Isolation and identification of the pathogenic fungi of Polygonatum cyrtonema Hua root rot in Hunan Province

【Objective】 Clarify the regularity of outbreak and pathogenic fungi of Polygonatum cyrtonema Hua root rot in Hunan, and provide a scientific basis for the comprehensive control of P. cyrtonema root rot and GAP(Good Agricultural Practice for Chinese Crude Drugs) planting.【Method】 Samples with typical symptoms of root rot were collected in Hunan, the pathogen of P. cyrtonema Hua root rot was isolated and purified by plate isolation and purification. The classification status of the pathogen was determined based on their morphological characteristics and r DNA-ITS sequence, and Koch's rule was used to prove the pathogenicity of fungal strain isolated from P. cyrtonema Hua.【Result】 The P. cyrtonema Hua root rot in Hunan was the most serious at growth stage(May-July), with the average incidence of 12% and 20% when serious;the incidence site was mainly root. Four strains(G1-G4) were isolated from the healthy junction of P.cyrtonema Hua rhizome suffering from typical root rot. The isolated and purified strains G1, G2 and G4 were amplified by PCR to obtain DNA fragments with a length of 511, 573 and 573 bp bands, respectively. Due to PCR amplification bands mixed, strain G3 sequencing was failed. According to BLAST homology comparison of pathogen r DNA-ITS sequence, the sequence of strain G1 shared the high identity of 99.22% with Fusarium foetens(GenBank accession number NR_159865.1), while the sequence of strains G2 and G4 had 99.81% similarity with F. hostae(GenBank accession number NR_171109.1). Strain G1 grew rapidly on PDA medium, and after 7 d of culture, colony diameter was 6.7 cm, aerial mycelium was dense, felt shape, white to pink purple;and after 7 d of culture, colony diameters of strains G2 and G4 were 6.2 cm, aerial mycelium was radial, white to pale yellow. Isolates G1, G2 and G4 were infected onto the rhizomes of healthy P. cyrtonema Hua plants, and both were strongly pathogenic and showed typical symptoms of root rot onset. P.cyrtonema Hua root infected by G1 began to decompose and brownish 10 d after infection with obvious fishy smell;10 d after strains G2 and G4 infection, P. cyrtonema Hua root turned brown, then the tubers in the rotten part of the diseased spot appear depressed.【Conclusion】 Different geographical locations, cultivation methods and P. cyrtonema Hua varieties can lead to differences in the occurrence of P. cyrtonema Hua root rot and its pathogens, which increases the difficulty of the prevention and control of P. cyrtonema Hua root rot to a certain extent, and brings safety risks to the processing of later products. F. foetens and F. hostae are the pathogens that cause P. cyrtonema Hua root rot in Hunan.