Seedborne Fungi Of Sudangrass (Sorghum Sudanense) And Their Control

Sudangrass(Sorghum sudanense(Piper) Stapf) is an important annual gramineous sorghum forage in China.With the increasing of planting areas,disease became one of the main limiting factors for sudangrass production.The information on the seedborne fungi which may the main reason caused sudangrass disease and the information on sudangrass disease control are scare.In this study,seedbome fungi of 8 cultivars of sudangrass detection,fungi invasiveness to seedlings of sudangrass,and fungi pathogenicity to seeds and seedlings of sudangrass were determined;The fungicides and the methods of seed treatment to control the seedborne disease of the grass was also studied.The results were summarized as the follows:1.Twenty fungal species of 16 genera were isolated and identified from 8 cultivars of sudangrass.Among the fungi isolated,Alternaria alteranata,Alternaria sp.,Ascochyta sp.,Aspergillus niger,A.spergillusflavus,Bipolaris sorokiniana,Curvularia lunata, Drechslera turcnica,Fusarium monilifome,PeniciUium sp.,Rhizopus stolonifer and Trichothecium roseum were the most common isolated,and Cladosporium sp.,F. avenaceum,F.graminearum,Phoma sp.,Phytophthora sp.,Rhizoctonia solani Stemphylium sarciniforme and Verticillium sp.were isolated frequently.Seeds surface sterilization reduced the percentage of fungal isolation.Seventeenth species belonging to 14 genera were isolated and identified from seeds without surface sterilization and sixteenth species belonging to 12 genera were isolated and identified from surface sterilized seeds.For the sites of the fungi isolated from the seeds,in order of decreasing frequency of fungal species,were seed coat(13),pericarp(12),endosperm(10) and embryo(7).2.All the 20 fungi isolated from the seeds of sudangrass was observed grown on the surface of the root of sudangrass seedlings and caused lesion on the root except Alternaria sp.,Aspergillus spp.,Penicillium sp.and Rhizopus stolonifer.The effects of of the isolated seedborne fungi(exclude R.solani)on the germination and seedling vigor index of seeds inoculated with spore suspension were studied by using the standard blotter method and the paper towel method.Compared with the uninoculated treatment,the germination of seeds,shoot length and root length of seedlings were significantly decreased by inoculation of the most fungi(P＜0.05).Among which,B. sorokiniana,C.lunata,D.turcnica,F.avenaceum,F.graminearum,F.monilifome and Tr. Roseum shown the highest pathogenesis to sudangrass.The percentage of seed germination were reduced by 27.5%,16.7%,27.5%,35.3%,31.6%,34.4%and 19.5%respectively; The shoot length of seedling were reduced by 44.7%,40.8%,49.0%,46.5%,58.7%,39.6%and 46.9%respectively;The root length of seedling were reduced by 61.8%, 32.3%,56.4%,61.1%,60.0%,57.7%and 47.3%respectively.Based on the above results,we concluded that B.sorokiniana,C.lunata,D.turcnica, F.avenaceum,F.graminearum,F.monilifome,R.solani and Tr.Roseum were the pathogeic fungi of the sudangrass seeds.3.Among the four fungicide tested in this study,seeds of 0007,1044 and 89-106 treated with oxadixyl shown the best inhibition to fungi infection,the inhibition reached 87.8%,89.4%and 92.1%respectively(P＜0.05).Meanwhile seeds treated with oxadixyl significantly increased the root length of the seedlings of 0007,1044 and 89-106 by 12.2%, 7.24%and 20.1%respectively,and also increased the shoot length by 12.7%,10.6%and 9.4%respectively.