GE system: Because of the lack of information available to define a real GE system, different GE systems are used, in which two levels of yield gene number (20 and 40), three levels of epistasis for yield genes (no epistasis, digenic epistasis, and trigenic epistasis), and two levels of pleiotropy (absent and present) will be considered for simulation, giving 12 GE systems.
However, the reverse is true in GE systems with trigenic epistasis but no pleiotropy (Table 7).
When the [F.sub.2] population of the same cross was inoculated with SMV-G7, a 63 (R+N):1 (S) trigenic
ratio was obtained (Table 2).
Estimation of the higher order interactions found in tetraploids, including duplex dominance, trigenic
and tetragenic effects, would require the determination of all five genotypic classes at each locus.
For the ensuing discussion, I have termed individuals with four different linkats as tetragenic; three linkats, trigenic; two linkats in equal proportions, dilinkat duplex; two linkats with one present in a single copy, dilinkat simplex; one linkat, nulliplex.
Thus, within each population, no trigenic or tetragenic individuals will be present, but the pure hybrid between them will include 1/4 tetragenic individuals.
Besides the associative effects of the trigenic
series controlling seed color, germination tests likely reflect genetic differences in embryo receptivity to endogenous inhibitors (McCrate et al., 1982).
The model assumed no epistasis and no more than two alleles per locus (i.e., no trigenic
or quadragenic effects).