The Effect of Some Isolates of Fungi That Cause Melon Root Rot Disease on the Germination of Melon (Cucumis melo L.) Seeds and Seedlings

Abstract

This study was conducted at the Plant Diseases Laboratory of the Agricultural Pest Control Section, Agricultural Protection Directorate, Ministry of Agriculture, Baghdad, Iraq, and aimed to isolate and diagnose the common fungi associated with melon root rot disease and test their pathogenic ability to inhibit melon seed germination and infect seedlings. Isolation and diagnosis of fungi associated with root samples from melon plants that showed symptoms of discoloration, root rot and plant wilting from five regions in Iraq: Samarra, Dujail, Balad, Abu Ghraib and Al-Yusufiah, identified 38 isolates (F1 – F38) belonging to the fungi Alternaria alternata, Curvularia lunata, Fusarium spp., Macrophomina phaseolina, Monosporacus sp., Pythium aphanidermatum and Rhizoctonia solani. Results of testing the pathogenicity of the isolates on melon seeds by using water agar (WA) culture medium showed differences among isolates in their ability in reducing the germination rate of melon seeds, with a significant difference to the control treatment. , and the isolates F23 and F24 of M. phaseolina and F8 and F34 of R. solani differed from all other isolates due to their high pathogenicity, as they completely inhibited seed germination, with a highly significant difference from the control treatment, where germination rate reached 93.33%. Testing the pathogenicity of the most pathogenic isolates in pots and under shade conditions confirmed that the two isolates of the fungus R. solani (F8 and F34) produced significantly the highest incidence and severity of infection, reaching 100% for both isolates.

Keywords:

Melon root rot, Fusarium spp., M. phaseolina, R. solani, pathogenicity.