Study On The Secondary Metabolites And The Pathogenicity Of Alternaria Alternata,a Pathogen Of Panax Notogineseng

Black spot is a common and popular disease for Panax notoginseng,which hampers the sustainable development of notoginseng cultivation.From the diseased plants,isolate BS-45 was isolated and was testified as a pathogenic fungus by inoculating on healthy leaves with mycelia and extract of culture broth.It was designated as Alternaria alternata on the basis of molecular and morphological characteristics.Twenty-two compounds were isolated from the culture on rice medium,and were identified as known fungal toxins by analysis of their MS and NMR spectra data.Tests in vivo developed with healthy notoginseng leaves were carried out.Alternariol 9-methyl ether(1)could decrease the content of fiber(94%),and the activity of peroxidase(POD,55.78%)and catalase(CAT,83.33%).Alternariol(3)could decrease the content of fiber(93.6%),and the activity of total superoxide dismutase(T-SOD,90.9%)and catalase(CAT,87.73%).Altenuene(6)could decrease the content of chlorophyll(Chl,60.76)and fiber(66.67%),and the activity of T-SOD(77.94%)and CAT(93.41%).5’-Epialtenuene(9)could decrease the activity of POD(48.64%),T-SOD(96.94)and CAT(74.71%).Alternarlactone B(13)could decrease the content of fiber(66.67%),and the activity of TSOD(61.36%)and CAT(90.86%).4H-1-Benzopyran-4-one,7-hydroxy-2-(hydroxymethyl)-5-methyl-(20)could decrease the activity of POD(50.07%),T-SOD(53.91%)and phenylalaninammo-nialyase(PAL,42.95%).5-Carbometh-oxymethyl-2-heptyl-7-hydroxychromone(21)could decrease the content of fiber(69.39%)and the activity of CAT(92.34%).These results indicate that toxins produced by Alternaria alternata could destroy the content of fiber and lower the enzymes involved in the normal biological procedure,which can cause the disease on the leaves of P.notoginseng.