Mushroom lineage explained: what a cross is, how isolates descend from it, and how to read the lineage explorer

01What a cross actually is

A mushroom, like most fungi, reproduces sexually. Its spores carry half a genome each; two compatible spores meet, their mycelia fuse, and the resulting organism carries genetic material from both. A breeder makes a cross by bringing material from two chosen lines together so that the offspring carry both. The most controlled version uses monokaryotised cultures, single-nucleus lines that can only pair one way, which is the technique behind What The Fungi's Frosty Pearlz 393. The result is a new line with two named parents, and the card writes it as Parent A x Parent B.

02From cross to isolate

A fresh cross is a population, not a single thing: the offspring vary. A breeder selects the expression they want (colour, form, spore output) and works that one expression until it comes true generation after generation. That stabilised selection is an isolate, and it gets its own name. DreadMaw is an isolate from Gamma Decay; Blue Vootwo is an isolate from Blue Voodoo. The isolate guide explains what that means on the slide.

03Generations and f numbers

Each round of taking spores from the line and starting again is a generation, counted from the original cross: f1, f2 and so on. A higher f number means more generations of selection, which usually means a more settled line. "El Toque f2 (El Choco x Toque f8)" is a second-generation cross whose Toque parent had already been through eight.

04Crosses across species

Some of the most interesting branches in the tree cross species boundaries. Natal Moon pairs an Ochra (previously natalensis) parent with a cubensis one, and its descendants Blue Voodoo, Golden Satellite and Brass Barnicles inherit that. Under the microscope the two species' spores are close, so the hybrids are a study in their own right: print colour and size range sit somewhere between the parents.

05Reading the explorer

1. Open the lineage explorer. Every strain in the library is a node; every link between two nodes is a documented parent-child relationship.
2. Pick a strain from the list, or search for it by name, and its parents appear above it and its descendants below.
3. Follow a family: Blue Ravioli down to Blue Voodoo and Gamma Decay, then to Blue Vootwo and DreadMaw.
4. Use it to build a collection by lineage. A parent and child on adjacent slides is a controlled comparison.

Where a line's parentage is undocumented (Golden Teacher, Blue Ravioli, most old classics) it appears as a root: the tree begins with it. That is honest. The explorer draws what is known and leaves out what is not.