One of the major factors limiting global food and fibre production is the loss of crop yields due to plant disease. Pesticides are used to control many plant diseases, but pathogens are becoming increasingly resistant, and new disease control methods are needed. One such approach is the use of biological control agents. Pseudomonas protegens Pf-5 is one of the best characterised biocontrol bacteria and in lab studies has the ability to control crop diseases. However, field trials of biocontrol bacteria often show unreliable colonisation and persistence on plant surfaces, hindering their efficacy.
We used Transposon Directed Insertion Site Sequencing (TraDIS) to identify genes important for surface attachment, a crucial step in bacterial colonisation of plant surfaces and biocontrol activity. TraDIS combines a dense library of randomly generated loss-of-function mutants with massive parallel sequencing to allow the simultaneous study of all non-essential genes in the genome and en masse identification of important genes. We identified 55 genes important for Pf-5 seed surface attachment, with many involved in cell wall and cell membrane biogenesis. Other important functions included cell cycle control, transcription, energy production, and inorganic ion and nucleotide metabolism and transport. Targeted knockouts and mutant phenotype characterisation of specific genes within this set will provide information on their roles in attachment. A greater understanding of the genes important for attachment to plant surfaces may improve our ability to effectively use biocontrol bacteria in Australian agriculture.