Tar Spot: An Understudied Disease Threatening Corn Production in the Americas.

Tar spot of corn has been a major foliar disease in several Latin American countries since 1904. In 2015, tar spot was first documented in the United States and has led to significant yield losses of approximately 4.5 million t. Tar spot is caused by an obligate pathogen, Phyllachora maydis, and thus requires a living host to grow and reproduce. Due to its obligate nature, biological and epidemiological studies are limited and impact of disease in corn production has been understudied. Here we present the current literature and gaps in knowledge of tar spot of corn in the Americas, its etiology, distribution, impact and known management strategies as a resource for understanding the pathosystem. This will in tern guide current and future research and aid in the development of effective management strategies for this disease.

New neotropical species of Phyllachorales based on molecular, morphological, and ecological data.

Species of tropical tar spot fungi (Phyllachorales, Ascomycota) are obligate biotrophic plant parasitic fungi associated with living leaves of a wide range of families of host plants, mainly in tropical and subtropical regions. In this study, samples of tropical tar spot fungi were collected in forests in Costa Rica and Panamá. To identify taxa, we used morphology and information on host plants and combined multigene phylogeny of four genes: the large subunit nuclear ribosomal DNA (28S rDNA), the small subunit nuclear ribosomal DNA (18S rDNA), the complete internal transcribed spacer region of ribosomal DNA (nuc rDNA ITS1-5.8S-ITS2; ITS), and the translation elongation factor 1-α (tef1). Here we propose one new species in the genus Camarotella and eight new species in Telimena with their morphological descriptions, illustrations, and sequence data. The newly described species are Camarotella licaniae on Licania arborea (Chrysobalanaceae) and in the genus Telimena: T. billiae on Billia rosea (Sapindaceae), T. drymoniae on Drymonia multiflora (Gesneriaceae), T. hydrangeae on Hydrangea sp. (Hydrangeaceae), T. miravallensis on Symplocos panamensis (Symplocaceae), T. protii on Protium sp. (Burseraceae), T. rinoreae on Rinorea sp. (Violaceae), T. semialarii on Semialarium mexicanum (Celastraceae), and T. triseptata on Tapirira mexicana (Anacardiaceae). The new name Telimena nitens on Schlegelia brachyanta (Schlegeliaceae) is presented and 10 species of Phyllachora are transferred to Telimena, leading to the new combinations T. canarii, T. galavisii, T. insueta, T. ruelliae, T. scutiformis, T. serjaniicola, T. spicatae, T. subrepens, T. symploci, and T. symplocicola. Additionally, revisions of tar spot fungi on host families Burseraceae, Sapindaceae, and Symplocaceae are provided, and four new synonyms are proposed.