Pleiotropic Phenotypes of the Tomato Mutant Enable Resistance to .

Quantitative disease resistance (QDR) is the most common form of disease resistance in crops, but it is challenging to understand at the cellular level due to the involvement of many genes and biological processes. , the causal agent of bacterial wilt disease, is a destructive plant pathogen of Solanaceous species that is best controlled by quantitatively resistant varieties, but few QDR genes are known. We previously found that a tomato auxin pathway mutant known as () has enhanced resistance to . Here, we show that, as with wild-type quantitatively resistant tomato plants, resistance in is the result of multiple mechanisms. Mock-inoculated roots have endogenously higher levels of the plant defense hormone salicylic acid (SA). However, the SA-deficient double mutant is still resistant to , indicating that SA-independent pathways are also required for resistance. Scanning electron microscopy revealed that colonization of the root xylem is delayed in . We found an increased number of lignified xylem cells and altered root vasculature anatomy in , and root length was not impacted by treatment. Similar to the wilt-resistant wild-type tomato Hawaii7996, RNA sequencing results suggested that may tolerate -induced water stress better than the wilt-susceptible parent. Thus, resistance in is due to several pathways, including preactivated SA defenses, physical barriers in the xylem, and an ability to tolerate water stress. The pleiotropic nature of this single mutation appears to mimic quantitative resistance. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.