Recombinase polymerase amplification did not detect Xylella fastidiosa subsp. multiplex in peach seeds from phony peach disease trees

Phony peach disease (PPD), caused by Xylella fastidiosa (Xf) subspecies multiplex (Xfm), is an important disease of peach in the southeastern United States. Seed transmission of Xf has not been reported for PPD, and research published in 1933 indicated seedlings grown from seeds of PPD trees did not develop the disease. Recombinase polymerase amplification (RPA) is a relatively new and rapid molecular detection process that has been commercialized as AmplifyRP® XRT + for Xf. We utilized this test to determine whether the Xf bacterium could be detected in peach seeds collected from PPD-infected trees. Initially, 25 seeds and 25 excised embryos were individually tested for Xf using qPCR, and Xf was not detected. In a more extensive study, 300 individual seeds were tested for Xf using RPA, and all seed were again negative for Xf. Our studies provide no new evidence to support vertical transmission of Xf from Xf-infected peach trees to peach seeds. However, prior to concluding that vertical transmission does not occur, additional studies to observe and test seedlings produced from seed collected from PPD trees should be conducted.