Abstract

Microbes encounter various environmental factors which frequently cause detrimental effects on their population dynamics. Ralstonia solanacearum is a devastating bacterium causing a deadly and very complex disease of many agronomically important crops. To better control the disease, information about responses of distinct strains of this bacterium to environmental factors is certainly important but still insufficient. In this study, effects of salinity, excess copper, extreme pHs, drought and light on the propagation and survival of a representative of R. solanacearum strains in Taiwan, Pss4, were assessed. Our results showed that salinity negatively affected Pss4 multiplication in rich media at a dose-dependent manner, but resulted in negligent effects on its survival in sand and in water. In the presence of excess copper, similar negative effects on Pss4 culturability in rich media and at a less level on that in sand occurred. Additionally, Pss4 multiplication in rich media was substantially reduced at pH 9.0 and at a less degree at pH 5.0. Moreover, the survival of this bacterium in sand was sensitive to drought, but it sustained under incident light in water. The results were compared with previous studies on distinct R. solanacearum strains prevalent in different geographic regions and discussed in detail. The information gathered from this study would pave to the way for future studies on field samples to advance disease epidemiology and develop feasible strategies for disease control in Taiwan.

中文摘要

在自然環境中，微生物常遭遇對其族群動態有害的因子。植物青枯病菌 (Ralstonia solanacearum) 是一種可造成眾多重要作物致死萎凋病的複雜病原細菌，為了尋求有效的病害防治策略，全面性地了解自然環境因子對於青枯病菌族群動態的影響自然是十分重要且必需的，但目前人們對於這方面所知仍十分有限，且所得訊息常是各地而異。在本研究中，我們針對一株具地區代表性的臺灣番茄青枯病菌株，分析高鹽、過量銅、極端pH 值、乾旱及光照等因子對此菌之增殖與存活的影響。結果顯示：(1)在優養條件下，高鹽對此菌的增殖有不良影響，但對於在沙土或水中的病菌存活則並無顯著的影響；(2)過量銅對優養條件下的病菌增殖有不良影響，而對在沙土中病菌存活的影響則較小；(3)在pH 值為9.0 或5.0 的優養條件下，病菌的繁殖大大降低；(4) 乾旱對在沙土中病菌的存活影響極大，而光照對病菌在水中存活的影響則並不顯著。此外，我們也進一步將這些結果與在全球其他地區針對當地青枯病菌菌株所得之結果進行比較分析。本研究所得之資訊與建立之分析系統，將有助於未來全面性分析臺灣田間樣本中青枯病菌之族群動態及環境因子對其增殖與存活的影響，並期望對於青枯病流行病學及防治策略有所助益。

Keyword: Ralstonia solanacearum, multiplication, survival, environmental factors. 青枯病菌、增殖、存活、環境因子。