Rubber () is an economically important crop in Thailand, especially in the southern part of Thailand where the climate is suitable for cultivation. In our recent survey of rubber plantations, rubber trees infected with several fungal pathogens resulting in leaf spot, leaf blight, and in severe cases, leaf defoliation, were observed in the field. These symptoms have not been observed previously and can be considered a novel leaf fall disease. To date, the pathogens causing leaf diseases on rubber trees in Thailand have been characterized to be caused by fungi in the genera , and . However, species in the genus , as fungal pathogens that cause leaf spots on rubber trees in Thailand, have not been characterized. Therefore, the aim of this study was to identify and characterize associated with rubber leaf spot disease with morpho-molecular studies combined with pathogenicity tests. Morphological characteristics revealed that isolates PSU-108, PSU-109, PSU-110, and PSU-111 belong to sp., whereas multigene phylogenetic analyses with actin (), calmodulin (), chitin synthase-1 (), glyceraldehyde-3-phosphate dehydrogenase (), and internal transcribed spacer (ITS), identified these isolates as . Hence, this report suggests as the causal agent of leaf spot disease on rubber tree leaves. The findings in this study could be helpful for the development of appropriate measures to manage plant disease in rubber tree fields.

中文翻译：

---

与泰国南部橡胶树（Hevea brasiliensis）叶斑病相关的暹罗炭疽菌的形态和分子特征

橡胶（）是泰国重要的经济作物，特别是在气候适宜种植的泰国南部地区。在我们最近对橡胶种植园的调查中，在田间观察到橡胶树感染了多种真菌病原体，导致叶斑病、叶枯病，严重时导致叶片落叶。这些症状以前没有观察到，可以被认为是一种新型落叶病。迄今为止，引起泰国橡胶树叶部病害的病原体已被定性为由 、 和 属真菌引起。然而，该属物种作为引起泰国橡胶树叶斑的真菌病原体，尚未得到表征。因此，本研究的目的是通过形态分子研究结合致病性测试来识别和表征与橡胶叶斑病相关的疾病。形态学特征显示，分离株 PSU-108、PSU-109、PSU-110 和 PSU-111 属于 sp.，而肌动蛋白 ()、钙调蛋白 ()、几丁质合成酶-1 ()、甘油醛-3- 的多基因系统发育分析磷酸脱氢酶 () 和内转录间隔区 (ITS) 将这些分离株鉴定为 . 因此，该报告表明它是橡胶树叶上叶斑病的病原体。这项研究的结果可能有助于制定适当的措施来管理橡胶树田的植物病害。