64种植物提取物的离体抗真菌活性评价

测定了64种植物的甲醇提取物对荔枝霜疫霉菌(Peronophythora litchii Chen ex Ko et al.)和香蕉炭疽病菌(Colletotrichummusae(Berk.et Curt.)Arx)的离体抗菌活性.试验结果显示,在提取物质量浓度为0.01 g/mL时,对荔枝霜疫霉菌菌丝生长的抑制率高于50%的植物共有30种,对霜疫霉菌孢子囊萌发的抑制率高于50%的植物共有26种;对香蕉炭疽病菌菌丝生长的抑抑制率高于50%的植物共有18种,对香蕉炭疽病孢子萌发的抑制率高于50%的植物共有6种;对两种病原菌的菌丝生长与孢子萌发抑制率均大于50%的植物有开口箭(Tupistra chinensis Bak.)和苍耳(Xanthinum sibiricum Patrin).     

1株新分离拮抗酵母菌株对芒果炭疽病生防效果及其分类鉴定

从海南芒果园取样分离到1个新拮抗酵母菌株(LZ5),通过离体和活体抑菌实验,发现其对芒果采后炭疽病菌(Colletotrichum gloeosporioides Penz.and Sacc)有明显的抑菌效果。活体接种实验结果表明,1×108cfu·m L-1的酵母菌对刺伤接种的芒果采后炭疽病具有显著的生防效果,接种第4天和第6天对照组的病斑直径分别为5.80,26.3 mm,而处理组仅分别为0.33,17.6 mm,接种第4天对照组的发病率已达100%,而处理组仅为20%。此外,该菌株可以在芒果伤口处快速繁殖,在接种24 h后酵母细胞数为初始值的62.6倍,随后基本保持稳定。经鉴定该拮抗酵母菌属于季也蒙毕赤酵母(Meyerozyma guilliermondii)。     

炭疽病病原菌侵染对茶树叶片生理特性的影响

本试验筛选出一株强致病力茶树刺盘孢菌株ZRG,并测定其侵染后对茶树叶片相对电导率,丙二醛(MDA)含量,超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)等抗氧化酶活性及其基因表达量的影响,探究茶树刺盘孢对茶树叶片生理特性的影响.结果表明:ZRG侵染48 h内,茶树叶片相对电导率明显增高;MDA先是快速积累,含量上升,随后下降;POD、SOD和CAT活性都出现不同程度的上升,随后下降.qRT-PCR验证结果显示,POD、SOD和CAT相关基因的表达先上调后下降,三者相互协调配合,起到清除过剩自由基的作用.     

广西杧果象牙品种果腐病病原菌种类鉴定

广西杧果象牙品种发生的果腐病,经病原鉴定,其种类为杧果炭疽菌(Colletotrichum gloeosporioides(Penz.)Sacc.)和杧果大茎点菌(Macrophoma mangiferae Hingoroai et Sharma)。这2种菌均可侵染杧果引起果腐病,其病状虽有相似性,但病症有明显差异。杧果炭疽菌果腐病病斑上生轮纹状小黑点,其顶端有黄褐色颗粒状物;杧果大茎点菌果腐病病斑生小黑点,小而密,其上无颗粒状物。     

Rare β-Resorcylic Acid Derivatives from a Halophyte-Associated Fungus Colletotrichum gloeosporioides JS0419 and Their Antifungal Activities

Six new β-resorcylic acid derivatives (1–5 and 7) were isolated from a halophyte-associated fungus, Colletotrichum gloeosporioides JS0419, together with four previously reported β-resorcylic acid lactones (RALs). The relative and absolute stereochemistry of 1 was completely established by a combination of spectroscopic data and chemical reactions. The structures of the isolated compounds were elucidated by analysis of HRMS and NMR data. Notably, compounds 1–3 had a β-resorcylic acid harboring a long unesterified aliphatic side chain, whereas the long aliphatic chains were esterified to form macrolactones in 4–9. Among the isolated compounds, monocillin I and radicicol showed potent antifungal activities against Cryptococcus neoformans, comparable to clinically available antifungal agents and radicicol showed weak antifungal activity against Candida albicans. These findings provide insight into the chemical diversity of fungal RAL-type compounds and their pharmacological potential.     

Effect of GRAS compounds on mycelial growth, pectic enzyme activity and disease severity of postharvest pathogens on rambutan (Nephelium lappaceum)

The GRAS compounds cinnamaldehyde (at 30 ppm), acetaldehyde (at 70 ppm), benzalde-hyde (at 50 ppm) and potassium metabisulphite (at 250 ppm) either completely inhibited or significantly reduced thein vitro mycelial growth ofGliocephalotrichum microchlamydosponim,Colletotrichum gloeosporioides andBotryodiplodia theobromae, the causative fungi of brown spot, anthracnose and stem end rot, respectively, of rambutan fruits,Nephelium lappaceum. The four compounds also significantly reduced the severity of all three diseases and the activity of pectic lyase and polygalacturonase enzymes secreted by the three fungi.     

