Pathogen identification and control fungicide screening of a novel soybean root rot
In order to identify the species of pathogenic fungi responsible for a novel soybean root rot in Guangdong,understand their biological characteristics,and screen effective fungicides to control the dis-ease,the pathogenic fungi were isolated from the roots and stem bases of infected soybean plants using a tissue isolation method.The fungi were identified based on their morphology and through a combined phylo-genetic analysis of 3 genes(rDNA-ITS,TEF-1α,and RPB2).Subsequently,the isolated pathogenic fun-gi were inoculated into the roots and stem bases of the original soybean cultivar Guixia No.2,either alone or in combination,to determine their pathogenicity.The effects of various media,temperatures,carbon and nitrogen sources,pH,light and fungicides on mycelial growth,as well as the lethal temperatures of the pathogens'conidia were measured.The results showed that two fungal strains with different characteristics were isolated from the roots and stem bases of infected soybean plants,identified as Fusarium neocosmos-poriellum and F.falciforme,respectively.The later was first reported in soybeans in Guangdong,China.In-oculation experiments showed that both fungal strains,whether individually or in combination,could cause symptoms similar to those of soybean root rot disease observed in the field.F.neocosmosporiellum exhibited the fastest growth at 28 ˚C and pH 7,effectively using a variety of carbon and nitrogen sources,with lac-tose and peptone identified as the most effective carbon and nitrogen sources,respectively.The lethal tem-perature for conida was 51 ˚C for 10 min.In contrast,F.falciforme showed the highest growth rate at 25 ˚C and pH 7,with a strong capacity for using carbon and nitrogen sources.Lactose,sucrose,and maltose were the most effective carbon sources,while peptone was the optimal nitrogen source.The lethal tempera-ture for conidia was 54 ˚C for 10 min.Different light treatments did not affect the mycelial growth of either strain.The fungicide prochloraz exhibited the strongest inhibitory effect on both strains.In summary,the pathogenic fungi responseble for the novel soybean root rot disease in Guangdong were F.neocosmosporiel-lum and F.falciforme.These two fungi demonstrate strong environmental adaptability and sensitivity to pro-chloraz,making it the preferred choice for controlling the novel soybean root rot disease.
root rot of soybeanFusarium spp.pathogen identificationbiological characteristicsmultigene phylogenetic analysisfungicide screening
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