大豆茎溃疡病菌子囊壳诱导及孢子萌发方法探索

大豆茎溃疡病是为害大豆的重要病害,世界上十大大豆生产国中已有7个国家发现大豆茎溃疡病菌的分布,对当地农业造成严重威胁[1]。该病是我国进境植物检疫性有害生物[2],目前没有发生为害的报道。大豆茎溃疡病菌以菌丝和子囊壳在大豆植株及其残体上越冬,子囊壳在干燥35 d     

CLIMEX-GIS预测大豆北方茎溃疡病菌在中国的潜在分布

大豆北方茎溃疡病菌是大豆的重要病原菌,广泛分布于世界主要大豆产区,造成严重的产量和品质损失。本文应用生物模型CLIMEX结合GIS软件预测大豆北方茎溃疡病菌在中国的适生区,并根据EI值划分相应的适生等级。结果表明,大豆北方茎溃疡病菌在我国绝大部分地区适合生长,其中东北地区、华北地区和云贵高原地区处于中适生区或高适生区。该菌在我国还未报道,通过分析其在我国潜在分布区对于防止病菌的传入、传播和蔓延有重要的检疫意义。     

加拿大进境燕麦种子中大豆北方茎溃疡病病菌的检疫鉴定

从来自加拿大的燕麦种子中分离到3株可疑真菌,经形态特征鉴定、分子生物学鉴定及致病性测定,确定截获的3株真菌均为大豆北方茎溃疡病病菌(Diaporthe phaseolorum var.caulivora)。这是我国口岸首次从进境的燕麦种子中截获该病菌。     

基于MAXENT的大豆南北方茎溃疡病菌在中国适生区的预测

利用MAXENT生态位模型和GIS系统,对大豆南北方茎溃疡病菌在我国的适生区进行预测.模型分析结果表明,这两种病菌在我国的潜在适生区域广泛.大豆北方茎溃疡病菌除了我国的宁夏、海南省外,其它省市均有该菌的适生分布区,其中适生等级高的地区主要在江苏、安徽、浙江、上海、江西和湖北6省.大豆南方茎溃疡病菌除了宁夏、青海、西藏外,我国的其它地区均为该菌的潜在适生区域,其中适生等级高的地区主要集中在江西、上海、江苏、安徽、浙江、河南以及陕西南部、四川东部和重庆的部分地区.     

引起大豆苗期根腐病的大豆拟茎点种腐病菌鉴定

对10个引起大豆根腐病的真菌分离物进行鉴定。结果表明,这些分离物形态学上与大豆拟茎点种腐病菌相似。用ITS通用引物进行PCR扩增,该菌株与拟茎点种腐病菌MP4PL11PS(GenBank登录号HQ130441.1)同源性达98%。因此,确定该菌株为大豆拟茎点种腐病菌。     

大豆南方茎溃疡病菌的分离与鉴定

在对美国进境大豆进行检疫时，从混杂的豆秆上发现并分离到了大豆南方茎溃疡病菌，通过形态学和分子生物学鉴定，确定该菌为Diaporthe phaseolorum（Cke．＆ Ell.）Sacc．var．meridionalis Morgan-jones。该病原菌是国外近年来在大豆生产中新发生的危险性病原真菌，国内未见报道。     

进境油菜籽中黑胫病菌和茎基溃疡病菌的检测

为准确鉴定从进境澳大利亚油菜籽样品中分离的真菌分离物,利用形态学特征、PCR检测、序列分析以及致病性测试等方法对分离物6382-43和6382-51进行了鉴定试验。结果表明,分离物6382-43的形态特征和油菜茎基溃疡病菌Leptosphaeria maculans相似,菌丝生长较慢,菌落边缘不规则,不产生色素。油菜茎基溃疡病菌特异性引物LmacF/LmacR检测为PCR阳性;ITS区序列和油菜茎基溃疡病菌的序列相似性为99.8%;接种幼嫩油菜子叶产生油菜茎基溃疡病的典型症状。分离物6382-51的形态特征和油菜黑胫病菌L.biglobosa相似,菌丝生长较快,菌落边缘规则,产生色素;油菜黑胫病菌特异性引物LbigF/LmacR检测为PCR阳性;ITS区序列和油菜黑胫病菌的序列相似性为100%;接种幼嫩油菜子叶产生油菜黑胫病的典型症状。根据分离物的形态特征、PCR检测结果、序列分析以及致病性测试结果,将进境澳大利亚油菜籽样品中的真菌分离物6382-43和6382-51分别鉴定为油菜茎基溃疡病菌Leptosphaeria maculans和油菜黑胫病菌L.biglobosa。     

