Abstract
Diseases of soybean caused by Cercospora spp. are endemic globally throughout the soybean production regions and are part of the late cycle disease complex. Research into the genus Cercospora in soybean has historically been underrepresented in terms of species diversity due to a dependence of differentiation on morphological characteristics, symptomology, and host associations. Previous studies indicated two species, C. kikuchii and C. sojina, to be infective on soybeans. However, recent research, including molecular analytical methods, shows that a broader range of species can be associated with the disease. Therefore, the objective of this study was to identify the predominant species of Cercospora associated with the late cycle disease complex in soybean in Brazil and investigate the pathogenicity of the identified species in greenhouse experiments. For this purpose, 43 isolates of Cercospora spp. from Brazil were analyzed using a multi-locus phylogenetic approach with five different loci from the gDNA. Furthermore, cloning was performed on 11 leaf samples, to correctly identify the species present. Of the 43 isolates, 41 were identified as Cercospora sp. Q, one as C. kikuchii and one as C. cf. sigesbeckiae. In all the 11 cloned leaf samples, C. sp. Q was the predominant species. However, C. kikuchii, C. cf. flagellaris, C. cf. nicotianae and C. sp. P were also detected in many samples, although at much lower frequencies. Furthermore, infection of soybean plants under greenhouse conditions was achieved for the predominant species (C. sp. Q). This study proofs the pathogenicity of Cercospora sp. Q on soybeans, shows that C. sp. Q is suggest to be the most frequent species of Cercospora infecting soybean in Brazil and confirms that the late cycle disease complex can involve more than one species of Cercospora simultaneously. However, further studies are required to identify and establish improved markers for the molecular differentiation between Cercospora species.