Comparison of leaf and pod disease reactions of beans (Phaseolus vulgaris L.) inoculated by different methods with strains of Xanthomonas campestris pv. Phaseoli (Smith) dye

Summary Common blight disease in beans (Phaseolus vulgaris), caused by the bacterium Xanthomonas campestris pv. phaseoli, reduces crop yield and seed quality. Information is needed on the variation of leaves and pods disease reaction to strains of the bacterium after different inoculation methods. Phaseolus vulgaris cultivars Red Kidney Charlevoix, GN Harris, GN 1140, and GN Emerson were inoculated with three different strains of Xanthomonas campestris pv. phaseoli at two inoculum concentrations (10⁸ and 10⁶ bacterial cells/ml) using water soaking, multiple needle, and razor blade inoculation on leaves, and razor blade scratch, dissecting needle, and razor blade cut inoculation on pods. Differential cultivar disease reactions of leaves, pods, or both to the bacterial strains were observed in some cases. Significant interactions among cultivars, inoculation methods, strains, and inoculum concentrations (leaves) were found. A rapid leaf chlorosis developed 6 to 7 days after inoculation. Strains of bacteria did not show specificity in inducing this reaction, but rapid leaf chlorosis was associated with high inoculum concentration and with the water soaking and multiple needle methods. Another experiment was conducted to count the number of living bacterial cells deposited in the leaf tissue after inoculation by different methods. The number of bacteria deposited by water soaking or multiple needle was higher than that deposited by razor blade.Published as Paper No. 8584, Journal Series, Nebraska Agricultural Experiment Station. Research was conducted under Project No. 20–36.     

Genetic Analysis of Resistance to Xanthomonas campestris pv. oryzae (Ishiyama) Dye in a Rice Breeding Line ARC 10464

The genetics of resistance to three Indian pathotypes of Xanthomonas campestris pv. oryzae, namely, IX01, IX08 and IX09, was studied in a landrace of Indica rice ‘ARC 10464’. Resistance to each of the two pathotypes IX01 and IX09 was governed by two independently-inherited dominant genes while a single dominant gene was operative against patho-type 1X08. The joint segregation tests conducted on F₂ plant progenies (F₃ families) using pathotypes IX01, IX08 and IX09 suggested that the gene/(s) effective against each of the pathotypes are different.     

Inheritance of resistance to Xanthomonas campestris pv phaseoli in tetary bean (Phaseolus acutifolius)

Summary The F1, F2 and F3 from two crosses within Phaseolus acutifolius were exposed to Xanthomonas campestris pv phaseoli to analyse the inheritance of resistance. The resistant parent, PI 319.443, gave a hypersensitive reaction in leaves and pods with small necrotic lesions. Based on the resistance of F1, the segregation in F2 and the reaction of F3 plants and lines, it is concluded that resistance in leaves and pods is governed by one dominant gene. Comparisons are made with the resistance to X. campetris in P. vulgaris.     

野油菜黄单胞菌中6-磷酸海藻糖合成酶注释基因的功能鉴定

6-磷酸海藻糖在微生物碳代谢调节及抗逆生理中起着极其重要的作用。在野油菜黄单胞菌野油菜致病变种(Xanthomonas campestris pv.campestris,Xcc)8004菌株的基因组中,XC1076注释为6-磷酸海藻糖合成酶。利用突变和表型检测技术,对XC1076进行功能鉴定,结果显示,XC1076的Tn5gusA5插入突变体006B12,在含3%NaCl的NYGB培养基中生长明显缓慢,在含葡萄糖为惟一碳源的NCM培养基中几乎不能生长,反式互补能够基本恢复野生型表型,这说明XC1076与碳代谢调控和抗高渗有关。这些表型实验结果揭示,XC1076的ORF编码的蛋白具有6-磷酸海藻糖合成酶活性。致病生化因子检测显示,XC1076与Xcc胞外酶和胞外多糖的分泌无关。     

水稻白叶枯病菌新鉴别品种的筛选及其菌系的研究

 利用云南、日本和国际水稻研究所(IRRI)共19个稻白叶枯病鉴别品种,测定了来自云南不同地区的76个稻白叶枯病菌菌株。结果证明稻白叶枯病菌菌株与品种间具有特异性的交叉互作关系。.菌株间致病力的差异表现为质的差异。试验结果,初步以IR₂₆、Heen-Dikwee-1、珍白18、早生爱国3号、Tetep、窄叶青8号、IR₈和南粳33这8个品种作为新筛选的1套鉴别品种,其特点是品种与菌株具有明显的互作,鉴别能力强,可用来研究云南稻白叶枯病菌系。可将云南省36个稻白叶枯病菌株区分为22个菌系。     

