黄瓜根分泌物中的7,8-苯并黄酮及其对枯萎病发生的影响

分别提取黄瓜枯萎病感病品种津研4号和抗病品种中农10号的根分泌物,感病品种根分泌物甲醇提取液能够刺激枯萎病菌的菌丝生长,而抗病品种根分泌物甲醇提取液则抑制病原菌生长。利用LC-MS/MS技术分别对感病品种和抗病品种根分泌物中的差异物质进行分析鉴定。与感病品种津研4号相比,抗病品种中农10号根分泌物中含有7,8-苯并黄酮(7,8-BF),含量为0.02μg/株。50μg/mL的7,8-BF能够显著抑制黄瓜枯萎病菌菌丝生长和孢子萌发,而100μg/mL的7,8-BF能显著抑制抗感品种侧根形成,但是抗病品种的耐受力高于感病品种。用7,8-BF处理黄瓜种子,枯萎病侵染程度显著降低。当7,8-苯并黄酮浓度为50μg/mL时,感病品种病情指数从71.7降为30.8,达到中抗水平。     

枯萎病菌对西瓜不同抗感品种丙二醛含量及某些保护酶活性的影响

 本文以西瓜为材料,研究了西瓜苗期感染枯萎病菌(Fusarium oxysporum Schlecht.)后根部细胞内丙二醛含量、超氧化物歧化酶和过氧化氢酶活性的动态变化。结果表明,受枯萎病菌侵染的幼苗细胞内MDA含量的增加比率,抗病品种克伦生低于感病品种早花;SOD酶活性的下降比率,抗病品种克伦生低于感病品种早花;CAT酶活性增减的幅度,抗病品种克伦生低于感病品种早花。抗病品种克伦生在染病后的短时间内(48h左右)能使细胞内MDA、SOD酶和CAT酶的代谢基本恢复到正常状态,其自我调节和恢复正常状态的能力显著大于感病品种早花。     

玉米灰斑病抗性机制中活性氧代谢的作用

研究了玉米灰斑病菌侵染四个抗病和感病的玉米品种时，叶片内部活性氧代谢酶及细胞过氧化产物含量的动力学变化。结果表明，抗、感病品种的SOD、CAT及POD酶活性在病茵侵染后都变化显著，抗病品种各酶活性变化幅度比感病品种大。叶片内过氧化产物MDA含量则相反，抗病品种沈试29在接种第13天时叶片MDA含量只为18．46nmol／g，而感病品种铁单9为23．14nmol／g，抗病品种比感病品种增加幅度小。说明活性氧代谢在植物抗病机制中起着重要作用，抗病品种对活性氧代谢的酶调节能力强，病菌侵染后细胞过氧化程度低，在痛菌侵染时活性氧清除酶活性最大增加值与发病程度呈显著正相关。     

谷子抵御白发病菌侵染的生理生化及基因表达分析

 白发病已成为我国谷子生产上的重要病害,不仅造成产量下降,还对谷子品质构成威胁。有关谷子品种响应白发病菌侵染的生理生化机制研究尚未见报道。本研究采用病菌卵孢子和谷粒混合的接菌方法分别接种抗病品种‘G1'和高感品种‘晋谷21'(JG21),并测定抗感谷子的植株形态指标、光合参数、防御酶活性、抗氧化酶活性、可溶性糖及脯氨酸含量,同时结合基因表达分析,旨在明确谷子响应白发病菌侵染机制。结果表明,白发病菌侵染抗感品种后,植株高度及叶面积均表现出不同程度的下降,感病品种的株高降低幅度远大于抗病品种;与抗病品种相比,感病品种中除了胞间CO₂浓度显著升高外,其他光合参数显著下降,且均低于抗病品种。抗病品种中抗氧化酶和防御酶活性及脯氨酸、可溶性糖含量均升高,显著高于感病品种。抗病相关基因Seita.2G024600(PR1)、Seita.7G168700(PAL)、Seita.1G240200(PAL)和 Seita.9G462500(POD)在抗病品种中上调,而在感病品种中表达受到抑制或下调。以上光合参数、酶活性、Pro和可溶性糖含量变化等生理生化指标可作为抗性鉴定和种质筛选的参考,这些差异表达基因可能参与了谷子对白发病菌抗病调控。研究结果可为谷子抗病分子机制及分子改良育种提供理论基础。     