The role ofPseudomonas spp. and competition for carbon,nitrogen and iron in the enhancement of appressorium formation byColletotrichum coccodes on velvetleaf

Colletotrichum coccodes is currently being investigated as a mycoherbicide against the weed velvetleaf (Abutilon theophrasti). Two isolates ofPseudomonas spp. (Ps2 and Ps5) reduced the percentage of germ tubes and increased appressorial formation ofC. coccodes on detached leaves of velvetleaf. A study was conducted to see whether this effect could be attributed to competition for nutrients or iron betweenC. coccodes andPseudomonas spp. Ps2 and Ps5 had no effect on early spore germination, but reduced the percentage of germ tubes at 24 and 30 h, compared to the nontreated control. This reduction was diminished by the addition of nutrients but not Fe³⁺. Ps2 and Ps5 stimulated the formation of dark-coloured appressoria without germ tubes (AWGT), but this stimulation was diminished by the addition of nutrients or Fe³⁺. Germ tube branching at 30 h was also inhibited by the bacteria, but was not diminished by the addition of nutrients or iron. EDTA stimulated conidial germination at 10 h, which was reduced by the addition of Fe³⁺. However, EDTA did not stimulate the formation of appressoria (AWGT). These results suggest that the reduction in the percentage of germ tubes and the increase in the percentage of appressoria induced by the bacteria may be due to the competition for carbon or nitrogen. Iron competition may also be involved in the stimulation of appressorial formation, but not in the reduction in germ tube percentage and branching. Phylloplane bacteria may compete for carbon, nitrogen and iron, limiting the saprophytic phase of the pathogen on the phylloplane and accelerating the development of the parasitic phase. This may enhance the field efficacy ofC. coccodes as a biocontrol agent against velvetleaf.     

Induction of hypericins and hyperforin in Hypericum perforatum L. in response to biotic and chemical elicitors

Hypericum perforatum L. produces hyperforins, a family of antimicrobial acylphloroglucinols; and hypericins, a family of phototoxic anthraquinones exhibiting anti-microbial, anti-viral, and anti-herbivore properties in vitro. To determine whether these secondary metabolites are part of the specific plant defense systems that are mediated by methyl jasmonate or salicylic acid, we used meristem cultures to assess the effects of exposure to exogenous application of these chemical elicitors. Levels of hypericins in plant tissue increased in response to both elicitor treatments; total hypericin levels increased as much as 3.3 times control levels when treated with 200 μ methyl jasmonate for 14 days. Increased hyperforin concentrations were detected when plantlets were treated with 1 m salicylic acid or 50 μ methyl jasmonate. For assessing responses to a biotic elicitor, greenhouse-grown plant materials were inoculated with the plant pathogen, Colletotrichum gloeosporioides. Levels of hypericins increased twice as much as the control when inoculated with 1 × 10⁴ spores per ml; higher doses of spores overwhelmed the plant defenses. The elevation of hypericins and hyperforin in response to chemical and biotic elicitors suggests that these secondary metabolites are components in the inducible plant defense responses of H. perforatum.     

Effect of ammonium carbonate and sodium bicarbonate on anthracnose of papaya

Colletotrichum gloeosporioides is the causal organism of anthracnose inCarica papaya L. (papaya, papaw). The effect of ammonium carbonate (3%) or sodium bicarbonate (2%) in aqueous solution or when incorporated into a wax formulation on anthracnose severity in inoculated or naturally infected fruits was examined. Both salts had significant effects, but that of ammonium carbonate was greater than that of sodium bicarbonate in controlling anthracnose. Ammonium carbonate (3%) incorporated into the wax formulation effectively reduced anthracnose incidence by 70% in naturally infected papaya and extended the storage life by maintaining the firmness, color and overall quality of the fruit in low temperature storage (13.5°C) and 95% r.h. for 21 days followed by 2 days under marketing conditions. The mode of action of ammonium carbonate on the control of anthroacnose appears to bevia complete inhibition of radial mycelial growth and conidia germination. http://www.phytoparasitica.org posting Aug. 14, 2002.     

Effects of Plant Defence Activators on Anthracnose Disease of Cashew

The plant defence activators acibenzolar-S-methyl (Benzo[1,2,3]thiadiazole-7-carbothioic acid-S-methyl ester, ASM), 2,6-dichloro-isonicotinic acid (DCINA), salicylic acid (SA), and dibasic potassium phosphate (K₂HPO₄) were tested for their ability to protect cashew (Anacardium occidentale) seeds and leaves from anthracnose disease caused by Colletotrichum gloeosporioides. No inhibition of the early stages of pathogen development was caused by concentrations equal to or lower than 1.1mM a.i. ASM, 1.2mM a.i. DCINA, 5mM SA and 50mM K₂HPO₄. Maximum reduction of the disease in detached leaves, without phytotoxic effects, was obtained with 0.07mM a.i. ASM and DCINA, 5mM SA, and 50mM K₂HPO₄, with a time interval of at least 72h between application of the activator and inoculation with the pathogen. On attached leaves, foliar sprays were slightly more efficient than soil drench treatments, with 5mM SA being the most effective treatment, while 50mM SA as well as 0.3mM a.i. ASM and DCINA caused phytotoxic effects. In field-grown plants, protection was conferred by a soil drench of concentrations as low as 12.6M a.i. ASM and DCINA and 2.6mM SA. These concentrations were not phytotoxic suggesting that plant defence activators have potential for control of anthracnose disease in the field.