栗疫菌营养体亲和型多样性比较及野生栗栗疫菌交配型的分子检测

在北京周边县区、湖北大老岭山区以及陕西安康地区分别调查栗疫病发生情况,采集病原栗疫菌(Cryphonectria parasitica)菌株并进行营养体亲和性试验.结果表明:北京板栗栽培区和陕西安康地区野生栗栗疫病发病率较高,局部地区危害严重;湖北大老岭山区栗疫病发病率低,危害轻微.北京地区菌株群体营养体亲和型多样性指数(Shannon-Wiener's diversity index)极显著低于湖北菌株群体和陕西菌株群体,而陕西与湖北菌株群体营养体亲和型多样性指数差异不显著.随机选取湖北、陕西野生栗栗疫菌部分菌株,利用特异性引物,通过普通PCR和巢氏PCR,对其交配型进行测定,发现陕西与湖北野生栗菌株群体中均存在MAT-1与MAT-2两种交配型的菌株.通过PCR扩增,在两地的野生菌株群体里均发现同时具有两种交配型基因的菌株,其中,陕西群体此类菌株比例较大,湖北菌株比例较小     

中国板栗品种对疫病的抗病性评价

通过在板栗离体枝条上接种栗疫病病原菌,对感染后的病斑进行观察,结果表明:不同板栗品种对疫病菌的感染程度不同,在供试的２１个品种和类型中,病斑较小的品种(类型)主要有北峪２号和兴隆城９号,其次为野生板栗、渤海所１８、燕魁、短花栗等７个品种和类型,以上品种抗病性较强,抗病性强的品种占供试品种的３３．３%;抗病性弱的品种有红光栗、怀黄、怀九等,抗病性弱的品种占取样量的３８．１%,以红光栗抗病性最弱,病斑面积显著地高于其它品种。不同生态品种群中均有抗性强的品种和抗性弱的品种。不同品种在感染病菌后对病菌的抗扩展能力不同:红光和怀黄品种的抗扩展能力最差,且病斑上病菌的分生孢子多;野生板栗的抗病性强,病菌侵染后有自愈现象;北峪２号和兴隆城９号感染病后病斑扩展速度显著慢于其它品种。通过试验把供试的品种分为抗性强品种、中度抗性品种。中度感病品种和抗性差的品种共４类。通过接种来源不同的毒性菌株,证明不同板栗品种对强毒性菌株的抗病性表现是一致的。     

Chestnut blight fungus in Croatia: diversity of vegetative compatibility types,mating types and genetic variability of associated Cryphonectria hypovirus 1

In order to improve understanding of its diversity, 338 isolates of Cryphonectria parasitica, the causal agent of chestnut blight, were sampled from 10 chestnut populations throughout chestnut‐growing coastal and continental areas of Croatia. Eighteen vegetative compatibility (VC) types were identified. The VC type EU‐1 was the most widespread, comprising 42·9% of the isolates, followed by EU‐2 (21%) and EU‐12 (14·2%). In respect to the occurrence of the main VC types, the C. parasitica populations in Croatia combined features of both northwestern and southeastern European populations. Perithecia and mating‐type ratios of approximately 1 : 1 were found in all populations, suggesting that sexual reproduction of the fungus is common in Croatia. Natural hypovirulence was also evident in all populations, with incidence of hypovirus‐infected isolates ranging from 12·7% in Istria‐Buje to 66·6% in the continental part of the country. A total of 36 hypovirus‐infected isolates sampled throughout Croatia were analysed in ORF‐A and ORF‐B by RT‐PCR/RFLP analysis. All viral isolates belonged to the Italian subtype of Cryphonectria hypovirus 1 (CHV‐1) and were closely related to the isolates found in other European countries. The RFLP patterns found were also identical or similar to the patterns of three isolates collected in Croatia 22 years ago, suggesting a slow evolution of the hypovirus.     

Characterization of mutants of the chestnut blight fungus (<Emphasis Type="Italic">Cryphonectria parasitica</Emphasis>) with unusual hypovirus symptoms

The type virus of the family Hypoviridae, Cryphonectria hypovirus 1 strain EP713 (CHV1-EP713), infects Cryphonectria parasitica, the filamentous causal fungus of chestnut blight, and reduces its virulence. This pathosystem serves as a model to study fungus-mycovirus interactions. We previously developed a genetic screening protocol for host factors associated with symptom induction by CHV1-EP713 and its mutants. In the procedure the standard field fungal isolate EP155 was transformed by cDNA from a mild hypovirus mutant Cys(72), launching virus infection, and mutagenized by random plasmid insertion with pHygR conferring hygromycin resistance. We now report an extension of the study to characterize different mutant strains, with different phenotypes than their parental strain TCys(72)-1. TCys(72)-1 is moderately reduced in pigmentation and sporulation compared to the uninfected wild-type strain EP155. Mutants sfb1, sfb2 and k202 were characterized biologically and molecularly in comparison to the previously isolated mutant (namA) and the parental strain. These mutants harbored one (sfb1) or more copies (sfb2 and k202) of the mutagenic plasmid, pHygR. The three mutants had similar biological attributes; that is, vegetative growth rate, conidiation and virulence (assay on apples) was reduced on potato dextrose agar media, relative to the parental strain and pigmentation was the same or slightly increased. Interestingly, viral dsRNA accumulation levels were apparently unaltered in these mutants. The screening method was efficient for mining fungal mutants with unusual hypovirus symptoms. Further, characterization of the mutants provides interesting insights into symptom induction by the hypovirus.     

不同抗性板栗品种的防御酶系对栗疫菌Cp-毒素的响应

对照.此外,抗病品种酶活性高于中抗品种和感病品种;防御酶的活性与品种抗病性之间呈正相关,毒素作用后防御酶活性的变化可作为衡量板栗抗病性强弱的指标.     

板栗疫病在广西区内的危险性分析

通过定性因素和定量指标体系相结合的方法对板栗疫病在广西的危险性进行评估,评估结果表明,此病害的危险性综合评价值为1.7128,属于中度危险性的林业有害生物。板栗疫病菌寄主范围广,此病在广西的分布已经相当广泛,但板栗疫病的病原菌不必补充为广西壮族自治区林业检疫性有害生物。通过采取栽培无病苗木、减少枝条和主干的伤口、削除枝条和主干的病斑和进行伤口的消毒、砍除重病枝等措施,可以有效地防治病害的发生。