Differentiation of xanthomonads causing the bacterial leaf spot of poinsettia in China from the pathotype strain of Xanthomonas axonopodis pv. poinsettiicola

In October 2003, a new bacterial disease with symptoms similar to those caused by Xanthomonas axonopodis pv. poinsettiicola was observed on poinsettia leaves at a flower nursery in Zhejiang Province of China. Three Xanthomonas strains were isolated from infected plants and classified as X. axonopodis. They were differentiated from the pathotype strain LMG849 of X. axonopodis pv. poinsettiicola causing bacterial leaf spot of poinsettia by comparison of pathogenicity, substrate utilization and BOX-PCR genomic fingerprints.

菜豆普通细菌性疫病病原菌鉴定

【目的】明确中国北方地区菜豆普通细菌性疫病病原菌。【方法】应用菌落特征、油菜黄单胞菌菜豆变种诊断试剂检测、致病性测定、16S rDNA和16S-23S rDNA ITS序列分析、特异PCR检测、脂肪酸分析及生理生化反应特征对病原菌分离物进行鉴定。【结果】从病害样品和菜豆种子样品中均分离到类似黄单胞杆菌的细菌分离物,选取25个代表分离物进行致病性测定,有24个分离物在菜豆品种"英国红"上导致典型菜豆普通细菌性疫病症状。结合16S rDNA及16S-23S rDNA ITS序列比对分析、特异性PCR检测及生理生化反应的结果,24个分离物中7株被鉴定为地毯草黄单胞菌菜豆变种,17株为褐色黄单胞菌褐色亚种。【结论】中国北方地区发生的菜豆普通细菌性疫病由地毯草黄单胞菌菜豆变种或(和)褐色黄单胞菌褐色亚种引起;褐色黄单胞菌褐色亚种在中国属首次报道。

进境菜豆种子中普通细菌性疫病菌的分离和鉴定

对经甘肃口岸进境的30批菜豆Phaseolus vulgaris种子进行了普通细菌性疫病菌的检测,利用选择性培养基MT从波兰进境菜豆种子上分离到1株细菌597,对该分离物进行菌落形态特征观察、致病性测定、16S rDNA及16S-23S rDNA ITS序列分析和特异性PCR检测。结果表明,该分离物在MT培养基上菌落呈黄色、圆形、黏稠、表面光滑向外隆起、菌落周围有水解圈。分离物597接种菜豆幼苗后导致叶片枯萎,接种点干枯。结合菌落形态、16S-23S rDNA ITS序列、特异性PCR检测结果,将分离物597鉴定为地毯草黄单胞杆菌菜豆致病变种Xanthomonas axonopodis pv.phaseoli。

Activity of Secondary Bacterial Metabolites in the Control of Citrus Canker

This study investigated the protective effects of secondary bacterial metabolites, produced by Pseudomonas sp. (bacterium strain LN), on citrus canker disease caused by Xanthomonas axonopodis pv. citri (Xac 306). The LN bacteria strain was cultured in liquid medium and the supernatant free-cells was treated with methanol (AMF) and ethyl acetate (AEF), respectively, and then the extract was concentrated, filtrated, lyophilized and fractionated by vacuum liquid chromatography (VLC). After VLC, eight fractions were obtained. All fractions’ activity against Xac 306 by agar well diffusion assay and minimum inhibitory concentration but in different concentrationswere tested. Cytotoxicity effects were observed in all fractions in 50 μg·mL-1 concentration. The comet assay demonstrated that the fractions EAF, VLC2 and VLC3 presented no genotoxic effects at tested concentrations. In plants only VLC3 showed significant results (p<0.05), reducing the incidence of citrus canker lesions.

菜豆种子普通细菌性疫病菌检测

由Xanthomonas axonopodis pv.phaseoli和Xanthomonas fuscans subsp.fuscans引起的菜豆普通细菌性疫病是严重影响菜豆生产的限制因子之一,可造成严重的产量和品种损失。染菌种子是病原菌传播的主要途径。本研究对5个菜豆主要产区的60份菜豆种子样品进行普通细菌性疫病菌检测。在MT选择性培养基上有36份种子样品浸提液检测到目标病原菌,种子样品带菌量为2.49×102～5.20×107CFU/粒。选择36个分离物接种感病品种"英国红"植株,所有分离物均引起接种植株发病。特异PCR检测结果表明,有20个分离物为X.fuscans subsp.fuscans,16个分离物为X.axonopodis pv.phaseoli。试验结果表明,我国一些菜豆主产区商业种植和研究用种子多数污染普通细菌性疫病菌,建议建立无菌种子生产区和加强种子管理,以有效控制病害发生。

菜豆普通细菌性疫病菌在土壤和植株残体中的越冬能力

为评估菜豆普通细菌性疫病菌地毯草黄单胞杆菌菜豆致病变种或褐色黄单胞菌褐色亚种在土壤及植物残体中的越冬能力,对采自黑龙江、内蒙古、山西、河北及新疆的18块菜豆生产田的20份土壤及14份植物残体样品进行病原菌分离和鉴定。在MT选择性培养基上有12个土壤样品和13个植株残体样品提取液产生典型的类似黄单胞菌菌落。选取29个分离物进行致病性测定,有27个分离物对菜豆品种"英国红"致病。利用地毯草黄单胞杆菌菜豆致病变种和褐色黄单胞菌褐色亚种的特异性引物X4c/X4e及褐色黄单胞菌褐色亚种特异性引物Xf1/Xf2对29个分离物进行多重PCR检测,其中17个分离物为地毯草黄单胞杆菌菜豆致病变种,10个分离物为褐色黄单胞菌褐色亚种。结果表明,菜豆普通细菌性疫病菌可以在黑龙江、内蒙古、山西、河北的一些菜豆种植区的土壤及植株残体中越冬存活。