长蠕孢菌产孢条件的研究*

对番茄褐斑病原菌—长蠕孢菌产孢条件进行了研究,结果表明燕麦片琼胶培养基、Czapek培养基和PDA+番茄叶片能促进产孢子,V8汁、PSA和番茄汁培养基抑制产孢;碳源果糖明显促进产孢,甘露醇抑制产孢子;氮源氯化铵促进产孢,蛋白胨和硫酸铵抑制产孢;光照和紫外线照射对长蠕孢菌产孢有明显促进作用,特别是紫外线照射60~80min时产孢量达到最大;偏低温或偏高温以及微碱性环境能促进长蠕孢菌产孢,温度为15℃或30℃,pH8~9时最有利于产孢。     

小麦长蠕孢菌毒素

小麦长蠕孢菌(Helminthosporium sativum)在21—25℃的Fries溶液中振荡培养时产生的毒素,易引起与病原菌感染小麦类似的特征性病状。培养滤液的浓缩物,经丙酮沉淀,正丁醇-氯仿萃取,二次硅胶柱层析等程序,将毒素部分纯化,毒素的硅胶TLC层析表明,毒素层离组分至少为6种,在紫外灯下和碘蒸气中观察,显蓝紫色光斑和棕黄色斑,它们的Rf值依次为0.12,0.16,0.25,0.36,0.43,0.54,并具有倍半萜类化合物特有的紫外吸收带,它们的最大吸收值(max)分别为270,285,287,290,287,287nm,与国外报道乙醚提取物的紫外吸收特性相近(sommereyns & Closset,1978)。生物检测结果表明,上述组分均为毒素活性部分,它除能溶于ε为10以上的溶剂外,对热和光稳定,最适pH 4—7,极端pH下,毒素活性被钝化,回调最适pH后,活性仍可恢复,即令高温蒸煮也不丧失活性。毒素对小麦叶组织伤害能力及其活性与温度,毒素浓度和剂量,作用时间的变化呈正相关。     

长蠕孢一新种

本文报告寄生于小麦(Triticum aestivum L.)上的长蠕孢一个新种——小麦生长蠕孢(Drechslera triticicola sp.nov.),其分生孢子形态,培养性状,对小麦的致病力及其寄主范围等,与已报告的寄生于小麦或禾本科植物上的长蠕孢菌明显不同。     

中国长蠕孢属的分类研究II. 四川省的两个新种

报道生于四川省枯树枝上的长蠕孢属两个新种,假喙长蠕孢Helminthosporiumspurirostrum和四川长蠕孢Helminthosporiumsichuanense。假喙长蠕孢的分生孢子可产生假喙,这是首次报道长蠕孢属的一个新的特征。四川长蠕孢与黄檀长蠕孢H.dalbergiae较相似,但是黄檀长蠕孢的分生孢子大(长58-125靘,宽12-14靘),分生孢子梗细(宽10-12靘)。研究标本保存在山东农业大学植物病理学标本室(HSAUP)。     

中国长蠕孢属的分类研究II. 四川省的两个新种

报道生于四川省枯树枝上的长蠕孢属两个新种,假喙长蠕孢Helminthosporiumspurirostrum和四川长蠕孢Helminthosporiumsichuanense。假喙长蠕孢的分生孢子可产生假喙,这是首次报道长蠕孢属的一个新的特征。四川长蠕孢与黄檀长蠕孢H.dalbergiae较相似,但是黄檀长蠕孢的分生孢子大(长58-125靘,宽12-14靘),分生孢子梗细(宽10-12靘)。研究标本保存在山东农业大学植物病理学标本室(HSAUP)。     

中国长蠕孢属的分类研究Ⅱ.四川省的两个新种

报道生于四川省枯树枝上的长蠕孢属两个新种,假喙长蠕孢Helminthosporium spurirostrum和四川长蠕孢Helminthosporium sichuanense。假喙长蠕孢的分生孢子可产生假喙,这是首次报道长蠕孢属的一个新的特征。四川长蠕孢与黄檀长蠕孢H.dalbergiae较相似,但是黄檀长蠕孢的分生孢子大(长58-125μm,宽12-14μm),分生孢子梗细(宽10-12μm)。研究标本保存在山东农业大学植物病理学标本室(HSAUP)。     

蚧镰孢菌的生长及产孢研究

蚧镰孢菌孢子萌发及产孢的最适温度是 2 8℃ ,菌生长的适温是 2 4℃～ 2 6℃。孢子萌发受 pH值影响较小 ,菌生长以 pH6.5～ 8.5为最适 ,而 pH8.5时产孢最多。菌的生长也可以调节培养液的pH值 ,使其达到最适生长的 pH范围。光照对该菌的生长及产孢也有一定影响。蚧镰孢菌能利用多种碳源和氮源 ,也能以几丁质为唯一碳源和氮源生长 ,但生长很差。Ca2 、Fe2 等金属离子以及硫胺素、核黄素、叶酸等维生素的加入可使产孢量增加 ,而维生素的作用更明显。该菌的产孢高峰期一般在 2 1天左右 ,而且在相同条件下 ,接种量越大 ,产生最大量孢子所需的时间越短。     

