First report of Melon yellow spot virus infecting balsam pear (<Emphasis Type="Italic">Momordica charantia</Emphasis> L.) in Japan

A new disease causing necrotic spots and yellowing on leaves of balsam pear (Momordica charantia) was found in Kochi Prefecture, Japan. In this study, we identified the causal pathogen as Melon yellow spot virus (MYSV) based on morphology of virus particles, serology, and the nucleotide sequence of the nucleocapsid protein gene. This is the first report of natural infection of balsam pear by MYSV. We propose the name spotted wilt for this new disease of balsam pear.     

Genetic diversity and pathogenicity of <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> isolated from wilted Welsh onion in Japan

Thirty isolates of Fusarium oxysporum from wilted Welsh onion plants were examined for their diversity in nucleotide sequences of the ribosomal DNA (rDNA) intergenic spacer (IGS) region and for pathogenicity with regard to five Welsh onion cultivars. Phylogenetic analysis based on the IGS sequences revealed polyphyletic origins of the isolates and a relationship between phylogeny and pathogenicity; low virulence isolates differed genetically from those with high and moderate virulence. Mating type analysis revealed that all F. oxysporum isolates were MAT1-1 idiomorphs, suggesting that the pathogens may be clonal in the fields examined.     

Pathogenic variation and molecular characterization of <Emphasis Type="Italic">Fusarium</Emphasis> species isolated from wilted Welsh onion in Japan

Thirty-two isolates of Fusarium species were obtained from wilted Welsh onion (Allium fistulosum) grown on nine farms from six regions in Japan and identified as F. oxysporum (18 isolates), F. verticillioides (7 isolates), and F. solani (7 isolates). The pathogenicity of 32 isolates was tested on five commercial cultivars of Welsh onion and two cultivars of bulb onion in a seedling assay in a greenhouse. The Fusarium isolates varied in the degree of disease severity on the cultivars. Five F. oxysporum isolates (08, 15, 17, 22, and 30) had a higher virulence on the cultivars than the other isolates. The host range of these five isolates was limited to Allium species. Molecular characterization of Fusarium isolates was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the internal transcribed spacer (ITS) regions of ribosomal DNA. The 32 isolates were grouped into eight types (four types for F. oxysporum, one for F. verticillioides, and three for F. solani). Restriction patterns of the ITS region were not related to pathogenicity. However, the haplotypes obtained with five enzymes (RsaI, HinfI, HaeIII, ScrFI, and MspI) and the phylogenetic analysis permitted the discernment of the three Fusarium species. The PCR-RFLP analysis should provide a rapid, simple method for differentiating Fusaruim species isolated from wilted Welsh onion in Japan.     

Screening of cultivated and wild adzuki bean for resistance to race 3 of <Emphasis Type="Italic">Cadophora gregata</Emphasis> f. sp. <Emphasis Type="Italic">adzukicola</Emphasis>, cause of brown stem rot

Two diseases of adzuki bean, brown stem rot (BSR, caused by Cadophora gregata f. sp. adzukicola) and adzuki bean Fusarium wilt (AFW, caused by Fusarium oxysporum f. sp. adzukicola), are serious problems in Hokkaido and have been controlled using cultivars with multiple resistance. However, because a new race of BSR, designated race 3, was identified, sources of parental adzuki bean for resistance to race 3 were needed. Therefore, we examined 67 cultivars and lines of cultivated and wild adzuki bean maintained at the Tokachi Agricultural Experiment Station using a root-dip inoculation method. Consequently, nine adzuki bean cultivars, one wild adzuki bean accession and 30 lines (including two lines resistant to all the three races of BSR and AFW) were confirmed to be resistant or tolerant to race 3 of BSR, and we found a cultivar Akamame as well as a wild adzuki bean Acc2515 to be a new source for a resistance gene to the race 3. This cultivar also holds promise as a source of resistance against other races of BSR and AFW.     

To what extent are soil amendments useful to control Verticillium wilt?

The genus Verticillium includes several species that attack economically important crops throughout the world. The control of Verticillium spp. becomes especially difficult when they form microsclerotia that can survive in the field soil for several years. It has been common practice to fumigate soil with chemicals such as methyl bromide and/or chloropicrin to control soil‐borne fungal pathogens. Other chemicals that are used against Verticillium spp. are the antifungal antibiotic aureofungin, the fungicides benomyl, captan, carbendazim, thiram, azoxystrobin and trifloxystrobin and the plant defence activator acibenzolar‐S‐methyl. However, the potential risks involved in applying phytochemicals to crop plants for both the environment and human health, together with their limited efficacy for controlling Verticillium‐induced diseases, support the need to find alternatives to replace their use or improve their efficacy. Soil amendment with animal or plant organic debris is a cultural practice that has long been used to control Verticillium spp. However, today the organic farming industry is becoming a significant player in the global agricultural production scene. In this review, some of the main results concerning the efficacy of several soil amendments as plant protectors against Verticillium spp. are covered, and the limitations and future perspectives of such products are discussed in terms of the control of plant diseases. Copyright © 2009 Society of Chemical Industry     

