But Is It Good to Eat?

This is the Week of the Fungi on STC, a spo­radic un­der­tak­ing. It is our way to hail the start of the mush­room col­lect­ing sea­son, which in most tem­per­ate re­gions is in the fall.

by Elio

If you are into wild mush­room­ing, the ques­tion you'll be asked most of­ten by some­one hold­ing a spec­i­men is: Is it good to eat? I some­times an­swer with a dys­pep­tic: Be­fore I tell you, would you rec­og­nize it if you saw it again? But now I have a more friendly an­swer: Go ahead, cook the mush­room, then do real-time PCR. Japan­ese re­search­ers (from 7 dif­fer­ent labs) re­cently re­ported that this works very well, at least for telling four poi­so­nous species apart from 27 ed­i­ble ones. The PCR primers they used were de­signed for the rDNA ITS (In­ter­nal Tran­scribed Spacer) re­gions of the poi­so­nous species – a re­gion of­ten used in fun­gal and other work. The poi­so­nous mush­rooms gave a clear sig­nal, the ed­i­ble ones did not.

En­toloma rhodopolius from Japan. This spe­cies is also found in North Amer­ica and Eu­rope where it sel­dom causes poi­sonings. Source: Chiba Mu­seum

What kinds of spec­i­mens did they test? Some were col­lected spec­i­mens, oth­ers cul­ti­vated. But most im­por­tantly, they ap­plied the tech­nique to cooked mush­rooms. Cook­ing mush­rooms ren­ders them rather dif­fi­cult to iden­tify. I should know. When din­ing with friends in a restau­rant that serves a dish with "wild" mush­rooms, I'm of­ten asked: So, what is it I'm eat­ing? I can usu­ally guess the broad group to which the tasty morsel be­longs (bo­letes, chanterelles, morels, maybe shiita­kes), but that's about it. No way could I say with cer­tainty that the mush­room is ed­i­ble. Of course, I could re­sort to the old gag: You can eat any mush­room once! But the au­thors took this to heart and cooked up their mush­rooms be­fore an­a­lyz­ing them. The pa­per even pro­vides their recipes for bak­ing, deep fry­ing, stir-fry­ing, or cook­ing them tem­pura style.

The four species of poi­so­nous mush­rooms they in­cluded are re­spon­si­ble for 85% of the re­cently re­ported mush­room poi­son­ings in Japan. These are not among the more com­mon Amer­i­can or Eu­ro­pean cul­prits, but there is no rea­son to be­lieve that the tech­nique could not be adapted to our poi­so­nous species, as well.

Car­ry­ing a PCR ap­pa­ra­tus into the woods for iden­ti­fi­ca­tion pur­poses wouldn't be too handy, but with their tech­nique you don't have to. Bring the spec­i­mens home, cook them up how­ever suits you, then – please! – PCR them be­fore eat­ing.