Species Diversity Analysis Of Citrus Root Fungi And Effects Of Major Fungi Species To The Growth Of Citrus Jiunos Seedlings

The root fungi of plants are abundant in resources,some species promote plant growth,some other species are plant pathogens.It is important to study on species diversity of plant root fungi and to utilize root fungi to promote the healthy growth of plant root.In this article,high-throughput sequencing technology and tissue isolation method were used to analyze the root fungi species of healthy,yellowing and Huanglongbing-infected plants of citrus,inoculation tests were conducted to understand the effects of different root fungi on the growth of Citrus junos seedlings,in order to provide a theoretical basis for the protection and utilization of citrus root fungi.The mian results were as follows:(1)The results of high-throughput sequencing of potted Citrus reticulate cv.Shatangju root samples showed that Ascomycota,Basidiomycota and Glomeromycota were dominant phyla of root fungi.The relative abundance(43.14%)of Fusarium solani in Nectriaceae family of Ascomycota was highest in the brown roots of healthy plants.The relative abundance(40.70%)of Ceratobasidiaceae family of Basidiomycota was highest in the white roots of healthy plants,followed by Nectriaceae family(9.42%),in which the relative abundance of Fusarium solani was 8.05%,the third was Glomeraceae family of Glomeromycota,the relative abundance was7.09%.The relative abundance of Fusarium solani in both brown roots and white roots of citrus Huanglongbing-infected plants was highest(the relative abundance was 54.82%in the brown roots,12.01% in the white roots).(2)The results of high-throughput sequencing of potted Orah mandarin white root samples showed that Ascomycota,Glomeromycota and Basidiomycota were dominant phyla of root fungi.The relative abundance of Fusarium solani was highest in both brown roots and white roots of healthy and yellowing plants,60.35% in the brown roots of healthy plants,41.74% in the white roots of healthy plants,47.08% in the brown roots of yellowing plants,14.29% in the white roots of yellowing plants.(3)The results of high-throughput sequencing of Orah mandarin root samples collected from orchard showed that Ascomycota and Basidiomycota were dominant phyla of root fungi.The relative abundance(18.99%)of Cladophialophora in Herpotrichiellaceae family of Basidiomycota was highest in the white roots of healthy plants.The relative abundance(25.62%)of Fusarium keratoplasticum in Nectriaceae family was highest in the white roots of citrus Huanglongbing-infected plants.Fusarium solani was not annotated in all samples.(4)Total 17 species with 92 strains were identified from the white roots of healthy plants of Orah mandarin collected from orchard,21 species with 180 strains were identified from the white roots of citrus Huanglongbing-infected plants by morphological and molecular biology identification.The fungi species with more than 6% relative isolation frequency were Fusarium oxysporum(31.54%),Chaetomium globosum(7.89%),Fusarium solani(7.89%),Chaetomium cochliodes(7.53%),Fusarium fujikuroi(6.81%)and Macrophomina phaseolina(6.09%).(5)Comparing the high-throughput sequencing results of root fungi of Citrus reticulate cv.Shatangju and Orah mandarin,In potted Citrus reticulate cv.Shatangju and Orah mandarin,the relative abundance of Ceratobasidiaceae was the highest in the white roots of healthy Citrus reticulate cv.Shatangju,but the species were not annotated.The relative abundance of Fusarium solani in Fusarium genus of Nectriaceae family was highest in other root samples,and the relative abundance of Fusarium solani in the brown roots was higher than that in the white roots;The relative abundance of Fusarium solani in the roots of Citrus reticulate cv.Shatangju Huanglongbing-infected plants was higher than that of healthy plants,and the relative abundance Fusarium solani in the roots of Orah mandarin yellowing plants was lower than that of healthy plants.However,Fusarium solani was not annotated in the white roots of Orah mandarin collected in orchard.Comparing the results of high-throughput sequencing and tissue isolation of Orah mandarin collected in orchard.,it was found that the relative abundance of Fusarium fungi in Huanglongbing-infected plants(39.84%)were higher than that in healthy plants(15.09%),and the relative isolation frequency of Fusarium oxysporum of Fusarium genus in Huanglongbing-infected plants(22.58%)was higher than that in healthy plants(8.96%).(6)Thirty species of root fungi were inoculated into the soil of potted Citrus junos seedlings,the results showed that 6 species promoted the growth of Citrus junos seedlings,including Chaetomium globosum,Trichoderma virens,Trichoderma hamatum,Penicillium janthinellum,Aspergillus sydowii and Acrocalymma vagum;11 species inhibited the growth of Citrus junos seedlings,including Fusarium fujikuroi,Polyschema sclerotigenum,Penicillium koreense,Penicillium raperi,Aspergillus niger,Curvularia lunata,Albifimbria verrucaria,Neopyrenochaeta acicola,Alternaria alstroemeriae,Talaromyces radicus and Talaromyces wortmannii.The other root fungi(such as Fusarium solani,Fusarium oxysporum,etc.)had no effect on the growth of Citrus junos seedlings.