Variations in abscisic acid, indole-3-acetic acid, gibberellic acid and zeatin concentrations in two bean species subjected to salt stress

Common bean (Phaseolus vulgaris L.) is sensitive to drought and salinity, while an ancestral legume, tepary bean (P. acutifolius A. Gray) is cultivated successfully where high temperature and drought are common (Lazeano-Ferrat and Lovatt, 1999). Hence, P. acutifolius is a potential source of stress tolerant traits for P. vulgaris through interspecific hybrids. This study comparatively evaluated the effects of salt stress on leaf relative water content (RWC), soluble protein, the phytohormones indole acetic acid (IAA), gibberellic acid (GA(3)), zeatin, and abscisic acid (ABA) levels in P. vulgaris and P. acutifolius. With the exception of ABA, stress-induced changes in hormonal levels putatively related to stress tolerance have not been investigated previously in either species. Treatment with 50 mM, 100 mM and 150 mM NaCl reduced relative water and protein content in P. vulgaris, but did not affect relative water content and increased protein content in P. acutifolius. Varietal differences between P. vulgaris and P. acutifolius were also observed in hormonal content during the stress period. ABA levels in salt-treated plants of P. vulgaris increased but did not change in P. acutifolius versus the controls. Both IAA and gibberellin levels increased in leaves of P. acutifolius but decreased in P. vulgaris under salt stress. In salt-treated plants, zeatin concentrations in leaves of P. vulgaris decreased within 24-72 h after treatment. However, P. acutifolius responded to all tested NaCl levels by increasing zeatin concentrations after short-term NaCl treatment.