肉桂酸加剧蚕豆枯萎病发生的根际微生物效应

通过盆栽和室内试验研究了肉桂酸处理对蚕豆种子萌发,幼苗生长及尖孢镰孢菌菌丝生长,蚕豆枯萎病发生,根际微生物的活性、多样性和群落结构的影响。结果表明：肉桂酸处理抑制了蚕豆种子萌发及幼苗生长,并随处理浓度增加,抑制效应加强,对叶片数和根系的抑制效应最为显著。肉桂酸低浓度处理时显著促进尖孢镰刀菌菌丝生长,而高浓度处理则抑制菌丝生长。肉桂酸在100和200 mg · L^-1处理时显著提高了蚕豆枯萎病的病情指数,显著增加了根际土壤中镰刀菌的数量,降低了微生物的活性（AWCD值）、多样性和丰富度指数。主成分分析表明,肉桂酸处理明显改变了蚕豆根际微生物群落结构,糖类、羧酸类和氨基酸类是区分肉桂酸处理导致土壤微生物群落变化的敏感碳源。肉桂酸处理降低了根际微生物多样性,促进病原菌的增殖,加剧了蚕豆枯萎病的发生,证实肉桂酸是蚕豆连作障碍中的自毒物质。     

棉花黄萎病病原菌大丽轮枝菌的快速分子检测

大丽轮枝菌Verticillium dahliae是引起棉花黄萎病的土传病害病原真菌。快速及时地检测出大丽轮枝菌,对棉花黄萎病的早期预警及后期防治具有重要意义。采用聚合酶链式反应(polymerase chain reaction,PCR)检测技术对已报道大丽轮枝菌的检测引物进行验证、筛选和改进,获得1对改进的特异性PCR引物VDS-F/VDS-R。在优化的反应体系与扩增条件下,能特异性地从大丽轮枝菌基因组扩增出l条约520 bp的产物条带,检测灵敏度达到10~(-2)ng/μL;利用该引物可特异性地从含有大丽轮枝菌的土壤及棉花植株组织中检测出病原菌;采用巢氏PCR法对人工病土的检测灵敏度达到了10个孢子/g土。表明本引物的PCR检测体系可用于棉花黄萎病的早期快速检测。     

环烷基磺酰胺类化合物对辣椒疫霉的抑制作用

采用菌丝生长速率法,以甲霜灵、氟吗啉原药和10%氰霜唑悬浮剂作对照药剂,从20种环烷基磺酰胺类化合物中筛选出N-(2,4,5-三氯苯)-2-羟基环烷基磺酰胺(化合物149)和N-(2-三氟甲基-4-氯苯)-2-羟基环烷基磺酰胺(化合物104)2种对辣椒疫霉菌丝生长有抑制作用的化合物,其EC50分别为9.58μg/mL和15.96μg/mL。对辣椒疫霉生育阶段抑制试验结果表明,化合物149和104对孢子囊形成均有较强的抑制作用,EC50分别为0.03μg/mL和4.62μg/mL,其中化合物149的抑制率高于对照药剂90%氟吗啉原药;化合物149和104抑制辣椒疫霉游动孢子释放和萌发,其中化合物104的EC50为0.18μg/mL,高于对照药剂90%甲霜灵原药;化合物149和104对辣椒疫霉菌丝生长量均表现出较好的抑制效果。     

抗黄瓜枯萎病丛枝菌根真菌与根围促生细菌组合菌剂的筛选

 丛枝菌根真菌(AMF)和植物根围促生细菌(PGPR)同时接种具有促生防病的作用。本试验旨在评价AMF与PGPR组合菌剂防治黄瓜枯萎病(Fusarium oxysporum f. sp. cucumerinum )的效果,以获得高效生防菌剂。于温室盆栽条件下将AMF Funneliformis mosseae(Fm)、Glomus intraradices(Gi)和 Glomus versiforme(Gv)与PGPR菌株(PR2-1、PS1-3、PS1-5、PS2-6和PS3-2)不同组合菌剂处理黄瓜(Cucumis sativus, 品种:香翠16号),测定各处理对黄瓜植株生长量、枯萎病防治效果和黄瓜产量的影响。供试AMF+PGPR各组合菌剂处理能不同程度的增加黄瓜根系AMF侵染率和根围细菌的定殖数量、促进黄瓜生长发育和降低枯萎病危害程度。其中,以Fm+PS3-2和 Gv+PS2-6组合菌剂促生和增产效果最好, 以Fm+PS1-5、Fm+PS3-2和Gv+PS2-6组合菌剂防治枯萎病效果最好。综合评价筛选获得高效组合为Fm+PS3-2和Gv+PS2-6。这两个处理可使黄瓜枯萎病病情指数分别下降50.0%和58.4%,防效达到54.5%和63.7%,具有一定的田间应用潜力。     

新疆榆树黄萎病病原菌鉴定

2013年以来,在石河子大学农学院试验站榆树苗上,出现了一种病害,可导致叶片褪绿,变黄,萎蔫,甚至枯死,剖茎检查可见维管束变成褐色。采用常规组织分离法对病茎组织进行分离、纯化获得单孢纯培养菌株;通过常规纸钵撕底蘸根法对其进行致病性测定;用形态学和rDNA-ITS序列分析方法对病原菌进行鉴定。结果表明,分离菌株的菌落形态、分生孢子梗和分生孢子的形态都与大丽轮枝菌(Verticillium dahliae)一致;经分子生物学鉴定,该菌的rDNA-ITS序列与中国棉花黄萎病菌(V.dahliae)的ITS序列(登录号EU 835817.1)相似性达99.0%,故将引起新疆榆树黄萎病的病原菌鉴定为大丽轮枝菌(V.dahliae)。