Physiology-based identification of X-disease infected cherry trees
Author: Kelsey Galimba
Published: 2026
Summary: The cherry industry is in need of more convenient and efficient detection methods for cherry X-disease, a phytoplasma-based disease that causes small, pale, unpalatable fruit. In this project, we aimed to take advantage of the documented physiological changes that have been shown to be caused by related phytoplasmas in related plant hosts, in order to develop a physiology-based assay capable of detecting X-disease infected sweet cherry trees. Phytoplasma infections have been shown to cause a build-up of starch in the leaves of apple, grape, coconut, papaya, jujube and citrus. To determine if this occurs in X-disease infected cherry as well, we tested starch levels in leaves, comparing both young and older infected and uninfected trees. Starch levels varied between leaves, but no correlation was present between infection and starch level. We also explored field-based methods to detect starch in the field. The first, an iodinebased assay, also did not result in a correlation between infected and uninfected leaves, which is expected given the lack of differences in starch levels. The second method, which relies on spectral readings and analysis, could potentially detect starch levels or some other difference independent of starch. However, our analyses did not reveal any signature that correlated with infection status of trees. This project explored methods that could have been valuable for Xdisease detection, but it appears that the physiological changes present in infected cherry trees differ from other crop/disease changes and will likely not be useful tools in this situation. Further studies into spectral diagnostics should focus on different scanning methods and/or include wavelengths outside of the range we used.