谷子抵御白发病菌侵染的生理生化及基因表达分析

 白发病已成为我国谷子生产上的重要病害,不仅造成产量下降,还对谷子品质构成威胁。有关谷子品种响应白发病菌侵染的生理生化机制研究尚未见报道。本研究采用病菌卵孢子和谷粒混合的接菌方法分别接种抗病品种‘G1'和高感品种‘晋谷21'(JG21),并测定抗感谷子的植株形态指标、光合参数、防御酶活性、抗氧化酶活性、可溶性糖及脯氨酸含量,同时结合基因表达分析,旨在明确谷子响应白发病菌侵染机制。结果表明,白发病菌侵染抗感品种后,植株高度及叶面积均表现出不同程度的下降,感病品种的株高降低幅度远大于抗病品种;与抗病品种相比,感病品种中除了胞间CO₂浓度显著升高外,其他光合参数显著下降,且均低于抗病品种。抗病品种中抗氧化酶和防御酶活性及脯氨酸、可溶性糖含量均升高,显著高于感病品种。抗病相关基因Seita.2G024600(PR1)、Seita.7G168700(PAL)、Seita.1G240200(PAL)和 Seita.9G462500(POD)在抗病品种中上调,而在感病品种中表达受到抑制或下调。以上光合参数、酶活性、Pro和可溶性糖含量变化等生理生化指标可作为抗性鉴定和种质筛选的参考,这些差异表达基因可能参与了谷子对白发病菌抗病调控。研究结果可为谷子抗病分子机制及分子改良育种提供理论基础。     

黑痣病菌毒素对马铃薯幼苗生理生化抗性相关物质的诱导

为了探讨马铃薯抗黑痣病机制,采用毒素接种脱毒组培苗的方法,研究了黑痣病菌毒素对马铃薯不同抗性品种幼苗体内病程相关蛋白、木质素及游离脯氨酸含量的影响及其与抗黑痣病的关系。毒素处理后,感病品种大西洋和抗病品种底西芮幼苗几丁质酶和β-1,3-葡聚糖酶活性均明显升高,36 h升高幅度均达到最大,感病品种升幅大于抗病品种。底西芮和大西洋木质素及游离脯氨酸含量也大幅增加,但抗病品种的增加幅度大于感病品种。研究表明,黑痣病菌毒素诱导几丁质酶和β-1,3-葡聚糖酶活性升高以及木质素和游离脯氨酸含量增加是马铃薯幼苗抵抗毒素胁迫的内在机制;木质素、游离脯氨酸含量与品种抗病性呈正相关,而几丁质酶、β-1,3-葡聚糖酶活性变化则不是引起品种抗性差异的主要原因。     

玉米灰斑病抗性反应中酚类物质代谢作用的研究

 研究了玉米灰斑病菌(Cercospora zeae-maydis)侵染前后的4个玉米品种苯丙氨酸解氨酶、过氧化物酶、多酚氧化酶及木质素含量的变化。3种酶比活性在病菌侵染后都发生明显的先增后降的变化,而抗病品种的变化要明显大于感病品种的变化,尤其是苯丙氨酸解氨酶最大增加活性与品种抗病性呈现极显著的相关性。4个品种的木质素含量在病菌侵染的第9 d时增加到最大值,以后略下降,而且抗病品种的木质素含量峰值高于感病品种的峰值。     

小麦品种对小麦白粉病菌侵染信号传递初探

 通过测定抗病性不同的小麦品种在接种小麦白粉病菌后钙调素含量的变化发现其存在差异。如抗病品种钙调素含量高峰出现在接种后4 h,即寄主与白粉病菌接触阶段。而感病品种接种后24 h出现钙调素含量高峰。比较测定了不同的钙调素抑制剂对小麦品种抗白粉性的影响,发现10mmol/L TFP和5 mmol/L CPZ处理使抗病品种变为高度感病,50 mmol/L CPZ处理使小麦感染白粉菌后反应型下降,表明钙调素与小麦抗白粉性有关。     

