Identification of Pathogens in Cucumis melo and Assessment of Control Effect of Inflorescence Extracts from Allium galanthum
The disease caused by Fusarium sp.was found on Cucumis melo in Kashgar,Xinjiang.The pathogen was isolated,purified and identified,and its pathogenicity was elucidated according to Koch's postulates.The biotoxicity assay of the pathogen was conducted by using varying concentrations of methanol extract from the inflorescence of Allium galanthum.The control effect was evaluated using'Xinmixa 11'as the test material.The results showed that the colonies of the pathogen were radial,white and round,producing a light pink pigment.The conidial peduncle was bifurcated and branched,and the conidia were fusiform or falcate,obtuse at both ends or gradually becoming sharp at both ends,containing septa,mostly 3-5 septa,with a size range of(23.53-48.99)μm×(5.66-11.47)μm.Combined analysis of ITS,gene sequence,the pathogen was identified as Fusarium chlamydosporum.The pathogen caused root,stem,leaf wilt and fruit decay by infecting surface or wound of the plant.The results showed that the extract inhibited mycelial growth and spore yield,and the extract at 150 mg/mL completely inhibited the mycelial growth of the pathogen.The control efficacy of 150 mg/mL extract:amistar 1:1(V:V)on the infected plants reached 56.63%,and that of 150 mg/mL extract on infected fruits reached 21.01%and effectively reduced the melon disease index.The extract inhibited the osmoregulatory ability of F.chlamydosporum,increased fungal permeability,and affected normal metabolism,leading to growth inhibition.Additionally,it inhibited the activities of total cellulose enzyme,carboxymethyl cellulase,and β-glucosidase.After spraying the extracts,the antioxidant enzyme activities of host melon plants were elevated,MDA content was decreased,and the disease resistance of the plants was enhanced.A.galanthum is a plant source with good biocontrol effect and application prospect because of its preventive effect against F.chlamydosporum and its ability to improve the disease resistance of Cucumis melo.
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