The 3-Hydroxy-2-Butanone Pathway Is Required for Pectobacterium carotovorum Pathogenesis

Pectobacterium species are necrotrophic bacterial pathogens that cause soft rot diseases in potatoes and several other crops worldwide. Gene expression data identified Pectobacterium carotovorum subsp. carotovorum budB, which encodes the α-acetolactate synthase enzyme in the 2,3-butanediol pathway, as more highly expressed in potato tubers than potato stems. This pathway is of interest because volatiles produced by the 2,3-butanediol pathway have been shown to act as plant growth promoting molecules, insect attractants, and, in other bacterial species, affect virulence and fitness. Disruption of the 2,3-butanediol pathway reduced virulence of P. c. subsp. carotovorum WPP14 on potato tubers and impaired alkalinization of growth medium and potato tubers under anaerobic conditions. Alkalinization of the milieu via this pathway may aid in plant cell maceration since Pectobacterium pectate lyases are most active at alkaline pH

Optimal environmental conditions for the infection and development of Puccinia purpurea on sorghum

Although rust can reduce grain yields of late-planted sorghum crops in Queensland, little research has been conducted on environmental parameters affecting infection and development. The effects of temperature, leaf wetness period, plant growth stage, urediniospore concentration and darkness period on the development of rust (Puccinia purpurea) on the inbred Sorghum bicolor line IS8525 were evaluated separately by artificial inoculation of plants under controlled conditions. Rust developed between 16 and 28 °C, with the optimum temperature being 20 °C. Disease severity (pustules cm−2) increased as the length of leaf wetness increased from 4 to 24 h. Infection occurred when plants were exposed to full light, full darkness and varying periods of darkness for the first 24 h after inoculation; 16 h of darkness resulted in the highest rust severity. Plants of IS8525 and of the more resistant line IS12539 inoculated 21–49 days after sowing developed higher levels of rust than others inoculated at, or close to, flowering (63 days after sowing). Rust severity also increased with increasing urediniospore concentrations, but leaf death occurred on young plants inoculated with the highest concentration (50 mg 100 mL water−1). The findings of this study have been used to develop an inoculation technique to detect putative pathotypes of P. purpurea in Australia

Pectobacterium and Dickeya: Environment to Disease Development

The soft rot Pectobacteriaceae (SRP) infect a wide range of plants worldwide and cause economic damage to crops and ornamentals but can also colonize other plants as part of their natural life cycle. They are found in a variety of environmental niches, including water, soil and insects, where they may spread to susceptible plants and cause disease. In this chapter, we look in detail at the plants colonized and infected by these pathogens and at the diseases and symptoms they cause. We also focus on where in the environment these organisms are found and their ability to survive and thrive there. Finally, we present evidence that SRP may assist the colonization of human enteric pathogens on plants, potentially implicating them in aspects of human/animal as well as plant health