Untersuchungen zum endophytischen Befall von Fusarium proliferatum (Matsushima) Nirenberg in geernteten Stangen von Spargel (Asparagus officinalis L.)

Zusammenfassung Erstmalig wurden mit den vorliegenden Untersuchungen Spargelstangen zur Haupterntezeit auf endophytischen Pilzbefall untersucht. Sie zeigen, dass im Ernteprodukt zwar Fusarium proliferatum als potenzieller Mykotoxinbildner zu finden ist. Eine mögliche natürliche Kontamination mit Fumonisinen bestätigte sich nicht. Von den mit F. proliferatum infizierten Stangen wies nur eine Stange mit grau-rosa-orange farbenen Gewebeveränderungen an der Basis sichtbare Symptome auf. Allgemeine Rückschlüsse auf eine mögliche Gefährdung oder Nichtgefährdung des Verbrauchers beim Verzehr von mit F. proliferatum kontaminierten, symptomlosen Stangen können aus der Analyse nicht gezogen werden. Hierzu müssen weitergehende Untersuchungen zur Wirt-Pathogen-Interaktion erfolgen und die phänotypischen und genotypischen Einflussfaktoren in diesem Prozess noch näher untersucht werden.     

辣椒素的抑菌作用及其对某些保护酶活性的影响

 本文对辣椒素的抑菌作用和对寄主体内3种保护酶活性的影响进行了研究,结果表明3.57μg/mL-50.00μg/mL的辣椒素对辣椒枯萎病菌的菌丝生长都有明显的抑制作用,浓度愈高,抑制作用愈强。20μg/mL辣椒素对另外供试的8种病原菌的菌丝具有强烈的抑制作用,其中对番茄灰霉病菌抑制作用最强。辣椒素处理辣椒后1-6 d内,SOD、POD和CAT酶活性的平均增减比率值均明显高于对照,而且对根部和叶部3种保护酶活性的影响显著不同。     

Fusarium confers protection against several mycelial pathogens of pepper plants

Inoculation of nonhost pepper ( Capsicum annuum ) plants with the tomato wilt pathogen, Fusarium oxysporum f.sp. lycopersici (FOL), caused no symptoms and the fungus was not recovered from any part of the plant. FOL, however, partially protected pepper plants from subsequent infection with Phytophthora capsici , Verticillium dahliae or Botrytis cinerea by significantly reducing the percentage of diseased plants and the appearance and intensity of symptoms. FOL did not inhibit the mycelial growth of these pathogens in vitro . The protection induced by FOL against Botrytis was inhibited by 1-methylcyclopropene (MCP), an inhibitor of ethylene perception, suggesting the involvement of this hormone in the signalling of FOL-induced resistance. The activities of β-1,3-glucanase and peroxidase 48 h after FOL induction were similar to those in control plants. Chitinase activity, however, was higher in the stems of plants inoculated with FOL. A study of the levels of phenolic compounds revealed that cell-wall-bound phenolics were more abundant in plants treated with FOL, especially in stems, while soluble phenolic contents did not differ.     

禾谷镰刀菌和稻瘟病菌基因组中的微卫星序列比较

利用禾谷镰刀菌Fusarium graminearum和稻瘟病菌Magnaporthe grisea基因组测序结果,对这两种植物病原真菌基因组中的微卫星(SSR)序列进行了系统地分析和比较.结果表明,在禾谷镰刀菌基因组中,共发现4679个SSR序列,总长度为96.2kb,占基因组全长的0.27%.平均7.7kb碱基中有一个大于15 bp的SSR序列.在稻瘟病菌基因组中共发现16398个SSR系列,其总长度达到330kb,约占整个基因全长的0.85%,平均2.36kb碱基中就分布有1个SSR序列.在禾谷镰刀菌基因组中,数量最多的是五碱基重复序列,其次是六碱基重复序列;稻瘟病菌基因组中数量最多的是单碱基重复序列,其次为三碱基重复序列和五碱基重复序列.两基因组中数量最少的都是二碱基重复序列.尽管这两种植物病原真菌都属子囊菌,基因组大小也十分接近,但无论是在SSR的总体数量上,还是在各类SSR的分布上,两种植物病原真菌都存在十分显著的差别.     

