Notes last updated/edited on 15-Dec-18
This collection was found at the NJMA foray by Ms. Kyoko Okabe. I am leaning toward Caloboletus sp., but Butyriboletus peckii (the current name) is a conceivable possibility as per the information in North America Boletes(2000, as Boletus peckii) and Boletes of Eastern North America (2016), both by Bessette-Roody-Bessette.

Collection Description:
Pileus: 4.5-5.7 cm wide, 1.3-1.5 cm thick in the middle when measured from the surface to the juncture with the stipe, pulvinate/cushion-shaped, margin with a narrow band of sterile tissue; surface dry, slightly subtomentose to smooth and glabrous, not staining when rubbed, dull pinkish-red (near oac498 to oac518 to oac539 when fresh), fading somewhat over time post collection, but still retaining the original hue even after drying/preservation; context whitish to pale yellow, soft (with a marshmallow consistency/texture), readily bluing upon exposure to air; odor fungal but with a rancid note; taste bitter.
Pore Surface: buff-yellow to dull medium yellow, becoming grayish/dingy yellow (younger fb) to olivaceus-buff post collection (older fb), instantly bluing when bruised and then gradually resolving pale brown; pores circular and minute, 3-4 per mm; tubes 5-7 mm at the widest point (near the stipe), same color as the pores surface, bruising blue when cut
Stipe: 6.0-6.7 cm long (measured in sections), 1 cm thick at apex, 1.4-1.8 cm thick at the base, curved and enlarged downward, dry, solid, with a bright lemon yellow apex, dark rose-red to pinkish-red directly below to the middle and brownish (possibly due to handling) in the bottom section, distinctly reticulate from the apex down to the mid-length, at which point the reticulation becomes a network of shallow vertical ridges, quickly transition to a smooth surface toward the bottom section; the reticulation is yellow in the apex and red below, staining bluish and then brownish upon handling; the base section is covered with a whitish coating/bloom; mycelium is possibly white; context is whitish to pale yellow in the upper section (just like in the cap) and readily staining blue upon exposure to air, reddish to deep raspberry red below and dingy yellow in the base.
Spore print: a light coating of spores was directly deposited on a glass slide, but its color could not be visualized against a white background; however, the color appears to be olivaceus-brown when the slide is held up against natural light.
Spore measurements: [20/1/1], L x W = (9.1-) 9.3-11.2 x (3.3-) 3.5-4.0 μm in lateral (dorsi-ventral) view; L’ x W’ = 10.3 × 3.7 μm; Q = (2.60-) 2.67-2.94 (-3.00); Q’ = 2.82. Not amyloid, not dextrinoid, and light greenish-buff in Melzer’s; equilateral and generally oblong in face-view (dorsal/ventral) and somewhat to subtly inequilateral and approximately oblong in lateral-view, smooth and thin-walled, cylindrical based on the Q-ratio range.
Smith and Thiers (1971) list spore lengths reported by Peck as 0.00035-0.00040" (8.9-10.2 μm). After re-examining Peck’s type, they updated the spore measurements to 9-12 (-13) x 3.5-5 μm. Bessette’s NAB gives spore measurements as 10-14 × 3.5 -5 μm.
Macrochemical tests: KOH = dingy yellow/mustard yellow on pileipellis, erased bluing then pale orange on cap context; NH3 = dingy yellow/mustard yellow on pileipellis, erased bluing then pale yellow on cap context; FeSO4 = gray to bluish gray on pileipellis, erased bluing then bluish-gray on blotted cap context (difficult to interpret).
Habitat: The collector couldn’t remember the particulars of the habitat, but the boletes grew by the stream. I recall that area being surrounded by deciduous trees, including oak and beech.

DNA Sequencing Results (last updated on 20-Dec-18):
> A clean and contiguous nrLSU sequence of 1443 bps was obtained from this voucher. There is a single ambiguous character, a “Y”, corresponding to either “C” or “T”. A BLASTn search of the first 961 characters (to the LR5 primer) did not return any matching or very close hits. When the search results were sorted by % identity, there was no clear indication of this sequence clading in Caloboletus. However, a phylogram built in GenBank from representative well-identified accession associated with a number of genera of yelllow- or red-pored bluing boletes from this hit list gave a clear indication of the association with Caloboletus.
Since B. peckii was not on this hit list, I aligned the sole published nrLSU sequence of the alleged collection of peckii (accession JQ326999) with that of MO246697 separately. JQ32699 is only 649 nucleotides long, and it overlays with the 270—>918 bp fragment of my sequence. Even though there are no gaps, the two sequences are 23 bases off, corresponding to only 96.0% similarity. Obviously these two entities are not conspecific.
> A clean and contiguous 913 bp TEF-1-alpha sequence was also obtained from this voucher. There are 6 ambiguous characters: two “Y” (C/T) and four “R” (A/G). Four of these (2 x “R” & 2 x “Y”) are present in the 610 bps region circumscribed by the EF1-983F and EF1-1567R primers.
Other than the few ambiguities present here, this sequence is a perfect match to the corresponding regions in those of obs 286214 (my other NJ collection) and Robert G.‘s obs 283600 from CT, making these three collections conspecific. These three sequences finally published in GenBank on 10-Dec-18 (MH318614, MH337297, and MH347321).
The only previously published TEF-1 accession of the alleged collection of peckii (JQ327026) is 1117 bps long. Its alignment with MH318614 (this obsie) revealed that common overlap is only 621 bps long. There are a total of 58 mismatching positions, corresponding to the very low similarity of 91%.
A BLASTn search of a 610 bps sequence fragment (the region between & including the EF1-983F and EF1-1567R primers) produced a hit list from which a phylogram was built in GenBank to probe the phylogenetic relationships. It’s been annotated for clarity and uploaded to this post.

