Time of arrival during plant disease progression and humidity additively influence colonization of lettuce.

UNLABELLED

The interplay between plant hosts, phytopathogenic bacteria, and enteric human pathogens in the phyllosphere has consequences for human health. has been known to take advantage of phytobacterial infection to increase its success on plants, but there is little knowledge of additional factors that may influence the relationship between enteric pathogens and plant disease. In this study, we investigated the role of humidity and the extent of plant disease progression on colonization of plants. We found that high humidity was necessary for the replication of on diseased lettuce, but not required for ingress into the UV-protected apoplast. Additionally, the pv. vitians (hereafter, )infected lettuce host was found to be a relatively hostile environment for when it arrived prior to the development of watersoaking or following necrosis onset, supporting the existence of an ideal window during infection progress that maximizes survival. growth studies in sucrose media suggest that may allow to benefit from cross-feeding during plant infection. Overall, this study emphasizes the role of phytobacterial disease as a driver of success in the phyllosphere, demonstrates how the time of arrival during disease progress can influence fate in the apoplast and highlights the potential for humidity to transform an infected apoplast into a growth-promoting environment for bacterial colonizers.

IMPORTANCE

Bacterial leaf spot of lettuce caused by pv. vitians is a common threat to leafy green production. The global impact caused by phytopathogens, including . , is likely to increase with climate change. We found that even under a scenario where increased humidity did not enhance plant disease, high humidity had a substantial effect on facilitating growth on -infected plants. High humidity climates may directly contribute to the survival of human enteric pathogens in crop fields or indirectly affect bacterial survival via changes to the phyllosphere brought on by phytopathogen disease.