PCR-based differentiation of Fusarium oxysporum ff. sp. lycopersici and radicis-lycopersici and races of F. oxysporum f. sp. lycopersici

The pathogenic type (form and race) of Fusarium oxysporum, which generates wilt symptoms on tomato, was rapidly identified with a polymerase chain reaction (PCR)-based technique. We compared the partial nucleotide sequences of endo polygalacturonase (pg1) and exo polygalacturonase (pgx4) genes from isolates of F. oxysporum ff. sp. lycopersici (FOL) and radicis-lycopersici (FORL) from Japan and designed specific primer sets (uni, sp13, sp23, and sprl) based on the nucleotide differences that appeared among the pathogenic types. PCR with the uni primer set amplified a 670∼672-bp fragment from all isolates of FOL and FORL. With the sp13 primer set, an amplicon of 445 bp was obtained only from isolates of FOL race 1 and 3. With the sp23 primer set, a 518-bp fragment was obtained from isolates of FOL race 2 and 3. The sprl primer set yielded a 947-bp fragment from isolates of FORL, but not from FOL. A combination of amplifications with these primer sets effectively differentiated the pathogenic types of F. oxysporum in tomato.     

尖镰孢酯酶同功酶的测定及其在专化型鉴定上的应用

对尖镰孢（ＦｕｓａｒｉｕｍｏｘｐｓｐｏｒｕｍＳｃｈｌ．）酯酶同功酶的测定结果表明：不同培养条件对尖镰孢酯酶同功酶有明显影响，其酶带数，酶带颜色深浅、宽窄和Ｒｆ值都有明显差异，以培养液成分和培养液偏碱时影响较大，培养温度和培养天数影响较小。在同一培养条件下重复测定同一专化型，酶谱表现稳定，没有差异。测定黄瓜、西瓜、瓠瓜、冬瓜、棉花和芝麻上的尖镰胞的酯酶同功酶谱明显不同。这个方法可用于鉴定尖镰胞的专化型。     

Stem rot of jewel orchids caused by a new forma specialis,Fusarium oxysporum f. sp. anoectochili in Taiwan

Stem rot of Anoectochilus formosanus (Af) caused by Fusarium oxysporum (Fo) is a major limiting factor to jewel orchid production in Taiwan. Fo causes discoloration in vascular tissues. However, some newly collected Fo isolates from Af stem rot do not cause vascular discoloration, suggesting changes may have occurred in the pathogen. Among recent Fo isolates from Af there are two colony types, the cottony alba (CA) and the sporodochial (S). In order to confirm that both colony types cause Af stem rot, 200 isolates were obtained from diseased stems in Nantou County and characterized by colony type and whether or not the infected plants had vascular discoloration. Isolates of both the CA and S types caused stem rot of Af; some isolates in each colony type caused vascular discoloration whilst others did not. Pathogenicity tests with 22 isolates resulted in stem rot disease severity ratings on Af of 3·1–4·0 and 2·1–4·0 with CA and S type colonies, respectively. The same isolates failed to cause disease on Cattleya, Dendrobium or Phalaenopsis plants. Phylogenetic analysis of partial intergenic spacer sequences showed that these isolates were distinguishable from other formae speciales of Fo and could be separated into two groups correlated with the CA or S type colonies with high bootstrap. Based on pathogenic, morphological and molecular characterizations, the Fo that causes stem rot of Af is proposed to be a new forma specialis, F. oxysporum f. sp. anoectochili, with different pathotypes.     

A Monitoring System for Green Fluorescence Protein Gene-transformed Fusarium oxysporum in Melon Seedlings

Using melon seedlings at the cotyledon stage and genetically marked fungi, a system for monitoring pathogenic and nonpathogenic Fusarium oxysporum was devised in the present study. Protoplasts were prepared from three formae speciales (melonis, radicis-lycopersici and fragariae )of F. oxysporum and transformed with a synthetic gene for green fluorescence protein. Transformants were primarily isolated in the presence of hygromycin B and then screened by the emission of bright green fluorescence. Roots of melon seedlings were inoculated with fluorescing microconidia of these fungi, and fungal infection behavior was traced. Using fluorescence microscopy, we directly observed not only the fungus at the root surface, but also the mycelia elongating in the trachea of roots. Both pathogenic and nonpathogenic fungi germinated and hyphae elongated superficially on the surface of root. Only pathogenic fungi caused root necrosis at the inoculation site. Hyphae grew within the stem to induce constriction or cracking of lower hypocotyls, then causing wilting of the seedlings. Infection behavior of genetically marked pathogenic and nonpathogenic F. oxysporum could be successfully monitored after inoculation of cotyledons of seedlings. Received 6 June 2001/ Accepted in revised form 3 August 2001     

