Two new species of rust fungi (Pucciniales) from the Brazilian Amazon: Aecidium margaritariae on Margaritaria and Uromyces amapaensis on Jatropha

Two new species of Pucciniales fungi on plants of the Fabid clade are described from samples deposited in the herbarium of Museu Paraense Emilio Goeldi, collected in the state of Amapá, in the Brazilian Amazon. They are Aecidium margaritariae found on Margaritaria nobilis (Phyllanthaceae), and Uromyces amapaensis on Jatropha gossypiifolia (Euphorbiaceae). The microstructures of the specimens were analyzed using optical and scanning electron microscopy. Aecidium margaritariae is characterized by the presence of globose, subglobose to slightly ellipsoid aeciospores with warty walls and smooth areas usually in the basal portion. Uromyces amapaensis is distinguished by the presence of uredinia with paraphyses which are thickened and rounded at the tip, and pedicellate and smooth teliospores. Descriptions, illustrations, and taxonomic comments are presented for each species.


INTRODUCTION
In the fungi order Pucciniales, a very specific relationship between the parasitic fungus species and its host plant is observed. This specificity is a peculiar feature that favors the classic taxonomy of this group of fungi that cause rust in plants. It is used as an aid in the identification of the species, complementing morphological and molecular studies of the different stages of their complex life cycles (Cummins and Hiratsuka 2003;Passador 2009, 2014;Aime et al. 2006Aime et al. , 2018. About 3,000 species of fungi are reported for the Brazilian Amazon, including those of the order Pucciniales (Basidiomycota), represented by 199 known species causing rust on plants, of which 55 occur in the northern Brazilian state of Amapá (França et al. 2010;Carmo et al. 2016;Carvalho et al. 2018;Furtado et al. 2018;Flora do Brasil 2020). According VOL. 51(3) 2021: 244 -249 ACTA AMAZONICA to estimates, the Brazilian Amazon harbors about 50,000 botanical species (Cardoso et al. 2017), which suggests that many rust species likely remain undiscovered in this biome.
A taxonomic revision of Pucciniales specimens collected on Fabids and deposited in the herbarium of Museu Paraense Emílio Goeldi (Pará, Brazil) revealed the presence of two undescribed species. Here we describe the two new species of Pucciniales, which were found growing on the host species Jatropha gossypiifolia and Margaritaria nobilis, for the Brazilian Amazon in Amapá state.

MATERIAL AND METHODS
The Pucciniales specimens analyzed in this study were collected in the state of Amapá (Brazil) and were deposited in the João Murça Pires Herbarium (MG) of Museu Paraense Emilio Goeldi (MPEG). The identification of the host plants was carried out in collaboration with botanical taxonomists and technicians from the MPEG, following APG IV (2016) and Tropicos (https://www.tropicos.org/nameSearch).
The identification of the Pucciniales specimens followed the observation of sori under a Leica EZ4 stereomicroscope to examine the lesions on the plant tissue and the presence of spores, and the preparation of semi-permanent slides of sori, spores and other microstructures in slightly heated drops of lactoglycerol (distilled water + lactic acid + glycerin) to be analyzed using Zeiss Axiolab optical microscopy (Neergaard et al. 2000;Aparecido and Passador 2009). Twenty-five spores randomly selected from each specimen were measured. Size variation was expressed by minimum and maximum values. Illustrations of the microstructures were made using an optical microscope attached to a digital camera. For the examination of the surface of fungal structures in scanning electron microscopy (SEM), the methodology of França and Sotão (2009) was adopted. Dry leaf material with rust fungi was hand cut with a razor blade into small pieces of approximately 4 × 4 mm. The samples were mounted onto aluminum stubs with adhesive carbon tape and coated with gold. The images were obtained in a Tescan Mira3 SEM and recorded in digital mode.
Uromyces amapaensis represents a new species of rust fungi occurring on Jatropha. Five species are known to affect these plants: Phakopsora arthuriana Buriticá & J.F. Hennen, Uromyces agnatus Arthur, U. cnidoscoli, U. jatrophae Dietel. & Holw. and U. oaxanacus Dietel & Holw. (Monoson & Prose 1983, Hennen et al. 2005. Uromyces amapaensis is easily differentiated from the other Uromyces species mentioned earlier by the presence of a few paraphyses with thickened tips and pedicellate and smooth teliospores. Berndt (2002) recorded U. cnidoscoli on Jatropha sp. in Argentina. The Argentinean specimen presented transversely ellipsoidal, grossly warty, dark brown teliospores and pedicels whose apical parts dilated appreciably in aqueous medium. Before that, only the type had been reported from Brazilian collections (Goiás state), in which only teliospores had been observed, however, Berndt (2002) was able to report the presence of spermogonia, aecia and uredinia in the species. Hennings (1895) described U. cnidoscoli on Cnidoscolus vitifolius (Mill.) Pohl and commented that Aecidium cnidoscoli Henn. probably belonged to the life cycle of this species.
Until now, nine species and two varieties of rust fungi have been described on Euphorbiaceae in the Brazilian Amazon, occurring on Maprounea Aubl. (Aecidium maprouneae var.

CONCLUSIONS
This study adds two new species of rust fungi to the Brazilian and Amazonian mycobiota. Aecidium margaritariae is the second species of rust fungus found on Margaritaria nobilis, while Uromyces amapaensis is the fifth species of rust fungi described on Jatropha gossypiifolia. Our finds increase the known Brazilian mycobiota, highlighting the need to explore new areas in the Amazon region, where fungal diversity remains underestimated.