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Agaricus (Basidiomycota) is a genus of saprobic fungi that includes edible cultivated species such as Agaricus bisporus, the button mushroom. There has been considerable ecological, nutritional and medicinal interest in the genus, yet the extent of its diversity remains poorly known, particularly in subtropical and tropical areas. Classification of tropical species has for a large part followed the classification of temperate species. The objective of our study was to examine to what extent this system of classification is appropriate for tropical Agaricus species. Species from temperate sections were therefore compared to the major clades of tropical species using a phylogenetic approach. ITS1+2 sequence data from 128 species were used in the phylogenetic analysis. Specimens included four species of genera closely related to Agaricus, 38 temperate species representing the eight classical sections of the genus, and 86 putative species of Agaricus from tropical areas of Africa, Asia and the Americas. Bayesian and maximum likelihood analyses produced relatively congruent trees and almost identical clades. Our data show that (i) only about one-third of tropical species belong to the classical sections based on temperate species; the systematics of the genus therefore needs to be expanded; (ii) among the remaining two-thirds of tropical species, those from the Americas and those from Africa and/or Asia group in distinct clades, suggesting that secondary diversification occurred in these two areas; (iii) in contrast, several clades of classical sections contain American and African+Asian species along with temperate species. In this study, we used approximately 50 distinct species from a small area of northern Thailand, most probably being novel species. This diversity indicates that Agaricus is a species-rich genus in the tropics as well as in temperate regions. The number of species and the hypothetical paleotropical origin of the genus are discussed.

Medicinal mushrooms have currently become a hot issue due to their various therapeutic properties. Of these, Agaricus subrufescens, also known as the "almond mushroom", has long been valued by many societies (i.e., Brazil, China, France, and USA). Since its discovery in 1893, this mushroom has been cultivated throughout the world, especially in Brazil where several strains of A. subrufescens have been developed and used as health food and alternative medicine. This article presents up-to-date information on this mushroom including its taxonomy and health promoting benefits. Medicinal properties of A. subrufescens are emphasized in several studies which are reviewed here. In addition, safety issues concerning the use of this fungus will be discussed.

Using a combination of morphological and molecular data, the genus Micropsalliota is shown to represent a monophyletic lineage in the Agaricaceae sister to Hymenagaricus. Features that distinguish the genus from Agaricus and allied genera include usually small, gracile basidiomes with a membranous partial veil, dextrinoid basidiospores with an apically thickened endosporium and lack of a germ pore, capitate or subcapitate, conspicuous cheilocystidia, and incrusted pileipellis hyphae that turn green in ammonia solution. We provide a monographic treatment of 23 taxa of Micropsalliota from Northern Thailand, of which 13 taxa represent new distribution reports for Thailand and 10 represent new taxa, including M. allantoidea, M. bifida, M. furfuracea, M. lateritia var. vinaceipes, M. megarubescens, M. megaspora, M. pusillissima, M. rubrobrunnescens var. rubrobrunnescens, M. rubrobrunnescens var. tibiicystis, and M. suthepensis. Included in this monograph are comprehensive descriptions, illustrations of micromorphological features, photographs of basidiomes, comparisons with allied species, phylogenetic trees inferring relationships amongst Thai species based on nrITS and nrLSU sequence datasets, and a key to aid in diagnosis.