Factors affecting formation of hymenia of Thanatephorus cucumeris (teleomorph of Rhizoctonia solani AG 2-2 IIIB), the causal agent of Chinese amaranth foliage blight

Abstract

測試七種土壤覆蓋貿材對莧菜葉枯病原菌Thanatephorus cucumeris (teleomorph of Rhizoctonia solani AG 2-2IIIB) RSA-03和RSA-09兩菌株形成有性世代的影響，結果發現BVB No. 4栽培介質可穩定地誘使莧菜葉枯病菌大量形成子實層。進一步，修正Naito氏等之土壤覆蓋法(soil-cover-culture method)生產擔抱子的流程如下：將R. solani接種於含1% (w/v)酵母抽取物之Potato-yeast extractdextrose agar (PYDA)培養基平板（內徑9公分），在28℃下培養四天，隨後覆蓋90 ml土壤［含有40% (v/v) BVB No.4栽培介質及40-50% (v/v)水分］，移置於濕室中四天後，在覆蓋的土壤表面可穩定產生大量絨毛狀灰白色的子實層。本研究修正過的栽培介質土壤覆蓋法(peat moss- soil-cover-culture method)所產生的子實層表面積約為Naito氏上壤覆蓋法所生產者的三至四倍。莧菜葉枯病菌RSA-03和RSA-09兩菌株形成有性世代的最適溫度與酸鹼值分別為24-28℃及pH5-7。在土壤中加人有機、無機添加物及農藥等均會干擾本菌子實層的形成，其中土壤中添加l%(v/v）魚粉、苦茶粕及苦楝可顯著抑制本菌產生子實層與擔抱子。此外，土壤注人鋅錳乃浦、免賴得、貝芬替、福多寧、五氯硝苯、依普同及賓克隆等化學農藥，亦皆會抑制本菌子實層的形成。 In the study, Naito's soil-cover culture method was modified for production of hymenia of Thanatephorus cucumeris, the causal agent of Chinese amaranth foliage blight. Result showed that the peat moss-soil-cover culture method (PSC method) was more effective in producing hymenia of both T. cucumeris RSA-03 and RSA-09 isolates. The procedures of PSC method were as follows: (1) to inoculate each Rhizoctonia isolate onto potato-yeast extract-dextrose agar plate in a 9-cm petri dish, (2) to incubate the fungus at 28 for 4 days until its colony completely covered the agar plate surface, (3) to cover the agar plate surface with 90ml soil [included 40% (v/v) BVB No. 4 peat moss and maintained the soil moisture at 40-50% (v/v)], (4) to keep the soil-cover plates in moist chamber. Hymenial formation was observed after incubation for 4 days. The PSC method was suitable for hymenial formation of the pathogen and enable to enhance markedly 3-4 fold amount of hymenial production as compared to Naito's soil-cover-culture method. The factors affecting hymenial formation of the pathogen included temperature, humidity, light, aeration, and culture substrate. The suitable temperatures and pH values of covered soil for R. solani RSA-03 and RSA-09 hymenial formation were the range of 24 - 28 and pH 5 - 7, respectively. Covered soils amended with various organic matters and fungicides did significantly influence the hymenia formation of T. cucumeris RSA-03 and RSA-09. Result showed that the hymenia of the fungus were completely inhibited by 1%(v/v) fish meal, tea seed pomace and chinaberry meal. All the tested fungicides, such as mancozeb, benomyl, carbendazim, flutolanil, PCNB, iprodione and pencycuron were significantly effective in inhibiting the hymenial formation