Help me understand this breed chart

Im still al little confused at what is happening at F2/F3 and how/why is it separating into two groups and then mating again at F6 for a P1

wouldn't the mating of the two F5's just create more pheno's to be weeded out??

It looks like the breeder found traits he liked at the f2 level, one good male and 2 females, then crossed the f2 male with both f2 females. That makes an F3 A-line and an F3 B-line, one for each of the F2 females that the breeder used F2 male pollen on. It looks like they continued selecting for a desired trait/traits from within each successive generation after that, independent of each other; A selecting within the A line, B selecting within the B line. When the breeder let enough generations go that he was happy with the chances of a seed producing his desired traits, he figured he could re-cross them and get a good shot at getting everything he wanted at the P1 cross.

For example, imagine he wanted a bushy, potent, high yielding result. The F2 male is bushy, one F2 female is potent, and one F2 female is high yielding. He breeds the 2 female lines with the intention to stabilize line A as 'bushy/potent' and line B as bushy/high-yielding. Through the passing generations he selects the best examples of his desired traits, trying to stabilize them or increase the chances of any given seed of that generation have those traits. Eventually he's happy with his F6 generation, confident that his A line have a high chance of giving him something bushy and potent and that his B line will give him something bushy and high-yielding. Now all that's left is to bring them back together and try to get the awesome plant of bushy, potent, and high-yielding, all in one seed.

The mating of 2 F5's could have created trash and probably did make some bad ones in real life. Just remember that at Generation 5, the previous 2 generations were all dedicated to trying to isolate that one desired trait combo that the breeder wanted, and 'bad' or 'random' ones just didn't get chosen to breed into the next gen. Also, look at each entry not as one plant, but maybe 10, or 100 plants, but just simplified for the purposes of making a chart.

The plants in every cross after F2 and before P1 were selected in order to reduce the amount of random traits appearing in the next generation and increase the chance that desired phenos appear in those seeds.

I hope that makes sense. Cheers!

Ravener, thanks a lot. I have been doing some reading, and will be doing more after a few book purchases. I totally get what your saying. This is in fact just one of many different ways to create, clean up and harden a "strain". I could be in it after P1 and do the P2,P3,P5,P5 & P6 and then end up back crossing with the initial recurrent parent and then doing it all over again in a back cross BC1,BC2,BC3, etc until I have isolated exactly what I want and created a very true breed. Wow. This is all a lot to take in at one time.

half a lives work to create, perfect and back crossing to keep from inbred depression.... awesome. Im doin this. Watch for a "Morbid Angel" strain in the next few years!!