The Study Of Pathogenic Fungi With Panax Notoginseng Root Rot

Root-rot diseases have been hindering the industries of Panax notoginseng. They are also regarded as one of important factors inducing continuous cropping obstacle of P. notoginseng. Two symptoms-yellow rot and acute green withered rot, are the most serious root rots, cause great loss in the growth period of notoginseng. In-depth investigation on the pathogenic fungi will be helpful in revealing the pathogenic phenomena and mechanisms in root rot diseases of P. notoginseng, and in developing biological control approaches. Thus, the study of pathogenic fungi is still very meaningful and valuable. Based on high-through sequencing method, the population compositions of fungi associated with roots of P. notoginseng indicated that there were significant differences in fungal community between rotten roots and healthy roots. One hundred and twenty-five taxa at genus level were detected from healthy roots, and unclassified Mortierellales, Mortierella were two dominant groups. Detected fungal OTUs from sudden wilt rotten roots distributed in16taxa, in which Fusarium was the dominant group, accounted for73.37%, followed by Cylindrocarpo, Ilyonectria and Monographella, accounted for9.57%,6.41%,9.57%, respectively. Fungal OTUs from yellow rotten roots of also distributed in16taxa, two dominant groups were unclassified (75.47%) and Ilyonectria (24.02%).Thirty-four fungal isolates were obtained from sudden wilt rotten roots, and16isolates from yellow rotten roots with culture-depedent approach. On the basis of morphological characteristics and phylogenetic analysis of ITS gene sequence, the isolates from sudden wilt rotten roots were assigned to11orders,16families and17genera, they were Penicillium, Mycocentrospora, Cladosporium, Fusarium, Trichoderma, Colletotrichum, Diaporthe, Phoma, Alternaria, Mortierella, Mucor, Epicoccum, Chaetomium, Cylindrocarpon, Periconia, Botrytis, and Plectosphaerella. The isolates from yellow rotten roots were assigned to7orders,11families and11 genera, they were Trichoderma, Fusarium, Clonostachys, Epicoccum, Alternaria, Phoma, Cladosporium, Galactomyces, Mortierella, Mucor, and Plectosphaerella.Among the50isolates, PH30321, PH30372, PH30365, PH30340, PH30308were identified as Fusarium oxysporum、Cylindrocarpon olidum、Alternaria tenuissima、 Phoma herbarum and Fusarium oxysporum, which were reported as root-rot pathogens of P. notoginseng. Other fungal isolates were reinoculated with healthy detached notoginseng roots to verify their virulence to P. notoginseng. Healthy roots co inoculated with isolates PH30355, PH30353, PH30306decayed after one week, which indicates that these isolates should be potential pathogens for P. notoginseng.Based on morphological characteristics and phylogenetic analysis of ITS gene sequence, the isolates PH30353, PH30355, PH30306were identified as Plectosphaerella cucumerina, Fusarium flocciferum and Epicoccum nigrum, respectively, and they were first reported as pathogens to P. notoginseng.