Biological control of Verticillium wilt of greenhouse cucumber by Talaromyces flavus

Talaromyces flavus, a fungal antagonist, was isolated from soil samples collected from cucumber greenhouses in Varamin district, Tehran province, Iran. The antagonistic effects of T. flavus isolates against Verticillium albo-atrum, the causal agent of greenhouse cucumber wilt were investigated under laboratory and greenhouse conditions. T. flavus colonies were recovered after three weeks from soil samples plated on a selective medium. Effects of volatile and non-volatile extracts of T. flavus isolates on V. albo-atrum growth were investigated in the laboratory, and five isolates that inhibited V. albo-atrum more strongly, were selected for greenhouse experiments. The infection index in the greenhouse was compared in a split plot trial with five isolates applied to the soil, the seed, or both seed + soil, arranged in a randomized complete block design with four replications. The greenhouse experiments on the different T. flavus treatments indicated that there was no significant difference among them. Of the five T. flavus isolates, the most effective was Tf-Cu-V-60. The interactions between the T. flavus treatments and the T. flavus isolates showed that the lowest infection index was achieved when the soil was treated with Tf-Cu-V-60. The study showed that T. flavus may control greenhouse Verticillium wilt of cucumber

Biological control of Polymyxa betae, fungal vector of rhizomania disease of sugar beets in greenhouse conditions

Rhizomania is one of the most important diseases of sugar beet around the world – including in Iran. The disease causes a severe decrease in sugar yield and is a limiting factor in sugar beet cultivation. Control of the disease is very difficult due to the long-term survival of its fungal vector (Polymyxa betae) in the soil. In this study, we investigated the effects of antagonistic fungal isolates on the population of the resting structure (cystosorus) of P. betae, under greenhouse conditions. Antagonistic fungi, including Trichoderma harzianum and Talaromyces flavus, were isolated from soil samples collected from sugar beet infested fields in the Semnan Province of Iran. In the next step, their inocula were prepared through reproduction on rice bran. For evaluation of the efficacy of antagonists in greenhouse conditions, a split plot trial was conducted and performed. The main factor was three different methods of application of T. flavus as the soil treatment, seed treatment, and a combination of both methods. The sub-factor was the use of different fungal isolates. To determine the cystosorus population of the fungal vector, seedling roots in all treatments were stained with lactic acid and fuchsine (lactofushine), 60 days after sowing. The number of cystosorus in one gram of root was counted using a light microscope and hemocytometer. At the end of the study, average root weight in different treatments was also measured to select and introduce the best treatments in regard to their effects on root weight. According to the results, the number of cystosorus in 1 g of root was different in various treatments and those treatments containing TF-Su-M-1, TF-Su-M-2, TH-Su-M-1, and TH-Su-M-2 used as a soil application method were more effective in the reduction of the cystosorus population and root weight increase. Among the above-mentioned treatments, maximum reduction of cystosori population and the increase in root weight were observed in TH-Su-M-1 and TF-Su-M-2 through the soil application method

Evaluation of Pseudomonas and Bacillus Bacterial Antagonists for Biological Control of Cotton Verticillium Wilt Disease

Verticillium wilt is considered the most important disease of cotton in the world, including Iran. Cultural practices and the use of resistant varieties are the most common strategies used to control Verticillium wilt of cotton. These strategies are not always available or effective. In recent years, biological control using fungal and bacterial antagonists, has been applied to control some cotton diseases including damping-off. In this study, we investigated the possibility of biological control of Verticillium wilt of cotton using bacterial antagonists. Suspension of eight bacterial strains of Pseudomonas fluorescens and Bacillus spp. isolated from different rhizospheric soils and plant roots in the Iranian cotton fields, were prepared with a concentration of 108 cfu/ml. Ten cotton seeds (cv Varamin) were then coated with each bacterial suspension and were planted in soil pre-inoculated with Verticillium dahliae microsclerotia. The efficacy of bacterial antagonists in reducing wilt disease was evaluated by determination of the disease index in different treatments. The results indicated that most isolates were effective in reducing disease (compared to the untreated control) 90 days after sowing. Isolates B5, B6, B2, B7, and B3 were the most effective, respectively, in reducing wilt index. In contrast, isolates B1, B4, and B8 did not significantly reduce the disease. In general, P. fluorescens isolates were more effective than Bacillus isolates. This study suggests that bacterial antagonists might be potential biological control agents of cotton