Genome sequences of plant associated Rhodococcus spp. isolates from Tunisia

Now published in Microbiology Resource Announcements, 9:e00293-20. Phytopathogenic isolates of Rhodococcus spp. are known to cause disease on herbaceous and woody species (Putnam and Miller, 2007; Miller and Putnam 2010). In 2011, two distinct Rhodococcus species designated as PBTS1 and PBTS2 caused serious losses to the pistachio industry in California and Arizona (Stamler et al, 2015a, b, 2016). On ornamental plants, major disease symptoms caused by R. fascians were described as leafy galls and stems fasciations (Stes et al. 2013), while on woody trees the symptoms included stunted growth and proliferation of misshapen shoots known as witches’s brooms (Stamler et al, 2015a, b). The virulence strategy employed by the renowned R. fascians D188 consists of the disruption of plant hormone balance through the production and modulation of cytokinins and auxins (Pertry et al, 2009, 2010). The genes that are essential for cytokinin biosynthesis and modification are encoded by three virulence loci clustered on the fas operon which is located on a linear plasmid of R. fascians (Crespi et al, 1992; Francis et al, 2012). Complete genome and plasmid sequences for R. fascians D188 were previously reported (Francis et al, 2012; Creason et al, 2014) as well as the two pistachio Rhodococcus PBTS 1 and PBTS 2 isolates (Stamler et al, 2016). Four distinct Rhodococcus species isolates from symptomatic almond rootstocks, pistachio tree and ornamental plants in Tunisia were used in this study. The ornamental Rhodococcus isolate B10 was shown to cause stunting and shoot proliferation on Iresine herbestii plants in pathogenicity assays (Dhaouadi et al, 2019). The two almond Rhodococcus isolates GS6 and SB10 and the pistachio Rhodococcus isolate K5 developed shoot proliferation and stunting on both the host of origin and the pea seedlings bioassays (Unpublished data). It is well known that the population structure of R. fascians tends to be diverse from one host to another and from a region to another (Creason et al, 2014). Here, we provide a first insight into the genetic diversity of phytopathogenic Rhodococcus in Tunisia through the genome sequencing and assemblies of four isolates collected from pistachio, almond and the ornamental plant Iresine herbestii.