哈茨木霉几丁质酶诱导及其对水稻纹枯病菌的拮抗作用

 在实验室条件下分别以几丁质和水稻纹枯病菌(Rhizoctonia solani)细胞壁作唯一碳源诱导哈茨木霉(Trichoderma harzianum)菌株NF9、TC3和P1产生几丁质酶,用硫酸铵沉淀法制备几丁质酶粗提液。上述木霉菌株内切几丁质酶活性(对胶体几丁质浑浊度的减少率)分别为79.8%、74.4%和76.0%,均显著高于非诱导的阳性对照。培养第5 d几丁质诱导的木霉菌株NF9和TC3内切几丁质酶活性显著高于由水稻纹枯病菌细胞壁诱导的酶活性。体外测定表明,通过诱导的木霉菌株TC3、NF9和P1几丁质酶粗提液对水稻纹枯病病菌的拮抗圈直径可达38、21和23 mm,与非诱导的阳性对照比较有显著性差异。对木霉几丁质酶拮抗作用的特点及生防应用进行了讨论。     

Antagonism of local isolates of Trichoderma spp. on citrus root rot disease by Fusarium solani in the mekong delta of vietnam

The local isolates of Trichoderma spp. and Fusarium solani were colected from citrus orchards in the Mekong delta of Vietnam and isolated on PDA, PDB and TSM medium for antagonism and Koch‘s postulate testing. The results showed that the high chitinolytic enzymes content of Trichoderma     

The Relationship Between Pathogen-induced Systemic Resistance (ISR) and Multigenic (horizontal) Resistance in Plants

Plants have developed mechanisms to successfully co-exist in the presence of pathogenic organisms. Some interactions between plants and pathogens are based on recognition of specific elicitor molecules from avirulent pathogen races (avr gene products), which is described in the gene-for-gene resistance theory. Another type of resistance, multigenic (horizontal) resistance, is a less well-studied phenomenon that depends upon multiple genes in the plant host. All plants possess resistance mechamisms which can be induced upon pre-treatment of plants with a variety of organisms or compounds. This general phenomenon is known as induced systemic resistance (ISR). At least in some plant species, ISR depends on the timely accumulation of multiple gene products, such as hydrolytic enzymes, peroxidases or other gene products related to plant defences. The pre-treatment of plants with an inducing organism or compound appears to incite the plant to mount an effective defense response upon subsequent encounters with pathogens, converting what would have been a compatible interaction to an incompatible one. Our studies in three plant–pathogen systems clearly document that multigenic-resistant plants constitutively express specific isozymes of hydrolytic enzymes that release cell wall elicitors, which in turn may activate other defense mechanisms. ISR induces constitutive accumulation of these and other gene products prior to challenge. ISR is known to function against multiple organisms, and there is no specificity observed in the accumulation patterns of defense-related gene products when ISR is induced. It is therefore hypothesized that the constitutive accumulation of specific isozymes of hydrolytic enzymes, or other defense related gene products, is an integral part of both multigenic resistance and the phenomenon of ISR. Further, plants in which ISR has been activated appear to move from a latent resistance state to one in which a multigenic, non-specific form of resistance is active.     