儿茶素在棉苗对枯萎病抗性中的作用

 分析了枯萎病菌接种后棉苗组织内儿茶素含量的变化以及儿茶素对枯萎病菌及其多聚半乳糖醛酸酶活性的影响。健康棉苗组织中儿茶素含量随着棉苗的生长而增加。枯萎病菌接种后,病苗组织中儿茶素含量显著高于健康对照,而且抗病品种棉苗儿茶素含量的增加明显高于感病品种。经氟乐灵预处理的棉苗接种枯萎病菌后,儿茶素含量增加更快,增幅更大。说明儿茶素是品种抗性和氟乐灵诱发棉苗对枯萎病诱导抗性的机理之一。儿茶素可抑制枯萎病菌的菌丝生长、产孢及孢子萌发,对培养液中病菌的多聚半乳糖醛酸酶(PG)有抑制作用。儿茶素化学制品及棉苗组织提取液经TLC分离后获得的含儿茶素组分提取液对初步纯化的PG活性有明显的抑制作用。这些结果表明:儿茶素可能通过抑制病菌的菌丝生长、产孢以及其PG活性而在棉花对枯萎病的抗病性中起到作用。     

烟草低头黑病菌毒素对烟草丙二醛含量和某些防御酶的动态影响

 本文研究了烟草抗病品种(Burley21)和感病品种(NC82)在烟草低头黑病菌毒素诱导下,丙二醛(malondialdehyde,MDA)含量及超氧化物歧化酶(SOD)、过氧化物酶(POD)、多酚氧化酶(PPO)活性的动态变化。结果表明,在毒素的诱导下,MDA含量的增减比率抗病品种Burley21低于感病品种NC82。不论Burley21还是NC82,SOD、POD和PPO活性皆在前期表现为上升后期下降,但抗病品种较感病品种下降速度慢,而且POD在后期还表现为高活性。表明抗病品种(Burley21)具有比感病品种(NC82)更强的防御能力和抗膜脂过氧化能力。     

根际微生物多样性与棉花品种对黄萎病抗性的关系研究 II.不同抗性品种根际真菌区系分析及其对棉花黄萎病菌的抑制作用

对棉花抗黄萎病品种（春矮早和８６－ ６）和感病品种（中棉１７和豫棉１２）的根际真菌区系进行了分析。结果表明每个品种都有自己独特的根际微生物区系,抗病品种根际微生物种数多于感病品种,区系组成更为复杂。抗病品种根际真菌优势种主要是漆斑菌 （Ｍｙｒｏｔｈｅｃｉｕｍ ）、粘帚霉（Ｇｌｉｏｃｌａｄｉｕｍ ）、曲霉（Ａｓｐｅｒｇｉｌｌｕｓ）和青霉（Ｐｅｎｉｃｉｌｌｉｕｍ ）等,感病品种则多为头孢霉（Ｃｅｐ ｈａｌｏｓｐｏｒｉｕｍ ）、镰刀菌（Ｆｕｓａｒｉｕｍ ）、矛束孢（Ｄｏｒａｔｏｍｙｃｅｓ）、粘帚霉（Ｇｌｉｏｃｌａｄｉｕｍ ）和漆斑菌（Ｍｙｒｏｔｈｅｃｉｕｍ ）等。采用平板对峙培养法测定了不同抗性棉花品种根际真菌区系各成员对棉花黄萎病菌的抑制作用,发现抗病品种根际真菌区系中对黄萎病菌具有抑制作用的真菌种数和比率都高于感病品种,而且抗病品种根际真菌的优势种对棉花黄萎病菌的抑制作用较强。这种差异在苗期和现蕾期更为明显,花铃期则显著减小。研究结果表明棉花品种对棉花黄萎病的抗性与根际真菌区系组成及其对黄萎病菌的抑制能力有一定关系。     

Effect of method of inoculation, inoculum density and seedling age at inoculation on the expression of resistance of cocoa (Theobroma cacao L.) to Verticillium dahliae Kleb.

Soil drench and stem puncture inoculation were compared as methods for selecting cocoa cultivars with resistance to Verticillium dahliae. Disease progress was more rapid and induced symptoms were more severe following stem puncture and, under glasshouse conditions, differences between cultivars were detected 15 days after inoculation. Moreover, using stem puncture, inoculum densities of 10⁴ conidia/ml were sufficient to differentiate resistant and susceptible cultivars, whereas with the soil drench method, inoculum densities of 10⁷ conidia/ml were necessary. Although a substantially higher proportion of plants were affected by stem puncture inoculation, the resistance of cultivar Pound-7 remained effective at high inoculum densities of 10⁸ conidia/ml. With either method, older seedlings were more susceptible to V. dahliae than younger ones. However, with stem puncture, 15-day-old seedlings were sufficiently susceptible for a valid disease assessment. In contrast, with soil inoculation, 60-day-old plants were required. In a nursery trial with 15-day-old seedlings, seven cocoa genotypes previously selected as resistant, moderately resistant or susceptible to Verticillium dahliae , on the basis of root inoculation, were ranked in the same order when stem punctured. Stem puncture inoculation of young seedlings is cost-effective in terms of time and space, and is therefore recommended for screening of cocoa for wilt resistance, especially in large-scale breeding programmes.     

