臺灣梨赤星病及膠銹菌屬銹菌之研究

Abstract

本研究涵蓋梨赤星病之病原與相關的銹菌。調查發現臺中東勢區內梨赤星病的中間寄主龍柏至少有1,279株，當地的龍柏在梨赤星病冬孢子成熟期普遍帶有梨赤星病的冬孢子堆。在一個果園內，距離龍柏5-60公尺的範圍內梨與龍柏愈近，梨赤星病的罹病率及每葉平均病斑數量愈高。在另一個梨園，不同品種中台中一號梨受梨赤星病的感染最少。另一個案例中，施用殺菌劑的梨葉，其梨赤星病的罹病率與嚴重度低於未施藥的梨葉。計算2011年至2016年梨赤星病的進展指出2-3月當地的降雨可能導致梨赤星病發生嚴重。在臺灣中部地區，除了施用農藥在梨樹上及減少龍柏數量之外，近年來防治梨赤星病的替代策略還有噴施殺菌劑在龍柏植株上，本研究中也在實驗室內評估殺菌劑對龍柏上的梨赤星病感染源作用的效力，受測試的9種殺菌劑當中，波爾多液與三氟敏在推薦劑量及一定測試濃度下顯著抑制冬孢子發芽，其中，三氟敏在83 μg a.i./ml完全抑制冬孢子及擔孢子發芽。於膠銹菌與其他銹菌之分類學研究得知，臺灣有過去未曾描述的種類與未知的中間寄主，共蒐集到亞洲膠銹菌(Gymnosporangium asiaticum)、牛角膠銹菌(G. corniforme)、側絲膠銹菌(G. paraphysatum)、獨角膠銹菌(G. unicorne)、新高山膠銹菌(G. niitakayamense)、與一種在栒子屬植物上的膠銹菌。牛角膠銹菌被證實可於巒大花楸上產生銹孢子堆；感染梨樹的有亞洲膠銹菌與新發現的獨角膠銹菌；側絲膠銹菌只產生夏孢子堆在臺灣肖楠上；研究中將玉山假沙梨上的銹菌命名為新高山膠銹菌。除了膠銹菌之外，亦證實草野柄銹菌(Puccinia kusanoi)在玉山箭竹與大葉溲疏間異主寄生。這些銹菌的形態描述，以及包含核糖體大次單元片段序列、內轉錄區間、小次單元片段序列之分子特徵都在本研究中呈現。

Pathogens of pear rust diseases and related rust fungi were investigated in this study. Field surveys showed that more than 1,279 junipers (Juniperus chinensis), the alternate host of pear rust diseases, were found in Dongshi, Taichung. Junipers in this region generally harbored telia of pear rust diseases during the period of teliospores maturation. In one orchard, incidences of the pear rust diseases and the average lesion numbers per leaf increased with decrease of the distance between pear trees and junipers within a range of 5 m – 60 m. In another pear orchard, pear cultivar Taichung No.1 had the lowest pear rust infections among different cultivars. The case in the other orchard showed that pear leaves with fungicide treatments had lower disease incidences and severities compared to those without fungicide treatments. The disease progresses in 2011-2016 were calculated and it suggested that rainfalls in February and March posed a risk of severe pear rust infections in this region. Additional to pesticide application on pear trees and reduction the number of junipers, spray of pesticides on junipers has recently become an alternative strategy to manage the disease in central Taiwan. In vitro evaluation of efficacy of fungicides on pear rust inocula were carried out in this study. Among 9 fungicides tested, Bordeaux mixture and trifloxystrobin inhibited teliospore germination significantly at recommended dosages and at various concentrations. Trifloxystrobin completely stopped germination of teliospores and basidiospores at 83 μg a.i./ml. Taxonomy of Gymnosporangium spp. and other rust fungi in Taiwan showed previously undescribed species and unknown host lineages. Gymnosporangium asiaticum, G. corniforme, G. paraphysatum, G. unicorne, G. niitakayamense, and an undescribed Gymnosporangium sp. on Cotoneaster sp. were found in this study. G. corniforme was demonstrated to produce its aecial stage on Sorbus randaiensis. The pear rust fungi included G. asiaticum and newly discovered G. unicorne. G. paraphysatum was only found to produce uredinia on Calocedrus formosana. Remarkably, we proposed the name G. niitakayamense for the rust on Photinia niitakayamensis. Additional to the rust fungi in Gymnosporangium, we unraveled that the rust fungus Puccinia kusanoi alternated between Yushania niitakayamensis and Deutzia pulchra. The morphological descriptions and the molecular characteristics, including the SSU rDNA, ITS region, and LSU rDNA, of the rusts were provided in this study.