Characterization of increased Pantoea stewartii resistance in maize pan1 mutants
P. DOBLAS IBANEZ (1), L. Smith (1) (1) University of California San Diego, U.S.A.

Pantoea stewartii is a gram negative bacterium that is the etiological agent of Stewart’s wilt, the most grave bacterial disease of maize in the Midwest and Northeast of USA. It is a hemibiotrophic vascular pathogen that is vectored by the corn flea beetle, which introduces the bacterium into both the leaf intercellular spaces, where it causes water-soaked lesions (WSL), and the vasculature. P. stewartii preferentially colonize the xylem, leading to systemic spread and characteristic wilting symptoms. We have discovered that maize pan1 mutants, that lack a LRR receptor-like kinase, show increased resistance to P. stewartii. In order to characterize the resistance phenotype, we used two inoculation methods to separate the WSL formation (whorl inoculation) from the xylem colonization and wilting (scratch inoculation). We found that pan1 mutants are more resistant than the wild type to both the development of WSL after whorl inoculation and the wilting symptoms produced by the xylem plugging after scratch inoculation. Taking advantage of a GFP-tagged bacterial strain we report that pan1 mutants are less susceptible to xylem colonization and systemic spread. Furthermore, the dissemination rate of P. stewartii within the leaf xylem is impaired in pan1 mutants. Also, preliminary analysis of SA- and JA/ET-induced gene expression shows no increase in pan1 mutants, suggesting that the resistant phenotype is not the consequence of a constitutive activation of these defense pathways.

Abstract Number: P17-516
Session Type: Poster