| Cultivation of medicinal plants in Gansu Province, china, plays a pillar role in the local economy. However, diseases on these plants caused by pathogens are so serious that the quality and yield of the medicinal plants in Gansu Province suffered serious impact. Hence, this paper focuses on the classification of the pathogen of Sphaeropsidales on the medicinal plants in Gansu Province.Using the traditional research methods of plant pathology, this paper surveys the plant diseases and collects the samples of diseases in Gansu Province, and identifies the pathogens on the collected samples; then it studies the cultivating and spore germination characteristics of12Septoria spp. isolates; and it investigates the biological characteristics and nutritional utilization of the representative strains; finally, it constructs the phylogenetic tree of the12Septoria spp. isolates, and identifies their species by combining with the phenotype of the isolates.The achievements of the paper can be summarized as follows:(1) The variety, distribution, severity and prevalence of diseases caused by Sphaeropsidales on the medicinal plants in the major producing regions of Gansu Province are surveyed, and the phenotypic characteristics of the Sphaeropsidales are identified by means of traditional methods in Plant Pathology. The conclusions are as follows:In the92medicinal plants,11families and21species are infected by Septoria, in which16species can be named, and8ones are unidentified;15families and30species are infected by Ascochyta, in which15species can be named, and19ones are unidentified;17families and23species are infected by Phyllosticta, in which15species can be named, and9ones are unidentified;4families and5species are infected by Phoma, in which2species can be named and3ones are unidentified.(2) Symptoms (i.e. shape, size, color etc.) of the disease spots of the diseases on the medicinal plants caused by Septoria, Ascochyta, Phyllosticta, Phoma are analyzed and summarized.(3) A new anamorph species was found:Stigmella lycii X.R. Chen&Yan Wang. Conidiomata pycnidial, subglobose, blackish,161.5-172.3μm diam; Ostiole indefinite; Conidia hyaline when young, at maturity pale olive-brown and muriform, oval, ellipsoid, pyriform, irregular and mulberry-shape,19.9-52.8×12.8-32.9μm, composed of12-35cells,2.55-11.47×2.55-10.97μm. It can cause brown spot on Lycium chinense Mill.. Lesions on leaves are larger necrotic blotches, somewhat zonate, with distinct margins. This disease was distributed in Jingtai County and Jinyuan County in Gansu Province. Severe infections caused by this pathogenic fungus usually results in premature leaves and fruit fall. This disease incidence is95%-98%, severity is3-4degrees.(4) The characteristics of the cultivation and spore germination of12Septoria spp. strains were observed by the conventional cultivation methods of plant pathology, the results showed that the cultivation characteristics can be divided into four:mycelial colony, intermediate mycelial colony, intermediate colony, and yeast-like colony. Mycelial colony: representative strains are S. codonopsidis, S. lamii, S. saposhnikoviae, pathogen of Angelica sinensis leaf spot(Septoria sp.), pathogen of Radix Glehniae leaf spot (Septoria sp.). Intermediate mycelial colony: representative strains are S. bupleuri, S. microspora, S. dearnessii (Strain TCM-2). Intermediate colony: representative strains are S. cirsii. Yeast-like colony: representative strains are pathogen of Lonicera japonica leaf spot (Septoria sp.), pathogen of Rheum spp. leaf spot (Septoria sp.), S. dearnessii (Strain TCM-3). The spores of the species of mycelial colony and intermediate colony can both germinate from the two ends or their sides, and can generate germ tube; but the spores of the species of intermediate colony and yeast-like colony generate small sub-spores or generate spores from the short mycelia.(5) The biological characteristics of two strains in mycelia colony: the pathogen of Angelica sinensis leaf spot (Septoria sp.), S. codonopsidis, and three strains in intermediate colony: S. bupleuri, S. microspora, S. dearnessii were studied. The results are as follows: The temperature range of the mycilium growth, spore production, spore germination of the5Septoria spp. strains is5-30℃, the optium is20-25℃,15-20℃,15-20℃; The growth and spore germination of the5Septoria spp. is slow, at the optium temperature, the spore germingation rate is beyond5%after12hours, and after72hours, beyond50%. Continuous illumination is a favorable condition for mycilium growth of the5Septoria spp., can stimulate spore production of Septoria sp., S. bupleuri and S. dearnessii; Continuous darkness can stimulate spore production of S. codonopsidis and S. microspora. Continuous illumination can stimulate spore germination of4strains of Septoria spp. except S. microspora. The pH range is4.0-10.0, acidic condition is a favorable condition for mycilium growth, spore production and germination; the optium spore germination pH of the5Septoria spp. are pH6.0, pH5.0, pH6.0, pH7.5, pH7.5and pH6.5respectively; spore can germinate at pH4.51-9.19, the optium pH of the5Septoriaspp. are pH5.58, pH6.49, pH7.00, pH7.0, pH5.58and pH6.49. The pore germination were best in water. The spore germination was facilitated by nutrition solution, especially the host tissue extract. Cultivation using the12carbon source and13nitrogen source can not stimulate the growth rate and distinguish the culture characteristics of the5Septoria spp..(6) The phylogenetic tree is constructed by means of rDNA ITS, and the results from genotype and that from phenotype are integrated to identify the Septoria species of the pathogens of the medicinal plant diseases, which shows that the result from genotype and that from phenotype are consistent. Angelica dahurica leaf spot is caused by S. Dearnessii, Bupleurum chinense leaf spot is caused by S. bupleuri, Codonopsis pilosula leaf spot is caused by S. codonopsidis, Gentiana macrophylla leaf spot is caused by S. microspora, Cirsium setosum leaf spot is caused by S. cirsii, Leonurus artemisia leaf spot is caused by S. lamiicola. The pathogen of Rheum spp., Leonurus rtemisia, Angelica sinensis, Glehnia littoralis leaf spots and one strain of the pathogen of Angelica dahurica leaf spot all belong to Septoria spp., and they are unnamed. |
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