| Plumeria rust caused by Coleosporium plumeriae is one of the mainly disease of plumeria,yellow round small spots were appeared on the obverse side of diseased leaves,orange-yellow powdery uredinia were observed on the reverse side of diseased leaves,diseased leaves falling off earlier,and tree vigor weakening,ornamental value decreasing.Plumeria rust with hyperparasitism were covered by white mycelia on the uredinia at the reverse of diseased leaves.In the study,the hyperparasitic fungus of C.plumeriae was isolated and its species was identified,its hyperparasitism was confirmed,its host range were determined,the artificial culture conditions were optimized,and its the hyperparasitic rates were tested.These research results would provided theoretical basis for the biological control of plumeria rust and other plant rusts.The research results as follows:1.The hyperparasitic fungus of C.plumeriae was identified as Simplicillium subtropicum.Combined the morphological characteristics and the nucleotide sequence analysis of 3fragments including ITS region,SSU and LSU genes,the hyperparasitic fungus of C.plumeriae was identified as S.subtropicum.This is the first report that S.subtropicum was the hyperparasitic fungus of C.plumeriae.2.Total 11 species pathogenic fungi of plant rusts were inoculated with S.subtropicum,only 3 species pathogenic fungi were hyperparasited.C.plectranthi,C.paederiae,Melampsora larici-populina,Puccinia polysora,P.kuehnii,P.thaliae,P.polygoni-amphibii,Phakopsora euvitis,Tranzschelia pruni-spinosae,Cerotelium fici,and P.paullula were inoculated with S.subtropicum,only three of them,including C.plectranthi,C.paederiae and M.larici-populina were hyperparasited.This is the first report that S.subtropicum was the hyperparasitic fungus of the 3 species pathogenic fungi of plant rusts.3.The basic conditions of largest colony diameter of S.subtropicum on agar media plates were determined.On 10 tested media,the largest colony diameter of S.subtropicum was on oat meal agar medium incubated at 28℃for 7 d.While Czapek-Dox medium was basic medium incubated at 28℃for 7 d,it was found that the colony diameter was largest while carbon source was soluble starch and nitrogen source was beef extract.On potato dextrose agar medium,the optimal condition for S.subtropicum growing were p H 6 and temperature28℃;and darkness could promote the colony growth.4.The basic conditions for largest sporulation capacity in liquid and solid media were clarified.In 20 liquid media,the largest sporulation capacity of S.subtropicum was in 2%rice bran liquid medium.While Czapek-Dox liquid medium was basic medium,it was found that the sporulation capacity was largest while carbon source was soluble starch and nitrogen source was beef extract,peptone,or tryptone respectively;The sporulation capacity was largest while the ratio of starch and beef extract was 20:9.In rice bran liquid medium,the optimal conditions for the conidia producing of S.subtropicum were 8 m L of initial inoculation amount of conidia with concentration of 1.0×10~8conidia/m L,200 r/min of oscillating incubator rotational speed,7 d of incubation time.In 10 solid media,the largest sporulation capacity of S.subtropicum was in cornmeal and wheat bran medium,in whichthe sporulation capacity was largest while the ratio of material and water was 1:1.2.In which the sporulation capacity was largest while supplementary carbon source was soluble starch,and nitrogen sources was beef extract,peptone,or tryptone.5.The uredinia on the reverse side of plumeria rust leaves were sprayed with the conidia concentration of S.subtropicum cultured with liquid media in indoor and in field respectively,the hyperparasitic rates were observed and counted after sprayed for 7 d.Under the indoor experiment with detached leaves,among 20 liquid media,sprayed with conidia concentration was 1.0×10~6conidia/m L,conidia suspension liquid from rice bran liquid medium had the highest hyperparasitic rate,it was 86.00%.Under the field condition,sprayed with conidia suspension liquid from rice bran liquid medium,the hyperparasitic rate was 64.23%. |
