Study On The Latent Colletotrichum In The Main Citrus Leaves In Sichuan Province

Citrus anthracnose is a serious and widespread fungal disease worldwide.In China,citrus anthracnose occurs in various producing areas and is one of the main and common diseases in citrus production.The purpose of this experiment is to further clarify the species of latent anthracnose pathogen of several main citrus varieties in Sichuan.During 2018-2019,2720 disease-free leaves were collected from 20 citrus varieties in Meishan,Pujiang and Jintang of Sichuan Province.Through routine tissue separation and purification,it was found that the disease-free leaves were generally latent with fungus.The fungus carrying rate of Colletotrichum was 41.30%,that of other fungus was 27.20%,and that of total fungus was 68.50%.Detection rate of latent Colletotrichum,interregional: Meishan > Pujiang > Jintang;interseasonal,summer > winter.Between varieties,in Meishan: Shougan > Chunjian > Buzhihuo > Qingjian> Aiyuan > Wogan >Sanhongyou;in Pujiang: Shougan > Qingjian > Chunjian > Buzhihuo >Wogan> Aiyuan >Sanhongyou;in Jintang: Shougan > Wogan> Qingjian> Buzhihuo> Chunjian >Aiyuan>Sanhongyou,;leaf age: old leaves(65.81%)>young leaves(16.8%).There were significant differences in the amount of latent bacteria in leaves between different varieties,winter and summer,old leaves and young leaves.Among them,most varieties in Meishan and Pujiang areas have significant differences,while most varieties in Jintang area have no significant differences.247 representative strains were selected from the three main cultivars Chunjian,Aiyuan and Buzhihuo,and identified with GAPDH gene.Colletochum tested could be divided into 6 major categories.Then,65 strains selected from The Colletotrichum gloeosporioides species complex were identified as 2 species,Colletotrichum gloeosporioides and Colletotrichum fructicola,using 6 genes of ITS,GAPDH,ACT,TUB,CHS and Ap Mat.The 29 anthracnose pathogen strains selected from The Colletotrichum boninense species complex were accurately identified as c.karstill and c.citricola by 5 gene sequences of ITS,GAPDH,ACT,TUB and CHS.For the 12 strains divided into other species complex,5 genes of ITS,GAPDH,ACT,TUB and CHS were selected for identification,which were identified as C.truncatum,C.tropicicola and C.cliviicola.Among all strains tested,C.gloeosporioides was the dominant species,with 89 strains,accounting for 35.63% of the total strains.The species and quantity of latent Colletotrichum pathogen in citrus were different in the same area.The species and quantity of latent Colletotrichum pathogen of the same variety of citrus were also different in different areas.The species and quantity of latent Colletotrichum were higher in summer than in winter.The determination result of pathogenicity showed that,after inoculation,the citrus fruit had appeared sick spots in the third day,and 7 kinds of latent Colletotrichum pathogen selected were all pathogenic to the citrus,while C.gloeosporioides,C.fructicola,these 3 kinds of latent Colletotrichum pathogen had strong pathogenicity to the citrus fruit.It was also found that the pathogenicity of different Colletotrichum pathogen strains to citrus was significantly different.