Abstract
The ability of seed-borne bacterial pathogens (Acidovorax citrulli, Clavibacter michiganensis subsp. michiganensis, Pseudomonas syringae pv. tomato, Xanthomonas euvesicatoria, and Pseudomonas syringae pv. glycinea) to infest seeds of host and non-host plants (watermelon, tomato, pepper, and soybean) and subsequent pathogen transmission to seedlings was investigated. A non-pathogenic, pigmented strain of Serratia marcescens was also included to assess a null-interacting situation with the same plant species. Flowers of host and non-host plants were inoculated with 1×106 colony forming units (CFUs)/flower for each bacterial species and allowed to develop into fruits or umbels (in case of onion). Seeds harvested from each host/non-host bacterial species combination were assayed for respective bacteria by plating on semi-selective media. Additionally, seedlots for each host/non-host bacterial species combination were also assayed for pathogen transmission by seedling grow-out (SGO) assays under greenhouse conditions. The mean percentage of seedlots infested with compatible and incompatible pathogens was 31.7 and 30.9% (by plating), respectively and they were not significantly different (P = 0.67). The percentage of seedlots infested with null-interacting bacterial species was 16.8% (by plating) and it was significantly lower than the infested lots generated with compatible and incompatible bacterial pathogens (P = 0.03). None of the seedlots with incompatible/null-interacting bacteria developed symptoms on seedlings; however, when seedlings were assayed for epiphytic bacterial presence, 19.5 and 9.4% of the lots were positive, respectively. These results indicate that the seeds of non-host plants can become infested with incompatible and null-interacting bacterial species through flower colonization and they can be transmitted via epiphytic colonization of seedlings. In addition, it was also observed that flowers and seeds of non-host plants can be colonized by compatible/incompatible/null-interacting bacteria to higher populations; however, the level of colonization differed significantly depending on the type of bacterial species used.
Highlights
Seedborne phytopathogenic bacteria act as primary inoculum source for many important vegetable diseases
We investigated four important steps in the seed transmission process through flowers; namely, flower colonization, seed infestation, seed colonization and seedling transmission of five different seedborne bacterial pathogens (A. citrulli, C. michiganensis subsp. michiganensis, P. syringae pv. tomato, X. euvesicatoria, and P. syringae pv. glycinea) with their respective compatible and incompatible hosts
Inoculum was prepared by transferring single colonies of each bacterial strain from 48-h old cultures on nutrient agar (NA) (A. citrulli, C. michiganensis subsp. michiganensis, and S. marcescens), yeast extract-dextrose–CaCO3 (YDC) (X. euvesicatoria) or King’s medium B (KMB)
Summary
Seedborne phytopathogenic bacteria act as primary inoculum source for many important vegetable diseases Examples of these include watermelon fruit blotch [1,4,23,33,47,48,50], bacterial canker of tomato [21,43], bacterial speck of tomato [30], bacterial spot of pepper [26,27,42], and bacterial blight of soybean [28], which are caused by Acidovorax citrulli [35,38], Clavibacter michiganensis subsp. Many of the major vegetable seed producers have moved their seed production to areas of the world that are less conducive to bacterial diseases, but seedborne bacterial diseases still cause millions of dollars in losses annually [5,20]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
