First report of leaf spot caused by Alternaria argyroxiphii on African mahogany trees (Khaya senegalensis)

Alternaria argyroxiphii is reported for the first time as the cause of leaf spot on African mahogany trees (Khaya senegalensis). The disease was first observed in African mahogany field plantations in Perdões, Minas Gerais, Brazil, in October, 2012. Morphological characteristics and phylogeny of the pathogen were determined, and pathogenicity assays assessed the species specificity. Leaf spot was the major symptom observed. Phylogenetic analyses of the combined dataset of the Alternaria major allergen gene (Alt a 1) and glyceraldehyde-3-phosphate dehydrogenase (gpd) showed that the recovered isolates clustered into Alternaria sect. Porri and much resembled A. argyroxiphii, with 99% booststrap support and Bayesian posterior probability of 1.0. This was largely concordant with morphological characteristics (on potato carrot agar) of A. argyroxiphii, including large conidia and long beaks. A pathogenicity test, carried out to fulfil Koch’s postulates, confirmed A. argyroxiphii as a causal agent of leaf spot of K. senegalensis

Two new species of Calonectria (Hypocreales, Nectriaceae) causing Eucalyptus leaf blight in Brazil

In recent decades, commercial Eucalyptus plantations have expanded toward the warm and humid regions of northern and northeastern Brazil, where Calonectria leaf blight (CLB) has become the primary fungal leaf disease of this crop. CLB can be caused by different Calonectria species, and previous studies have indicated that Calonectria might have high species diversity in Brazil. During a disease survey conducted in three commercial plantations of Eucalyptus in northeastern Brazil, diseased leaves from Eucalyptus trees with typical symptoms of CLB were collected, and Calonectria fungi were isolated. Based on phylogenetic analyses of six gene regions (act, cmdA, his3, rpb2, tef1, and tub2) and morphological characteristics, two new species of Calonectria were identified. Five isolates were named as C. paragominensis sp. nov. and four were named as C. imperata sp. nov. The pathogenicity to Eucalyptus of both species was confirmed by fulfilling the Koch’s postulates