(1) All seed potatoes entered for certification are classified on the basis of production phases as follows:

(a) Prenuclear (PN) - Micropropagated potatoes or seed potatoes grown in a greenhouse or screenhouse under sanitary conditions free of insects, weeds that can harbor potato diseases or other sources of disease contamination.

(b) Nuclear (N) - First field production year.

(c) Generation 1 (G1) - Second field production year.

(d) Generation 2 (G2) - Third field production year.

(e) Generation 3 (G3) - Fourth field production year.

(f) Generation 4 (G4) - Fifth field production year.

(g) Generation 5 (G5) - Sixth field production year.

(2) If a seed lot fails to meet the standards established in this chapter for its class, then it will be reclassified to the earliest generation for which it meets established standards.