What You Should Know
Morchella rufobrunnea is a species of ascomycete fungus in the family Morchellaceae. A choice edible species. It grows in disturbed soil or woodchips used in landscaping as a saprotroph. Reports from the Mediterranean under olive trees (Olea europaea), however, suggest the fungus may also be able to form facultative tree associations.
Young fruit bodies have conical caps with pale ridges and dark grayish pits; mature specimens are yellowish to ochraceous-buff.
The surface of the fruit body often bruises brownish orange to pinkish where it has been touched or injured. Mature fruit bodies can grow to a height of 9.0–15.5 cm (3.5–6.1 in).
Morchella rufobrunnea differs from other Morchella species by its urban or suburban habitat preferences, in the color and form of the fruit body, the lack of a sinus at the attachment of the cap with the stipe, the length of the pits on the surface, and the bruising reaction.
Other names: Blushing Morel, California Landscaping Morel, Western White Morel.
Morchella rufobrunnea Mushroom Identification
Saprobic when growing in tree-less environments, but perhaps potentially mycorrhizal in other locations; limited to the disturbed ground in North America; originally recorded from the Gulf Coast of Mexico on a road bed; found with frequency in winter and early spring in coastal California and Oregon landscaping sites, usually in the year following the disturbance to the ground.
6-12 cm tall and 2-5 cm wide; conical or nearly so, especially in youth, but occasionally egg-shaped or nearly round; pitted and ridged, with the pits primarily arranged vertically, at least when young; when young with bluntly rounded to flattened, nearly white ridges and dark brown to black pits; when mature with sharpened or eroded, yellowish to brownish yellow pits and ridges; bruising salmon to orangish or reddish-brown; completely attached to the stem; hollow.
2-9 cm high and 1-2.5 cm wide; more or less equal, but sometimes swollen at the base; whitish to grayish, yellowish, or brownish; bruising orangish to rusty or reddish-brown; bald or finely mealy with granules; hollow.
Pale orange or yellowish-orange.
Spores 19-25.5 x 12-17 µ; smooth; elliptical; without oil droplets; contents homogeneous. Asci 8-spored. Paraphyses cylindric with rounded to subclavate or subcapitate apices; septate; hyaline in KOH. Elements on sterile ridges 75-125 x 7-15 µ; septate; hyaline to brownish in KOH; terminal cell clavate, widely fusoid, or more or less cylindric with a rounded to subacute apex.
Morchella rufobrunnea Look-Alikes
Is similar in appearance, but produces smaller and slender fruit bodies with very few or no transverse interconnecting ridges.
Rufescent and very similar to M. rufobrunnea. It is found in mountainous forests and maquis and forms a marked sinus at the attachment of the cap with the stem, which is pure white. At maturity, it develops more or less parallel, ladderlike interconnecting ridges.
Is widely distributed in North America, north of Mexico, and has similar colors to mature fruit bodies of M. rufobrunnea, but lacks the bruising reaction.
Found in hardwood forests of eastern North America, has a smaller fruit body than M. rufobrunnea, up to 9.4 cm (3.7 in) tall and up to 2.7 cm (1.1 in) wide at its widest point.
Found in riparian and upland ecosystems from Virginia to northern Mississippi, usually in association with the American tulip tree (Liriodendron tulipifera).
Has a more oval-shaped cap.
Morchella rufobrunnea Taxonomy and Etymology
The first scientifically described specimens of Morchella rufobrunnea were collected in June 1996 from the Ecological Institute of Xalapa and other regions in the southern Mexican municipality of Xalapa, Veracruz, which is characterized by a subtropical climate. The type locality is a mesophytic forest containing oak, sweetgum, Clethra and alder at an altitude of 1,350 m (4,430 ft). In a 2008 study, Michael Kuo determined that the "winter fruiting yellow morel"—erroneously referred to as Morchella deliciosa—found in landscaping sites in the western United States was the same species as M. rufobrunnea. According to Kuo, David Arora depicts this species in his popular 1986 work Mushrooms Demystified, describing it as a "coastal Californian form of Morchella deliciosa growing in gardens and other suburban habitats". Kuo suggests that M. rufobrunnea is the correct name for the M. deliciosa used by western American authors. Other North American morels formerly classified as deliciosa have since been recategorized into two distinct species, Morchella diminutiva and M. virginiana (=M. sceptriformis).
Molecular analysis of nucleic acid sequences from the internal transcribed spacer (ITS), the elongation factor EF-1α, and the RNA polymerase II (rpb1, rpb2) regions, suggests that the genus Morchella is naturally divided into three lineages. Morchella rufobrunnea and its sister-species M. anatolica, both belong to an early diverging lineage that is basal to the /Esculenta clade ("yellow morels") and the /Elata clade ("black morels"). Ancestral area reconstruction tests indicate that the genus has existed in its current form since the late Jurassic (roughly 154 million years ago), when it is estimated to have evolved from a common ancestor. Although the genus was originally assumed to have emerged in western North America, updated ancestral reconstructions inferred from an enlarged 79-taxon database, suggest that the /Rufobrunnea lineage, and thus genus Morchella, originated in the Mediterranean region.
The specific epithet rufobrunnea derives from the Latin roots ruf- (rufuous, reddish) and brunne- (brown).
Morchella rufobrunnea Cultivation
Morchella rufobrunnea is the morel that is cultivated commercially per US patents 4594809 and 4757640. This process was developed in 1982 by Ronald Ower with what he thought was Morchella esculenta; M. rufobrunnea had not yet been described. The cultivation protocol consists of preparing a spawn culture that is mixed with nutrient-poor soil. This mixture is laid on nutrient-rich soil and kept sufficiently moist until fruiting. In the nutrient-poor substrate, the fungus forms sclerotia—hardened masses of mycelia that serve as food reserves. Under appropriate environmental conditions, these sclerotia grow into morels.
The fruit bodies of Morchella rufobrunnea have been cultivated under controlled conditions in laboratory-scale experiments. Primordia, which are tiny nodules from which fruitbodies develop, appeared two to four weeks after the first watering of pre-grown sclerotia incubated at a temperature of 16 to 22 °C (61 to 72 °F) and 90% humidity. Mature fruit bodies grew to 7 to 15 cm (3 to 6 in) long.
The early stages of fruit body development can be divided into four discrete stages. In the first, disk-shaped knots measuring 0.5–1.5 mm (0.02–0.06 in) appear on the surface of the substrate. As the knot expands in size, a primordial stipe emerges from its center. The stipe lengthens, orients upward, and two types of hyphal elements develop long, straight and smooth basal hairy hyphae and short stipe hyphae, some of which are inflated and project out of a cohesive layer of tightly packed hyphal elements. In the final stage, which occurs when the stipe is 2–3 mm (0.08–0.12 in) long, immature caps appear that have ridges and pits with distinct filament-like paraphyses. Extracellular mucilage that covers the ridge layer imparts shape and rigidity to the tissue and probably protects it against dehydration.
Photo 1 - Author: Nina House (Creative Commons Attribution 4.0 International)
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