Isolation, identification and pathogenicity of wilting causes of some cucurbits in Syria

Abstract

The research was carried out in the Biodiversity laboratory, National Commission for  Biotechnology in Damascus during 2020-2022  aiming to  isolate and identify the causes of wilt of cucurbits from the roots of some cucurbit crops. Thirty samples were collected from four governorates (Damascus countryside, Daraa, and Deir ez-Zor) and from different host crops (cucumber, squash, melon, and watermelon). The fungal isolates were purified and characterized morphologically, in addition to  study their pathogenicity (incidence and  severity of infection) for each isolate on its host. 10 fungal isolates were described in the laboratory, all of which belong to the type Fusarium oxysoporum, and their host specialization was confirmed. cucumerinum and isolates FO3 and FO4 of Fusarium oxysporum and isolates FO5 and FO6 from Fusarium oxysporum f.sp. melonis, while the isolates FO7, FO8, FO9, FO10 were of Fusarium oxysporum f.sp. niveum. Micro- and macroconidia were produced in all previous isolates, and the diameter of the colony ranged between 3.8 cm - 5.8 cm, after three days of incubation at 27±3°C on PDA medium, while the severity of infection ranged between 11.6%-69.3%. The isolate FO7 from watermelon from Dara’a region was the strongest isolate in terms of colony diameter, degree of infection and severity followed by isolate FO5 from cantaloupe from Deir-ez-Zor region..

In this research, it was possible to select the two most virulent fungal isolate to be used in experiments with bacteria isolated from the soil of the rhizosphere of healthy plants isolated from the same fields.

Key Words: Cucurbit wilt, Fusarium oxysporum, Watermelon, melon