Studied On Population Structure And Plant Pathogenic Of Fusarium On Alfalfa Crown And Root In Arid Irrigation Area

1. Population structure of Fusarium.spp on Alfalfa crown and rootAlfalfa diease samples were collected from Gansu Hexi Jintai irrigation areas, in different seasons .and 257 isolates of Fusarium strains were gained,they had been identified as 9 species by the growth rate and the characteristics on the PSA, PDA and CLA. The dominant specie was the Fusarium solani. 93 isolates of Fusarium solani were gotten and its isolate frequency was 36.41%. Other main species were F. semitectium F. fusarioides, and F.oxysporoum, the isolate frequencies were 25.27%, 10.20%, and 8.89% respectively.2. The variety of Alfalfa crown and root Fusarium populationThe population of Fusarium changed among the different growth period of alfalfa, The dominant specie was aways the Fusarium solani. 67 isolates of Fusarium were obtained in the April samples.52,99 and 39 isolates of Fusarium were respectively obtained in June August October samples.3. The pathogenicity of Fusarium spp.Different Fusarium species had the different pathogenic, and different strains had differences in pathogenicity through the plate inoculation method, in the alfalfa variety of Debao.All of the stains of Fusarium solani. F. semitectium. F.oxysporoum. F.acuminatum. and F. camptoceras were the pathogenic isolates.But F. fusarioides15#. F.avenaceum5#, F. equiseti1# , 2# and F.spp13#,14#,15#, 16# were the weak pathogenic or non-pathogenic isolates. F fusarioides and F.camptoceras causing the crown and root rot of alfalfa were the first record.4. Pathogenicity of weak pathogenic Fusarium spp. on varities of alfalfaWeak pathogenic isolates on Debao showed different pathogenicity on other ten varieties, Most of them showed the weak pathogenicity, F.spp14# and F. fusarioides 14# were the non-pathogenicity. 5. Effect of seedling growth by non-pathogenic Fusarium.spp.10 different alfalfa varieties inoculation by weak pathogenic and non-pathogenic isolates ,The result showed all of the treated seedlings radicle length were short than comparison.Only the F.spp13# could promoted the quantities of radicle siginificiently different.The others could not.6. Studied on Non-pathogenic Fusarium control seedling rotUsing solution of weak-pathogenic and non-pathogenic Fusarium.spp germinated the seed of alfalfa .It could control the Fusarium seedling rot in the plate.But meanwhile we found the weak pathogenic and non-pathogenic stains could enlarge the distructure same pathogenic Fusarium species.