棉花体内的假单胞菌及其对棉苗根病的防效

ISOLATION OF PSEUDOMONADS FROM COTTON PLANTS AND THEIR EFFECT ON SEEDLING DISEASES

A large amount of endophytic bacteria existed in cotton (Gossypiihirsutum 1.) seeds,immature embryoes and roots and leaves of seed-lings.The number of endophytic bacteria in roots of seedlings was about10~5 cells per gram,in leaf of seedlings was about 10~4 cells per gram,inseeds and embryoes was about 10~3 cells per gram (fresh weight). Two isolates L_29 and B_2 were identified as Pseudomonas spp..Theywere strongly antagonistic to Colletotrichum gossypii and Rhizoctonia so-lani.The time of entire inbition of growth for L_29 was 96 and 40 hrs.,respectively,and for B_2 was 96 and 32 hrs.,respectively. In sterile soil ifested with Colletoirichum gossypii B_2 and L_29 couldsignificantly reduce seedling death rate of 31.3% and 27.4%,respec-tively,comparing with control.In nonsterile soil,the two strains alsoshowed reduction of cotton diseases.The seedling death rate in treat-ment with B_2 was 59.5% and in treatment with L_29 was 30.1% comparedwith control.