> Once a common taxon, nowadays Boletus peckii Frost in Peck is an infrequently encountered North American bolete.1 Interestingly, the aforementioned field guides by Bessette et al. draw a morphological parallel with Baorangia bicolor, the only significant difference between the two being the reticulation usually seen in peckii and its unpalatable taste.
> In 2014, B. peckii, along with a number of other bolete taxa from Boletus sect. Calopodes Fr. emend. Lannoy & Estadès, was transferred by A. Vizzini into Caloboletus Vizzini gen. nov.2 Morphologically, it differs from the typical members of Caloboletus (now delimited by a number published molecular studies) by the color of its cap; however, its inherently bitter taste is one of key defining traits of this genus.
> In 2015, Zhao et al. transferred C. peckii into Butyriboletus D. Arora & J.L. Frank based on the phylogenetic analysis of the aforementioned alleged peckii collection, known as “voucher 3959”.3 According to N. Siegel (see his comment below) and Reference #1, voucher 3959 – collected by R. Petersen in Tennessee in 1963 – could very well be a misidentified collection of Boletus speciosus or perhaps another member of North American Butyriboletus.
> In terms of gross morphology, MO246697 is a very good match to the original description of B. peckii.4 The bitter taste, the yellow pore surface bruising blue, the reticulated stipe, and the bluing of the flesh all point to Caloboletus as the likely generic placement for MO246697. Furthermore, the nrLSU and TEF-1 sequences of MO246697 do not match the corresponding molecular data of Petersen’s peckii voucher. The well-document record of MO246697 and the apparent absence of any pictures and/or a description of voucher 3959, further make the identity of Petersen’s collection of peckii questionable. Phylogenetically, MO246697 shows a strong affinity to Caloboletus. Analysis of the TEF-1 sequence in GenBank/BLASTn is attached to this post.
The two plausible conclusions drawn from this discussion are that MO246697 is Boletus peckii and that Vizzini was right in making peckii a member of Caloboletus based on the morphology alone.

Species Lists


Smaller fb
Larger fb
Dried specimens
Mounted in Melzer’s and viewed at x1000
Mounted in Melzer’s and viewed at x1000
Mounted in Melzer’s and viewed at x1000

Proposed Names

41% (3)
Recognized by sight: Gestalt morphology typical of the genus, bitter taste, color of stipe context similar to Caloboletus sp. in obs 217160
18% (4)
Used references: 1) North American Boletes by Bessette-Roody-Bessette
2) MO observations
29% (1)
Recognized by sight
86% (1)
Recognized by sight: See discussion in this obsie
Based on microscopic features: Spore size and shape
Based on chemical features: BLASTn of TEF-1-alpha sequence — see attached phylogram
29% (1)
Recognized by sight

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

= Observer’s choice
= Current consensus


Add Comment
Thanks, Don
By: I. G. Safonov (IGSafonov)
2017-01-02 18:09:25 PST (-0800)

Now we shall wait and see if the story is to be continued. :-) One thing I still need to be is to measure some spores.

Thorough write-up!
By: Ryan Patrick (donjonson420)
2017-01-02 17:49:35 PST (-0800)

Great information Igor.

Exsiccatae picture posted
By: I. G. Safonov (IGSafonov)
2016-08-08 13:22:00 PDT (-0700)

Scott, lack or presence of bug/fly larvae infestation in fruiting bodies could be either a totally random event, or there could exist a real connection between the chemistry/biochemistry of a fruiting body and its effect on insects (e.g., the Fly Agaric). For this bolete, it would be a notable feature only if it consistently comes bug free, but even then without the involvement of science it’s still a conjecture. Speaking of bugs, if memory serves, I’ve never seen the European C. cibarius even with a single larval tunnel. Here, in the USA, a bug free C. lateritius is a rare occurrence; there tunnels are there, alright, but I never saw a single larva inside the mushrooms. Go figure…

A photo of the dried specimen might be good
By: Scott Pavelle (Scott Pavelle)
2016-08-08 11:27:08 PDT (-0700)

I have noticed that some species show distinctive traits when dried, like the one I’ve been calling pseudosensibilis (dries to a dark brown) and the bulbous-bicolors (dries to a pure, clean-looking yellow). Certain other mushrooms gain a notable odor when dried (Rubr. rhodosanguineus).

