新疆瓜尔豆细菌性疫病病原鉴定

Identification of pathogen of guar bacterial blight in Xinjiang

【目的】明确新疆克拉玛依种植的瓜尔豆(Cyamopsis tetragonoloba L.)新爆发的细菌性病害的病原,以防止该病害在新疆瓜尔豆上进一步扩散和蔓延,保证该地区瓜尔豆产业的可持续发展。【方法】从新疆瓜尔豆产区采集发病叶片、茎干及豆荚等组织进行病菌分离,对分离后的菌株采用喷雾法和针刺法进行致病性测定,并根据采集地点、田间发病症状和发病组织的不同,选取9个代表菌株观测其培养特性和生理生化特征;同时选取3个代表菌株进行16SrDNA测序。【结果】该病害在整个瓜尔豆生长季均可以发生,危害叶片、茎干、叶柄、荚柄、豆荚和种子,造成叶枯、落叶、茎干爆裂、顶枯、豆荚和种子不能成熟或变黑坏死。从发病植株上共获得21个具有致病性的细菌菌株,菌株的致病性表现与田间症状基本一致。9个代表性菌株在YEPG培养基上培养72h后形成淡黄色奶油状的圆形菌落,在KB培养基上无黄绿色荧光反应;均为革兰氏阴性、杆状、严格的好氧型细菌;烟草过敏性坏死反应均为阳性;接触酶阳性,氧化酶阴性,耐盐性表现为耐20~30g/L NaCl。选取的3个代表菌株的16SrDNA序列与Xanthomonas axonopodis菌株XV 938的同源性达99.95%。【结论】将引起该病害的病原确定为地毯草黄单胞菌瓜尔豆致病变种(Xanthomonas axonopodis pv.cyamopsidis),该病害确定为瓜尔豆细菌性疫病。

【Objective】This study identified the pathogen of guar bacterial blight,a new bacterial disease observed on field-grown guar(Cyamopsis tetragonoloba L.)in Karamay,Xinjiang.It could help to prevent its further spread and support sustainable guar production in Xinjiang.【Method】Samples of diseased leaves,stems,petioles,pods,and seeds were collected and isolated.Pathogenicities of isolated bacterial strains were tested by spraying and puncturing methods.Then 9strains were selected for determination of cultural characteristics and physiological and biochemical characteristics based on location,symptoms and infected tissues.At last,16 SrDNA of three strains were amplified and sequenced.【Result】Field symptoms included large angular necrotic lesions at leaf tips,black streaks on petioles and stems,cracking stems,defoliation,wilting or top-withering,vascular necrosis,and dieback.A total of 21 strains with pathogenicitywere obtained and the pathogenicity was consistent with field symptoms.After 72 hculture of the selected9 strains on YEPG medium,yellow-pigmented,opaque,and round colonies were isolated and no yellowgreen fluorescence was observed.These strains were aerobic and gram-negative rods.They were positive for H2 S,esculin,oxidase,and tobacco hypersensitivity,and their maximum salt tolerance was 20-30g/L NaCl.The 16 SrDNA sequences of the selected three strains shared 99.95%identity with Xanthomonas axonopodis strain XV 938.【Conclusion】Based on morphology,pathogenicity tests,16 SrDNA sequencing,and host plant specificity,the pathogen was confirmed as X.axonopodis pv.cyamopsidis(synonym:X.campestris pv.cyamopsidis(Patel et al.,1953).