根际微生物多样性与棉花品种对黄萎病抗性关系研究──Ⅰ.根际微生物数量与棉花品种对黄萎病抗性的关系

对抗、感黄萎病6个棉花品种的根际线虫、真菌、细菌和放线菌的数量在苗期和现蕾期采用选择性培养基和直接观察法进行了分析。分析结果表明：棉花对黄萎病的抗性与根际真菌和放线菌数量呈正相关;与根际线虫数量负相关;与根际细菌数量无显著相关性。     

Colonization of resistant and susceptible lettuce cultivars by a green fluorescent protein-tagged isolate of Verticillium dahliae

Interactions between lettuce and a green fluorescent protein (GFP)-expressing, race 1 isolate of Verticillium dahliae, were studied to determine infection and colonization of lettuce cultivars resistant and susceptible to Verticillium wilt. The roots of lettuce seedlings were inoculated with a conidial suspension of the GFP-expressing isolate. Colonization was studied with the aid of laser scanning confocal and epi-fluorescence microscopes. Few differences in the initial infection and colonization of lateral roots were observed between resistant and susceptible cultivars. Hyphal colonies formed on root tips and within the root elongation zones by 5 days, leading to the colonization of cortical tissues and penetration of vascular elements regardless of the lettuce cultivar by 2 weeks. By 8 to 10 weeks after inoculation, vascular discoloration developed within the taproot and crown regions of susceptible cultivars well in advance of V. dahliae colonization. Actual foliar wilt coincided with the colonization of the taproot and crown areas and the eruption of mycelia into surrounding cortical tissues. Advance colonization of stems, pedicels, and inflorescence, including developing capitula and mature achenes was observed. Seedborne infection was limited to the maternal tissues of the achene, including the pappus, pericarp, integument, and endosperm; but the embryo was never compromised. Resistant lettuce cultivars remained free of disease symptoms. Furthermore, V. dahliae colonization never progressed beyond infected lateral roots of resistant cultivars. Results indicated that resistance in lettuce may lie with the plant's ability to shed infected lateral roots or to inhibit the systemic progress of the fungus through vascular tissues into the taproot.     

韭菜等几种植物根系分泌物对棉花黄萎病菌的影响

通过水培法收集韭菜、大葱、野薄荷、藿香和薰衣草的根系分泌物,研究其对大丽轮枝菌菌丝生长、孢子萌发的影响,并通过室内盆栽试验研究了植物根系分泌物对大丽轮枝菌微菌核萌发的影响。结果表明,5种植物根系分泌物对大丽轮枝菌菌丝生长和孢子萌发均表现为抑制作用;随着浓度的升高,抑制作用增强,而在同一浓度下,随着处理时间的延长,根系分泌物对孢子萌发的抑制作用逐渐减弱。盆栽试验表明,植物根系分泌物对大丽轮枝菌微菌核的萌发均表现为抑制作用,且微菌核对韭菜根系分泌物最为敏感。5种植物中,韭菜根系分泌物的抑制作用最强,野薄荷次之,藿香最弱。     

Phenological and phytochemical changes correlate with differential interactions of Verticillium dahliae with broccoli and cauliflower

