DROUGHT STRESS IS RESPONSIBLE FOR MORE CROP LOSS THAN ANY OTHER ABIOTIC OR BIOTIC STRESS, THUS MAKING IT A CRITICAL GOAL IN MANY BREEDING PROGRAMS. BUT PROGRESS HAS BEEN SLOW, PRIMARILY DUE TO BOTH THE COMPLEXITY OF CONDITIONS THAT HAVE BEEN CATEGORIZED UNDER THE GENERAL TERM "DROUGHT", AND BECAUSE OF THE COMPLEXITY AND BREADTH OF INDIVIDUAL PLANT PROCESSES AND TRAITS WHICH CONTRIBUTE TO "TOLERANCE" TO WATER SCARCITY. IN ADDITION, THE CONCEPT OF SUCCESSFUL DROUGHT TOLERANCE IN CROP SPECIES DIVERGES FROM MANY ESTABLISHED PARADIGMS REGARDING PLANT DROUGHT TOLERANCE IN GENERAL, BECAUSE CROPS MUST DO MORE THAN SURVIVE - THEY MUST CONTINUE TO YIELD UNDER DROUGHT. IN ADDITION, THE TWO CONDITIONS OF SURVIVAL AND PERFORMANCE UNDER DROUGHT DEPEND ON DIFFERENT PHYSIOLOGICAL AND GENETIC MECHANISMS. ALL THESE FACTORS HAVE LED TO THE LACK OF TRUE BREAKTHROUGHS IN SOLVING THE ISSUE OF BREEDING FOR CROP DROUGHT TOLERANCE.FROM AN EXPERIMENTAL VIEW, THE CURRENT "DROUGHT TOLERANCE" BREEDING PARADIGM UTILIZES A FOCUS ON ISOLATED TRAIT APPROACHES, USUALLY AIMED AT SCORING SURVIVAL UNDER SEVERE DROUGHT SCENARIOS. THIS SELECTION OF SURVIVORS UNDER SEVERE WATER DEFICIT ACTUALLY TENDS TO SELECT FOR MALADAPTIVE PHENOTYPES WHEN PLACED IN REAL-WORLD PRODUCTION SCENARIOS. FOR EXAMPLE, GENOTYPES SELECTED FOR TIGHT STOMATAL CONTROL OVER TRANSPIRATION WOULD SHOW HIGH SURVIVABILITY IN THE TYPICAL RESEARCH DROUGHT SELECTION SCENARIO, BUT WOULD LIKELY EXPERIENCE YIELD LOSS UNDER MOST PRODUCTION SCENARIOS DUE TO THEIR LOSS OF PHOTOSYNTHETIC CAPABILITY. IN ADDITION, IF SELECTION WAS AIMED AT DEEP ROOTS, A TRAIT NOW CONSIDERED TO FIT THE CURRENT "DROUGHT TOLERANT" PARADIGM, THIS MAY SELECT FOR PHENOTYPES THAT ARE MALADAPTED TO CURRENT IRRIGATED PRODUCTION SCENARIOS WHERE ENERGY SPENT ON DEEP ROOTS WOULD NOT TYPICALLY BE REWARDED UNDER MILD OR MODERATE DROUGHT CONDITIONS. THEREFORE, ADAPTABILITY HIGHLY DEPENDS ON THE SET OF CONDITIONS UNDER WHICH SELECTION OCCURS, LEADING TO CONCLUSIONS THAT "DROUGHT TOLERANCE" CAN BE CLAIMED FOR A MYRIAD OR TRAITS OR GENES IF TESTED UNDER THE APPROPRIATE CONDITIONS, OR THE "RIGHT DROUGHT SCENARIO".