activation of tomato plant defence responses against bacterial wilt caused by Ralstonia solanacearum using DL-3-aminobutyric acid (BABA)

In this study, we investigated the ability of DL-3-aminobutyric acid (BABA) to protect tomato against bacterial wilt caused by Ralstonia solanacearum. This was combined with studies of accumulation of total phenolic compounds, free and total salicylic acid (SA), and activity of enzymes related to plant defence, i.e., polyphenol oxidase (PPO) and catalase (CAT). Under greenhouse conditions, tomato plants pre-treated by soil drenching with BABA profoundly reduced disease severity of bacterial wilt compared to plants receiving a soil drench with water. Thus, BABA reduced leaf wilting index by 75.3 % and vascular browning index by 69.9 %, without any in vitro inhibitory activity on the pathogen. BABA treatment significantly reduced the population of R. solanacearum in stems of tomato plants and additionally also significantly increased both fresh and dry weight of roots and shoots of tomato plants compared with the inoculated control. Application of BABA resulted in a high increase in PPO activity both in plants with and without inoculation. Compared to water-treated plants, treatment with BABA also induced a significant increase of total phenolic compounds as well as of free and total SA in leaves of both inoculated and non-inoculated tomato plants at all sampling times. CAT activity decreased in tomato plants treated with BABA in comparison with the water-treated control plants and the decrease in activity correlated with an increasing total SA accumulation. These findings suggest that BABA treatment resulted in induction of resistance to bacterial wilt in tomato.     

Identification and use of a wild plant with antimicrobial activity against Ralstonia solanacearum, the cause of bacterial wilt of potato

Fresh aerial tissue and roots of 14 wild plants in Okinawa prefecture were investigated for their antimicrobial activity against Ralstonia solanacearum , which causes bacterial wilt of potato. A 70% aqueous ethanol extract of fresh aerial tissue of Geranium carolinianum L. showed strong antimicrobial activity against R. solanacearum . This extract also showed antimicrobial activity against the pathogens causing common scab of potato and soil rot of sweet potato. The antimicrobial substance could be extracted with hot water, and was effective against R. solanacearum in soil. In the field test, a treatment combining incorporation of dried aerial tissue into the soil and solarization was highly effective for control of bacterial wilt of potato. These findings suggest that G. carolinianum L. could be used as a biological agent for the control of bacterial wilt of potato.     

ANTI-8098A生物杀菌制剂在连作重病区对茄子青枯病的防效测定

在福州市宦溪镇创新村蔬菜基地的同一地点连续3a进行的试验表明,生防菌———ANTI-8098A制剂当年使用,对连作重病区的茄子青枯病具有良好的防治效果。同时,该制剂对茄子植株的叶宽、叶长、叶片数、株高、着花数、着果数和果长都有显著促长作用,但防效不能持续至次年。生产上可于茄子小苗期开始施用ANTI-8098A制剂,用300倍液灌根,每株茄子施药液250g,于定植时、苗期(定植后20d)和成长期(苗期后20d)各使用1次。     

Interaction between silicon amendment,bacterial wilt development and phenotype of Ralstonia solanacearum in tomato genotypes

Silicon amendment significantly reduced bacterial wilt incidence expressed as area under disease progress curve for tomato genotypes L390 (susceptible) by 26.8% and King Kong2 (moderately resistant) by 56.1% compared to non-treated plants grown in hydroponic culture. However, wilt incidence in silicon-treated plants of genotype L390 reached 100% at 13 days post-inoculation (dpi), while in genotype King Kong2, plant death was retarded by 6 days, with 20% reduction of final wilt incidence. Bacterial numbers were significantly lower in silicon-treated compared to non-treated plants in King Kong2 at 2 dpi in midstems and in all organs at 5 dpi, and in Hawaii 7998 (resistant) in all organs at 2 dpi. Differences between genotypes were obvious on midstem level (5 dpi), where bacterial populations were generally significantly lower compared to roots. Increased tolerance was observed in genotypes L390 and King Kong2 with silicon treatment.Silicon accumulated in roots and was low in stems and leaves. Inoculation with Ralstonia solanacearum did not significantly affect silicon uptake and distribution. Negative correlations between root silicon content and bacterial numbers of midstems in genotypes Hawaii 7998 and King Kong2 suggested an induced resistance. Indications for an influence of host genotype and silicon treatment on the phenotypic conversion of R. solanacearum strain To-udk2-sb from fluidal to non-fluidal colonies in planta were observed.This is the first report on the effect of silicon on a bacterial disease and in a silicon-non-accumulator plant.     

Occurrence of bacterial wilt of peanut (Arachis hypogaea) caused by Pseudomonas solanacearum and opportunistic infection of aibika (Abelmoschus manihot) in Papua New Guinea

Pseudomonas solanacearum , the cause of bacterial wilt was isolated from stems, roots and developing cotyledons of peanut and the stem of a single aibika plant growing in a subsistence garden in Port Moresby. The garden had been cleared and planted to peanut after a fallow of at least 2 years. The bacterium could not be isolated from roots or rhizosphere soil of locally growing grasses and weeds, nor could seed transmission be demonstrated in peanut.     

Bacterial wilt of sweet potato caused by <Emphasis Type="Italic">Ralstonia solanacearum</Emphasis> in Taiwan

During the last decade, a new bacterial disease has impaired the yield of vegetable sweet potato (30–80%) in Taiwan. Infected plants developed stunting, root and stem rot, vascular discoloration and wilting. Ten bacterial isolates that caused the same symptoms in sweet potatoes after inoculation were reisolated and classified as Ralstonia solanacearum phylotype I biovar 4 based on physical and molecular analyses. Moreover, these isolates also caused wilting in convolvulaceous, solanaceaous and cruciferous plants. This report is the first of bacterial wilt of sweet potato caused by R. solanacearum in Taiwan.     

Stem canker and wilt of delphinium caused by Fusarium oxysporum f. sp. delphinii in Japan

Stem canker and severe wilt were observed on delphinium plants (Delphinium elatum) in Aomori Prefecture, Japan, in 2008. The fungus isolated from the diseased crown was identified as Fusarium oxysporum f. sp. delphinii on the basis of morphological characteristics, nucleotide sequences, and host range. The isolate induced similar stem canker and wilt symptoms in inoculated delphinium plants. We propose the name “stem canker and wilt” for the disease.     

Bacterial leaf blight of sweet pepper (Capsicum annuum) caused by Pseudomonas cichorii in Japan

Sweet peppers (cv. Tosajishi beauty) with leaf blight symptoms were observed in Kochi Prefecture, 2003. Initially, small spots formed on leaves, and later enlarged to brown to dark brown spots, and eventually blighted leaves fell. Several bacteria that caused the same symptoms were isolated and subsequently reisolated. These bacteria were identified as Pseudomonas cichorii on the basis of bacterial characteristics and the 16S rRNA gene sequence. This is the first report of bacterial leaf blight in the sweet pepper in the world.     

Bacterial leaf spot of hemp caused by Xanthomonas campestris pv. cannabis in Japan

Bacterial leaf spot disease of hemp was observed in Tochigi Prefecture, Japan in 1982 and characterized by necrotic lesions ca. 1–2 mm diameter on leaves with a yellow halo 2–3 mm wide. In this report, we describe the pathological, physiological and genetic properties of the causal bacterium. Our results indicated that this bacterium is identical with Xanthomonas campestris pv. cannabis reported in Romania.