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Old November 7, 2016   #15
JLJ_
Tomatovillian™
 
Join Date: Aug 2011
Location: Wyoming
Posts: 759
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This thread has had some great answers -- but it might be worth mentioning one of the techniques used by Fred Pritchard that relates to harvesting benefits of genetic diversity -- if you're interested in century old work.

He was the person at the USDA who in 1918 developed the tomato Marvel from Merveille des Marches and crossed it with Livingstone's Globe to create the famous Marglobe -- which was very important in the 1930's because of greatly improved disease tolerance as well as high quality production for commercial and home uses -- and which is ancestor to many modern varieties.

(Pritchard also developed many other valuable varieties of tomato.)

He compared parent-candidate varieties for intravarietal variation with respect to the property he wanted to introduce or intensify, then worked by selection with a candidate variety that had high intravarietal variation to create a new variety with the target trait more prominently and consistently present. Often, he then crossed that new variety with other varieties that had complementary traits, stabilized the cross and released the new market variety.

I think that has practical application for the many home gardeners who attempt to develop an improved version of some variety by selection -- for earliness drought tolerance, etc . That is, before investing -- and possibly wasting -- many generations selecting, it might be wise to spend a season growing a large number of the variety they want to improve, determine whether it has a lot of intravarietal variation with respect to the target property and if not, use another variety, or use crossing techniques instead of or prior to using selection to achieve an improved variety.

Below is one place Pritchard discusses some of his work. Note that his work was utilitarian rather than theoretical or research oriented -- his goal being to produce tomatoes with desired traits as fast as possible and get them out to growers to grow or to further develop.
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https://ia801703.us.archive.org/11/i...il1015prit.pdf


BULLETIN 1015, U. S. DEPARTMENT OF AGRICULTURE. March 28, 1922

DEVELOPMENT OF WILT-RESISTANT TOMATOES.

By Fred J. Pritchard, Physiologist, Office of Cotton, Truck, and Forage Crop
Disease Investigations.
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