本土白殭菌（Beauveria bassiana）菌株之特性差異比較

Biological characterization of Beauveria bassiana isolates from Taiwan

本土不同白殭菌（Beauveria bassiana）菌株之菌絲生長對溫度反應頗為一致，最適溫均在24℃，次為28℃或20℃。供試菌株中以編號Bb-2菌株表現最佳，在各不同溫度處理中均以其菌落最大。在28℃下，24小時，所有菌株之孢子發芽率可達90%以上，但在20小時進行比較，菌株間之孢子發芽情形則有明顯之差異。另外，菌株產孢能力差異極大，產孢量最高與最低者差達4百餘倍，由高而低依序為Bb-1、Bb-2、Bb-3、Bb-4、Bb-5、Bb-6、Bb-7、Bb-8。菌絲產量之高低順序為Bb-2、Bb-6、Bb-7、Bb-5、Bb-3、Bb-4、Bb-8、Bb-1。在酵素活性反應試驗中，Bb-1、Bb-2、Bb-5、Bb-7、Bb-8等菌的脂肪分解酶（lipase）活性明顯較Bb-3、Bb-4、Bb-6強。澱粉酶（amylase）之作用則以Bb-1、Bb-2、Bb-4較佳，Bb-8最差。蛋白酶（protease）活性以Bb-1、Bb-7兩菌株最高，次為Bb-6，Bb-5及Bb-8菌株再次之，最差為Bb-3。在107 conidia/ml濃度下，Bb-2、Bb-6、Bb-7、Bb-8菌株可使99%以上之供試三齡小菜蛾（Plutella xylostella）幼蟲罹病死亡，Bb-3、Bb-4、Bb-5三株菌僅分別有50.2、51.9與46.5%之幼蟲死亡率。白殭菌對四齡甜菜夜蛾（Spodoptera exigua）幼蟲之病原性極強，除Bb-7菌株所引起之幼蟲死亡率不及50%外，其餘各菌株均達90%以上。田間防治試驗結果發現Bb-1、Bb-2、Bb-8三菌株可使小菜蛾蟲數在處理一週後明顯降低。Bb-3菌株處理區小菜蛾蟲數雖未減少，但亦無明顯增加，處理組與對照組比較，均有顯著的防治效果。但平均每棵甘藍之重量，僅Bb-8菌株處理組較對照組及其他處理組重。以紫外線處理菌絲，八菌株中有Bb-1、Bb-2、Bb-3、Bb-4四菌株在經中波長紫外線（312nm，600μw/cm2）處理8小時後仍可生長，另四菌株則完全受抑制，差異頗大。

"The optimal temperature for mycelial growth of indigenous Beauveria bassiana isolates was 24℃, and suboptimal temperature was 28℃ or 20℃. Of the 8 isolates tested, only the colony of Bb-2 isolate showed the greatest radial growth on each temperature. There was a 400-fold difference in spore production between the highest and lowest. Isolates Bb-1 exhibited the highest spore production among B. bassiana isolates tested. Rate of conidial germination was above 90% when incubated at 28°C, for 24 hr, but there was a significant difference among isolates tested after 20 hr incubation. In the enzyme activity tests, the results showed that isolates Bb-1, Bb-2, Bb-5, Bb-7 and Bb-8 had higher lipase activity than Bb-3, Bb-4 and Bb-6. Isolates Bb-1, Bb-2 and Bb-4 exhibited higher amylase activity than other isolates tested. Isolate Bb-8 exhibited the lowest amylase activity among B. bassiana isolates tested. In protease activity test, isolates Bb-1 and Bb-7 exhibited the highest enzymatic activity, followed by Bb-6, Bb-5 and Bb-8. Isolate Bb-3 exhibited the lowest enzymatic activity. Bioassay showed that Bb-2, Bb-6, Bb-7 and Bb-8 isolates were virulent against 3rd instar larvae of Plutella xylostella. The mortalities of P. xylostella larvae caused by these four isolates ranged from 99.1% to 99.8%. All B. bassiana isolates tested except Bb-7 were strongly pathogenic to 4th instar larvae of Spodoptera exigua. All isolates of B. bassiana tested in field trials showed high control efficacy against P. xylostella within 2 weeks. Treatment with isolate Bb-8 resulted in the highest average weight of cabbage harvested per plant among all treatments. Among eight isolates of B. bassiana tested, only isolates Bb-1, Bb-2, Bb-3 and Bb-4 exhibited colony growth on V8 plates after exposure to UV-B irradiation (312 nm, 600 μw/cm^2) for 8 hr."