Lactarius Species (Mushrooms): In Vitro Culture and the Production of Sesquiterpenes and Other Secondary Metabloites
The genus Lactarius (family Russulaceae, class Basidiomycotina) is one of the largest and best known in North America and Europe (Burlingham 1908, 1910, 1913; Hesler and Smith 1979). Tropical species of Lactarius have been studied by several authors and a
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1 Introduction The genus Lactarius (family Russulaceae, class Basidiomycotina) is one of the largest and best known in North America and Europe (Burlingham 1908, 1910, 1913; Hesler and Smith 1979). Tropical species of Lactarius have been studied by several authors and are now known to occur in Asia, Africa, and central and South America (Singer 1975; Singer et al. 1983; Montoya et al. 1996). There are more than 250 species distributed in both temperate and tropical regions of the world. Several species of Lactarius are edible, known for their delicacy, and are popular all over the world. Lactarius spp. are known as milk cap fungi because they produce a milky or juicy fluid or latex when broken. However, some older fruiting bodies or a few species that grow in dry or very wet weather may lack latex. Some species may have variable colors of latex, whereas in other species the color of latex will change when exposed to air. The genus Lactarius has both edible and poisonous species. In general, the species which have a peppery taste and have white latex that turns yellow or purple when exposed to air are poisonous. However, the bright color of the juice is considered to be an indicator that the species is edible. For example, L. deliciosus, a much coveted mushroom in Europe, has orange latex that turns green in contact with air. A typical Lactarius sp. consists of a cap, gills, and a stalk or stem (Fig. 1). The gills of the mushroom bear spores. Species of Lactarius are known to occur under conifer and broadleaf trees and form mycorrhizal associations with a wide range of temperate and tropical trees. Most of the land plants form mycorrhizal associations with a specialized group of soil fungi. In this association, both partners (plant and fungus) benefit from one another, i.e. the fungus derives nutrients and carbohydrates from the host plant, and in turn, the fungus helps the plant to obtain nutrients and water more efficiently from the soil. These fungi are considered to be far-reaching extensions of the root system. The fungal mycelia explore and extract nutrients from a volume of soil far beyond the capabilities of the roots alone. Some nutrients (mainly phosphate) are translocated through the mycelia to the mycorrhizae, where they are released to the roots for host utilization. Several different types of mycorrhizae are known, but ectomycorrhizae (colonize outDepartment of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada Canadian Forest Service, Northern Forestry Centre, 5320-122 Street, Edmonton, Alberta T6H 3S5 Canada 1
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Biotechnology in Agriculture and Forestry, Vol. 43 Medicinal and Aromatic Plants XI (ed. by Y.P.S. Bajaj) ©Springer-Verlag Berlin Heidelberg 1999
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L.S. Trifonov and P. Chakravarty
Fig. 1. Fruiting bodies of Lactarius deliciosus. (Courtesy of Dr. L.J. Hutchison)
side the roots) and endomycorrhizae (colonize inside the roots) are the most common. Several species of Lactarius form ectomycorrhizae with pines, spruces, firs, birches, alders, oaks, and several tropical tr
