Establishment of parameters for water stress tolerance evaluation on bean genotypes

Aiming to establish parameters for drought tolerance evaluation, fifteen ge notypes of bean (Phaseolus vulgaris L.) were evaluated during a water stres s period, applied at the pre-flowering stage through leaf water potential ( Psi(f)) and some other variables. Among the genotypes studied, A 222, A 285 , BAT 477, BAT 561 and IPA 7 showed highest Psi(f) during the water stress, indicating a better stomatal control by these genotypes, while the cultiva rs Carioca and Ouro Negro showed a more rapid recuperation, after being reh ydrated. All the Anthracnose tolerant genotypes evaluated presented an effi cient stomatal control. The potential for nitrogen biological fixation, eva luated by the number and weight of nodules, was significantly affected only on few genotypes. Leaf area and shoot dry weight were the morphological va riables more sensitive to water stress. The number of pods per plant was on ly affected on Xodo and CNF 0145 genotypes, while the Carioca, A 285, CNF 0 145, BAT 477, cv. 121 genotypes, and the LM 30036 line, showed a decrease o n the seed weight per plant, under water stress. Besides having the highest Psi(f), the A 222 and IPA 7 genotypes were the only ones that did not show a significant reduction on the leaf area and seed weight per plant, althou gh the first one had a low plant production under stress.