Occurrence and characterization of a new red-pigmented variant of Curtobacterium flaccumfaciens, the causal agent of bacterial wilt of edible dry beans in Iran Ebrahim Osdaghi & S. Mohsen Taghavi & Habiballah Hamzehzarghani & Amal Fazliarab & Robert M. Harveson & Jay Ram Lamichhane Accepted: 8 March 2016 # Koninklijke Nederlandse Planteziektenkundige Vereniging 2016 Abstract A number of crop diseases are emerging at an alarming rate worldwide. Bacterial wilt of dry beans, caused by Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), is one of them. In Iran, this disease was first reported in 2012, which, since then, has rapidly spread across the major dry bean growing areas of the country causing severe yield losses. Previously, only two colony variants (yellow and orange) of the pathogen had been described from Iran in association with bacte- rial wilt of dry beans. In this study, we describe a new red-pigmented variant of Cff, isolated from dry bean seeds stored in seed banks of Khomein Bean Research Station, the major seed supplier in the region. Because Cff is a quarantine pathogen in Iran and elsewhere, with a potential threat for dry bean productions, more knowl- edge about the biology of this pathogen and epidemiol- ogy of the disease it causes are a prerequisite for the development of effective disease management strate- gies. Within this framework, we performed phenotypic and genetic characterization of the red-pigmented vari- ant of the pathogen, in comparison with previously isolated yellow and orange variants, including pathoge- nicity, host range, bacteriocin production and genetic diversity. Our results showed a similar host range of different Cff variants although they differed in their aggressiveness. Yellow and orange variants of the path- ogen were more aggressive on cowpea and common bean, respectively while the red variant showed the same level of aggressiveness on both hosts. Orange- and red-pigmented strains were separated from yellow- pigmented strains in the phylogeny of gyrB sequences. All orange- or red-pigmented strains were clustered in a separate branch from yellow-pigmented strains, except strain CffK31, in phylogeny based on rpoB sequences. In BOX-PCR analysis, Cff strains used in this study were clustered in two distinct genetic groups, with yel- low variants of the pathogen separated from the orange and red variants. Overall, our results provide evidence of a remarkable diversity of Cff in Iran, which needs further in-depth investigation. Keywords Pigmentation . Dry beans . Emerging disease . Actinomycetes Introduction A number of Gram-positive bacteria that belong to the family of Microbacteriaceae are commonly known for Eur J Plant Pathol DOI 10.1007/s10658-016-0900-3 Electronic supplementary material The online version of this article (doi:10.1007/s10658-016-0900-3) contains supplementary material, which is available to authorized users. E. Osdaghi (*) : S. M. Taghavi : H. Hamzehzarghani : A. Fazliarab Department of Plant Protection, College of Agriculture, Shiraz University, Shiraz 71441-65186, Iran e-mail: eosdaghi@shirazu.ac.ir R. M. Harveson Panhandle Research & Extension Center, University of Nebraska, 4502 Ave. I., Scottsbluff, NE 69361, USA J. R. Lamichhane INRA, UAR 1240 Eco-Innov, BP 01, 78850 Thiverval-Grignon, France