淡紫拟青霉对尖孢镰刀菌的拮抗作用与机制分析

研究表明淡紫拟青霉次生代谢物质对尖胞镰刀菌的孢子萌发与菌落生长有明显的抑制作用.淡紫拟青霉与镰刀菌活体间存在明显的营养竞争作用;淡紫拟青霉菌能产生细胞壁降解酶和蛋白或多糖性质的拮抗性物质;此活性物质存在于胞内和胞外,胞外物质和胞内提取液-1对尖胞镰刀菌孢子生成的抑制率在90%以上,粗蛋白提取液和粗多糖提取液的抑制率在73%左右,丙酮提取液抑制率最低,仅为25.42%;淡紫拟青霉抑菌活性物质主要存在于水相中;活性物质对温度耐受力较差,100℃或80℃处理30 min,基本失去活性.     

香蕉枯萎病防治进展

香蕉枯萎病是一种对外检疫性病害，世界各生产区均有不同程度的发生，每年给农业生产造成巨大损失，是一种难以防治的土传病害。本文重点阐述了香蕉枯萎病的防治方法和未来发展趋势。     

Isolation of Pathogenicity Mutants of Fusarium oxysporum f. sp. melonis by Insertional Mutagenesis

Restriction enzyme-mediated integration (REMI) mutagenesis was used to isolate mutants of Fusarium oxysporum f. sp. melonis impaired in pathogenicity. The race 2 strain Mel02010 was transformed with linearized pSH75, conferring resistance to hygromycin B, with or without the enzyme used to linearize the plasmid. Addition of restriction enzymes did not affect the transformation frequency. A total of 2929 REMI transformants were tested for pathogenicity to three melon cultivars, Amus, Ogon 9 and Ohi. The race 2 strains are pathogenic to Amus and Ogon 9, but not to Ohi. Of 43 transformants with reduced pathogenicity on susceptible melon cultivars, 12 mutants were examined in detail for pathogenicity, vegetative growth and integrative mode of pSH75. The levels of pathogenicity varied among these mutants. Two mutants (B48 and B137) almost completely lost pathogenicity to both susceptible cultivars, and the others had reduced pathogenicity. Mutants B48, B241, B886 and X36 were also impaired in vegetative growth. Mutant B809 was a biotin auxotroph. By DNA gel blot analysis, nine mutants were found to contain a single copy of the transformation vector. These mutants may thus be useful in isolating genes involved in pathogenicity. Received 22 December 2000/ Accepted in revised form 16 April 2001     

Molecular characterization and in planta detection of Fusarium moniliforme endopolygalacturonase isoforms

The activation of Fusarium moniliforme endopolygalacturonase (endoPG) was studied during infection of maize plants. EndoPG is a plant cell wall degrading enzyme that cleaves the pectin component causing cell death. The authors generated several hybridoma cell lines producing endoPG specific monoclonal antibodies. One monoclonal antibody was selected and successfully used in Western blotting analysis to detect F. moniliforme endoPG secretion in vitro and in planta. Two F. moniliforme strains (FC-l0 and 62264) were used for the studies. Both strains revealed the expression of a single endoPG in vitro as in planta. EndoPG from strain FC-10 presented four isoforms whereas only two isoforms were revealed in the endoPG from strain 62264. Differences were also found in the sequences of the two endoPG genes indicating the presence of endoPG variability among F. moniliforme strains.     

