Observation 279831: Boletus sect. Boletus

Caps up to 14.5 cm across surface, dry, areolate and pitted in age.
Pores white when young(see tiny fb in center), turning yellow and not apparently staining.
White flesh of cap and stipe turning light yellow when cut.
Light reticulation on stipe.
Spore print olive brown.
Spores ~ 9.0-11.2(12.0) X 4.9-6.0 microns, elongate-ovoid, with oil droplets.
So far no luck with misc. keys.

Species Lists


Phylogram supplied by I. G. Safonov

Proposed Names

29% (1)
Recognized by sight
44% (2)
Recognized by sight: Not a typical Boletus s.s., but close enough to justify a proposal
Based on chemical features: nrITS sequence almost identical to that of obs 295394 from Louisiana

Please login to propose your own names and vote on existing names.

= Observer’s choice
= Current consensus


Add Comment
Specimen accessioned to the University of Utah fungarium
By: Dan Molter (shroomydan)
2018-10-10 12:41:59 PDT (-0700)

This specimen has been accessioned to the UT fungarium with the following number:


Wow! Partial veil…?!
By: Dave W (Dave W)
2018-04-13 06:11:00 PDT (-0700)

The coating appears to represent the “stuffing” seen on the young pore surface of eduloid types (and, according to Sutara, species of Butyriboletus). I found a paper by Josef Sutara which offers explanations of the “stuffing” http://www.czechmycology.org/_cmo/CM66205.pdf . Sutara discusses two hypotheses. One assertion is that the stuffing is a layer of hyphae and as such may be viewed as a type of partial veil. The second assertion, for which Sutara offers support in the paper, is summarized within the following quote (from the paper), “Pores of tubes in youth densely covered with a great number of conspicuously developed cheilocystidia which, in this stage, form a continuous layer on the lower surface of the hymenophore." Within the paper, Sutara suggests that microscopic characters of the eduloid “stuffing” correlate with certain molecular data. In light of this, the white material seen on the pore surface of the small mushroom may hold a key ID ingredient.

Perhaps the white material seen on the hymenium of the small mushroom may be the result colonization by a Hypomyces, or some sort of mold? I don’t think it’s this. But I do think it’s good to get any potential explanation onto the table.

If not for the small non-fusoid spores, I’d suggest these may represent what had previously been called the NA Boletus pinophilus (currently B. pseudopinophilus in the newer Bessette book).

If this critter turns out…
By: I. G. Safonov (IGSafonov)
2018-04-12 16:45:40 PDT (-0700)

…to be a porcini after all, it’s certainly the most remarkable pileate-stipititate representative of global Boletus s.s.

Yes…if you enlarge the small FB
By: Ron Pastorino (Ronpast)
2018-04-12 16:11:40 PDT (-0700)

in the 4th photo, one can see the partial veil and white pores. The spores on these are a little wider and a little more symmetrical than shown in Snell & Dick’s drawings.

Okay, I see…
By: Dave W (Dave W)
2018-04-12 15:53:30 PDT (-0700)

the report of “white pores” in the notes. So, likely no relationship between this and alutaceus.

By: I. G. Safonov (IGSafonov)
2018-04-12 14:44:39 PDT (-0700)

…which Snell & Dick originally put into Xerocomus, doesn’t have white pores and partial veil when young and its reported distribution range is limited by and large to the northeast.

Yes Dave, there does seem to be several similarities
By: Ron Pastorino (Ronpast)
2018-04-12 13:37:48 PDT (-0700)

with B. alutaceus. Is there any sequence data for that species in GenBank?

Spore morphology.
By: Dave W (Dave W)
2018-04-11 20:38:00 PDT (-0700)

Spore shape is not subfusoid. Q = L/W ~ 2, with 9 < L <11.2. These features seem unusual for sect. Boletus (small L; small Q). Looking through Boletes of E NA, the only species that resembles this and has similar spore morphology is Boletus alutaceus.

By: I. G. Safonov (IGSafonov)
2018-01-20 21:18:39 PST (-0800)

Thanks for posting the phylogram.

Thanks again Igor.
By: Ron Pastorino (Ronpast)
2018-01-20 21:17:30 PST (-0800)

I added a photo of your tree.
And I will contact Dr Dentinger.

DNA sequencing results and discussion
By: I. G. Safonov (IGSafonov)
2018-01-20 20:45:15 PST (-0800)

> A clean and contiguous TEF-1-alpha sequence of 943 bps was procured from this collection. There are no ambiguous characters. Dr. Kudzma was experimenting with different primers and was able to obtain a much longer fragment of the gene. It still includes most of the typically sequenced region between EF1-983F and EF1-1567R primers (this portion is 591 bps long) and continues beyond tef1R primer.
> A BLASTn search of the entire sequence gave an unusual hit list in that the top hit had only ~92% similarity and the hit pattern didn’t really show much clustering around any particular genus. The top hit is Boletus albobrunnescens. Though formally published only in 2014,1 B. albobrunnescens had made its first appearance as the sole representative of “Obtextiporus” – one of the 4 known lineages of Boletus sect. Boletus at the time, a.k.a. porcini sensu lato – in Dentinger et al. (2010).2
> Given lack of useful information provided in the BLASTn search hit list, a tree was generated in GB using the first 22 hits (92—>90 % similarity) after sorting the list by % identity. It shows MO279831 to be most closely related to B. albobrunnescens and both being part of the porcini clade. Both taxa share the next outer node with the core B. edulis group, aka porcini sensu stricto.

Boletus albobrunnescens: https://www.nybg.org/...

1 “New Porcini (Boletus sect. Boletus) from Australia and Thailand”: Mycologia 2014, 106(4), 2014, pp. 830–834
2 “Molecular phylogenetics of porcini mushrooms (Boletus section Boletus)”: Mol. Phylogenet. Evol. 2010, 57 , pp.1276-1292. This article can be requested from https://www.researchgate.net/....

By: I. G. Safonov (IGSafonov)
2018-01-20 20:33:20 PST (-0800)

No, no close matches, but I am still working on my brief commentary (to be posted soon).
This is a very, very interesting critter. I would vote it the USA bolete of the year (2017).
I am jumping the gun here a bit, but based on a GB-derived phylogram, which I cannot post here because I don’t have control of your obsie, it clades with the porcinis.
If I were you, I would contact Dr. Dentinger — http://mushroomobserver.org/observer/show_user/2980. I think he created a porcini project on MO, and is soliciting collections.

Thanks for posting the sequencing results Igor.
By: Ron Pastorino (Ronpast)
2018-01-20 19:56:41 PST (-0800)

So, no close matches?

By: I. G. Safonov (IGSafonov)
2017-06-24 19:04:25 PDT (-0700)

No one can come to your rescue this time. :-)
Very interesting collection. White pores with a PV (archytypal of the porcinis but known to occur in other boletes, e.g. B. auripes; not necessarily a plesiomorphic trait) maturing to greenish yellow, and reticulated stipes suggest Boletus s.s., but at the same type these don’t look like the porcini s.s. (edulis type) or the Alloboletus branch (separans & nobilis). The yellow upper stipe is quite striking. Still, I think it’s worthwhile to propose Boletus sect. Boletus.

Created: 2017-06-24 18:29:20 PDT (-0700)
Last modified: 2019-11-01 13:18:09 PDT (-0700)
Viewed: 429 times, last viewed: 2019-11-15 17:54:29 PST (-0800)
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