Morchella rufobrunnea

Morchella rufobrunnea, commonly known as the blushing morel, is a species of ascomycete fungus in the family Morchellaceae. A choice edible species, the fungus was originally described as new to science in 1998 by mycologists Gastón Guzmán and Fidel Tapia from collections made in Veracruz, Mexico. Its distribution was later revealed to be far more widespread after several DNA studies suggested that it is common in the West Coast of the United States, Israel, Australia, and Cyprus. M. rufobrunnea grows in disturbed soil or in woodchips used in landscaping, suggesting a saprophytic mode of nutrition. 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, grayish caps covered with pale ridges and dark 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, a characteristic for which the fungus is named, the New Latin rufobrunnea signifying 'rufus brown'. Mature fruit bodies grow to a height of 9.0–15.5 cm (3.5–6.1 in). M. 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. A process to cultivate morels now known to be M. rufobrunnea was described and patented in the 1980s. 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 are 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. sceptriformis (=M. virginiana). Molecular analysis of nucleic acid sequences from the internal transcribed spacer and elongation factor EF-1α regions suggests that the genus Morchella can be divided into three lineages. M. rufobrunnea belongs to a lineage that is basal to the esculenta clade ('yellow morels'), and the elata clade ('black morels'). This phylogenetic placement implies that it has existed in its current form since the Cretaceous era (roughly 145 to 66 million years ago), and all known morel species evolved from a similar ancestor. M. rufobrunnea is genetically closer to the yellow morels than the black morels. M. anatolica, described from Turkey in 2012, is a closely related sister species. The specific epithet rufobrunnea derives from the Latin roots ruf- (rufuous, reddish) and brunne- (brown). Vernacular names used for the fungus include 'western white morel', 'blushing morel', and—accounting for the existence of subtropical species in the 'blushing clade'—'red-brown blushing morel'. Fruit bodies of M. rufobrunnea can reach 6.0–21.0 cm (2.4–8.3 in) tall, although most are typically found in a narrower range, 9.0–15.5 cm (3.5–6.1 in). The conical to roughly cylindrical hymenophore (cap) is typically 6.0–8.5 cm (2.4–3.3 in) high by 3.0–4.5 cm (1.2–1.8 in) wide. Its surface is covered with longitudinal anastomosed ridges and crosswise veins that form broad, angular, elongated pits. Young fruit bodies are typically dark grey with sharply contrasting beige or buff ridges, while mature specimens fade to ochraceous-buff. The cylindrical stipe is often strongly wrinkled, enlarged at the base and measures 30–70 cm (12–28 in) by 1–2.5 cm (0.4–1.0 in) thick. It is typically covered with a dark brown to greyish pruinescence, often fading at maturity, a useful character to discriminate it from similar species, such as M. tridentina or M. sceptriformis. The stipe and hymenophore often exhibit ochraceous, orange or reddish stains, although this feature is neither constant nor exclusive to M. rufobrunnea and can be seen in a number of Morchella species, such as Morchella tridentina (=Morchella frustrata), M. esculenta, M. guatemalensis, the recently described M. fluvialis (Clowez et al. 2014), and most likely M. anatolica. In deposit, the spores are pale orange to yellowish orange. Ascospores are egg-shaped, measuring 20–24 by 14–16 µm when mature, but smaller (14.5–19 by 9–10 µm) in immature fruit bodies. They are thin-walled, hyaline (translucent), and inamyloid. The cylindrical asci (spore-bearing cells) are 300–360 by 16–20 µm with walls up to 1.5 µm thick. Paraphyses measure 90–184 by 10–18.5 µm (6–9 µm thick if immature); they are hyaline, have 1–2 (–3) septa in the lower half and slightly enlarged, subcapitate tips. The flesh is made of thin-walled, hyaline hyphae measuring 3–9 µm wide. The stipe is a textura globosa, with scattered or locally fasciculate, polymorphic terminal elements measuring 15–70 × 12–16 μm. Morchella rubobrunnea is an edible fungus; it has been described variously as 'one of the tastiest members of the morel family', and alternately as 'bland in comparison to other morel species'. Individual specimens over 1 pound (0.45 kg) have been reported.