以亞磷酸防治薑軟腐病及防治藥劑篩選

Abstract

薑 (Zingiber officinale Rosc.) 為多年生宿根性單子葉植物，是重要香辛類佐料蔬菜，主要產區包括臺東、南投、苗栗及花蓮等。目前臺灣薑產業遇到的最大瓶頸為連作障礙，且以Pythium myriotylum Dreschler所引發的薑軟腐病為最主要因子。臺灣多年來鮮少關於薑軟腐病的田間病因調查資料，為探討造成薑軟腐病的其他可能成因，本研究自臺東知本、龍田、銅礦、臺東區農業改良場、初鹿牧場及南投集集等地區的薑田採集罹病植株和土壤樣本進行菌株分離及PCR檢測，鑑定結果發現所分離的菌株有主要為P. myriotylum，但也包括一些Pythium splendens Braun和一株Pythiogeton ramosum Minden。進一步以菌絲塊接種，發現僅P. myriotylum可以在薑植株造成黃化萎凋及塊莖褐化水浸狀等病徵，但P. splendens和Py. ramosum都無法成功侵染。針對罹病薑塊莖，以Pmy5/ITS2引子對進行PCR，在樣本LT-2、TG-1、YC-1、TC-2、TC-3和TC-4皆可檢測到P. myriotylum；附著在塊莖的土塊 (bulk soil, Bs) 和薑塊莖表面取下的土壤 (rhizome soil, Rs) 樣本LT-1Bs、LT-1Rs、LT-2Bs和LT-2Rs也可以檢測到P. myriotylum。這些結果顯示，以薑塊莖或是土壤可以直接檢測薑軟腐病是否由P. myriotylum引起。另關於薑軟腐病的防治，臺灣目前的推薦藥劑只有依得利，為瞭解田間的P. myriotylum菌株是否已發展依得利的抗藥性，本研究自台東龍田、台東市和台東銅礦等地區的P. myriotylum菌株進行敏感性分析，發現依得利的半效應濃度 (EC50) 約為0.02 ppm，明顯低於目前推薦之田間施用濃度。除此之外，以培養基試驗測試發現滅達樂、三氟敏及百克敏對於P. myriotylum菌絲生長的抑制效果與依得利相似，氟比拔克抑制菌絲生長能力較差，但實際適用情形還需後續以盆栽及田間試驗加以驗證。另外，也測試中和後亞磷酸的防治效果，發現施用濃度為1,000 ppm時即可有效防治薑軟腐病，將施用濃度提升至5,000 ppm的防治效果更佳。這些結果顯示在臺東田間引起薑軟腐病的病源仍以P. myriotylum為主，滅達樂、三氟敏、百克敏和中和後亞磷酸具有防治薑軟腐病的潛力。

Ginger (Zingiber officinale Rosc.) is an important perennial monocot species, with its rhizome widely used as a spice worldwide. The annual cultivated area of ginger is about 1,000 hectares in Taiwan, including Taitung, Nantou, Miaoli and Hualien counties. The biggest challenge for cultivation of ginger in Taiwan is ginger soft rot caused by Pythium myriotylum. It’s been a long time since last survey of ginger soft rot in the field of Taiwan. This study aims to exploreadditional pathogens of ginger soft rot. The ginger rhizomes and soil samples were collected from Nantou Jiji and different areas of Taitung, including Zhiben, Longtian, Tonggong, Taitung District Agriculture and Research Extension Station (TTDARES) and Chulu Ranch, and were used for pathogen isolation and PCR detection. Most of the isolates were found to be P. myriotylum, while some were Pythium splendens and one strain was Pythiogeton ramosum. In this study, P. myriotylum causes leaf yellowing in the ginger leaves and watery dark brown lesion in the rhizomes of ginger, whereas neither P. splendens or Py. ramosum infect the ginger plants. P. myriotylum was detectable in the ginger rhizome samples LT-2, TG-1, YC-1, TC-2, TC-3 and TC-4 as well as in the soil samples LT-1Bs, LT-1Rs, LT-2Bs and LT-2Rs using PCR. These results indicate that PCR can distinguish whether the soft rot symptoms were caused by P. myriotylum. Currently, etridiazole is the only recommended chemical fungicide in Taiwan for controlling ginger soft rot. To know the possibility that field isolates of P. myriotylum might have developed fungicide resistance, P. myriotylum isolates from Taitung Longtian, TTDARES and Tonggong were analyzed for their sensitivity toward etridiazole. The results showed that the EC50 values of etridiazole was approximately 0.02 µg/mL, much lower than the concentration recommended by the government. According to the results of fungicides amended assay, metalaxyl, trifloxystrobin and pyraclostrobin were found to have hyphal growth inhibitionactivity similar to etridiazole and better than flupicolide plus propamocarb hydrochloride. Furthermore, the application of 1,000 mg/L neutralized phosphorous acid (NPA) effectively prevented the occurrence ginger soft rot, and 5,000 mg/L NPA gave even better prevention. These results demonstrate that P. myriotylum is still the main pathogen causing ginger soft rot in the Taitung area, and provide alternative strategies for the control of the disease.