ABTRACT

This study was carried out for screening promising bacteriophage possess potential ability in lysis pathogenic bacteria Xanthomonas sp. which cause g bacterial leaf blight disease on onion and expressed good effect in controlling the disease in nethouse conditions. By the direct method and enrichment method, there were 10 bacteriophages isolated from 12 strains Xanthomonas sp. different from 4 provinces: An Giang, Bac Lieu, Soc Trang, Vinh Long and Can Tho city. A mong them, bacteriohages with coded ?Xan6, ?Xan16, ?Xan17A, ?Xan17B, ?Xan31 showed higher parasitic efficiency to many Xoo strains and bacterial strain XanBL11 (Hiep Thanh - Bac Lieu) was parasitized by almost isolated bacteriophages with proportion 10/10. Survey lytic ability of 5 bacteriophages on Xanthomonas sp. strain XanBL11 in in vitro, two bacteriophages ?Xan31, ?Xan16 showed the highest lytic ability on bacterial lawn with the biggest diameter of plaque in different time course observation. Evaluation the effect of bacteriophages in controlling the disease in nethouse condition, results showed that treatments bacteriophage ?Xan31 gave higher disease prevention than others bacteriophage treatments and treatment phage mixture showed lowest disease reduction. However all these phage treatments still lower efficiency in disease reduction as compared to Starner.