桉树无性系抗青枯病性能的测选初报

用WFT接种技术对47个桉树无性系进行了对青枯病的抗性测定 ,通过青枯病株率计算和逐步聚类分析 ,认为31个无性系是抗病品系 ,10个无性系是感病品系 ,6个无性系是高感品系。在31个无性系抗病品系中 ,经生产实践证明 ,其中MLA、ZU6、W5、LH1、LH2、LH3、SH1、M1等8个无性系显示出很强的抗病性 ,至今未发生青枯病株。大面积推广应用优良抗病无性系造林 ,防治桉树青枯病的大面积发生 ,目前已取得初步成效。     

Involvement of gacA Gene in the Suppression of Tomato Bacterial Wilt by Pseudomonas fluorescens FPT9601

Pseudomonas fluorescens FPT9601, a plant growth-promoting rhizobacterium (PGPR) isolated from tomato rhizosphere, can protect tomato (Lycopersicon esculentum Mill) from bacterial wilt disease caused by Ralstonia solanacearum. This strain produces antibiotics 2,4-diacetylphloroglucinol (2,4-DAPG) and hydrogen cyanide (HCN). It also produces proteases and uncharacterized siderophores (Sid). A mutant strain SM2214, obtained by Tn5 insertion, did not produce 2,4-DAPG, HCN or proteases, but overproduced Sid. Marker-exchange mutagenesis confirmed that a single transposon insertion caused the multiple phenotypic changes of this mutant. Complementation of the mutant with a 1.3-kb DNA fragment that was amplified from genomic DNA of the wild-type P. fluorescens strain by PCR could restore the lost functions of the mutant strain. Nucleotide sequencing revealed that the fragment contained a 642-bp open reading frame (ORF) highly homologous to the regulator responser gene gacA. The in vitro anti-bacterium test and plant protection experiment under greenhouse conditions indicated that the gacA gene played an important role in the suppression of tomato bacterial wilt disease. Received 20 November 2000/ Accepted in revised form 19 January 2001     

烟草青枯菌FQY_4的抗生素类抗/耐药性相关基因分析

为探明烟草青枯菌基因组中抗/耐药性基因作用机理。在烟草青枯菌FQY_4基因组测序的基础上,结合培养青枯菌的半选择性培养基中抗生素的使用,采用基因注释及同源基因比较法,分析青枯菌FQY_4基因组携带的抗/耐药性相关基因。结果显示:青枯菌FQY_4染色体上和巨大质粒上分别有6个和12个与多抗/耐药性相关的基因,包括多粘菌素耐药蛋白基因、膜融合蛋白CmeA基因、二甲基腺苷转移酶基因、膦胺霉素耐药性蛋白基因、外膜多耐药性系统相关基因和抗四环素基因序列。     

Control of tomato bacterial wilt and root-knot diseases by Bacillus thuringiensis CR-371 and Streptomyces avermectinius NBRC14893

Ralstonia solanacearum and Meloidogyne incognita are two soilborne pathogens that cause serious damage and great losses in the production of tomato. For this purpose, a bacterial isolate, Bacillus thuringiensis CR-371, and an actinomyces isolate, Streptomyces avermectinius NBRC14893, were examined for their ability to protect tomato from root-knot nematode and bacterial wilt diseases under glasshouse conditions. Treatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 followed by challenge inoculation with R. solanacearum and M. incognita significantly decreased disease severity of bacterial wilt alone, root-knot nematode alone, or mixed infection by both pathogens compared to the control. Furthermore, pretreatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 significantly reduced bacterial proliferation of R. solanacearum both in pathogen alone inoculated plants and in plants co-inoculated with R. solanacearum and M. incognita. In conclusion, our results suggest that the treatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 simultaneously suppresses bacterial wilt and root-knot nematode diseases. Therefore, B. thuringiensis CR-371 and S. avermectinius NBRC14893 could provide new options for integrated pest management strategies against plant diseases, especially against bacterial-nematode disease complexes that cause synergistic yield losses.     

影响木麻黄青枯病抗性测定的几项因素的研究

木麻黄无性系对青枯假单胞杆菌的抗病性测试受到植物材料、接种条件及病级测定三方面因素的影响。研究表明在无根苗与有根苗上病害的发生具有一致性特征，并且与高度相关，但无根苗更为感病。在三种龄期的无根苗中，以木质化的褐梗最为感病，绿梗次之，嫩枝较为抗病。青枯菌在连续培养１４天后接种致病力不减。病害的相对强度在直射光、散射光及灯光等三种光照条件下无明显区别。病害强度随着接种浓度的增加而增高，但当达到一定程度后便趋缓。研究认为在室内以中等浓度的青枯菌液接种木麻黄无根褐梗苗是快速测定其抗性的一个可靠方法，并就采用相对病害强度代替发病株率作为病级指标等问题进行了讨论。     

不同浓度抗菌肽对辣椒青枯病菌抑菌活性的研究

实验室条件下研究不同浓度抗菌肽对辣椒青枯病菌的抑菌活性及药效结果表明:不同浓度抗菌肽均有抑菌作用且效果稳定。以浓度为2.5 mg/L时增效作用最明显,EC50为69.533 0 mg/L;其次是1.4 mg/L,EC50为226.376 1 mg/L;1.0 mg/L对辣椒青枯病菌的抑制活性较低。     

拮抗番茄青枯病菌株的筛选及生防试验

从广东省不同地方不同作物的根围及根际土壤中筛选到番茄青枯病病菌具抑菌效果的菌株２０个。盆栽试验表明,这些菌株可推心茄青枯病发生１０－３５天,防治效果高达８０％     

防治番茄青枯病内生细菌的分离与筛选

从番茄健株根内分离获得内生细菌 ,对其进行平板拮抗番茄青枯菌试验 ,得到 18株拮抗菌。温室控病试验表明 ,0 1 144和 0 1 182号菌株的控病效果分别为 48.6 %和 42 .8%,经鉴定两者均属芽孢杆菌属 (Bacillsspp)。     

青枯菌胞外酶对木麻黄的致病作用研究

对三个致病性不同的木麻黄青枯菌ＰｓｅｕｄｏｍｏｎａｓｓｏｌａｎａｃｅａｒｕｍＥ．Ｆ．Ｓｍｉｔｈ产生的胞外酶活性测定显示,聚半乳糖醛酸酶（果胶酶）活性在各菌株之间无明显差别,但纤维素酶活性差别明显,并随菌株的致病性上升而增加,菌株致病性与酶活性具有高度正相关（ｒ＝０．９６）。