Research On The Diversity And Ecological Functions Of Endophytic Alternaria In Maize (Zea Mays L.)

Endophytic fungi generally refers to fungi that grow in the plant body during a certain stage or the whole life history,and does not cause the host obvious disease.Its long-term collaborative evolution with the plant forms a complex,special relationship that can be mutually beneficial.It may be a potential pathogen,or potential facultative saprophytic fungi.Alternaria alternata is widely found in nature and is generally considered to be saprophytic or facultative bacterial parasite,which can cause a variety of crop diseases.Alternaria sp.is a dominant species of endophytic fungi of the piant,but there is little understanding of the life history and ecological function of endophytic Alternaria.Through the study of the endophytic Alternaria of maize,it is of great significance to elucidate the relationship between endophytic Alternaria and host and understand the life history and ecological function of endosperm.In this study,the analysis of endophytic Alternaria that reserved in the laboratory,indicated that endophytic Alternaria has universality and diversity in the distribution of maize.and 10 representative morphotypes were analyzed by phylogenetic analysis based on the rDNA ITS sequence.The strains of endophytic Alternaria were clustered with small-spored Alternaria and could not be classified by ITS sequence.So they were identified by morphological methods.Ten strains of Alternaria were small-spored Alternaria,and through preliminary identification: Y1 is A.Alternata,Y4 is A.catalpae,Y5 and Y6 are classified as A.tenuissima species-group,Y8 is A.peponicola,Y9 is A.ellisii,Y10 is A.platycodonis,Y11 is classified as A.alternata species-group,Y12 is A.triticimaculans,Y13 is A.coicis.The effects of the ability of Phosphate-solubilizing,effect on growth and development of maize,degradation ability were studied.The ecological function of Alternaria was discussed,and some biological characteristics were studied with a strain with the strongest enzyme producing ability.In the dissolved phosphate test,10 strains of Alternaria were unable to form a transparent circle on the PVK plate,so it was judged that it did not have the effect of dissolving phosphorus.There were no significant effects of 10 strains on maize germination rate,plant height,stem diameter and root length.Ten strains of Alternaria were found to be no pathogenic to maize.In the plate confrontation experiment with four maize pathogens,10 strains of Alternaria showed inhibitory effect on four pathogens of maize.The strain Y6 had the highest inhibitory rate of 697% for Fusarium graminearum.The inhibitory rate of strain Y13 was 53.08% for Exserohilum turcicum and that of strain Y8 was 67.03% for Curvularia lunata.The inhibition rate of strain Y12 was 53.08%for Bipolaris zeicola.The results showed that the endophytic Alternaria had certain saprophytic ability through the study of cellulase,laccase activity and degradation ability of corn stalks.The cellulase activity of the strain Y13 was the strongest through the cellulase activity.Through the screening of guaiacol and aniline blue plate,10 strains of Alternaria can produce laccase but do not have manganese peroxidase and lignin peroxidase activity.Laccase activity was determined,and the activity of strain Y13 was the highest.The results showed that the cellulase and laccase activity of strain Y13 were the highest,and the strain Y13 was used as the representative of the corn stalk degradation experiment.The weight loss rate of the straw in the experimental group was 22% at 10 days,20 days and 30 days respectively,34.7% and 41.2%,respectively,which were 10%,11.7% and 12.5% higher than those in the control group,indicating that strain Y13 had better degradation ability to straw.The results showed that the optimum carbon and nitrogen sources of strain Y13 were maltose,lactose and peptone,respectively.The lignin activity of the strain Y13 was different at different carbon and nitrogen sources,and the laccase activity was the highest when the carbon source was maltose and lactose.The lignin activity was the highest when the nitrogen source was peptone,which is the same with the optimum carbon and nitrogen Consistent source.Through the above research,it was found that the endophytic Alternaria belonged to the small-spored Alternaria,but there were some differences in morphology,physiology and genetics.The endophytic Alternaria of maize in the growth and development period of maize,as an endophytic fungus exists in the plant,may enhance the resistance of maize to pathogens.The endophytic Alternaria can produce cellulase and related enzymes,which can degrade maize straw,after the end of the endophytic,it can continue to live by saprophytic.This study is of great significance in elucidating the ecological function of endophytic Alternaria,guiding maize cultivation,controlling decease,and developing and utilizing the resources of Alternaria.