Monosporascus root rot and vine decline of melon (MRRVD) is a destructive disease complex mainly occurring in semiarid cultivation areas. In the last decade, in the melon producing area of Sardinia (Italy), yield reductions up to 100% were recorded due to the occurrence of MRRVD. The present study aimed to undertake a two-year survey of fungal pathogens associated with MRRVD grown as a monocrop in two locations in Central Sardinia, Sinis, and Sassu, and to investigate the possible role of soil fungal diversity in the disease development. Melon plants were affected by similar symptoms but colonized by a set of soil-borne fungal pathogens different between surveyed sites and cropping seasons, including Plectosphaerella melonis, P. cucumerina, Fusarium solani, Macrophomina phaseolina and Monosporascus cannonballus. Olpidium bornovanus and O. virulentus were isolated using bait plants and detected by NGS analysis. Bait plants had a general decrease in biomass and yellowing of foliage. The presence of most of the isolated pathogens was also confirmed by the NGS analysis of the soil microbiome. Our results confirm that among the fungal complex implicated in the occurrence of RRVD in Sardinia, O. bornovanus along with O. virulentus likely assume a key role in the development of the disease alone and possibly in association with other pathogens. Differences in the pathogenic fungal spectrum here recorded in symptomatic roots may be associated with agricultural practices, soil physicochemical characteristics, and fungal community composition and function profile.

单孢菌根腐烂和葡萄藤的腐烂（MRRVD）是一种破坏性疾病，主要发生在半干旱栽培区。在过去的十年中，在撒丁岛（意大利）的甜瓜产区，由于MRRVD的出现，单产下降了100％。本研究旨在对在中撒丁岛，Sinis和Sassu的两个地方以单作作物形式生长的与MRRVD相关的真菌病原体进行为期两年的调查，并调查土壤真菌多样性在疾病发展中的可能作用。瓜类植物受到类似症状的影响，但被一系列土壤传播的真菌病原菌所定植，这些病原菌在调查地点和种植季节之间存在差异，其中包括甜菜侧柏，黄瓜黄瓜，枯萎镰刀菌，菜豆大红菜和Monosporascus cannonballus。使用诱饵植物分离出婆罗双鱼（Opipidiumbornovanus）和恶性疟原虫（O.virulentus），并通过NGS分析对其进行检测。诱饵植物的生物量普遍减少，叶片变黄。土壤微生物组的NGS分析也证实了大多数分离的病原体的存在。我们的研究结果证实，中真菌在复杂的RRVD在撒丁岛，发生牵连O. bornovanus随着O. virulentus可能假设在疾病的发展中起关键作用单独和可能与其他病原体的关联。 有症状根源中此处记录的病原性真菌谱的差异可能与农业实践，土壤理化特性以及真菌群落组成和功能特征有关。