Evidence of post-formed structures during systemic Curtobacterium flaccumfaciens pv. flaccumfaciens infection in resistant Phaseolus vulgaris genotypes

Abstract

Abstract Bacterial wilt of the common bean caused by Curtobacterium flaccumfaciens pv. flaccumfaciens results in economic losses. The aim of this study was to analyze the colonization of C. flaccumfaciens pv. flaccumfaciens in resistant, moderately resistant, and susceptible genotypes of common bean plants. The genotypes Ouro Branco and IPA 9 (resistant), Diacol Calima (moderately resistant), and CNFRS 11997 and CNFP 10429 (susceptible) were inoculated in the epicotyl, with 100 µL of bacterial suspension of the BRM 14933(Cff25). Disease severity was evaluated 21 days after inoculation (DAI), on a scale from 1 to 9. The samples for SEM were dehydrated in an ethyl alcohol series, critical-point dried with liquid carbon dioxide (CO2), and coated with gold and analyzed using a scanning electron microscope. Ouro Branco and IPA 9 (resistant) plants exhibited low colonization, the formation of filaments surrounding bacterial cells and vestures more developed in the pit the xylem vessels. Diacol Calima (moderately resistant) plants presented lower levels of colonization and filament formation than that of resistant cultivars. CNFC 10429 and CNFRS 11997 (susceptible) showed high levels of colonization in the xylem and vessel obstruction, preventing water and nutrient flow, which explains the symptoms of wilt and plant death. Thus, resistance to C. flaccumfaciens pv. flaccumfaciens can be explained by plant’s capacity to limit pathogen propagation as a cell defense mechanism, suggesting that this is a factor in post-formed structural resistance that occurs in this pathosystem. Keywords: susceptibility; bacterial wilt; plant-pathogen interaction.

Keywords

• susceptibility
• bacterial wilt
• plant-pathogen interaction