Even though survival rates for mangrove restoration in Vietnam have often been low, there is no information on fungal pathogens associated with mangrove decline in Vietnam. Therefore, this research was undertaken to assess the overall health of mangrove afforestation in Thanh Hoa Province and fungal pathogens associated with tree decline. From a survey of 4800 Sonneratia trees, the incidence of disorders was in the order of pink leaf spot > shoot dieback > black leaf spot for S. caseolaris and black leaf spot > shoot dieback > pink leaf spot for S. apetala. Approximately 12% of S. caseolaris trees had both pink leaf spot and shoot dieback, while only 2% of S. apetala trees had black leaf spot and shoot dieback. Stem and leaf samples were taken from symptomatic trees and fungi were cultured in vitro. From ITS4 and ITS5 analysis, four main fungal genera causing leaf spots and shoot dieback on the two Sonneratia species were identified. The most frequently isolated fungal taxa were Curvularia aff. tsudae (from black leaf spot),Neopestalotiopsis sp.1 (from stem dieback), Pestalotiopsis sp.1 (from pink leaf spot), and Pestalotiopsis sp.4a (from black leaf spot). The pathogenicity of the four isolates was assessed by under-bark inoculation of S. apetala and S. caseolaris seedlings in a nursery in Thai Binh Province. All isolates caused stem lesions, and Neopestalotiopsis sp.1 was the most pathogenic. Thus, investigation of fungal pathogens and their impact on mangrove health should be extended to other afforestation projects in the region, and options for disease management need to be developed for mangrove nurseries.

中文翻译：

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越南无瓣海桑和干果海桑的红树林枯死和叶病

尽管越南红树林恢复的成活率通常很低，但没有关于越南红树林减少的真菌病原体的信息。因此，本研究旨在评估清化省红树林造林的整体健康状况以及与树木衰退相关的真菌病原体。根据对 4800棵海桑树的调查，病害的发生顺序为粉红色叶斑病 > 茎枯死 > 黑叶斑病S. caseolaris和黑叶斑病 > 茎枯死 > S. apetala粉红色叶斑病。大约 12% 的S. caseolaris树同时出现粉红色叶斑病和新梢枯死，而只有 2% 的S. apetala树木有黑色叶斑病和新梢枯死。茎叶样本取自有症状的树木，真菌在体外培养。从 ITS4 和 ITS5 分析中，确定了导致两种海桑属植物叶斑和芽枯死的四个主要真菌属。最常分离的真菌类群是弯孢菌。tsudae（来自黑叶斑病）、Neopestalotiopsis sp.1（来自茎枯死）、Pestalotiopsis sp.1（来自粉红叶斑病）和Pestalotiopsis sp.4a（来自黑叶斑病）。四种分离株的致病性是通过树皮下接种S. apetala和S. caseolaris 来评估的太平省苗圃中的幼苗。所有分离株都引起茎病变，Neopestalotiopsis sp.1 是致病性最强的。因此，真菌病原体及其对红树林健康影响的调查应扩展到该地区的其他造林项目，并需要为红树林苗圃制定疾病管理方案。