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Old December 11, 2018   #176
Zone9b
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Join Date: Jul 2014
Location: Central Florida
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Quote:
Originally Posted by Fred Hempel View Post
I think you are right that changes in field conditions do partially explain the "reduced resistance over time" that we sometimes see.
There may be cases where pathogens evolve in a field after successive years of tomato growing (even if you are practicing crop rotation). But this is hard to separate from the effects of simple buildup of diseases that can occur in a field over time if tomatoes are consistently grown.
Either way, the increasing genetic uniformity that comes with the selection of an OP variety is not the sole reason one might see poorer vigor and/or disease resistance over time.

Does this mean that my old school attempts to improve the productivity of an OP variety in my harsh growing conditions is of little, if any, value? I continue to choose the largest tomato from the best vine to save seeds from. This has seemed to work well for me on at least one variety. This fall season it produced its largest tomato yet after growing for approximately 7 seasons, also its productivity is very good. Thanks,
Larry
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