Cauliflower (Brassica oleracea var. botrytis subvar. cauliflora) is susceptible to wilt caused by Verticillium dahliae but broccoli (B. oleracea var. italica subvar. cyamosa) is not. Infection of broccoli and cauliflower by a green fluorescent protein-expressing isolate of V. dahliae was examined using epifluorescence and confocal laser-scanning microscopy to follow infection and colonization in relation to plant phenology. Plant glucosinolate, phenolic, and lignin contents were also assayed at 0, 4, 14, and 28 days postinoculation. V. dahliae consistently infected and colonized the vascular tissues of all cauliflower plants regardless of age at inoculation, with the pathogen ultimately appearing in the developing seed; however, colonization decreased with plant age. In broccoli, V. dahliae infected and colonized root and stem xylem tissues of plants inoculated at 1, 2, or 3 weeks postemergence. However, V. dahliae colonized only the root xylem and the epidermal and cortical tissues of broccoli plants inoculated at 4, 5, and 6 weeks postemergence. The frequency of reisolation of V. dahliae from the stems (4 to 22%) and roots (10 to 40%) of mature broccoli plants was lower than for cauliflower stems (25 to 64%) and roots (31 to 71%). The mean level of aliphatic glucosinolates in broccoli roots was 6.18 times higher than in the shoots and did not vary with age, whereas it was 3.65 times higher in cauliflower shoots than in the roots and there was a proportional increase with age. Indole glucosinolate content was identical in both cauliflower and broccoli, and both indole and aromatic glucosinolates did not vary with plant age in either crop. Qualitative differences in characterized glucosinolates were observed between broccoli and cauliflower but no differences were observed between inoculated and noninoculated plants for either broccoli or cauliflower. However, the phenolic and lignin contents were significantly higher in broccoli following inoculation than in noninoculated broccoli or inoculated cauliflower plants. The increased resistance of broccoli to V. dahliae infection was related to the increase in phenolic and lignin contents. Significant differential accumulation of glucosinolates associated with plant phenology may also contribute to the resistant and susceptible reactions of broccoli and cauliflower, respectively, against V. dahliae.     

The use of GFP<Emphasis Type="Italic">-</Emphasis>transformed isolates to study infection of banana with <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">cubense</Emphasis> race 4

Fusarium oxysporum f. sp. cubense (Foc) is the causal pathogen of Fusarium wilt of banana. To understand infection of banana roots by Foc race 4, we developed a green fluorescent protein (GFP)-tagged transformant and studied pathogenesis using fluorescence microscopy and confocal laser scanning microscopy. The transformation was efficient, and GFP expression was stable for at least six subcultures with fluorescence clearly visible in both hyphae and spores. The transformed Foc isolate also retained its pathogenicity and growth pattern, which was similar to that of the wild type. The study showed that: (i) Foc race 4 was capable of invading the epidermal cells of banana roots directly; (ii) potential invasion sites include epidermal cells of root caps and elongation zone, and natural wounds in the lateral root base; (iii) in banana roots, fungal hyphae were able to penetrate cell walls directly to grow inside and outside cells; and (iv) fungal spores were produced in the root system and rhizome. To better understand the interaction between Foc race 4 and bananas, nine banana cultivars were inoculated with the GFP-transformed pathogen. Root exudates from these cultivars were collected and their effect on conidia of the GFP-tagged Foc race 4 was determined. Our results showed that roots of the Foc race 4-susceptible banana plants were well colonized with the pathogen, but not those of the Foc race 4-resistant cultivars. Root exudates from highly resistant cultivars inhibited the germination and growth of the Fusarium wilt pathogen; those of moderately resistant cultivars reduced spore germination and hyphal growth, whereas the susceptible cultivars did not affect fungal germination and growth. The results of this work demonstrated that GFP-tagged Foc race 4 isolates are an effective tool to study plant–fungus interactions that could potentially be used for evaluating resistance in banana to Foc race 4 by means of root colonization studies. Banana root exudates could potentially also be used to identify cultivars in the Chinese Banana Germplasm Collection with resistance to the Fusarium wilt pathogen.     

Verticillium wilt of olive in Syria1

Verticillium wilt of olive was first recorded in Syria in mid-1978 and confirmed as due to Verticillium dahliae. This article reports observations made in a comprehensive survey of the disease in nine provinces over 7 years. Percent infection varied from 0.85 to 4.5 in different provinces. Newly planted groves in lowland areas showed more infection than older groves in hilly areas. Isolation of V. dahliae was possible at all times of year. Young trees were more susceptible to wilt than older ones. The performance of 13 local cultivars against wilt was studied under natural field conditions and found to vary greatly from susceptible to resistant. Agricultural practices greatly affect spread of the disease. High disease incidence was observed in irrigated groves compared with non-irrigated, and correlated positively with number of ploughings. Verticillium wilt causes a loss between 1 and 2.3% of total olive production annually.