Underexplored Niches in Research on Plant Pathogenic Bacteria

SUMMARY Despite rapid advances on certain aspects of plant pathogenic bacteria, many economically important pathosystems are largely unexplored and biologically relevant life stages of even familiar systems remain poorly understood. We know remarkably little about end-stage disease, latent infections, survival away from the host, interactions among multiple microbes in a plant, and the effects of quantitative virulence factors. While no thoughtful researcher would dispute the effectiveness of reductionist experiments, we pro- pose that this approach be combined with a broader perspective that includes the ecology, histopathology, and community population biology of phytopatho- genic bacteria. We offer examples of exciting recent discoveries resulting from this natural history-based approach. In particular, in situ studies using biologi- cally realistic inoculation followed by analyses with microscopy, gene expression profiling, community analyses, or application of key computational tools can offer new insights into old questions. Research that combines cutting-edge tools with a biological perspec- tive is especially lacking on high-impact diseases of subsistence crops. Understanding the biology under- lying important practical issues such as copper resis- tance, eradication from seed and cuttings, and rapid, sensitive detection could be of significant utility. Over- all, we endorse a broader biological approach to re- search on plant pathogenic bacteria. CHOICES, CHOICES In response to significant advances in plant bacteri- ology, researchers can focus in to more deeply under- stand the discovery, or they can change the subject and turn to important questions that remain poorly un- derstood. This article encourages the second approach by pointing out some underexplored but important aspects of plant pathogenic bacteria. We first discuss considerations that may aid selection of research topics, and then suggest a necessarily incomplete set of specific questions and approaches that promise fresh and productive research. Ideally, our research programs would be designed to reveal fundamental biology of high-impact plant path- ogens, leading to useful disease management strate- gies. All too often our planning instead brings us to the intersection of the feasible, the fundable, and the familiar—hardly a path to novelty. We suggest that those seeking new directions should instead choose a study system that satisfies at least two of the criteria listed in Table I. In particular, research is urgently needed on destructive diseases of key tropical subsis- tence crops, such as Xanthomonas wilt of banana (Musa spp.) and bacterial blight of cassava (Manihot esculenta). A more widespread focus on research to reduce crop losses offers the additional benefit of increasing stake- holder support for plant bacteriology funding.