番茄褐斑病菌产毒培养条件及其毒素的致病范围

对番茄褐斑病菌(Helminthosporiurn carposaprum)产毒条件和毒素对不同番茄品种的毒性进行了研究,结果表明,不同的pH值、温度、光照条件、培养天数所制备的毒素毒力差异显著,病菌的最佳产毒条件是室温25℃,光照12 h、pH值为6、振荡培养15 d;不同植物对病菌毒素的敏感性不同。     

Phylloplane microorganisms as a potential biocontrol agent against Helminthosporium oryzae Breda de Hann,the incitant of rice brown spot

Abstract

Fifteen pathogenic isolates of Helminthosporium oryzae were established from 15 different rice growing areas representing nine districts: Madurai, Theni, Thanjavur, Thiruvarur, Nagapatinum, Tirunelveli, Trichy, Ariyalur and Cuddalore district of Tamil Nadu. The symptoms initially appeared on the leaves as small, oval, dark brown to black spots. Under favourable conditions, the fungus attacks grain and caused grain discoloration. The isolate, collected from Ammapettai of Thanjavur district was the most virulent (Grade 7.47, PDI 82.96) on rice plants followed by Trichy isolate I₂ (Grade 7.26; PDI 80.74) while I₁₅ (Cumbum) was the least virulent (Grade 1.8, PDI 20.00). The isolates of H. oryzae varied in size (length and width) of the conidia, colour and the number of cells per conidium. The maximum (39.1 μm) length of the conidium was observed in I₁₀ followed by I₁₁ (37.3 μm). The maximum (17.1 μm) conidial width was observed in I₈. The colour of the conidium varied from light brown (isolates I₃, I₆ and I₁₄) to brown, while there was no appreciable difference in the conidial shape. The number of cells varied from 2 – 4 among the isolates. Six phylloplane microorganisms were tested against the virulent isolate of H. oryzae. Among them, Cladasporium spp was very effective in inhibiting the mycelial growth and spore germination of H. oryzae followed by Penicillum spp and Aspergillus flavus while Bacillus subtilis was least effective in inhibiting the mycelial growth and spore germination of H. oryzae.     

利用组织培养技术选育玉米抗小叶斑病突变体

大叶斑病和小叶斑病是玉米最严重的病害,选育抗大、小叶斑病优良自交系及单交种是提高玉米产量的重要措施。Ｇｅｎｇｅｎｂａｃｈ等以玉米Ａ６１９ｃｍｓＴ愈伤组织为材料,筛选出对小叶斑病毒素具有抗性的愈伤组织与再生植株［１,２］,开辟了玉米抗病育种的新途径。...     

Target leaf spot of tomato incited by Corynespora cassiicola,an emerging disease in tomato production under Gangetic alluvial region of West Bengal,India

Abstract

Tomato (Lycopersicon esculentum Mill.) is a cosmopolitan vegetable and widely cultivated in almost all the countries of the world including India. Irreversible investment – production ratio for tomato cultivation in recent Indian agricultural systems arise the question, is there any biotic backlogs responsible for such a production loss. Our present investigation is based on this fact. Target leaf spot disease of tomato is caused by Corynespora cassiicola, a serious and emerging disease in India. Prolonged real time surveillance of this disease on tomato from 2010–11 to 2016–17, reflects some remarkable features of pathogenic progress in Gangetic alluvial region of West Bengal. This pathogen is the natural barrier for tomato production with a disease severity ranged between 35% and 58% which ultimately causes tremendous loss of tomato foliage and fruits. C. cassiicola was identified on the basis of morpho-cultural (ITCC Accession No. 7542) and molecular characterization (Genbank Accession No. KJ767193). Homology searching of internal transcribed spacer region of CcHaTom isolate was highly matched with Genbank Accession No. KP666184 (Cynodondactylon/India), AB873045 (Vitex negundo/India) and JN541214 (Malvaviscus concinnus/USA) with 95% similarity. Phylogenetic analysis established that KJ767193 and C. cassiicola retrieved sequences were conspecific from a common ancestral origin, which supports its neighbourhood with this fungal pathogen. Optimum temperature between 24 and 25?°C, coupled with 80–85% relative humidity triggered the disease progress. From the emerging scenario, C. cassiicola infecting tomato is the real threat for indigenous cultivars.     

Selection of brown spot-resistant rice plants from Helminthosporium oryzae toxin-resistant calluses

Helminthosporium oryzae toxin induced electrolyte leakage from rice callus tissues and caused their browning and death. A virulent isolate of the pathogen invaded and colonised callus tissues rapidly, while a less virulent and a nonpathogenic isolate colonised calluses only weakly if at all. Addition of the toxin to calluses permitted colonisation of calluses by the nonpathogenic isolate. Four toxin-resistant calluses were selected and plants regenerated from two of these resistant calluses showed resistance to the pathogen. This resistance was heritable and stability of resistance was observed in the R₁, R₂ and R₃ generations.     

