Preliminary Study On Identification Of Pathogen Fungi And Biological Control In Morchella Cultivation

Morchella is a kind of rare edible fungi with high nutritional value,which has always been favored by consumers.However,in recent years,with environmental changes and excessive picking,wild Morel has been in short supply.Therefore,the artificial cultivation of Morel began to develop vigorously.The environmental conditions required for the growth of Morel are very strict.At present,the cultivation of Morel is still based on the natural environment,so the open cultivation environment has led to the occurrence of Morel disease.However,the present research reports about Morel disease and the pathogenic bacteria rarely,so the isolation and identification of the pathogenic bacteria of Morchella is important for Morel industry.In this study,The fruiting bodies of diseased Morel were collected from the Morel cultivation base in Nanchong Shishun Agriculture Co.Ltd.,and used as the material for the experiments of the isolation and identification,the detection of pathogenicity,the study of biological characteristics of pathogenic bacteria and the preliminary screening of pathogenic mechanism and disease treatment.The main results of this research are as follows.(1)Five fungal strains with different morphologies were isolated from six diseased Morchella fruiting bodies,numbered as M-1,M-4,M-5,M-8 and M-10.Then,based on the combination of morphology and ITS r DNA sequence analysis,the strain M-1 was identified as S.strictum,M-4 was M.alpina,M-5was Pestalotiopsis,M-8 was M.racemosus,and M-10 was Geomyces.The results of pathogenicity test showed that only M.alpina and Pestalotiopsis were pathogenic to Morchella among five strains,and the pathogenic symptom of Pestalotiopsis was consistent with that of Morchella naturally occurring.It shows that the Pestalotiopsis is the main pathogenic bacteria of the Morel disease,and the M.alpina is a suspected pathogenic bacteria.(2)The biological characteristics of two strains were studied,including the selection of the most suitable medium,the most suitable p H value,the most suitable temperature,the most suitable carbon source and the most suitable nitrogen source.The results of the study showed that the most suitable growth medium for M.alpina was PDA medium,the most suitable p H value was 5,the most suitable temperature was 30℃,and the most suitable carbon source and nitrogen source were maltose and sodium nitrate;the most suitable growth medium for Pestalotiopsis was PSA medium,the most suitable p H value was 7,the most suitable temperature was 25℃,and the most suitable carbon source and nitrogen source were maltose and sodium nitrate.(3)The pathogenic mechanism of two strains was studied,including the identification of chitinase and cellulase production,the use of soluble sugars in the hyphae of Morel and changes of the defensive enzyme activity of Morchella fruiting bodies during pathogen infection.The results showed that none of the two strains produced visible transparent circles on the culture medium after the identification of chitinase and cellulase,and it was found that their chitinase and cellulase activity were low extremely after the measurement.Then,M.alpina and Pestalotiopsis could use the soluble sugars of Morel,and the use rate of Pestalotiopsis was greater than that of M.alpina.In addition,two strains will change the activity of defensive enzymes in Morchella fruiting bodies.With the growth of fruiting body,the activity of SOD in Morchella inoculated with Pestalotiopsis was higher than that of control group,while the activity inoculated with M.alpine was lower than that.the activity of POD in Morchella inoculated with Mortierella alpine was lower than that of control group,while the activity inoculated with the strain of Pestalotiopsis was higher than that.the activity of CAT in Morchella inoculated with M.alpine,Pestalotiopsis was higher than that of control group.(4)The results of the antibacterial experiment of ten plants on two strains showed that A.sativum had a good inhibitory effect on two strains.In addition,C.frutescens had an inhibitory effect on Pestalotiopsis,Z.bungeanum and Ginger had an inhibitory effect on M.alpine and Pestalotiopsis.For five herbal medicines,although A.carvifolia could inhibit the mycelial growth of M.alpine,the inhibitory effect was not strong and the inhibition rate was only 29%.In addition,five herbal medicines had no inhibitory effect on mycelial growth of Pestalotiopsis.However,the five herbal medicines had good inhibitory effect on the spore production of two strains,especially for Pestalotiopsis.The inhibitory rate of H.cordata and L.japonica on Pestalotiopsis was 90%,followed by T.mongolicum and S.nigrum with 80%.