Fungal Endophytic Diversity Of Two Wild Rosa Species With Different Powdery Mildew Susceptibilities

Powdery mildew(PM)is one of the most serious diseases in rose production,however,there is no better way to control it until now.The wild Rosa with strong PM resistance is the most important species for improving Rosa hybrid PM resistance.Previous studies have demonstrated that endophytes are beneficial to host plant’s disease resistance.Therefore,the fungal endophytic diversity and community structure of Rosa multiflora(strong resistant to powdery mildew)and Rosa multiflora var.carnea(susceptible to powdery mildew)at the different developing stage of PM were studied.Endophytic fungi(EF)were isolated by traditional fungal endophytes isolation methods and strains were identified according to the morphological charateristics and the rDNA internal transcribed spacer(ITS)analysis,and the ecological role of fungal endophytes on PM resistance was worthy of further study.The main results were showed as follows:(1)A total of 2003 culturable EF were isolated from 2880 segments of 24 samples of wild Rosa,of which 1333 isolates were from Rosa multiflora and 670 isolates were from R.multiflora var.carnea,the quantity of EF in Rosa multiflora was always higher than that in R.multiflora var.carnea(P< 0.05,Chi-square test).(2)The isolation rate(IR)showed that: The average IR of EF in two wild Rosa species ranged from 0.11 to 1.23,the average IR of EF in Rosa multiflora ranged from 0.66 to 1.23,the average IR of EF in R.multiflora var.carnea ranged from 0.11 to 0.69.The average IR of EF in Rosa multiflora was always higher than that in R.multiflora var.carnea(P< 0.05).(3)The colonization rate(CR)showed that: The average CR of EF in two wild Rosa species ranged from 9.72% to 84.17%,the average CR of EF in Rosa multiflora: June(50.83%)< May(54.45%)< August(73.06%)< July(84.17%),the average CR of EF in R.multiflora var.carnea: May(9.72%)< June(35.00%)< July(45.83%)< August(52.50%).The average CR of EF in Rosa multiflora was always higher than that in R.multiflora var.carnea(P< 0.05).(4)The composition showed that: The isolated fungi of Rosa multiflora were identified to 27 taxa,including Botryosphaeria,Arthrinium phaeospermum and Phyllosticta capitalensis.And the isolated fungi of R.multiflora var.carnea were also identified to 27 taxa,including Pestalotiopsis,Xylaria and Colletotrichum.The dominant genera of Rosa multiflora were C.gloeosporioides,Phomopsis amygdali and C.truncatum,while the dominant genera of R.multiflora var.carnea were A.alternata,C.truncatum and P.capitalensis.However,A.alternata,C.truncatum and P.amygdali were the dominant genera of two wild Rosa species at the different developing stage of PM.In June,July and August,C.gloeosporioides was the significantly dominant genera in Rosa multiflora.Contrary to the dominant genera,some endophytes showed host specificity or only found in one stage of PM.Seimatcsporium sp.was only in Rosa multiflora,Coprinellus sp.was only in R.multiflora var.carnea,A.phaeospermum was only in the stems of Rosa multiflora in May and July,Chaetomium globosum was only in the stems of Rosa multiflora in July ang August and in the leaves of R.multiflora var.carnea in August.(5)The Shannon Index(H′)showed that: The H′ of EF in Rosa multiflora were 2.41,2.39,2.38 and 1.85,respectively.The H′ of EF in R.multiflora var.carnea were 1.88,2.15,2.31 and 2.52,respectively.(6)Sorenson′s coefficient similarity index(CS)showed that: The CS of EF in Rosa multiflora ranged from 0.58 to 0.88,and the CS of EF in R.multiflora var.carnea ranged from 0.53 to 0.89.The highest CS of EF was in R.multiflora var.carnea beween June and July or in June between Rosa multiflora and R.multiflora var.carnea,that was 0.89.