Decrease in the incidence of cucumber Fusarium wilt in Varamin greenhouses using Talaromyces flavus

Abstract

Fusarium wilt caused by Fusarium oxysporum f. sp. cucumerinum is one of the most important greenhouse cucumber diseases. The chemical methods are not possible easily for controlling this disease, and the most suitable of the control method is introduced as biological control using antagonistic agents. Since, the study of antagonistic mechanisms is an important subject in biological control, therefore in this study for isolating pathogenic and antagonistic agents, plant and soil sampling was carried out in the Varamin infected greenhouses. Then, based on the inhibitory percent of the pathogenic agent growth, caused by the antagonistic mechanisms of the different isolates related to the antagonistic fungi, Talaromyces flavus and Trichoderma harzianum, three effective isolates of each one in terms of the most inhibitory effect were selected and the efficacy of the every isolate in biological control was investigated, using three application method (seed coating, addition to soil, both seed coating and addition to soil). In the next step, based on the results of the greenhouse experiment, the four effective treatments containing T. flavus and T. harzianum isolates, in terms of the efficacy in decreasing cucumber Fusarium wilt disease were evaluated in Varamin cucumber greenhouse, during three consecutive crop years. These treatments included TF-Cu-V-59 as soil treatment, TF-Cu-V-60 as seed treatment, TH-Cu-V-13 as soil treatment and THCu- V-13 as soil and seed treatment. Each experiment was performed with a randomized complete block design (RCBD) in five treatments (each of four above-mentioned treatments and unhealthy control) and four replications. The treatments were evaluated as calculating disease severity percent and total yield. Statistical results in compound analysis form for three consecutive years showed that the interaction effect between treatment and year was significant; as a result, analysis of data was carried out for each year, separately. The results related to first and second years showed that among all treatments, the most effective treatment was TF-Cu-V-59 as soil treatment in terms of efficacy in disease control and increasing yield. However, the results related to third year showed that all treatments containing antagonistic isolates decreased disease severity percent and increased yield significantly, compared to unhealthy control. In spite of a significant difference among antagonistic treatments, in terms of disease severity percent and yield, in first and second years, these treatments were not different significantly in third year. It could be presumed that due to the residues of T. flavus bioformulations related to previous years in soil, the population of the above-mentioned antagonistic fungus has been improved using antagonistic treatments containing T. flavus in these treatments; consequently there was no significant difference among these treatments in terms of measured parameters.