Genus Suillus Research Articles

Aluminium in wild mushrooms and cultivated Agaricus bisporus

The aluminium content in wild mushrooms (n = 271, 19 species) and in cultivated Agaricus bisporus (n = 15) was determined by graphite furnace atomic absorption spectroscopy. With an aluminium content of 30 – 50 μ/g dry matter (DM) Boletus and Xerocomus species, the most well-known and most popular mushrooms, proved to be poor in aluminium. Several species of the genus Suillus, Macrolepiota rhacodes, Hypholoma capnoides as well as individual samples of Russula ochroleuca and Amanita rubescens contained high aluminium concentrations of about 100 μg/g DM and more. Cultivated Agaricus bisporus had the lowest aluminium content, i. e. 14 μg/g DM. The site, its geological origin as well as the mushroom species influenced the aluminium content in the fruitbodies: these factors require further investigation. Mushrooms do not contribute significantly to aluminium intake by humans.

The mating system of Suillus bovinus

Basidiospores from sporocarps of Suillus bovinus collected in Sweden gave rise to homokaryons, which were paired on agar plates for analysis of mating type. These tests showed a bipolar sexual incompatibility. Heterokaryons were recognized by their formation of clamp connections, by a growth rate higher than that of the homokaryons, and by morphological and cytological characteristics. S. bovinus is the third species in the genus Suillus found to possess a bipolar sexual incompatibility.

Accelerated evolution of a false-truffle from a mushroom ancestor.

THE false-truffles (Hymenogastrales) are a group of basidomycetous fungi that produce underground truffle-like basidiocarps. They are generally believed to be independently derived from several mushroom lineages, but extensive morphological divergence often obscures recognition of these phylogenetic connections. Comparisons of mitochondrial DNA now demonstrate a surprisingly close relationship between species of false-truffles in the genus Rhizopogon (Hymenogastraceae) and the mushroom genus Suillus (Boletaceae). The striking morphological differences separating all Suillus species from Rhizopogon imply an acceleration in the rate of morphological change relative to molecular change during the evolution of these false-truffles from their mushroom ancestors. This acceleration can best be explained by rapid morphological divergence resulting from selective pressures which may have acted on a small number of developmental genes.

Acid phosphatase, alkaline phosphatase, and nitrate reductase activity of selected ectomycorrhizal fungi

Seventeen isolates, encompassing five genera and eight species of ectomycorrhizal fungi, were compared for acid phosphatase, alkaline phosphatase, and nitrate reductase activity. Isolates within species differed in enzyme activity and isozyme patterns by host specificity and site (as exemplified by the genus Suillus). Host and site may have affected phosphatase enzyme activity. Generally, the Douglas-fir associates, which dominate in mesic sites, have higher acid phosphatase activity than pine associates, which mostly occupy xeric sites; however, pine associates from mesic sites also have higher acid phosphatase activity (e.g., S. tomentosus). In four isolates of Amanita muscaria, the effect of site was also apparent. Two of them, which have significantly higher acid phosphatase activity than the others, were isolated from mesic sites. The isozyme pattern of the genus Suillus appeared to be separated by host groups. Other isolates with only one species also differed more or less by host groups. They shared at least one band within host groups, except for the two isolates of Paxillus involutus from different hosts. The P. involutus S-403 isolated from an orchard showed much higher nitrate reductase activity than all other isolates. No apparent differences in nitrate reductase activity were found between the other isolates.

A new approach to the phylogeny of the order Boletales (Basidiomycotina)

An analysis employing parsimony and character compatibility methods is carried out for selected species in the various families constituting the order Boletales s.l. The results indicate that Paxillaceae is polyphyletic, actually representing a primitive matrix from which many of the other families have evolved. Gyrodontaceae is also polyphyletic, and its various genera should be included within other families. The analysis does not support that Xerocomaceae and Boletaceae should be regarded as two separate families. It indicates that the genus Suillus should be included within Gomphidiaceae. On the other hand, it strongly contradicts any relationship between Suillus and Chalciporus on one hand, and Strobilomyces on the other. The latter genus must be very isolated from the other genera analysed. The gastroid families Rhizopogonaceae and Chamonixiaceae seem to have derived from progenitors related to Boletaceae and Gyroporus (here regarded within Paxillaceae) respectively. Coniophoraceae is probably derived from precursors related to the more primitive representatives in Paxillaceae.

Macrochemical reactions of species in the family Boletaceae

Macrochemical reactions are reported on 15 species of Suillus, 3 of Fuscoboletinus, 2 of Gyroporus, and 1 species each of Boletellus, Boletinellus, Pulveroboletus, and Strobilomyces, together with a number of tests on species of Tylopilus and Boletus not available for an earlier paper. Three species of Suillus and three Boletus species are new records for Nova Scotia, and two of these are new for Canada. Also included are tests for a new species of Boletus to be described in another paper.Similarities in the macrochemical tests are used to divide 13 of the species of genus Suillus into two groups. Suillus luteus was selected as the type for group 1 and S. americanus for group 2. Two species did not belong to either group and were distinctly different from each other. Two species of Fuscoboletinus could be placed with group 2, but the third, F. paluster, differed widely. Boletus piperatus, which has been placed in Suillus by some authors, does not appear to be related on the strength of these tests. No attempt was made to group other species in Boletus or Tylopilus.

Notes on Boletes. VII

In Mycologia 33: 422. 1941, the species californicus Murr. was placed in Gyrodon as a new combination. This change was an unfortunate error, for study of the type-material shows that Murrill had it correctly placed in the genus Rostkovites of his system or the more recently proposed Suillus (= Ixocomus Quelet the Viscipelles of Boletus of Fries and Peck-see Mycologia 34: 406. 1942). Not only do the spores place this species in the old Viscipelles of Boletus (or the genus Suillus) but also the glandulardotted tube-walls and mouths, and stipe. The surface of the pileus is very fibrillose-tomentose to more or less fibrillose-scaly and is probably more or less viscid under moist conditions. All these characters immediately remind one, however, of the species hirtellus Peck (= tomentosus Kauff.) and especially its more fibrillose-patchy to fibrillose-scaly variety mutans Peck. The only differences are the much more tomentose or fibrillose condition of the surface of Murrill's species and the spores slightly larger (8-11.5 x 3-4.5 j as against 7-11 x 2.5-3.5 ji) and slightly deeper olivaceous. While heretofore no collection of hirtellus or its variety mutans has been seen with these extremes of surface clothing and of spore size and color, nevertheless it appears that californicus belongs in the hirtellus complex. Therefore, until more collections than the type are available for determining