Regardless, a photo with notes about the dried form would be a good thing to add into the database for anyone who may decide to check this observation in connection with a future test of the sample.

About the lack of bugs… I can’t help but think of that as a notable feature. Bugs are ubiquitous. The fact that one mushroom attracts them while another resists them has to be significant if a pattern can be established. Somehow, some way, the resistant species must be producing a chemical that makes it unattractive – and that requires a genetic difference, right?

In this particular case I wonder if the chemical in question isn’t the same thing that makes it taste bitter. Maybe it’s just sour grapes biasing my thinking, but it seems to me that I tend to find beautiful, bug-free specimens the bitter Tylopilus species a lot more often than I find bug-free specimens with better eating characteristics (bulbous-type bicolors excluded).

Thank you, Scott and Bill,
By: I. G. Safonov (IGSafonov)
2016-08-08 10:30:25 PDT (-0700)

for the compliment. I was very excited about this collection as I felt it was something one would see literally once in the blue moon. That’s why I sat down and wrote an actual description in the style of NAB, as if I was describing a new taxon. This took a long time, but in being diligent I thought perhaps part of this collection could officially go to NYBG… if they want it. Now I am thinking obs 71766 collected in this park five years ago could have been the same thing even though the colors in the stipe are different.
Scott, the pictures and documentation posted herein is all I have. The mushrooms have already been dried and tucked away in the fridge. The only way get additional details on the habitat is to have Kyoko show me the actual spot, and that’s probably not going to happen. I will post the spore measurements and pix later this week.
The fruiting bodies appeared to be roughly middle-aged and en plein forme (surprisingly not buggy at all!), but the hot and dry weather began to take a toll on them. That’s why I think the cap context was a bit spongy/mushy. The stipes were still firm, however. I am glad we got them in this condition though – the morphology is well developed and the overall shape is excellent for the age.
Bill, I did notice the reticulation being somewhat more prominent in the larger fb and a bit more subtle in the other one. The reticulation also appeared uneven in each fb in terms of extent/coverage and “quality”, i.e. one side of the stipe being more “striking” that the other. Perhaps this assessment is subjective as I peered at the mushrooms for too long. :-)

good documentation for this collection…
By: Bill (boletebill)
2016-08-08 08:20:20 PDT (-0700)

….and there’s so much to learn about this group. One of the lessons of this collection, for me, is that the photos of one specimen clearly illustrates reticulation, while the photos of the other specimen do not show the reticulation so DRAMATICALLY….that photo group is a good comparison of how any single character can vary.

A wonderful collection, Igor!
By: Scott Pavelle (Scott Pavelle)
2016-08-08 05:45:51 PDT (-0700)

Congrats on recognizing it so quickly as something special. I wouldn’t venture a guess on the ID, but will ask you to add more photos and observations.

Close ups (though these are quite good, actually), chemical tests, dried specimens, comments on the moisture level in the ground, companion fungi, or any odd features of the forest… If it really is this rare species, you never can know which details will turn out to be most helpful down the road.

On the texture, how old were the fb’s and did they have the same marshmallowy softness? I’m wondering how much was age versus natural state or bugginess.

By: I. G. Safonov (IGSafonov)
2016-08-07 19:57:41 PDT (-0700)

Yes, I am aware of the transfer of Boletus peckii into Caloboletus and then to Butyriboletus.
So, basically the identity of Petersen’s bolete may be in question. Z. L. Yang’s paper doesn’t indicate the source and age of the B. peckii voucher 3959 used in his research; however, it does list the accession numbers for the nrLSU and TEF1-alpha sequences for that material. Indeed, GenBank says voucher 3959 came from TN (
Hopefully, I will have this collection sequenced by the end of the year.

This appears to be peckii
By: Noah Siegel (Noah)
2016-08-07 18:48:56 PDT (-0700)

And I think it’s worth mentioning…
That it was said that peckii was a bitter bolete, (Peck referenced it as a Calopodes).

It was put into Butyriboletus by K. Zhao, Z.L. Yang & Halling, based on a genetic sequence from Ron Petersen’s 1963 collection from Tennessee, (which could have been speciosus…)

Vizzini made the combination into Caloboletus because of it’s reported bitter taste.