加拿大进境油菜籽加工过程中油菜茎基溃疡病菌的检测与鉴定

从加拿大进境油菜籽中随机选取船载油菜籽、筒仓油菜籽、菜籽粕和下脚料4类加工过程的样品调查油菜茎基溃疡病菌的发生情况。结果表明,18份船载油菜籽、7份筒仓油菜籽和11份下脚料样品的油菜茎基溃疡病菌PCR检测都呈阳性,而8份菜籽粕样品全为阴性。3份阳性样品的病原菌分离、鉴定与致病性测试结果证实了PCR的检测结果。     

进境美国大豆中大豆茎褐腐病菌的截获

 从进境的美国大豆豆秆样品中分离到2株疑似大豆茎褐腐病菌Phialophora gregata的分离物247-8和8300-5,2株分离物在PGM培养基上菌落圆形,边缘规则,白色至暗褐色,表面隆起,粗糙,轮纹状。分生孢子卵形至椭圆形,无色,平滑,单胞,平均大小4.3 μm×1.9 μm。分生孢子梗具有瓶梗状结构,无色,无隔膜或有隔膜,大小(5~16)μm×(2~3) μm,呈桶型或长颈瓶型。特异性引物BSRIGS1/2、BSR1/2和Pgl/4分别扩增分离物247-8的DNA得到预期1 022 bp、483 bp和499 bp的产物;分离物8300-5的DNA经PCR扩增分别得到834 bp、483 bp和499 bp的预期条带。2株分离物的ITS区序列完全一致,与GenBank中大豆茎褐腐病菌(登录号AB190396、DQ459387、DQ459386和AF132804)的序列相似性为100%。人工接种大豆幼嫩植株茎基部均产生大豆茎褐腐病菌的典型症状。根据分离物形态特征、PCR检测、序列分析以及致病性测试结果,将进境美国大豆样品中的分离物247-8和8300-5鉴定为大豆茎褐腐病菌P. gregata。     

进境澳大利亚大麦夹杂油菜茎基溃疡病菌的检疫鉴定

采用常规平板分离法, 从进境澳大利亚大麦中夹杂的油菜籽上获得1株疑似油菜茎基溃疡病菌的菌株01829?通过致病性测定?形态学观察?特异性引物扩增?ITS序列比对分析, 对01829进行了种类鉴定?结果表明:菌株01829在PDA培养基上生长较慢, 菌落边缘不整齐, 产生大量分生孢子器和分生孢子; 采用特异性引物对LMR1-D和Lmb分别进行PCR检测, 结果均有预期扩增片段产生; 基于ITS序列构建的系统发育树中, 菌株01829和GenBank中其他油菜茎基溃疡病菌相关序列聚在同一分支; 菌株01829接种油菜子叶和茎基部, 在子叶和茎基部接种部位分别引起叶斑和凹陷溃疡斑?根据上述试验结果, 将菌株01829鉴定为油菜茎基溃疡病菌, 这是我国口岸首次从进境澳大利亚大麦中截获油菜茎基溃疡病菌?     

无患子枝干新病害-溃疡病病原鉴定

 无患子(Sapindus mukorossi Gaerth.)为无患子科无患子属的一种落叶乔木, 在东南亚各国、我国淮河以南各省及台湾省均有分布^[1]。无患子种仁富含油脂, 含油率高达40.7％, 因其树种树型美观, 秋季叶色金黄, 被广泛应用于城乡园林绿化中。     

Viability and release of Neonectria ditissima ascospores on apple fruit in Brazil

During European canker monitoring in an apple experimental orchard, 14 mummified fruit (two and three trees with 10 and four positive records in 2018 and 2019, respectively) showed perithecia. Perithecium production on apple fruit, confirmation of pathogenicity of Neonectria ditissima isolated from mummified fruit, and ascospore release from fruit tissues has rarely been reported, and their role in the epidemiology of European canker has been largely overlooked. Thus, the objectives of our study were to (a) prove the presence of both conidia and ascospores of N. ditissima in mummified fruit in an experimental field, confirming pathogenesis in different apple cultivars, and (b) monitor production of the two types of inoculum in infected apple fruit over time. Canker incidence in this orchard was 47% of trees with symptoms in 2018 and 48% in 2019. Molecular and morphological tests confirmed that the fungus detected in the mummified apple fruit was N. ditissima. Apple fruit with sporodochia and perithecia washed immediately after collection from the orchard showed conidia but no ascospores of N. ditissima. However, after 4 days’ incubation, perithecia on mummified fruit showed many ascospore cirri. Koch's postulates were fulfilled on apple plants and mature fruit. Fruit inoculated with N. ditissima released spores for over a year under Brazilian field conditions. The release of both spore types peaked in May (Brazilian leaf fall) and October (spring); release of conidia also peaked in February (early harvest). These results support our hypothesis that fruit can serve as primary inoculum for European canker in Brazilian apple orchards.     