水稻白叶枯病菌基因XOO2193的突变体构建及其毒力和胞外多糖分析

水稻白叶枯病菌是一种引起水稻白叶枯病的植物病原细菌,水稻白叶枯病是世界水稻生产中最严重的细菌性病害之一。本研究采用携带同源序列的自杀质粒pK18MobGⅡ整合的办法构建了水稻白叶枯病菌中国菌株13751编码6-磷酸葡糖酸内酯酶的基因XOO2193的非极性突变体GNM2193。对突变体的表型分析发现其毒力在杂交水稻品种特优63上显著减弱,突变体在非寄主植物蓖麻上不能引起过敏反应。此外,突变体胞外多糖的产量是野生型的43.4%。用一段含有XOO2193基因的DNA片段对GNM2193进行功能互补,互补菌株在水稻上的毒力、引起过敏反应的能力和胞外多糖产量恢复到野生型水平。说明XOO2193基因与病菌的毒力和胞外多糖的产生有关。     

国外新引进水稻品种（系）对我国水稻白叶枯病致病型的抗性反应

采用成株期人工剪叶接种鉴定方法,评价451份新引进的国外水稻新品种（系）对我国田间流行的5个水稻白叶枯病致病型的抗性反应。结果显示国际水稻研究所新材料是水稻白叶枯病重要的抗源。本试验还筛选出一批抗性较好的抗性材料,可供育种家在选配亲本时选用。     

Symbiosis with bacteria enhances the use of chitin by the springtail,Folsomia candida (Collembola)

Summary The relationship between Folsomia candida and chitin-degrading microorganisms was studied. On chitin agar, 10¹⁰ bacteria were isolated per g faeces, and 3.8×10¹¹ bacteria per g gut contents, 1/3 of them showing a clear (chitin-free) zone around the colony. The most abundant chitin-degrading bacteria were Xanthomonas maltophilia and Curtobacterium sp. To determine the bacterial contribution in the use of chitin by F. candida, a feeding experiment was carried out. F. candida were fed with chitin, either amended with or without tetracycline as an inhibitor of bacteria. When tetracycline was omitted the biomass of F. candida was increased compared to those fed chitin with tetracycline. However, this result was observed only when the food replacement intervals were long enough to allow bacterial colonization before ingestion of the food. In a food-selection experiment, a preference for chitin colonized with microorganisms as opposed to sterile chitin was found. The results indicate that a mutualistic symbiosis of F. candida with chitinolytic microorganisms is likely to enhance chitin degradation. This relationship is not only intra-intestinal but also involves an extra-intestinal phase.Dedicated to the late Prof. Dr. W. Kühnelt     

核桃细菌性黑斑病病原分子鉴定及室内药剂筛选

为确定云南地区核桃细菌性黑斑病的病原菌并筛选防治核桃细菌性黑斑病的有效药剂,采用分子生物学方法鉴定病原菌,牛津杯法测试8种药剂对黑斑病病原菌的抗菌活性,测定8种药剂对黄单胞杆菌和成团泛菌,2种病原菌的室内毒力。结果表明：对2种病原菌均有抑菌活性的是3%噻霉酮、72%农用链霉素和16%苯甲·中生,其中3%噻霉酮和72%农用链霉素对成团泛菌和黄单胞杆菌的EC₅₀分别为3.89、9.97 mg/mL和4.93、14.94 mg/mL,有着较强的抑制作用。     

冬枣溃疡病病原初步鉴定

2003~2004年在山东省滨州市沾化县、无棣县等冬枣产区调查发现,冬枣生长前期在枣吊和叶片上发生了一种细菌性新病害。通过对典型病害样本进行病原菌分离、纯化获得20个菌株。从中选出4个菌株进行致病性测定,同时对其细菌形态、培养性状、染色反应、生理生化测定及血清学反应等性状进行了较为系统研究。结果表明,该地区冬枣溃疡病是由油菜黄单胞Xanthom onas campestrisPamm e(Dowson,1939)侵染引起的。