厚垣普奇尼亚菌Pochonia chlamydosporia产生的几丁质酶对南方根结线虫卵孵化的影响

 【目的】卵寄生真菌厚垣普奇尼亚菌Pochonia chlamydosporia产生的几丁质酶对定居性根结类和胞囊类线虫的卵壳消解起重要促进作用。线虫卵寄生真菌产生几丁质酶的特性是评价食线虫真菌生物防治潜力的重要生化指标之一。【方法】利用NAG法和pNP法分别测定7株不同来源厚垣普奇尼亚菌Pochonia chlamydosporia几丁质酶的降解酶系和外切酶活性。【结果】7个菌株都能够产生外切酶,其中QNAV97-2、NRRL13094、CFCC84963和 CFCC80919菌株能够产生几丁质降解酶系,几丁质酶活性染色检测分别有2条和4条具有几丁质酶活性的蛋白谱带,其中CFCC80919和QNAV97-2分别产生的38.9 kD和39.8 kD几丁质酶可能是已知的CHI43几丁质酶。具有几丁质降解酶活性的4个厚垣普奇尼亚菌对根结线虫的卵孵化抑制率为40.32%～55.15%,未测定出几丁质降解酶活性的3个菌株对根结线虫的卵孵化抑制率不足20%。显微观察处理的南方根结线虫卵壳变形和破坏。【结论】厚垣普奇尼亚菌系产生的几丁质酶能够消解南方根结线虫卵壳,特别是胚前发育期未成熟卵,抑制卵孵化或杀死卵,且在消解卵的过程中起重要作用。厚垣普奇尼亚菌的几丁质酶活性水平可能是造成该类菌杀线活性差异的原因之一。     

Mechanisms involved in biocontrol and plant induced resistance by Trichoderna asperellun (T. harzianum T-203)

Growing awareness of the environmental damage caused by the use of chemical substances for plant disease control in agriculture has raised the need to study biological alternatives, such as activating the defense response of plant crops by inducers not toxic to the environment. Trichoderna spp. are effective biocontrol agents for a number of soilborne pathogens, and are also known for their ability to enhance plant growth and to induce systemic resistance (ISR) in plants.     

Mechanisms involved in biocontrol and plant induced resistance by richoderma. asperellum (T. harzianum T-203)

Growing awareness of the environmental damage caused by the use of chemical substances for plant disease control in agriculture has raised the need to study biological alternatives, such as activating the defense response of plant crops by inducers not toxic to the environment. Trichoderma spp. are effective biocontrol agents for a number of soilborne pathogens, and are also known for their ability to enhance plant growth and to induce systemic resistance (ISR) in plants. In our laborator…     

Antagonism of local isolates of Trichoderna spp. on citrus root rot disease by Fusarium solani in the mekong delta of vietnam

The local isolates of Trichoderrma spp. and Fusariun solani were colected from citrus orchards in the Mekong delta of Vietnam and isolated on PDA, PDB and TSM medium for antagonism and Koch's postulate testing. The results showed that the high chitinolytic enzymes content of Trichoderma isolates can antagonise with Fusarium solani isolates by preventing the germination of Fusarium macroconidia in in-vitro condition. There are five promising isolates of Trichoderna spp. having high antagonism with Fusarium solani. These Trichoderma isolates also grew well in rice straws, maize stems, weeds and water hyacinth biowaste materials. These results supply the promising trend for biological control of root rot disease on citrus orchards of the Mekong delta.     

Cell wall degrading isoenzyme profiles of Trichoderma biocontrol strains show correlation with rDNA species

Species of the fungus Trichoderma, a genus of Hyphomycetes, are ubiquitous in the environment, but especially in soil. They have been used in a wide range of commercial applications including the production of hydrolases and in the biological control of plant diseases. A fundamental part of the Trichoderma antifungal system consists of a series of genes coding for a surprising variety of extracellular cell wall degrading enzymes (CWDE). Characterisation and identification of strains at …     

Defence reactions in two potato cultivars following infection with two races ofPhytophthora infestans

Summary The kinetics of accumulation of chitinases, glucanases and phytoalexins were studied in two potato cultivars, differing in their degrees of vertical and horizontal resistance, when infected with two races ofPhytophthora infestans. Tuber disks of cvs Kennebec (susceptible, low horizontal resistance) and Huinkul (tolerant, high horizontal resistance) were infected with either race “0” (avirulent) or “C” (complex, race 1.3.5.7.11) ofPhytophthora infestans. Extracts of tuber tissue (0–7 days) from cv. Kennebec infected with race “0” showed a strong increase in phytoalexin production and in chitinase and glucanase activities when compared with those infected with race “C”. These results indicate that race “C” is able to block defensive reactions. No significant differences were observed in cv. Huinkul infected with both races. The contribution of these reactions to horizontal resistance is unknown, and our results would not support a conclusive role for them in the interaction.