Characterization of Sporulation of Alternaria alternata f. sp. sphenocleae

Studies were conducted on agar media to characterize the factors for the optimization of sporulation of Alternaria alternata f. sp. sphenocleae , a fungal pathogen being evaluated as a biological control agent for Sphenoclea zeylanica (gooseweed). A. alternata f. sp. sphenocleae conidiation was affected by nutrition, temperature, light conditions, and moisture. On all agar media tested, except for half-strength potato dextrose agar (½ PDA) and V-8 juice agar (VJA), exposure to different light conditions did not have any significant effect on conidia production. However, when comparing ½ PDA and VJA, sporulation under constant near-ultraviolet (NUV) light at 28 o C increased markedly on VJA, but decreased substantially on ½ PDA. This trend, however, was opposite under dark conditions since ½ PDA produced the greatest number of conidia whereas a 75% reduction in conidia production occurred on VJA in the dark. On all the standard agar media evaluated, the most virulent conidia were obtained on ½ PDA at 28 o C under constant NUV incubated for 4 weeks. Sporulation of A. alternata f. sp. sphenocleae using the sporulation medium (S-medium) technique was rapid. Conidia were produced within 24 h and continuous sporulation was still observed until 120 h. The best primary agar media for conidia production were PDA, ½ PDA and VJA, while water agar was the poorest. Conidia production was optimized with the addition of 20 g l -1 of calcium carbonate (CaCO 3 ) and the addition of 2 ml of sterile distilled water on the medium. The most virulent conidia were produced when the primary agar was ½ PDA, the CaCO 3 concentration was 20 g l -1 , and the cultures were incubated at 18 o C in the dark. Conidiophore induction occurred on nutrient rich media and was stimulated by NUV, while formation of conidia proceeded in darkness after nutrients were depleted under warm dry or cool moist conditions. Culture media, growth conditions, and CaCO 3 affected the inoculum potential of A. alternata f. sp. sphenocleae conidia.     

Detection of Helminthosporium solani from soil and plant tissue with species-specific PCR primers

Two PCR primer pairs specific for Helminthosporium solani, which causes silver scurf on potato tubers, were designed from nucleotide sequences of the nuclear ribosomal internal transcribed spacer regions of H. solani. Both primer pairs amplified a single product with DNA from 48 North American and European isolates of H. solani, but not with DNA from 42 other fungi. Primers also amplified a single product with DNA extracted from silver scurf lesions on potato tubers and other plant tissue inoculated with spores of H. solani. Detection of the fungus in infested soil was only possible with nested PCR and after processing soil with a bead beater. Specific amplification of H. solani DNA can be used to study the saprophytic and pathogenic activity of this fungus in soil and plant tissue.     

Virulence of Helminthosporium tetramera for root rot and foliar blight on wheat and rice crops and characterization by RAPD-PCR

Abstract

Helminthosporium tetramera isolates were isolated and identified from root of wheat and rice crops and their aggressiveness was studied using aggressiveness analysis in the greenhouse. Isolates of H. tetramera were genetically characterized using Random Amplified Polymorphism DNA (RAPD). The investigations were based on two surveys of wheat and one survey of rice. In root aggressiveness analysis, the overall number of aggressive isolates was higher on wheat compared to rice. In the foliar aggressiveness test, the number of non-aggressive isolates was almost the same on wheat and rice varieties. RAPD was used to study the polymorphism and genetic variation within the population of H. tetramera that established to study correlation between taxonomical, aggressiveness and genetical characters. The H. tetramera tree is constructed based on the pattern of bands. This study highlighted the correlation between morphological, aggressiveness and genetic variations of H. tetramera.     

Carbohydrate involvement during infection of maize by Helminthosporium maydis

Germination and germ tube length of Helminthosporium maydis conidia did not exhibit much difference on fixed decolourized and living green leaves. However, appressoria, penetrations and colonizations were much less on decolourized host leaves and were enhanced significantly when sugars were added in the infection court. Few leached conidia germinated on the decolourized host leaves and appressoria, penetrations and colonizations effected on them by leached conidia were almost negligible. The presence of exogenous sugars and leaf leachates enabled the leached conidia to accomplish some penetrations and colonizations. Carbohydrate content of decolourized leaves and leached conidia was much less than the green leaves and non-leached conidia, respectively. Carbohydrates accumulated at the infection sites/green islands which also exhibited higher chlorophyll content.     

The possible involvement of cytokinins in the pathogenicity of Helminthosporium maydis

Green islands/infection sites recorded higher cytokinin activity than surrounding tissue as well as non-inoculated tissue. This activity in infected areas increased with time of incubation while in tissue surrounding the green islands and non-inoculated tissue, cytokinin activity decreased with time of incubation. The culture filtrate extracts of H. maydis had cytokinin activity which increased with growth of the fungus. Cytokinin activity of thin-layer Chromatographic fractions from tissue and culture filtrate extracts revealed that a major portion of the activity was confined to Rf zone 0.6 to 0.8 which co-chromatographed with zeatin and zeatin riboside. Presence of zeatin and zeatin riboside in tissue and culture filtrates was confirmed by high performance liquid chromatography. Cytokinin substances, such as zeatin and zeatin riboside, increase at infection sites with growth of the pathogen suggesting they may be involved in the pathogenicity of H. maydis on maize.