黑杨应答杨生褐盘二孢专化型侵染的基因差异表达

[目的]杨生褐盘二孢的单芽管专化型和多芽管专化型分别引起白杨组和黑杨组(包括青杨组)杨树的褐斑病,其分化机制有待阐明。[方法]本文在专化性互作体系建立的基础上,利用荧光染色标记研究了病菌孢子在专化性寄主侵染过程中的萌发发育情况,并通过RT-qPCR分析了黑杨寄主抗病相关基因在应答两专化型侵染过程中的不同表达。[结果]结果发现多芽管分生孢子在黑杨寄主上能完成发育并成功侵染,单芽管分生孢子也能成功萌发和发育,但不能侵入黑杨寄主;黑杨抗性基因在两专化型侵染发育过程中均能被诱导表达,但在表达时间和表达量上,除基因WRKY89的表达较为一致外,病程相关基因PR5、PR10、NPR1和LAR3在二者间的表达存在差异。[结论]研究结果初步表明病原专化型可能是寄主与病原专性互作的表型,这一认识将有助于进一步探明杨树褐斑病病原专化型形成和分化的机制。     

甜瓜枯萎病菌（Fusarium oxysporum）专化型的初步研究

本研究获得的甜瓜枯萎病病株9株分离物（南通市6株,新疆3株）,经PDA培养性状发现,其在菌落颜色、质地和生长速率方面存在差异,大型分生孢子的大小为(19.54～41.11)μm×(4.90～8.16)μm,与西瓜枯萎病菌的大型分生孢子有较大差异。胚根法成株期致病性测定结果发现,本研究的甜瓜枯萎病菌分离物在不同鉴别寄主和鉴别品种上致病性存在专化型和生理小种方面的差异,但分离物中不存在西瓜枯萎病菌。利用核糖体转录间隔区保守序列设计引物,PCR检测也证明本研究甜瓜枯萎病菌不同分离物中不存在西瓜枯萎病菌。     

瓜类枯萎病发生机理研究进展

对国内外瓜类抗枯萎病的致病因子及其生理分化、致病机理、抗病机制、抗性遗传、抗性筛选等进行了综述，并对该领域存在的问题以及发展方向进行了讨论．     

山西省重要作物萎蔫病病原镰刀菌(Fusarium)种类的鉴定(Ⅰ)

在分析国内外镰刀菌(Fusarium Link)种类鉴定现状的基础上,运用培养性状和形态特征综合分析的方法,对山西省三个地区七市县5种作物上采集的5个镰刀菌菌株进行了种类鉴定。鉴定出2个种,其中4个菌株属于镰刀菌属美丽组的尖孢镰刀菌(F.oxysporum Schl.),另一个菌株属于镰刀菌属李瑟组的串珠镰刀菌(F.moniliforme Shel-don)。5种作物病原镰刀菌种类分别是:棉花枯萎病菌(F.oxysporum)、西瓜枯萎病菌(F.oxysporum)、黄瓜枯萎病菌(F.oxysporum)、亚麻枯萎病菌(F.oxysporum)和玉米青枯病菌(F.moniliforme)。     

大麦条锈菌专化型鉴定及其致病性初步分析

【目的】对2012年采自甘肃省和青海省大麦(青稞)上的条锈菌进行了专化型鉴定和致病类型测定,并选用甘肃省和青海省的16份大麦上的条锈菌和11份小麦上的条锈菌对27份大麦品种进行了苗期致病性测定.【方法】采用涂抹接种及撒孢子粉接种的方法.【结果】16份大麦条锈菌标样均为大麦条锈菌小麦专化型,其致病类型鉴定为贵22-9、贵22-56、贵22-82、贵22-91、水11-13、水11-13(中四感)、水11-102、水11-157、水11-200、水11-203和小麦条锈菌5个未归类型。大麦条锈菌对大麦品种‘果洛’‘藏青25’‘昆仑1号’‘康青3号’‘昆仑12号’的毒性频率分别为56.25%、37.50%、25.00%、62.50%、21.43%,小麦条锈菌对大麦品种‘果洛’‘藏青25’‘昆仑1号’‘康青3’‘昆仑12号’的毒性频率分别为36.36%、18.18%、54.54%、45.45%、9.09%.【结论】大麦品种‘果洛’‘康青3号’‘藏青25’‘昆仑1号’和‘昆仑12号’可被采自大麦和小麦上的条锈菌侵染,为共同感病寄主.