My experience is limited, but here in central New Mexico where in a normal year our rainfall is a little over 7 inches/about 150mm (and we have been in a severe drought for some time now), and practically nothing will grow without some supplemental water in the best of times, I have found the most drought hardy food plants to be Swiss Chard (Beta vulgaris Cicla group), Chicory (Cichorium intybus), Daylilies (Hemerocallis), cultivated dandelions (Taraxacum officinale), certain Malvaceae species, and the American native desert Tepary beans (Phaseolus acutifolius)--I've grown the very drought hardy Sonoran variety that is native to the Sonoran desert and was domesticated by the Papago Indians. For fruit there are numerous fruit-bearing cacti, but I would also mention the extremely drought tolerant Chinese date (Zyziphus jujuba). Some of these you won't see on the "normal" American menu, but they all have a long history as food plants in their native habitats (and in my garden and on my table).

Good reply ! Thank you very much ! I have heard of the pitaya ,and the prickley pear what other cacti produce fruit ?

I have bought the dates in Chinatown years ago . How about desert chia, sunflowers, Galapagos prickley pear, carobe aloe vera , agave, mescal pitaya?