Erwinia amylovora populations resistant to oxolinic acid in Israel: prevalence, persistence and fitness

Oxolinic acid (OA) has been the only bactericide used against fire blight in pear and quince orchards in Israel since 1998. OA-resistant Erwinia amylovora strains (Ea-OA^R) were detected in several orchards in two restricted areas in the northern Galilee region during 1999–2001. In the following years, resistant strains could not be detected in some of these locations. Documenting the fate of Ea-OA^R strains in commercial orchards at eight sites in northern Israel during 2000/03 revealed that the resistant population appeared irrespective of the number of sprays applied and the severity of the disease. The persistence of the Ea-OA^R populations varied from site to site, ranging from 4 to 20 months; these differences could be attributed to the fire blight management activities of growers. Comparative studies on the fitness of Ea-OA^R and E. amylovora strains sensitive to OA (Ea-OA^S) were conducted in vitro and in planta using two strains of each group. In four of the six comparisons, disease incidence on detached blossoms inoculated with Ea-OA^S was significantly higher than that on blossoms inoculated with Ea-OA^R. In two experiments conducted on 8-year-old pear trees grown under netting, the colonization of Ea-OA^S in blossoms, annual shoots and perennial spurs was significantly higher than that of the Ea-OA^R. In two experiments conducted on 2-year-old trees grown under netting in an experimental station, the incidence of shoots exhibiting fire blight symptoms and the rate of symptom progress within the branches were significantly higher in trees inoculated with Ea-OA^S than in those inoculated with Ea-OA^R. The results of this study suggest that OA-resistant E. amylovora strains have lower fitness than wild-type strains. These findings may have implications for fire blight management.     

戊唑醇在苹果和土壤中的残留分析方法

本文建立了戊唑醇在苹果和土壤中残留的液相色谱分析方法.该方法仪器最低检出量为4×10-11g;最低检出浓度为0.002mg/kg;平均回收率为85.6%～102.2%;变异系数为2.85%～9.47%。     

Characterization of an endopolygalacturonase Gene cppg1 from Phytopathogenic Fungus Chondrostereum purpureum

Chondrostereum purpureum, a phytopathogenic fungus, produces endopolygalacturonase (endoPG) which has been suggested to have a causal role in the silver-leaf symptom of apple trees. In this paper, we detected C. purpureurn-derived endoPG at the infection sites using ELISA with a polyclonal antibody against endoPG I. A gene encoding endoPG I and its homolog were also isolated from the C. purpureum genome. The endoPG I gene was designated as cppg1. The cppg1 gene is the first fungal endoPG gene reported in the Basidiomycetes. Received 31 May 2000/ Accepted in revised form 13 September 2000     

山东苹果主要病虫害化学防治技术

山东省苹果园害虫优势种群是蚜虫、桃小食心虫、苹小卷、金纹细蛾、害螨等 ;病害主要是斑点落叶病、轮纹病。根据不同病虫害的发生发展规律和烟台农科院多年来的化学防治试验研究 ,明确了不同苹果品种上适用的有效药剂和不同药剂的杀虫 (菌 )谱、用药适期、施药方法 ,制定了相应的防治策略 ,提出了合理用药、交替施药和安全喷药等诸多注意事项     

苹果斯氏刺瘿螨发生与危害调查

斯氏刺瘿螨是四川省苹果上新发现的一种危害苹果叶片的害螨，以雌成螨在苹果芽的芽腋两侧越冬，翌年苹果芽萌动时开始出蛰。全年以５月中旬至６月中旬发生数量最多。气候温暖、低湿、少雨发生重，相反则轻。在调查的８个品种中，叶片多茸毛的品种受害重。天敌主要为捕食螨     

