以拮抗性木黴菌防治豇豆鐮胞菌萎凋病

Biological Control of Fusarium Wilt of Asparagus Bean by Trichoderma harzianum

由Fusarium oxysporum f. sp. tracheiphilum 所引起的豇豆鐮胞菌萎凋病，為豇豆生產最主要的限制因子，目前沒有有效的防治措施。本研究嘗試利用自田間分離之木黴菌(Trichoderma spp.)菌株，進行其對萎凋病菌的拮抗作用探討及其對豇豆萎凋病之田間病害防治評估。以自屏東縣里港鄉豇豆發病田分離之萎凋病菌F3 菌株作為供試的病原菌，分別以玻璃紙抗生法及對峙培養法探討木黴菌對萎凋病菌的抑制作用。以玻璃紙抗生法評估15 株木黴菌菌株對豇豆萎凋病菌的抑制效果，結果顯示15 株木黴菌皆不會產生對抗病原菌的抗生物質。對峙培養法的結果顯示，15 株木黴菌中共有7 株對F3 菌株生長的抑制率達70%以上，其中，T4、T10、T12 及T16 等4 個菌株不僅抑制萎凋病菌菌絲的直線生長，同時亦可覆蓋於病原菌的菌落上。測試此4 菌株於平板上的直線生長速度及產孢量，顯示T10 及T12 具有快速生長及大量產孢的特性，因此提供做為進行防治實驗的供試菌株。以電子顯微鏡觀察T10 及T12 菌株的形態特徵，並比對檢索表，確認T10及T12 兩株木黴菌菌株的分類地位皆屬於Trichoderma harzianum。以木黴菌T10及T12 混合菌株的孢子懸浮液、抑菌中藥五倍子萃取液、商品化枯草桿菌稀釋液及S-H 土壤添加物分別進行豇豆萎凋病的溫室非農藥防治試驗，並以化學藥劑撲克拉錳作為陽性對照組，結果顯示，豇豆植株處理木黴菌孢子懸浮液後，和無處理的對照比較可抑制萎凋病的發生率達27%，其效果雖不如化學藥劑撲克拉錳40%的病害抑制率，卻優於其他的處理組。以木黴菌、抑菌中藥五倍子萃取液及化學藥劑撲克拉錳進行豇豆萎凋病之田間防治實驗，在播種104 天後，經木黴菌處理的豇豆植株，其萎凋病的發病率只有38%，木黴菌T10 及T12 菌株對病害的防治效果明顯優於無處理64%的萎凋率以及化學藥劑撲克拉錳與抑菌中藥五倍子萃取液52%的萎凋率。顯示木黴菌T10 及T12 菌株有潛力開發成為防治豇豆萎凋病的生物農藥。

Fusarium wilt of asparagus bean caused by Fusarium oxysporum f. sp. tracheiphilum is one of the major limiting factors for asparagus bean production. At the present time, there is no effective control method for this severe disease. The main purpose of the study is to develop a biological method to control the disease. The Trichoderma isolates used in this study were collected from fields. F3 isolate of F. oxysporum f. sp. tracheiphilum was obtained from wilted asparagus bean plants collected from the field at Li-gang in Ping-tung County. The cellophane test and dual culture method were used in this study to assess the inhibition effect of Trichoderma spp. to F. oxysporum f. sp. tracheiphilum. The cellophane test showed that all tested isolates of Trichoderma did not produce antibiotics against F3 on 10% V-8A. The dual culture results showed that 7 out of 15 tested isolates of Trichoderma spp. could cause more than 70% inhibition of linear growth of F3 on PDA; Isolates T4, T10, T12 and T16 could grow over the colony of F3. Isolates T10 and T12 showed faster growth rate and more conidia production than T4 and T16, and were thereafter used in field control test. Isolates T10 and T12 were identified as T. harzianum according to their morphological characteristics, and hypha of T10 formed dense coils on the hypha of F3 when observed under a field emision scanning electron microscope. In greenhouse test, as compared with nontreated control, the disease inhibition rates of asparagus bean Fusarium wilt were 27, 20, 17, 5 and 40%, respectively, when infested soil were treated with Trichoderma spore mixture, Bacillus subtilis, Galla rhois water extract, S-H soil amendment mixture and 50% prochlorate manganese WP. In field trial, after 104 days, the disease incidence rates of asparagus bean Fusarium wilt were 38, 52 and 52% respectively, when infested soil were treated with Trichoderma spore mixture, Galla rhois water extract and 50% prochlorate manganese, while the disease incidence rate of untreated control was 64%. Isolates T10 and T12 of T. harzianum have the potential to be used as biological control microorganisms.