Distribution of Cucumber Root and Crown Rot Disease in Plastic Houses in Sulaymaniyah Governorate, Iraq and Molecular Diagnosis of the Causal Agents
Abstract
Al-Kanaani, F.B., E.M. Al-Maaroof and S.M. Ismail. 2026. Distribution of Cucumber Root and Crown Rot Disease in Plastic Houses in Sulaymaniyah Governorate, Iraq and Molecular Diagnosis of the Causal Agents. Arab Journal of Plant Protection, 44(2):155-167. https://doi.org/10.22268/AJPP-001385 Results obtained from the field survey on cucumber root and crown rot disease in greenhouses of Sulaymaniyah Governorate, showed that disease incidence range was 2.40-100% during the 2022 growing season. The highest disease incidence of 100%, was recorded on Sayff F1 hybrid in the Tainal (Tn-A) location. Isolation and diagnosis of pathogens from the roots and stem bases of cultivated cucumber hybrids showed the presence of Rhizoctonia solani at 30-60% in the diseased samples, followed by Fusarium oxysporum and F. solani (10-35%). Pathogenicity test of the isolates on cucumber seeds showed that R. solani isolates (Rs1, Rs13, Rs14 and Rs15) significantly outperformed all other fungal isolates, and caused complete failure in the cucumber seeds germination in the laboratory and cucumber seedlings emergence in the growth chamber at a rate of 86.11-100%, followed by Fusarium isolates (40-73% in the laboratory and 22.22-33.11% in the growth 165 Arab J. Pl. Prot. Vol. 44, No. 2 (2026) chamber). Isolate Rs14 of R. solani proved its high potential in inciting complete seed rot and seedlings death. The virulence of isolate Rs14 can be attributed to its high ability to withstand environmental conditions such as temperature, pH, and salinity. The optimal environmental needs of temperature, pH and salinity for this isolate was in the range 20-30°C, 5-8 and 0-50 mM, respectively. The results of BLAST analysis of ITS-rDNA sequence data supported the results of phenotypic diagnosis of the fungal isolates with a 99% similarity to the fungus R. solani. Isolate Rs14 was registered in the Global GenBank (NCBI) under the number PP777510.1. Keywords: Cucumis sativus, Rhizoctonia solani, soil borne diseases, PCR, fungi.