Observation 288997: Baorangia bicolor group

A single mature fruitbody growing in leaf litter in sandy soil in a grove of young white oaks. The collection site is just yards away from where B. bicolor of obs 73634 & obs 208545 and ‘Xerocomus’ sclerotiorum of obs 288112 have been found.

> The cap is plano-convex, 7.8 cm wide and 2 cm thick in the middle, pale yellow-cream in the disk and pale rose-pink elsewhere; surface bald and leathery in the disk and scruffy-granulose elsewhere (texture visualized well with a lens); the cap margin is devoid of a sterile flap; the cap flesh is light yellow, moist and mashmallowy, staining blue slightly and erratically/spotty at the junction with the stipe and occasionally above the tubes.
> The pores are yellow, large, angular and compound, i.e., honeycombed when looking into the tubes, bluing when injured. The tubes are 8 mm deep in the thickest section, concolorous with the pore surface and bluing upon injury.
> The shallowly S-shaped stipe is 10.5 cm long, flaring to 2 cm at the junction with the cap and of uniform width of 1.1 cm below the apex down to the base, lemon yellow at the apex and pale to medium reddish-orange below to about mid-point and burgundy-red in the bottom half; surface scruffy-punctate, especially in the bottom half, bluing when handled; basal mycelium white; the flesh is yellow, darker/richer that in the cap, with burdundy-red areas mostly in the bottom half and almost red in the base, staining blue erratically at the cap juncture and below, closer to the edge than cortex.
> Odor pleasant and fungal; taste is mild.
> Spore print is olive (brownish-green).
> Macrochemical Tests: KOH = amber brown in cap (pink area), medium muddy orange on cap flesh; NH4OH = pale dingy yellow on cap (pink area), grayish-blue (slate) on cap flesh.
> Spore measurements: [20/1/1], mounted in Melzer’s;
L x W = (8.4-)8.6~11.6 x (3.3-)3.5~4.0 μm; L x W = 10.0 × 3.7 μm;
Q = (2.18-)2.24~3.2; Q = 2.67; pale green and lacking oil droplets, fusiform in face-view (dorsal/ventral) and subtly inequilateral/subfusiform in side-view (dorsiventral) with a barely noticeable/practically nonexistent suprahilar plage.
Discussion: While not a dead ringer for the B. bicolor group gestalt, this mature mushroom has several morphological elements that hint at bicolor: the overall color scheme, the unstable cap pigment toward maturity, the yellow marshmallowy flesh, the spotty and erratic staining of the yellow flesh, and the spore size & shape. The fact that true bicolor has been observed growing in the immediate vicinity (obs 208545) also lends supporting evidence to bicolor connection. This collection has been marked for sequencing (nrLSU).

DNA Sequencing Results & Discussion (posted 18-May-2018):
> A clean and contiguous nrLSU sequence of 914 bps was obtained from this collection. The sequence starts from the middle of the ITS4 primer and ends on the last character preceding the LR5 primer. There are 6 ambiguous characters, all are a “Y” (C/T).
> A BLASTn of this sequence indeed shows this collection to clade in Baorangia bicolor group of North America. The top hits are:
KF030246: Boletus bicolor var. bicolor voucher MB07-001 = 867/873 = 99.3% similar (the 6 mismatching bases are the ambiguities in MO288997)
KF030247: Boletus bicolor var. subreticulatus voucher 3818 = 863/870 = 99.2% similar (6 of 7 mismatching bases are the ambiguities in MO288997)
KF030249: Boletus subluridellus voucher 3737 = 871/880 = 99.0% similar (6 of 9 mismatching bases are the ambiguities in MO288997)
KF030248: Boletus rufomaculatus voucher 4414 = 869/880 = 98.8% similarity (6 of 11 mismatching bases are the ambiguities in MO288997)
KF030990: Boletus cf. bicolor 3921 = 855/869 = 98.4% similar (6 of 14 mismatching bases are the ambiguities in MO288997)
As a side note, I doubt that Dr. E. E. Both, the collector and identifier of voucher 3737, mistook B. bicolor for B. subluridellus – the latter being a distinct taxon in Neoboletus with red pores and a pale yellow stipe devoid of any red tones; in all likelihood, this is a “clerical” error made during the sample processing or tabulation of sequencing data for the Nuhn et al. (2013) paper.
The genetic data in conjunction with the aforementioned macro- and micro-morphological particulars of this collection firmly place it in the Baorangia bicolor group. Still overall it’s a morphological outlier that originally fooled me into thinking that it could be something else. Subjecting this collection to sequencing was very beneficial, all things considered.
It has been hypothesized in the Boletes of Eastern North America that B. bicolor could be a species complex. Even if this is true, nrLSU is hardly the locus to solve the puzzle. It remains to be seen if the “bicolor group” will stand up to a rigorous molecular scrutiny.

Species Lists


Angular, compound pores
Photographed immediately following dissection
Bluing 4-5 min post dissection
Right half: NH4OH = pale grayish-blue; KOH = orange
Mounted in Melzer’s and viewed at x1000
Mounted in Melzer’s and viewed at x1000

Proposed Names

29% (1)
Recognized by sight: Might be in the bicolor group (see discussion below)
72% (2)
Recognized by sight: Some macro- & micro-morphological traits
Based on chemical features: nrLSU sequence & BLASTn results

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= Observer’s choice
= Current consensus


Add Comment
Thanks, Scott
By: I. G. Safonov (IGSafonov)
2018-05-27 11:23:33 AKDT (-0800)

Current wisdom says for both bar-coding and preliminary intergeneric phylogenies a protein-coding gene (TEF-1, RPB1/2) is more desirable that ITS, but a combo of TEF-1 with ITS has been used for the latter purpose before (e.g. Retiboletus). ITS is a pain in the neck to work with for a couple of reasons, as far as I know, but, given its historical status, it’s here to stay. I heard that RPB’s possess a superior resolution to that of TEF, but at this time GenBank has more TEF-1 sequences for boletes. REH likes ATP6, but for some reason that locus never took off for boletes.

Nice work. Thank you.
By: Scott Pavelle (Scott Pavelle)
2018-05-27 10:47:08 AKDT (-0800)

I’ve voted the result up based on the DNA analysis. Might as well have this show up early if anyone does a search.

What loci do you think would work better?

Created: 2017-09-02 12:21:14 AKDT (-0800)
Last modified: 2018-07-13 18:36:32 AKDT (-0800)
Viewed: 167 times, last viewed: 2019-07-09 23:52:07 AKDT (-0800)
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