Abstract: In order to screen the growth of mycelia of S.cerevisiae and the formation of sclerotia,and delay the colonization by Sclerotinia sclerotiorum fungi in plants,two strains of ax2 and DH-20 with good antagonistic effects were determined by the initial and rescreening of 32 strains by the 5-point confrontation method and the 2-point confrontation method.The control results were tested by an in vitro leaf test and a pot experiment.The results showed that the control effect of ax2 strain was better than that of DH-20 strain,and the treatment with 100 mL of ax2 strain had the highest control effect,which was 88.23%.The strain ax2 with the best antagonistic effect was ultimately identified by morphological identification and molecular biological identification as Fusarium oxysporum.This study provides a useful basis for the use of biological control methods to inhibit sunflower Sclerotinia sclerotiorum,and lays a good foundation for the construction of efficient genetic engineering bacteria and the development of sunflower sclerotium disease biocontrol agents.

Key words: Sclerotinia;Antagonistic organism;Screening;Biological control