Identification and characterizations of a few species of Fusarium infecting cucumber in greenhouse conditions

One of the most problematic and devastating diseases affecting cucumber production is Fusarium wilt (Cucumis sativus L.). The present study aimed to characterize Fusarium species isolated from three different regions of cucumber fields in Babylon province, Iraq and identify them based on morphological features and phylogenetic analyses. This study showed the presence of Fusarium incarnatum, F. solani and F. oxysporum in cucumber roots. Fusarium species were phylogenetically analyzed based on internal transcribed spacer (ITS) regions. All Fusarium isolates were pathogenic to cucumber cultivars but varied significantly in their growth and pathogenicity toward cucumber seeds during the experiment.  F. solani-2 was greater in growth and pathogenicity than all other Fusarium species. In contrast, F. solani-1 was the lowest. The data obtained from morphological and molecular studies sufficiently supported each other, and the phylogenetic trees based on ITS were distinguished. Closely related species and distinctly separated all morphological taxa. These findings are reported for the first time for the cucumber plant in Babylon province. All these ITS sequences showed homologous to those of Fusarium species isolates in the GenBank database with a similarity percentage of 99%. To the best of present knowledge, this is the first molecular record of F. incarnatum on the cucumber plants in Iraq. The study concluded that F. incarnatum was reported for the first time in Iraq and worldwide as a causal agent of wilt disease in cucumber plants. The three species of Fusarium have different pathogenic abilities, highlighting their disease incidence, growth, and pathogenicity.