Salinity-Induced Variation in Biochemical Markers Provides Insight into the Mechanisms of Salt Tolerance in Common (Phaseolus vulgaris) and Runner (P. coccineus) Beans

Abstract

The evaluation of biochemical markers is important for the understanding of the mechanisms of tolerance to salinity of Phaseolus beans. We have evaluated several growth parameters in young plants of three Phaseolus vulgaris cultivars subjected to four salinity levels (0, 50, 100, and 150 mM NaCl); one cultivar of P. coccineus, a closely related species reported as more salt tolerant than common bean, was included as external reference. Biochemical parameters evaluated in leaves of young plants included the concentrations of ions (Na+, K+, and Cl−), osmolytes (proline, glycine betaine, and total soluble sugars), and individual soluble carbohydrates. Considerable differences were found among cultivars, salinity levels, and in their interaction for most traits. In general, the linear component of the salinity factor for the growth parameters and biochemical markers was the most important. Large differences in the salinity response were found, with P. vulgaris cultivars “The Prince” and “Maxidor” being, respectively, the most susceptible and tolerant ones. Our results support that salt stress tolerance in beans is mostly based on restriction of Na+ (and, to a lesser extent, also of Cl−) transport to shoots, and on the accumulation of myo-inositol for osmotic adjustment. These responses to stress during vegetative growth appear to be more efficient in the tolerant P. vulgaris cultivar “Maxidor”. Proline accumulation is a reliable marker of the level of salt stress affecting Phaseolus plants, but does not seem to be directly related to stress tolerance mechanisms. These results provide useful information on the responses to salinity of Phaseolus.

Comparative analysis of drought responses in Phaseolus vulgaris (common bean) and P. coccineus (runner bean) cultivars

“…We have selected three cultivars of Phaseolus vulgaris and one cultivar of its congener P. coccineus, to perform a comparative analysis of the responses of the plants to water deficit treatments under controlled greenhouse conditions. This work extends and complements a previous study where different responses of the same cultivars to salt stress treatments were investigated (15). Here, we have focused on a basic, conserved mechanism activated in plants subjected to different abiotic stresses, including drought; namely, the synthesis and accumulation of specific osmolytes (proline, glycine betaine or soluble carbohydrates) to maintain cellular osmotic balance, which is disrupted under stress conditions.…”

“…The soluble sugar fraction (mono-and oligosaccharides) was analysed using a Waters 1525 high performance liquid chromatography coupled to a 2424 evaporative light scattering detector (ELSD), as previously described (15). Standards of glucose, fructose, sucrose, and myo-inositol were used to identify peaks by co-injection.…”

Effects of Drought and Salinity on European Larch (Larix decidua Mill.) Seedlings

“…When comparing ion levels between roots and needles, no differences were observed in Na + contents (in terms of DW), neither in control nor in salt-stressed seedlings; regarding Cl − , its concentration was slightly (but significantly) higher in needles than in roots, again in both non-stressed and salt-stressed seedlings. These results indicate that European larch responses to salinity do not include mechanisms blocking the transport of toxic ions from underground to aboveground parts of the plants, contrary to what has been described for most glycophytic taxa, including many crops [57,62], or for halophytic monocotyledonous species [63].…”

Identification of Salt and Drought Biochemical Stress Markers in Several Silene vulgaris Populations

“…These mechanisms appear to be constitutive, since these ions were present at high concentrations also in the leaves of nonstressed plants. The accumulation of high leaf Na + concentrations under low soil salinity conditions has been described for several halophytes, both in field [54] and greenhouse [111] experiments, and also (to a lesser extent) in typical glycophytes, such as some Phaseolus cultivars [20]. In S. vulgaris, specific mechanisms of tolerance to salinity seem to be based on the inhibition of additional transportation of toxic ions to the aerial parts of the plants, whereas accumulation of soluble sugars may contribute to tolerance to drought.…”

“…Lately, however, more emphasis is being placed on deciphering stress response mechanisms of some minor crops and many wild species with a wide spectrum of tolerance, some of them closely related to crop and model plant species. Some of these studies have found differences in the efficiency of stress responses in closely related species, or in different cultivars, ecotypes, or even individual populations of the same species [20].…”