cap is conicalor ovate
|stipe is bare|
spore print is creamto yellow
ecology is mycorrhizalor saprotrophic
Morchella rufobrunnea, commonly known as the blushing morel, is a species of ascomycete fungus in the family Morchellaceae. Originally found in Mexico, it was described as new to science in 1998 by mycologists Gastón Guzmán and Fidel Tapia. Its range was extended a decade later when a study determined that it was common in the West Coast of the United States, and in 2009, when it was reported growing in Israel. A saprophytic species, M. rufobrunnea grows in disturbed soil or in woodchips used in landscaping. Young fruit bodies have abruptly conical caps covered with pale ridges and dark pits. 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 in the color and form of the fruit body, the length of the pits on the surface, and the staining reaction. A choice edible species, a process to cultivate M. rufobrunnea was described and patented in the 1980s.
The first specimens of Morchella rufobrunnea were collected from the Ecological Institute of Xalapa and other regions in Xalapa, 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 later study by Michael Kuo, he 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. North American morels formerly classified as deliciosa have since been divided into two distinct species, Morchella diminutiva and M. virginiana.
Molecular analysis suggests that the genus Morchella can be divided into three lineages; M. rufobrunnea is in a monotypic lineage basal to the Esculenta clade ("yellow morels"), and the Elata Clade ("Black morels"). M. anatolica, described as new to science from Turkey in 2012, is closely related sister species.
The specific epithet rufobrunnea derives from the Latin roots ruf- (rufuous, reddish) and brunne- (brown). Common names given to the fungus include the "western white morel" and the "blushing morel".
Fruit bodies of M. rufobrunnea are from 6.0–21.0 cm (2.4–8.3 in) tall, although most are typically found in the narrower range, 9.0–15.5 cm (3.5–6.1 in). The conical to roughly cylindrical to egg-shaped 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 ribs and crosswise veins that form short or elongated hollows; in maturity, as the surface becomes more wrinkled, these hollows are less prominent. Young fruit bodies have a grayish surface color with ribs that are colored white to grayish, while mature specimens are yellowish to brownish. The cylindrical stipe measures 30–70 cm (12–28 in) by 1–2.5 cm (0.4–1.0 in) thick. White to cream to gray in color (yellowish to dark gray when mature), it is covered with tiny dark granules near the top and is irregularly wrinkled near the base. Mycelium at the base of the stipe is thin and compact, and colored white to pale yellow, sometimes with brownish-orange stains. The stipe and hymenophore bruise brown to brownish orange to pinkish when touched, or sometimes when maturing; older specimens may become completely reddish brown. M. rubobrunnea is a choice edible mushroom, and, according to one source, "one of the tastiest members of the morel family." Individual specimens over 1 pound (0.45 kg) have been reported.
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 (translucent), have a septum at the base, and comprise either one or two cells. The flesh is made of thin-walled, hyaline hyphae measuring 3–9 µm wide.
Field characteristics that distinguish Morchella rufobrunnea from other Morchella species include the preference for disturbed ground, its distinctive colors, and its bruising reaction. For example, M. guatemalensis has a color ranging from yellow to yellowish-orange, but never grey, and it has a more distinct reddish-vinaceous bruising reaction. Microscopically, it has smaller paraphyses, measuring 56–103 by 6.5–13 µm. The New Guinean species M. rigidoides has smaller fruit bodies that are pale ochre to yellow, without any grey. Its pits are less elongated than those of M. rufobrunnea, and it has wider paraphyses, up to 30 µm. M. esculentoides, widely distributed in North America, has a fruit body with a coloration similar to mature M. rufobrunnea, but it lacks the bruising reaction.
Habitat and distribution
Morchella rufobrunnea is a saprophytic species. Fruit bodies grow singly or in clusters in disturbed soil or woodchips used in landscaping. Large numbers can appear the year after wood mulch has been spread on the ground. Fruiting usually occurs in the spring, although fruit bodies can be found in these habitats most of the year. Other preferred habitats include steep slopes and plateaus, and old-growth conifer forests.
Morchella rufobrunnea ranges from Mexico through California and Oregon, USA. It has also been introduced to central Michigan from California. It is one of seven Morchella species that have been recorded in Mexico. In 2009, Israeli researchers used the internal transcribed spacer region of nuclear ribosomal DNA to confirm the identity of the species in northern Israel, where it was found growing in gravelly disturbed soil near a newly paved path at the edge of a grove. This was the first documented appearance of the fungus outside of North America. Unlike the North American version that fruits for only a few weeks in the spring, the Israeli populations have a long-season ecotype, fruiting from early November to late May (winter and spring). This period corresponds to the rainy season in Israel (October to May) and a period of low to moderate temperatures, ranging from 15–28 °C (59–82 °F) during the day and 5–15 °C (41–59 °F) at night.
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.
There are four stages of primordial development. In the first, disk-shaped knots measuring 0.5–1.5 mm 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. Finally, when the stipe is 2–3 mm long, pre-apothecia emerge in the apical end, and the ridges and pits have distinct paraphyses. Extracellular mucilage covers the ridge layer and helps give the tissue its shape and rigidity.
The fruit bodies have been cultivated under controlled conditions in laboratory-scale experiments. Mushroom primordia 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. There were five distinct developmental stages: sclerotium formation, sclerotium germination, asexual spore formation, formation of initial knots, and fruit body development.
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