本文对3个假单胞杆菌菌株(Pseudomonas spp.)及其嗜铁素(pseudobactin siderophore)缺失突变体防治桉树灰霉病进行了研究.平板拮抗活性测定表明,荧光假单胞杆菌(P.fluorescens) WCS374r菌株和恶臭假单胞杆菌(P.putida) WCS358r菌株通过对铁离子的竞争抑制灰霉菌的生长.在接种灰霉病菌之前10 h将WCS358r、WCS374r和WCS417r施用于受伤的桉树叶片后,可分别降低发病率48.9%、58.3%和40.3%;当将3种生防菌分别与灰霉病菌混合后接种桉树叶片,WCS358r和WCS374r仍然能够显著地降低发病率;在接种灰霉病菌12 h后再施用生防菌,WCS358r和WCS374r对病菌仍具有一定的抑制作用,而在24 h后施用生防菌,3个菌株均未表现显著的防治效果.WCS358r和WCS417r的嗜铁素缺失突变体无防病作用,而WCS374r的嗜铁素缺失突变体虽然还能有效地防治灰霉病,但与WCS374r相比,防病效果减弱.本试验结果说明假单胞杆菌的嗜铁素是控制桉树灰霉病的重要因子.

Three fluorescent Pseudomonas strains and their pseudobactin siderophore-minus mutants were investigated in suppression of eucalypt grey mould caused by Botrytis cinerea. Results from in vitro antagonistic tests showed that Pseudomonas fluorescens WCS374r and P. putida WCS358r inhibit mycelial growth of B. cinerea by competition for iron. When WCS358r,WCS374r and WCS417r were applied to wounded leaves 10 h prior to the inoculation of pathogen,they suppressed eucalypt grey mould,and reduced the percentage of necrotic spots on leaves by 48.9%, 58.3% and 40.3%,respectively. Strains WCS358r and WCS374r were effective as well when the mixture of either strain and pathogen was applied to wounds on leaves. However,if three strains were applied to wounds 12 h or 24 h posterior to inoculation of pathogen,the control effects decreased sharply. The pseudobactin-minus mutants of WCS358r,WCS374r and WCS417r partially or fully lost their suppressive ability of the disease. These results demonstrate that siderophores are important bacterial determinants in suppression of eucalypt grey mould.