[Darren Abbey]

green-fleshded (gf), yellow-flesh (r), and fasciated (fas) are all recessive.

P1 (gf/gf; r/r; fas/fas) x P2 (Gf/Gf; R/R; Fas/Fas) => F1 (Gf/gf; R/r; Fas/fas)

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Examining the the F2s... F1 x F1 => 25% gf/gf; 25% R/R; 25% fas/fas

You'd need to grow at least 64 to expect to find the combination you're looking for.

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Backcrossing to either parent...

BC1:: F1 (Gf/gf; R/r; Fas/fas) x gf/gf; r/r; fas/fas [beefsteak] => [50% Gf/gf, 50% gf/gf]; [50% R/r, 50% r/r]; [50% Fas/fas, 50% fas/fas]

BC2:: F1 (Gf/gf; R/r; Fas/fas) x Gf/Gf; R/R; Fas/Fas [pimpinellifolium] => [50% Gf/Gf, 50% Gf/gf]; [50% R/R, 50% R/r]; [50% Fas/Fas, 50% Fas/fas]

Will fail to get you the combination you're looking for.

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But, backcross one (BC1) will get you closer. 1/8 of the first backcross will be brown (green-flesh with red) and have large fruit. ([50% gf/gf]; [50% R/r]; [50% fas/fas])

Self such a plant and 3/4 of the next generation will be brown (green-flesh with red) and have large fruit. A third of these will have the combination of alleles (gf/gf; R/R; fas/fas) you're looking for.

I suspect there may be another recessive trait resulting in the large fruit compared to the pimpinellifolium parent, so it may be a bit more complicated. (1/16 of the backcross would have the intermediate state).