Document Type : Research Paper
Authors
Department of Plant Protection, Faculty of Agriculture, University of Kurdistan, Sanandaj, Iran
Abstract
Keywords
Extended Abstract
Introduction
Cucumber (Cucummis sativus L.) is one of the most important vegetables in the world. Cucumber Fusarium wilt caused by Fusarium oxysporum f. sp. cucumerinum (FOC), is one of the most typical soil-borne fungal pathogens that leads to reduced cucumber production. The symptoms of Fusarium wilt appear as stunting and wilting of the leaves, dark brown discoloration of the roots and necrosis of basal stem. Traditional management methods, including the use of crop protection, resistant cultivars and chemical fungal, have been suggested to control Fusarium wilt, but these methods are not economical, reliable or environmentally friendly (Meldrum et al., 2013., Nel et al., 2007). Other methods are investigated, including the use of biocontrol agents. Biocontrol of Fusarium wilt by means of different microorganisms could be used as an effective and sustainable approach to control Fusarium wilts (Lu shi et al., 2017). In this research, two endophytic fungal species (Fomes fomentarius and Coprinopsis urticicola) isolated from wheat plant, were evaluated against FOC in vitro, greenhouse and field conditions.
Materials and methods
The pathogenic fungal (FOC) was isolated from cucumber plants, cultured on PDA medium and purified for next experimental use. The pathogen was identified using morphology and molecular phylogenetic analysis. Pathogenicity test of pathogen was demonstrated on cucumber cv 2N NADA. Fungal endophytes were obtained from the plant pathology collection of University of Kurdistan. Antagonistic activity against the pathogen was evaluated through in vitro dual culture and volatile metabolite assays in a completely randomized design with five replications. For greenhouse and field experiments, Pathogen and fungal endophytes inoculum was prepared on sterilized wheat and incubated for 4 weeks. The cucumber cultivar 2N NADA susceptible to Fusarium wilt caused by FOC was planted in sterilized soil inoculated with pathogen and endophytes (30 g/kg soil) in greenhouse and field conditions. After 60 days of co-inoculation with biocontrol agents and pathogen, the severity disease was indexed and plant growth parameters of the cucumber were evaluated. Experiments were designed in a completely randomized design (with five replications and 6 treatments) in greenhouse conditions and a completely randomized block design (three replications and six treatments, three plots and each plot including five plants) in field conditions. Data were statistically analysed by standard analysis of variance (ANOVA) using SAS software (Version 8.2; SAS Institute, Cary, NC, USA, 2013). Differences among different treatments were analysed using Duncan’s Multiple Range Test (DMRT) at P≤0.05.
Results and Discussion
The results of this research showed that two endophytes were highly capable of inhibition the mycelial colony growth of FOC with inhibition over 67% and 61% respectively by dual culture and volatile metabolite assays as compared to untreated control treatments after 7 days of inoculation. In greenhouse conditions, both endophytes Fomes fomentarius and Coprinopsis urticicola were reduced disease severity 88.35% and 76.67% respectively. Also, these endophytes were reduced disease severity in field conditions over 77 %. The results of the greenhouse and field studies showed that both endophyte improved plant growth parameters. Several biocontrol agents such as Bacillus, nonpathogenic Fusarium, Pseudomonas, Trichoderma, Penicillium, Neurospora, Eupenicillium and Hypocrea strains were evaluated to control Fusarium wilt and reduced disease severity of cucumber wilt (Raza et al., 2017; Vos et al., 2014; Manzoor et al., 2019). Also, Trichoderma sp. and Beauveria sp. effectively reduced wilt disease and increased the plant fresh weight and seedling growth in tomato plants. Two selected fungal endophytes Fomes fomentarius and Coprinopsis urticicola showed in vitro antifungal activity against Gaeumannomyces graminis var. tritici by dual culture assay on PDA medium with 39.1% and 43.6% inhibition, respectively. The isolate C. urticicola caused maximum inhibition of take-all disease (89.8%) and reduced disease severity significantly (P ≤0.05) in comparison with the inoculated control (Gholami et al., 2019). Also, C. urticicola isolate produced siderophore, protease, pectinase, IAA, and gibberellin in vitro (Gholami et al., 2019). Microscopic observation of morphology of Gaeumannomyces graminis var. tritici hyphae revealed that C. urticicola isolate suppressed the mycelia growth and caused change in morphology of Gaeumannomyces graminis var. tritici so that it may be correlated with production metabolites or lytic enzymes such as protease and pectinase that caused abnormalities hyphae morphology (Prapagdee et al., 2008; Gholami et al., 2019).
Conclusion
Several endophytic fungal species are now successfully evaluated as biocontrol agents against plant pathogenic fungi as well as for plant growth promotion. The results of this research showed that Fomes fomentarius and Coprinopsis urticicola were capable of inhibiting more than 61, 76.6 and 76.7 percent of Fusarium oxysporum f. sp. cucumerinum in in vitro, greenhouse and field conditions. In addition, these endophytes were improved cucumber plant growth in greenhouse and field conditions. These strains can be used as a safe and suitable alternative to chemical fungicides in controlling Cucumber Fusarium wilt caused by Fusarium oxysporum f. sp. cucumerinum. To our best knowledge, this is the first report showing the antifungal activity of Fomes fomentarius and Coprinopsis urticicola against Fusarium oxysporum f. sp. cucumerinum and its efficacy for reducing disease severity and increasing yield under greenhouse and field conditions.
All authors contributed equally to the conceptualization of the article and writing of the original and subsequent drafts.
The data will be made available on request.
This research was supported by the Plant Protection Department of University of Kurdistan. We thank university of Kurdistan for providing research facility and support.
The study was conducted on plant-pathogen fungus and beneficial entophy-
tic bacteria that are abundant in the environment and do not require ethical
approva
The study was conducted on plant-pathogen fungus and beneficial entophytic fungi that are abundant in the environment and do not require ethical approval.
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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