Biological Activity of Four Trichoderma Species Confers Protection against Rhizoctonia solani, the Causal Agent of Cucumber Damping-Off and Root Rot Diseases

Abstract

The cucumber (Cucumis sativa L.) is often subjected to several fungal diseases. Rhizoctonia solani-induced cucumber damping-off and root rot are the most common diseases reported from the commercial greenhouses of the eastern area of Saudi Arabia. The objective of the current study is to explore the antagonistic activity of four Trichoderma species against R. solani in vitro and in vivo. Ten R. solani isolates (eight belonging to AG-4 and two belonging to AG-A and AG2-1) were studied. AG4 isolates were pathogenic to cucumber plants, while AG-A and AG2-1 isolates were non-pathogenic. Seven isolates of Trichoderma spp., named T. hamatum KSATR8, T. harzianum (KSATR9 and KSATR10), T. asperellum (KSATR11, KSATC, and KSAT1E), and T. longibrachiatum KSATS were isolated, and the identities of both R. solani and Trichoderma isolates were confirmed based on the phylogenetic analysis of the DNA sequence of the ITS region. The dual culture findings indicated that T. asperellum KSATC and KSAT1E exhibited the most significant inhibitory activities against R. solani, with values of 79.33 and 70.89%, respectively. Scanning electron microscope (SEM) images showed a considerable degradation in the cell wall and collapsing of R. solani hyphae by all Trichoderma species. Under greenhouse conditions, the application of T. asperellum KSATC and KSAT1E at concentrations of 2 × 108 conidia/mL revealed a reduction in root rot and damping-off incidence percentages with values that did not reveal a significant (p < 0.05) difference from those of Rizolex-T fungicide. Nevertheless, the efficacy of the fungicide attained 86.67%, being higher than that of T. asperellum KSATC, which reached 80%. Trichoderma asperellum KSATC and KSAT1E were the greatest in increasing peroxidase, catalase, and chitinase enzymes activities in cucumber plants. Conversely, a significant (p < 0.05) elevation in polyphenol oxidase enzyme (0.762 and 0.97 U/g FW) and total phenol content (0.55 and 0.62 mg/g FW) was recorded in cucumber plants treated with T. harzianum KSATR9 and KSATR10, respectively. The statistical analysis results displayed no considerable variations among cucumber plants regarding total chlorophyll content as a response to treatments with Trichoderma species and fungicides. Therefore, we endorse using T. asperellum KSATC and KSAT1E as an alternative to fungicides to manage root rot and damping-off in cucumbers.

Molecular Identification of Rhizoctonia solani Isolated from Cucumber (Cucumis sativus L.) and Its Biological Control

“…The results in the table (3) shows that the effect of biological control agents on the Percentage of infection of cucumber plants with the R. solani under field conditions record T. harzianum T22 treatment lowest rate of infection with the fungus R. solani reached 64.17%which was not significantly different from fungus based on the results of the impact of the varieties, the table also shows that the Dalal variety recorded the lowest infection rate 50.00%.From the results of the interactions between varieties and treatments, Beit Alfa with B. subtilis showed the lowest infection rate which was 30.00%.…”

“…The cucumber plant, Cucumis sativus L., is one of the most significant vegetable crops in the world and it is affected by many fungi pathogens in the field causing yield losses [1]. Cucumber plant is infected with various fungal diseases including damping-off and root rot disease caused by Rhizoctonia solani causing big loss in production in the both of greenhouses or in the fields [2,3]. Additionally to R. solani , there are other fungal genera are responsible for cucumber damping-off and root rot diseases, such as Fusarium oxysporum, F. solani, Phytopathora sp., Macrophomina phaseolina, Sclerortium rolfsi [4][5][6][7].…”