Enhancement of Antifungal Metabolite Production from Gamma-ray Induced Mutants of Some Trichoderma Species for Control Onion White Rot Disease

γ射線誘變木黴菌增生抗菌代謝物以防治洋蔥白腐病

Wafaa M. Haggag ； H. A. A. Mohamed

《植物病理學會刊》 11卷1期 (2002/03) Pp. 45-56

https://doi.org/10.6649/PPB.200203_11(1).0007

摘要

本研究利用γ射線誘導木黴菌 (Trichoderma spp.) 產生突變株，藉以探討其對木黴菌產生抗菌代謝物質之改善情形及其防治洋蔥白腐病菌 (Sclerotium cepivorum) 之功效。以劑量為 20 與 50 kilo-rad的γ射線照射T. harzianum, T. viride 及T. koningii 的孢子，穫得表現不同生長速率與拮抗能力的突變株。從每一種 (species) 木黴菌，選出兩株生長較快、產孢量較多、且抗菌能力較佳者進行試驗。將木黴菌野生株 (wild type) 與突變株進行液態培養，從濾液中萃取代謝物質，並經過 SDS-PAGE 電泳分析、或 HPLC 層析及檢定。結果顯示，與野生株比較，所有供試的Υ射線突變株均產生較高活性的胞外酵素 (exo-enzymes)。分析β-1,3 glucanase 與幾丁質分解酵素 (chitinase) 的同功異構酵素，T. harzianym與 T. koningii 的突變株產生的酵素量及形成的條帶 (bands) 最多。而 T. viride 突變株產生纖維素分解酵素 (cellulase) 與幾丁質分姐酵素的活性亦較高。經由 HPLC 分析，供試木黴菌突變產生的代謝產物 (包括酚化合物與抗生素 (gliotoxin, trichodermine 及 viridin) ) 均比野生株產生者大幅度增加。在田間受白腐病菌 (S. cepivorum) 自然污染的洋蔥田，接種木黴菌突變株後均能顯著地降低本病的發病度，且增加洋蔥產量。試驗顯示，木黴菌突變株較野生株更能顯著抑制病原菌在根圈土壤中生長，同時，突變株在土壤中的密度可以持續上升至 18 星期，而野生株的密度在 7 星期後即開始下降。

關鍵字

γ射線 ； 木黴菌 ； 突變 ； 抗生素 ； 抗菌代謝物 ； 胞外酵素 ； 酚化合物 ； 洋蔥白腐病

並列摘要

The influence of gamma-irradiation on improving production of anti-fungal metabolites and biological proficiency of the biocontrol agent Trichoderma species against Sclerotium cepivontm, the causal organism of onion white rot disease, was studied. Mutants of Trichoderma harzianllm, T. viride and T. koningii were generated by exposing their sporulated cultures to 20 and 50 kilo-rad doses of gamma irradiation. The isolated mutants dispJayed variation in growth and antagonistic activity. Two mutants with better growth rate, sporulation and antagonistic effect against the pathogen were selected from each species. Antifungal metabolites were extracted from the culture filtrates of the Trichoderma isolates, fractionated by PAGE or HPLC and assayed. Results showed that all selected mutant isolates produced highly active exo-enzymes compared to the wild type. Mutants derived from T. harziallum and T. koningii had the highest isozyme band umber and quantity of chitinase and β-1,3 glucanase. Mutants of T. viride also showed higher levels of cellulase and chitinase isozymes. Fractionation of the culture filtrates via HPLC revealed that production of the metabolites included phenolic compounds and antibiotics, including gliotoxin, trichodennine and viridin, were greatly increased over the wild-type in all selected mutants. In soil naturally infested with S. cepivorum, Trichoderma mutants significantly reduced the onion white rot disease incidence and improved the plant yield. Trichoderma mutants were effective in reducing the pathogen growth in rhizosphere soil Ornpared to the wild type strains. At the same time, population counts of mutants were dramatically increased in rhizosphere soil for 18 weeks compared to 7 weeks in wild types.

並列關鍵字

Antibiotics ； antifungal metabolites ； exoenzymes ； gamma radiation ； mutation ； onion white rot ； Sclerotium cepivorum ； Trichoderma species