Effects of Azoxystrobin on Mycotoxin Production in a Carbendazim-Resistant Strain ofFusarium sporotrichioides

Carbendazim-resistant (RS) and control (CS) strains ofFusarium sporotrichioides Sherb., previously developed in our laboratory, were exposed to graded concentrations of azoxystrob in in broth media under shake-culture conditions for 2, 3, 4 and 8 days. Azoxystrobin concentrations were 0, 1, 10 and 100 mg 1^-1 broth and cultures were incubated at a constant 25°C. Mycelial growth was significantly affected by strain (P<0.01), azoxystrobin concentration (P<0.001) and incubation time (P<0.001). Combined results for the four incubation times showed that CS yielded higher mycelial mass than RS (P<0.01) only in the absence of azoxystrobin. At fungicide additions of 1, 10 and 100 mg P^-1 mycelial growth was reduced (P<0.001) with minimal strain differences (P>0.05) at all three doses of azoxystrobin. Significant (P<0.05 or better) strain-fungicide interactions were recorded in trichothecene production following exposure to azoxystrobin. At 4 and 8 days of incubation, the 10 mg 1^-1 addition of azoxystrobin stimulated T-2 toxin synthesis (P<0.05) only in RS cultures. In contrast, T-2 toxin enhancement in CS cultures occurred only on day 8 but at a lower level of azoxystrobin (1 mg1^-1). Thus, the stimulation of T-2 toxin synthesis depended upon strain and azoxystrobin level. Production of diocetoxyscirpenol (DAS) was affected by a more complex set of interactions. Overall means showed that, in comparison with initial values (on day 2 or 3), DAS output maximized significantly(P<0.05) on day 4 in RS cultures and on day 8 in CS. Marked strain effects were observed on exposure to the 10 mg 1^-1 level of azoxystrobin. At this level, DAS production was enhanced in RS only after 4 (P<0.01 ) and 8 (P<0.05) days of incubation, while in contrast, CS reduced DAS production. As with T-2 toxin, DAS production in CS was stimulated (P<0.05 or better) only at low exposure levels of azoxystrobin. In the case of neosolaniol (NEO), however, the main effect of strain was significant (P<0.05), with CS producing consistently more of the mycotoxin than RS on day 4 of the experiment. At this point, the NEO:T-2 toxin ratio was also higher in CS (0.63) than in RS (0.12), a feature reported by us previously. In conclusion, the present investigation has shown for the first time that the development of resistance to one fungicide can affect trichothecene production inF. sporotrichioides on exposure to a second fungicide. These results have been incorporated into a new classification scheme for fungicide efficacy which is also presented in this paper. http://www.phytoparasitica.org posting Oct. 7,2001.     

Extracts of killedPenicillium chrysogenum Induce resistance against Fusarium wilt of melon

Dry fungal biomass ofPenicillium chrysogenum (dry mycelium), a waste product of the pharmaceutical industry, was extracted with water and applied to the roots of melon plants before or after inoculation withFusarium oxysporum f.sp.melonis (Font). Seedlings (4–6 days after emergence) treated with either acidic dry mycelium extract (DME) or neutralized dry mycelium extract (NDME) were protected against challenge infection withFom. A single drench with 2–5% DME applied 12–72 h before inoculation provided significant control of the disease compared with water-drenched, challenged seedlings. No protection was seen in plants treated 0–6 h before inoculation or 0–48 h after inoculation. Neither DME nor NDME (0.5–5%) had any effect on fungal growthin vitro, which implied that disease controlin vivo was mediated by induced resistance. The resistance induced by DME protected melon plants not only against race 1,2, but also against the three other races of the pathogen, indicating a race-non-specific resistance againstFom. Both DME and NDME significantly increased peroxidase activity and free L-proline content in seedlings 12 h and 48 h after soil drench, respectively. Resistance to Fusarium wilt was significantly associated with elevated levels of peroxidase activity but not with free L-proline content. Thus, peroxidase might be involved in the defense mechanisms activated by DME or NDME. http://www.phytoparasitica.org posting Aug. 31, 2001.