Cercospora cf. flagellaris and Cercospora cf. sigesbeckiae Are Associated with Cercospora Leaf Blight and Purple Seed Stain on Soybean in North America

Abstract

Cercospora kikuchii has long been considered the causal agent of Cercospora leaf blight (CLB) and purple seed stain (PSS) on soybean, but a recent study found C. cf. flagellaris associated with CLB and PSS in Arkansas (United States) and Argentina. Here, we provide a broader perspective on the distribution of C. cf. flagellaris on soybean and alternate hosts within the United States (Arkansas, Louisiana, Mississippi, Missouri, and Kansas). We used a multilocus phylogenetic approach with data from actin, calmodulin, translation elongation factor 1-α, histone 3, the internal transcribed spacer region of rDNA and the mating-type locus to determine that two species, C. cf. flagellaris (200 of 205 isolates) and C. cf. sigesbeckiae (five of 205 isolates), are associated with CLB and PSS in the United States. In our phylogenetic analyses, species-level lineages were generally well-supported, though deeper-level evolutionary relationships remained unresolved, indicating that these genes do not possess sufficient phylogenetic signal to resolve the evolutionary history of Cercospora. We also investigated the potential for sexual reproduction in C. cf. flagellaris in Louisiana by determining the frequency of MAT1-1/MAT1-2 mating-type idiomorphs within the Louisiana population of C. cf. flagellaris. Though the MAT 1-2 idiomorph was significantly more common in our collection, the presence of both mating types suggests the potential for sexual reproduction exists.

Draft Genome Sequence of Cercospora cf. sigesbeckiae , a Causal Agent of Cercospora Leaf Blight on Soybean

“…Cercospora cf. sigesbeckiae is a broad generalist pathogen infecting at least eight different plant families and causing Cercospora leaf blight (CLB) on soybean ( 1 ). Until recently, Cercospora kikuchii was thought to be the only causal agent of CLB, but phylogenetic analyses of cercosporoid fungi isolated from infected soybean revealed the presence of two other morphologically similar Cercospora species, including Cercospora cf.…”

“…sigesbeckiae from leaves and Cercospora cf. flagellaris from seeds and leaves ( 1 , 2 ). Prior to 2015, most records of Cercospora cf.…”

The AVR4 effector is involved in cercosporin biosynthesis and likely affects the virulence of Cercospora cf. flagellaris on soybean

“…flagellaris (Albu et al, 2016;Matsumoto and Tomoyasu, 1925;Suzuki, 1921;Walters, 1980), with C. cf. flagellaris being the dominant causal agent of CLB in the southern USA (Albu et al, 2016). In the USA, CLB was first reported in 1978 (Walters, 1980).…”

The G143A Mutation is Responsible for Strobilurin Fungicide Resistance in Cercospora cf. flagellaris, a Leaf Blight and Purple Seed Stain Pathogen of Louisiana Soybean

“…The objective of this study was to determine if the G143A or F129L mutations were responsible for QoI resistance in isolates of Cercospora cf. flagellaris, which recently was determined to be associated with CLB/PSS in Louisiana (Albu et al 2016).…”

“…flagellaris (98) from the radial growth assay study (Price et al 2015) were selected for molecular characterization along with 13 isolates from pokeweed from Illinois, Arkansas, and Louisiana, and two isolates from Louisiana cotton with unknown sensitivities. Culture preparation, DNA isolation, and PCR amplification were performed as described in Albu et al (2016). A portion of the cytochrome b gene of approximately 650 to 700 bp, containing the 129th and 143rd codon positions, was sequenced using the primers cyt-f2/cytb-r1 (Imazaki et al 2006) on the Applied Biosystems platform at Beckman Coulter Genomics (Danver, MA) using Big Dye Terminator chemistry.…”