Molecular Variability Within Diaporthe/Phomopsis helianthi from France

ABSTRACT Diaporthe/Phomopsis helianthi causes brown stem canker of sunflower (Helianthus annuus) and is responsible for considerable yield loss. This species shows considerable variation for morphological characters, growth, and pathogenicity. Molecular variability of two sample groups was assessed with amplified fragment length polymorphism (AFLP) markers. Isolates of the first sample were collected from infected sunflower tissues from the main regions in France where the crop is grown, whereas isolates from the second sample came from stems within a single field of sunflower. A soybean strain was taken as an outgroup for AFLP analyses. Within sample one, the greatest genetic distance among isolates was 0.97, whereas it was 0.44 within sample two isolates. For the whole of France, the average genetic distance was 0.68, whereas in the one field it was 0.12. Nei's genetic diversity indices were 0.20 and 0.06 for France and for one field, respectively. The greatest genetic distance was found between isolates from the most northern crops. The greatest genetic distance between D. helianthi isolates and the strain isolated from soybean was similar to that observed for D. helianthi isolates from different geographical areas. The problems in defining the genus Phomopsis are discussed. It is shown that internal transcribed spacer sequencing could be a useful criteria for Diaporthe/Phomopsis species determination. The considerable genetic variability of the pathogen could lead to the occurrence of new strains that could be more aggressive or more resistant to chemical control.     

麦类赤霉病菌在水稻上存活的进一步研究

 本文报道浙江省北部的麦-早稻-晚稻的三熟制地区,麦类赤霉病菌在麦收后能侵染早、晚稻的穗部和稻株基部叶鞘。经取样测定,8块田的平均穗感染率20.63%,谷粒感染率为5.51%,稻株基部感染率为19.38%。这一结果进一步证实翌年早春稻桩产生的玉米赤霉子囊壳,是在晚稻生长后期已被该菌侵染所致。除外,在水稻上还分离到弯角镰孢、同色镰孢和单阳镰孢。本试验采用小麦粒、琼脂培养基作为诱发镰孢属菌株产生分生孢子和禾谷镰孢的有性世代子囊壳,在菌株鉴定中有很好的实用价值。     

Geostatistical analysis of the distribution of Leptosphaeria species causing phoma stem canker on winter oilseed rape (Brassica napus) in England

In June/July 2001, 2002, 2003 and 2006, regional variation in distribution of the pathogens Leptosphaeria maculans and L. biglobosa that are causally associated with phoma stem canker was surveyed on winter oilseed rape crops in England. In 2001–2003, when isolates from basal cankers were visually identified as L. maculans or L. biglobosa based on cultural morphological characteristics, 70% were L. maculans and 30% L. biglobosa . In 2001, 2002, 2003 and 2006, when amounts of DNA of each species in basal cankers were determined by quantitative PCR, the abundance of L. maculans DNA was greater than that of L. biglobosa DNA in 77% of samples. When regional differences in amounts of L. maculans and L. biglobosa DNA were mapped geostatistically, quantities of L. maculans DNA were greater in cankers from southern England and those of L. biglobosa DNA were greater in northern England. A comparison with geostatistically mapped predictions made using a weather-based model describing stages in development of phoma stem canker epidemics suggested that these differences in Leptosphaeria populations may have been a consequence of differences in temperature after onset of leaf spotting between northern and southern England. Both PCR and morphological evidence suggested that the abundance of L. maculans in England has increased since the last surveys in the 1980s. Implications of these surveys for control of phoma stem canker are discussed.     

