1. (1) The following requirements apply specifically to tissue culture plant materials grown by organogenesis for scion and for rootstock:

   1. (a) Plants (explants) used to produce callus for tissue culture must be tested or indexed annually.
   2. (b) Plantlets (rooted shoots) regenerated from the tissue culture callus must be grown in a greenhouse or growth chamber and all measures and precautions must be taken to prevent the presence of any vectors in the greenhouse or growth chamber.
   3. (c) One regeneration of plantlets from the tissue culture callus will be certified under this program as G4 level material with no further testing or indexing provided all other requirements are met. This certification will last one year from the date of introduction of the plantlets into the greenhouse. Plantlets may be planted as G3 level registered plants provided all other requirements, including testing, are met for scion and for stool beds.
   4. (d) All other requirements for scion blocks and for stool beds must be met (see WAC 16-350-025 and 16-350-032).

2. (2) For tissue cultures originating through aseptic micropropagation, without callus formation, the following requirements apply:

   1. (a) With the exception of practices allowed in (b) of this subsection, registered G2 trees must be propagated directly from virus-tested G1 plants originating through the National Clean Plant Network-FT or other department-approved virus-tested sources.
   2. (b) Plants propagated from G1 material and maintained as G2 mother trees entirely under screenhouse conditions may serve as a source to establish a registered G2 tissue culture line. The source G2 mother trees shall be tested annually by the department.
   3. (c) All other requirements for scion blocks and stool beds must be met (see WAC 16-350-025 and 16-350-032).
3. (3) Upon approval from the department, plantlets produced from registered G2 tissue culture lines may retain G2 status if placed in new commercial growing media and maintained in an indoor insect proof facility. Routine testing by the department as outlined in this chapter shall apply.
4. (4) All other G2 plantlets shall become G3 when planted in growing media and must meet the requirements of this chapter.

[Statutory Authority: RCW 15.14.015. WSR 26-10-008, s 16-350-034, filed 4/27/26, effective 5/28/26.]