Development of Stem-base Pathogens on Different Cultivars of Winter Wheat Determined by Quantitative PCR

The progress of development of stem-base pathogens in crops of second winter wheat was plotted in nine experiments in three years. The amount of each pathogen present was determined by quantitative PCR. Where Tapesia yallundae was present in quantifiable amounts, it usually developed earlier than the other eyespot pathogen, T. acuformis. Both species were usually present in greater amounts on cultivars which are more susceptible to eyespot. The sharp eyespot pathogen, Rhizoctonia cerealis, developed more erratically than either of the Tapesia spp. and there were no consistent effects on different cultivars. Fusarium spp., the cause of brown foot rot, were rarely present in quantifiable amounts, but Microdochium nivale was usually present as one or both of the varieties nivale and majus. Late-season (after anthesis) decreases in M. nivale suggest that any brown foot rot symptoms attributable to this fungus would have fully developed earlier. Cultivar differences in amounts of M. nivale were most clear in stems during internode extension and when relatively large amounts of DNA were present. Such differences approximately reflected eyespot susceptibility, cv. Soissons containing most and cv. Lynx containing least DNA. The results emphasise the difficulty in relating diagnoses, by quantitative PCR or other means, at early growth stages when decisions to apply fungicides against stem-base disease are made, to later disease severity.     

Identification and pathogenicity of Neophysopella species associated with Asian grapevine leaf rust in Brazil

Asian grapevine leaf rust (AGLR) causes severe crop losses in Brazilian viticulture, mainly in latitudes <25°S. The purpose of this study was to identify the pathogen(s) involved with AGLR in Brazil, based on phylogenetic and morphological analysis and pathogenicity tests. In total, 56 monouredinial isolates from six Brazilian states were identified using the internal transcribed spacer 2 and the large subunit rRNA gene D1/D2 regions. All 50 isolates from the south-central region were classified as Neophysopella tropicalis, and the other six isolates from the north-east region as Neophysopella meliosmae-myrianthae. This result provides evidence that two pathogen introductions from different sources may have occurred in the country. For both species, paraphyses were cylindrical, incurved, aseptate, and hyaline, while urediniospores were short-pedicellate, obovoid or obovoid-ellipsoid, with the wall colourless or pale yellowish, evenly echinulate. Representative isolates from both species caused typical AGLR symptoms on Vitis vinifera 'Merlot' and V. labrusca 'Niagara Rosada'. Overall, regardless of the Neophysopella species, isolates caused similar leaf disease severities. Higher disease severity was observed in Niagara Rosada (average of 40.3% of diseased leaf area) compared to Merlot (20.5%). This study reports, for the first time, the characterization of Neophysopella species associated with AGLR in Brazil.     

Isolation and characterization of Streptomyces species from potato common scab lesions in Norway

The present survey was conducted to isolate and characterize Streptomyces species from common scab lesions of potato in Norway. Bacteria were isolated from scab lesions on tubers sampled in two consecutive years at different locations in Norway spanning ～1400 km from south to north. In total, 957 independent isolations from individual tubers were performed, with 223 putative pathogenic isolates obtained from 29 different potato cultivars and 130 different fields. Streptomyces europaeiscabiei was the most abundant species isolated from common scab lesions (69%), while 31% of the isolates obtained were S. turgidiscabies. Streptomyces scabies was not found. Pathogenicity of selected Streptomyces isolates was tested on potato. The ability of the bacterial isolates to infect potato was consistent with the presence of the txtAB operon. The results revealed no pattern in geographical distribution of S. europaeiscabiei and S. turgidiscabies; both could be found in the same field and even the same lesion. Four different pathogenicity island (PAI) genotypes were detected amongst the txtAB positive isolates: nec1+/tomA+, nec1–/tomA+, nec1+/tomA? and nec1?/tomA?. The current findings demonstrate that there is genetic variability within species and that the species are not spread solely by clonal expansion. This is thought to be the most comprehensive survey of Streptomyces species that cause common scab of potato in a European country.     