Morphological and molecular characterization of <Emphasis Type="Italic">Diaporthe (</Emphasis>anamorph <Emphasis Type="Italic">Phomopsis)</Emphasis> complex and pathogenicity of <Emphasis Type="Italic">Diaporthe aspalathi</Emphasis> isolates causing stem canker in soybean

The complex of Diaporthe (asexual morph) species occurring on soybean constitutes an important pathogenic group associated with diseases such as pod and stem blight, seed decay and stem canker. Stem canker, caused by Diaporthe aspalathi, has been reported as the most aggressive form of canker and its occurrence has limited soybean crop productivity in the southern United States. The main form of pathogen control is the use of stem canker resistant soybean varieties. In this study, strains of Diaporthe and Phomopsis were isolated from stem and seeds of soybean in different locations in South America during the years 1989–2014. Genomic DNA from 26 isolates were analyzed by PCR-restriction fragment length polymorphism (RFLP) and Amplified Fragment Length Polymorphism (AFLP) techniques, and sequencing of internal transcribed spacer (ITS) regions of ribosomal DNA. The molecular analysis of ITS sequences by alignment with those of ex-type strains deposited in GenBank and morphological characteristics allowed the identification of Phomopsis longicolla, D. phaseolorum var. sojae, D. caulivora and D. aspalathi. An analysis of the pathogenicity of 13 isolates of D. aspalathi inoculated in soybean genotypes carrying different resistance genes to stem canker (Rdm1, Rdm2, Rdm3, Rdm4, Rdm5 and Rdm?) enabled us to identify the occurrence of at least three races of D. aspalathi occurring in Brazil. Among the isolates identified as D. aspalathi, both molecular and phenotypic analyses showed clustering depending on the date of collection and pathogenicity, which revealed the existence of variability of the pathogen.     

Effects of Severity and Timing of Stem Canker (Leptosphaeria maculans) Symptoms on Yield of Winter Oilseed Rape (Brassica napus) in the UK

The relationships between yield loss and incidence (% plants with stems affected) or severity (mean stem score, 0–4 scale) of stem canker in winter oilseed rape were analysed using data from experiments at Rothamsted in 1991/92, Withington in 1992/93, Boxworth in 1993/94 and Rothamsted in 1997/98. Critical point models and area under disease progress curve (AUDPC) models were better than multiple point models for describing relationships between yield (tha^–1) and incidence or severity of stem canker for the four experiments. Since yield is influenced by many factors other than disease, % yield loss was calculated and critical point models and AUDPC models relating % yield loss to stem canker were constructed. The critical point models for % yield loss on stem canker incidence for three of the four experiments were similar, but differed from that for Rothamsted in 1991/92. There were also no differences between models of % yield loss on AUDPC of both incidence and severity for these three experiments. Therefore, general models of % yield loss (L) against AUDPC of incidence (X) or severity (S) of stem canker from growth stages 4.8 to 6.4 were derived from the combined data sets for the three experiments: L=–0.76+0.0075X (R²=35%, p<0.001), L=0.26+0.53S (R²=37%, p<0.001). The relationships between % yield loss and % plants with different stem canker severity scores at different growth stages were also analysed; the greatest yield losses were generally associated with the largest severity scores, for plants assessed at the same crop growth stage, and were also associated with the early development of stem lesions. Further analyses showed that % yield loss was related to incidence or severity of both basal stem cankers and upper stem lesions in experiments at Boxworth in 1993/94 and at Rothamsted in 1997/98.     

噻唑膦在不同介质不同pH条件下热贮稳定性

噻唑膦加工后的稳定性是剂型选择的关键,为了提高其稳定性,延长其持效期,本研究通过噻唑膦在几种介质中的热贮稳定性试验,研究了酸碱度及介质对噻唑膦化学稳定性及稳定剂环氧大豆油对噻唑膦水乳剂热贮稳定性的影响,从而探索出噻唑膦在不同介质中稳定的最佳pH范围。研究结果发现,噻唑膦在同一pH下不同介质中的稳定性表现为硅藻土膨润土水乳剂,当pH为4.5时噻唑膦的稳定性最佳,而且加入0.2%的环氧大豆油做稳定剂可使噻唑膦在水乳剂中的分解率控制在10%以下。总之噻唑膦在酸性介质中较稳定,在硅藻土和膨润土中的稳定性要高于水乳剂中的稳定性。     

一种值得关注的花生新病害：花生新赤壳菌基腐病

2010年在我国广东省首次报道了由侵管新赤壳菌(Neocosmospora vasinfecta)侵染引起的花生新赤壳菌基腐病.罹病花生植株萎蔫、植株茎基部和根系变黑腐烂,在潮湿条件下,罹病部位有浅红色子囊果.这是我国大陆首次报道的花生新病害.该病害在广东省的多个市县有发生,严重的发病率高达30％.除广东省外,该病在我国江西省也有分布和危害,其致病菌可进一步鉴定为侵管新赤壳菌非洲变种(N.vasinfecta var.africana).在广东省也发现了由侵管新赤壳菌侵管变种(N.vasinfecta var.vasinfecta)引起的大豆茎枯病.对侵管新赤壳菌的文献进行了简要的综述.