Good to see you are experimenting. With my crops I work more with “dry spell resistance” rather than drought resistance, as drought years here are pretty much crop killer years. Each summer now for the last 3-4 years we have experienced a mid summer dry spell lasting from 4-6 weeks. That is pretty hard on the plants and my goal is simply to keep them from dying, which means water rationing. Selecting for resistance along with water rationing seems to carry plants through until the rains come. I refuse to water with well water, so I save up as much rainwater as I can collect during the spring rains.
Production has been down these last couple of dry spell years but still getting mostly adequate harvests. At these times I closely observe plant hardiness for seed saving, this is when I can really advance resistance traits.
Drought years are very different, very hard on the crop plants resulting in poor harvests. I was taught to always harvest and put up extra during the good years to compensate for the bad years that will surely happen. Developing food plants and engaging in breeding work to select for such things as dry spell survivability and thriveability in my food plants to (hopefully) lessen the impact of natural stresses is also important to me. Following multiple strategies at the same time seems to be the best hedge.
Too much rain and not enough rain both make for bad years, in many ways I find that too much rain is worse on food quality and production, and I do not think there is any way to select for resistance to too much rain.
One thing about dry spells and droughts is that blight/disease/molds/rot are not nearly as bad, many of them non issues, as compared to during wet years. Insect pests can be bad during dry growing seasons, though.
During dry spells and droughts I water my tomato plants at the rate of approximately one gallon of captured rainwater per week. I water carefully so as not to splash onto leaves. I made soakers using a vertical PVC pipe with small drain holes drilled into the ground end. A 2 liter plastic bottle with the bottom cut off is epoxied to the upper end of the pipe. The pipe is sunk into the root area approximately 8-10 inches from the stem. I fill the bottle with water and it slowly drains down the pipe and into the soil precisely where it is needed. I do not use soaker hoses because I only water with captured rainwater. I like that my methods more closely mimic natural rainfalls, plus my hand watering method does not rely on pumps, electricity, machines, hoses, repair parts, etc. for my food production.
Yep, too much rain, not enough rain, too cloudy for too long, to sunny and hot for too long. We get it all and often alternating in the same year. No way in my estimation, that anything can adapt to that.
Something I’ve been focusing on for several years is fast maturity with the goal of getting a harvest between extremes and being able to start over if an early planting gets wiped out. Some frost tolerance is nice too, so as to allow for earlier planting or delayed harvests.
I’ve been told longer maturing of any specific crop yields better, but it requires a longer period without any of the mentioned extremes. I’d rather increase the chances of an actual harvest than hope for a bigger one.
Especially since you can use relay cropping of short-maturity plants in order to get a comparably high yield, if you want one. And you may even be able to sneak an extra generation in there, to get local adaptation going more quickly.