The Epidemic and Transmission Studies of Maize chlorotic mottle virus

玉米褪綠斑駁病毒(Maize chlorotic mottle virus, MCMV)可感染玉米造成葉片褪綠及黃化或壞疽病徵，嚴重時造成植株矮化、褐化枯死情形，蒐集田間樣本並將MCMV 鞘蛋白序列解序後進行親緣性分析，顯示台灣發生的MCMV 病毒與中國大陸及肯亞的MCMV 病毒株親緣性達98%-99%；而本病毒於玉米栽培區如雲林縣、嘉義縣及台南市等地造成大面積危害，玉米產量減少甚至絕收，已成為玉米栽培重要限制因子。由2014 年至2015 年田間調查結果顯示，全台皆有本病毒感染玉米植株，分析其流行趨勢發現本病毒於10 月至翌年5 月為發生盛期。檢測玉米鮮穗種子帶毒情形，顯示種子有極高機率帶有MCMV 病毒，此一情況提高種子傳毒風險，經由長出測試實驗也可獲得種子傳毒病株。MCMV 可藉由多種媒介昆蟲傳播，在台灣已知可以玉米薊馬進行傳播，玉米薊馬(Frankliniella williamsi Hood)以成蟲獲毒能力較若蟲佳，需要一定數量薊馬才能有效傳毒。為有效防治玉米MCMV 病害，應結合田間管理、使用適當的殺蟲劑及選擇耐性品種進行防治。 Maize chlorotic mottle virus, MCMV, was first reported in sweet corn in Taiwan in 2014. Symptoms of MCMV included mottle or mosaic developing into maize leaf chlorosis and necrosis. Moreover, severe plant stunting and death were observed. Phylogenetic analysis of full capsid protein sequence of MCMV isolated from maize field revealed that the invaded MCMV in Taiwan shared 98-99% identity with the Chinese and Kenyan MCMV isolates. MCMV causes severe yield loss in the main maize planting area in Taiwan, including Yunlin County, Chiayi County and Tainan City, and becomes the limiting factor of maize production in Taiwan. According to the field survey result during 2014 April to 2015 April, MCMV are widely distributed in Taiwan. Analysis of the virus disease epidemic demonstrates that MCMV is prevalent from October to the coming May next year. Detection of fresh seeds from ear of MCMV infected maize shows that seeds have very high rate contaminated with MCMV. The presence of MCMV in seeds raises the risk of virus transmission through seeds. To analyze the mode of MCMV transmission by maize thrips (Frankliniella williamsi Hood) in Taiwan, we assayed the maize thrips virus acquisition and transmission ability. The result demonstrates adult maize thrips have higher virus acquisition ability than larva. The result of virus transmission via maize thrips demonstrates that to be able to transmit virus efficiently we need to put sufficient thrips in one maize plants. The effective control of MCMV should be achieved by the integration of cultural practices with suitable insecticides and host tolerance