一种对桃小食心虫高毒力的斯氏线虫Steinernema sp.(CB-2Y)

本研究在室内用“沙埋法”比较了两种斯氏属昆虫病原线虫Steinernema sp.(CB-2Y)和S.feltiae Agriotos对桃小食心虫的侵染力,结果表明CB-2Y线虫对桃小食心虫幼虫和冬茧的侵染力都高于Agriotos线虫。接线虫笫7天桃小食心虫LD50,CB-2Y组为49条线虫,而Agriotos组为158条;冬茧的LD50分别为1330条和24046条。在桃小冬茧开始活动期(6月15日)分别施用两种线虫,一个月后检查桃小食心虫成虫羽化率,CB-2Y线虫的控制效果明显优于Agriotos,在1024条线虫/桃小食心虫冬茧时(75条/cm~2),越冬代桃小食心虫的羽化率分别为8.2％和29.2％。     

木霉对植物的促生及诱导抗性研究进展

木霉不仅能够直接抑制植物病原菌的生长,还可通过定殖于植物的根部引起植物新陈代谢的改变。本文综述了木霉在植物根部定殖后,通过产生植物生长调节剂、抑制或降解根际有害物质、增加养分利用率以促进植物生长以及通过产生激发子诱导植物形成胞壁沉积物、合成抗菌物质以诱导植物局部或系统抗性的研究进展,以期为进一步扩大木霉在农业生产中的应用提供参考。     

几种农药对草原毛虫的防效试验

采用喷雾法,用几种农药对草原毛虫进行防治,结果表明,生物源农药瑞·苏1.2%微乳剂对草原毛虫,速效性较好,持效期长,药后7~14d防治效果保持在80%~90%。     

应用生物防治棉蝗及星天牛——沿海防护林木麻黄病虫害综合控制技术研究报告

本研究筛选出蝗虫微孢子虫、蜡状芽孢杆菌及簇孢霉等微生物杀虫剂,并应用于防治棉蝗的感染率达77% 以上;应用从星天牛中分离的白僵菌防治星天牛,感染率达77.8% ;应用芜菁夜蛾线虫和蠹蛾线虫防治星天牛,感染率达90% 以上。为沿海防护林木麻黄病虫害的综合控制提供科学依据。     

侵染梨的苹果茎痘病毒基因组序列及小RNA分析

苹果茎痘病毒(Apple stem pitting virus,ASPV)是危害梨(Pyrus spp.)和苹果(Malus spp.)的重要病毒。本研究采用小RNA深度测序技术获得了ASPV基因组的部分序列,在此基础上设计引物对该病毒基因组进行RT-PCR扩增,通过序列拼接得到1个来源于玉露香(Yuluxiang)梨的ASPV分离物(YLX)长度为9 291个核苷酸(nt)(不包括基因组5'末端约30个核苷酸)的基因组序列,该序列与已报道的13个ASPV分离物的基因组核苷酸序列相似性为71.6%~80.7%,与多个来自苹果的ASPV分离物系统进化关系较近。首次分析了来源于ASPV基因组的干扰性小RNA(siRNA),发现来源于ASPV基因组链和互补链的siRNA长度均以21 nt和22 nt为主,siRNA的5'端具有一定的碱基偏好性。本研究结果为深入了解ASPV的分子特性提供了重要信息。     

赤眼蜂寄生行为研究（Ⅳ）—子代数量分配和子代性分配

本文在对赤眼蜂性控行为研究的基础上〔3〕,进一步探讨了不同种赤眼蜂在同一种寄主不同分布以及同一蜂种(松毛虫赤眼蜂 Trichogramma dendrolimi)在不同种寄主上的子代数量分配和子代性分配问题。研究结果表明,赤眼蜂具有根据寄主卵体积大小分配及调整其子代数量和子代性别的能力,在不同体积的寄主上具有明显不同的子代数量安排策略和子代性安排策略。在同一种寄主卵上,不同种的赤眼蜂对子代性分配的安排存在着较明显的种间差异.在米蛾卵上,松毛虫赤眼蜂的第一雄卵主要在其第一产卵序产出,稻螟赤眼蜂的第一雄卵主要在其第二产卵序产出,拟澳洲赤眼蜂产第一雄卵的位置比较分散,主要分布在前三卵序。松毛虫赤眼蜂大约每产6粒雌卵而产1粒雄卵;稻螟赤眼蜂和拟澳洲赤眼蜂大约每产5.33和3.37粒雌卵而产1粒雄卵(见表2).寄主卵的体积不同,雌蜂在不同寄主上所分配的子代数量也明显不同。松毛虫赤眼蜂在每粒米蛾卵上只安排1粒蜂卵;在每粒马尾松毛虫卵上平均安排18.64粒蜂卵;在每粒“人造卵”上平均安排33.15粒,在柞蚕卵上平均安排77.43粒蜂卵(见表3)。随着寄主卵体积的增大,雌蜂产第一雄卵的时间后移,在松毛虫卵上,松毛虫赤眼蜂雌蜂在产下第一粒雄卵后,大约以每产16粒雌卵而产1粒雄卵;在柞蚕卵上,大约每隔15粒雌卵产1粒雄卵;在“人造卵”上,产雄卵的间隔大约为9粒雌卵。