Disease resistance is very tricky, because there are cases where being homozygous for a resistance gene will result in a "cost" (less vigor, etc.). However, there must also be cases where homozygous is better. That said, disease resistance stacking at many loci is probably both very difficult to achieve, and will lead to vigor costs. And it is important to note that vigor is also one general way to "fight" disease, so reducing vigor reduces general disease resistance.
One reason I think I generally see better "general" disease resistance in hybrids is because my experience tells me very clearly that plant vigor is generally enhanced in hybrids -- probably due to the genetic diversity increase in hybrids (because the two parents will have alternate forms of genes at many loci, and thus more genes and more "solutions" to problems)
I do find that OPs have better resistance in earlier generations, when they are still genetically more diverse. I have had countless examples where OPs I am developing get "weaker" over time. My general selections are based on taste, but I still always try to also select for vigor when I have a number of plants in a population with equivalent taste.
I do not choose parents specifically to be more productive, and I don't follow disease markers or "vigor" markers.
I do try to start with parents that are generally decent with regards to vigor and disease resistance. And my parental lines clearly do have some genes that have been specifically put there by other breeders. I just don't follow them molecularly. But, I assume that I select for them in the field.
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Originally Posted by bower
Do you consider (1) as inevitable or is it more so by design? I mean if genes were stacked deliberately to get disease resistance, it stands to reason they will outperform.
Regarding OP's, do you find that they have better disease resistance in early generations of breeding( when less genetically stable), and that it is harder to find that by F5,6 and beyond? Or did the OP varieties you compared, simply have less in the way of disease resistance genes from the early stages? (less than tailored for resistance F1s I mean)
As regards productivity, I haven't been able to generalize about F1's being more productive and as I understand it, that is dependent on some very specific genes being present in the two parents. So I wondered, did you choose the F1 parents' genetics deliberately to get the 'extra productive' effect? And in the created OP's, would you generalize that there is a decline in vigor as they become closer to stable?
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