Marssonina coronaria, new causal agent of leaf spots in apple trees with low chilling requirements in central Argentina .

Abstract

During 2017-2018 years, a fungal disease caused signifi cant early defoliation on cvs `Caricia,`Princesa ́ and `Eva ́ apples trees in the center-east of the Province of Santa Fe. The symptomatology was consistent with that reported for Marssonina spp. With the purpose of characterizing the etiology of the disease, 9 isolates were obtained; being 4 characterized morphometrically and molecularly. After 60 days, the colonies reached 10 mm in diameter, with irregular margins and brown coloration. Conidia were hyaline, slightly curved, obovoid, unequally two-celled. The size was 15.23 ± 1.49 μm x 5.47 ± 0.52 μm. The isolates were identifi ed with 100% identity as Marssonina coronaria based on ITS gene phylogenetic analyses. The pathogenicity of the isolates was confi rmed. All inoculations produced symptoms and the pathogen was re-isolated, corresponding its characteristics with those initially mentioned. This study is the fi rst report of M. coronaria affecting apple leaves in Argentina and provides useful information to design management strategies.