山东、辽宁、河北苹果蠹蛾分布调查研究报告

苹果蠹蛾[Laspeyresia pomonella(L.)]是世界上为害苹果和梨的主要蛀果害虫,被许多国家和我国列为植物检疫对象。该虫在我国现仅分布于新疆。英联邦昆虫研究所(Common-wealth institute of entomology,C.I.E.)(1951,1976)根据陈方洁、王飞鹏(1936)及胡经甫(1938)的记述,将我国浙江(奉化)、河北、湖北、东北三省(辽宁、吉林、黑龙江)、北平(北京)及新疆等8个省、市、自治区划分为该虫分布区,从而严重影响我国苹果及梨的出口和外销。为了查清该虫在我国的分布情况,首先核对并纠正 C.I.E.制图所依据的上述两篇文章的错误,同时在张从仲等(1984—1985)在山东、辽宁等8省市大面积进行的苹果蠹蛾性诱剂监测的基础上,于1991年4—10月在山东、辽宁、河北苹果和梨主要产区及出口基地继续进行苹果蠹蛾性诱剂监测、果园调查及剖果检查,结果均未发现苹果蠹蛾成虫或幼虫。到目前为止,此虫仍局限分布于我国新疆。     

生草园捕食性天敌东亚小花蝽的人工操纵技术

在北京巨山农场果园中，分别在６月初和６月中旬，刈割苹果树行间的紫花苜蓿并将其放在树冠下后，东亚小花蝽既向割草区周围的紫花苜蓿上扩散，也向割草区苹果树上迁移。割草后３天，割草区周围紫花苜蓿上小花蝽数量增加２０％～１１９％，其增加量随距割草区距离的增加而减少，割草区苹果树冠上小花蝽数量比割草前增加２～３倍，蝽螨比可提高１４倍，树冠小花蝽增加的数量受小花蝽扩散能力和割草时间的影响。试验结果表明，适时刈割苹果园中的紫花苜蓿，对控制害螨有明显的作用     

苹果砧木M26离体叶片愈伤组织发生及分类研究

对苹果砧木Ｍ２６ 离体叶片愈伤组织的发生研究表明,取继代后３０ ～３５ ｄ 的试管苗顶部１～４ 叶位的叶片,沿与主脉垂直方向横切后,以叶背面朝上方式置于愈伤组织诱导培养基上,经观察在叶片近柄端切口处愈伤组织发生较早,产生量较多。最适的愈伤组织诱导培养基为：ＭＳ＋２ ,４ － Ｄ０ ．２ ～２ ．０ ｍｇ·ｌ－ １ ＋ＩＡＡ０ ．２ ～２．０ ｍｇ·ｌ－ １ ＋ ＢＡ０ ．５ ～１．０ ｍｇ·ｌ－ １ ＋ 蔗糖３ ％ ＋ 琼脂０．６％ 。将诱导产生的愈伤组织按外部形态、细胞特点及生理生化指标等分为三类,其中表面干燥致密、细胞内含物丰富、淀粉、蛋白质及干物质含量均较高的Ⅲ类愈伤组织的芽再生频率最高,可达８３ ．３３ ％ ,是能利用的愈伤组织类型。     

Protective Effects Against Erwinia amylovora Induced by hrp Mutants in the Whole Plant are Only Partially Mimicked in Cultivated Cells

A virulent strain of Erwinia amylovora, the causal agent of fire blight of Maloideae, and two of its non-virulent hrp mutants (a secretory and a regulatory mutant) were inoculated into apple cell suspensions either alone or in mixed inoculations. In single inoculations, death of 4- to 5-day-old apple cells occurred only when the concentration of the virulent strain of E. amylovora reached a threshold inoculum concentration of 10⁴CFUml^–1, while high concentrations of the hrp mutants were unable to kill apple cells. When mixed inoculated with the virulent parental strain, both hrp mutants protected apple cells from death caused by the virulent strain. The protective effect was associated with a decrease in the population level of the virulent strain and it was dependent on the non-virulent to virulent inoculum concentration suggesting a competition between the non-virulent mutant and the virulent strain. However, no differential protective ability between the two types of mutants could be noticed, contrary to previous results obtained with apple seedlings or apple flowers in which the regulatory mutant was significantly more effective than the secretory mutant. In conclusion, inoculation of apple cell cultures with E. amylovora does not seem to be a model suitable for investigating mechanisms leading to protection.     

渭北旱塬优质苹果种植的农业地质环境特征

渭北旱塬是我国苹果种植的最优气候区。以白水县为例，通过对其气候适生区内果园地质条件的对比分析，寻找出了具体地质要素间的差异，归结出了两类气候区内地貌、土壤母质类型、母质矿物质含量三类要素的组合类型，为进一步探讨地质条件对苹果品质的影响特征，细分气候优生区，促进该区苹果生产优质化提供依据。