Endophytic survival of Curtobacterium flaccumfaciens pv. flaccumfaciens in cultivated plants

ABSTRACT: Alternative hosts are important sources of survival for phytopathogenic bacteria. Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff) infects economically important crops and causes significant losses. However, little information is available on alternative hosts of this bacterium. This study determined the period of endophytic survival of Cff in upland cotton, forage peanuts, common sunflower, corn, cultivated tobacco, and buckwheat. Two experiments were conducted in a completely randomized block design, with four replicates. The plants were grown in pots and kept in a greenhouse. Plants were inoculated with a bacterial suspension of the isolate Cff bean 8 (108 CFU mL-1) using the toothpick method. Cff survival in plants was assessed in plant tissue collected 5 cm above the inoculation point at 30 and 60 days after inoculation (DAI). The tissues were macerated, and the resulting macerates were plated in culture medium; and subsequently, subjected to characterization tests to determine cell-wall type, detection using subspecies-specific polymerase chain reaction (PCR). Gram-positive bacterial colonies were re-isolated at 30 DAI from peanut, common sunflower, corn, and buckwheat and at 60 DAI from corn and buckwheat. No gram-positive bacterial colonies were recovered from upland cotton and cultivated tobacco. A 306 bp Cff-specific was amplified from Gram-positive isolates obtained from peanut, common sunflower, corn, and buckwheat and whereas at 60 DAI it was amplified only from colonies obtained from corn and buckwheat. The results provided important information about plant species that could provide living tissue for Cff survival.