The Use of Proline in Screening for Tolerance to Drought and Salinity in Common Bean (Phaseolus vulgaris L.) Genotypes

Abstract

The selection of stress-resistant cultivars, to be used in breeding programmes aimed at enhancing the drought and salt tolerance of our major crops, is an urgent need for agriculture in a climate change scenario. In the present study, the responses to water deficit and salt stress treatments, regarding growth inhibition and leaf proline (Pro) contents, were analysed in 47 Phaseolus vulgaris genotypes of different origins. A two-way analysis of variance (ANOVA), Pearson moment correlations and principal component analyses (PCAs) were performed on all measured traits, to assess the general responses to stress of the investigated genotypes. For most analysed growth variables and Pro, the effects of cultivar, treatment and their interactions were highly significant (p < 0.001); the root morphological traits, stem diameter and the number of leaves were mostly due to uncontrolled variation, whereas the variation of fresh weight and water content of stems and leaves was clearly induced by stress. Under our experimental conditions, the average effects of salt stress on plant growth were relatively weaker than those of water deficit. In both cases, however, growth inhibition was mostly reflected in the stress-induced reduction of fresh weight and water contents of stems and leaves. Pro, on the other hand, was the only variable showing a negative correlation with all growth parameters, but particularly with those of stems and leaves mentioned above, as indicated by the Pearson correlation coefficients and the loading plots of the PCAs. Therefore, in common beans, higher stress-induced accumulation of Pro is unequivocally associated with a stronger inhibition of growth; that is, with a higher sensitivity to stress of the corresponding cultivar. We propose the use of Pro as a suitable biochemical marker for simple, rapid, large-scale screenings of bean genotypes, to exclude the most sensitive, those accumulating higher Pro concentrations in response to water or salt stress treatments.

Ameliorative Effects of Exogenous Proline on Photosynthetic Attributes, Nutrients Uptake, and Oxidative Stresses under Cadmium in Pigeon Pea (Cajanus cajan L.)

“…Its application in a metal stress medium led to proline complex formation, reducing metal entry into plant tissues, thus creating more space for the free movement of nutrients [72]. Several studies have highlighted the ameliorative effects of exogenous proline on photosynthetic attributes under stress conditions [42,[44][45][46][47][48]75]. Exogenous proline in stress environments can stabilize the mitochondrial transport chain, enhance rubisco activity in carbon fixation, and thus accelerate the photosynthesis dark reaction [75].…”

“…Its exogenous application is also effective in the alleviation of abiotic stresses. Several manuals have highlighted its ameliorative role in various stress environments [42][43][44][45][46]. Shahid et al reported that exogenous proline improved antioxidant enzymes and the water status of pea plants under nickel stress [47].…”

Proline, Total Antioxidant Capacity, and OsP5CS Gene Activity in Radical and Plumule of Rice are Efficient Drought Tolerance Indicator Traits

“…When plants are exposed to water shortage, the production of proline increases. is increase sometimes reaches 100 times more than the normal synthesis rate [48][49][50][51]. We concluded that the drought-induced change in proline contents in radical and plumule can screen germplasm at the germination stage.…”

Comparative Studies on the Physiological and Biochemical Responses to Salt Stress of Eggplant (Solanum melongena) and Its Rootstock S. torvum

“…These data strongly support the direct participation of Pro in the mechanisms of salt tolerance in eggplant and related species. Although Pro accumulation in response to salt stress has been observed in many plants, its direct involvement in salt tolerance is not a general feature of Pro-accumulating species since other reports have shown higher Pro contents in the most susceptible genotypes of related species or cultivars of a given species [61]. The accumulation to high concentrations of this osmolyte in wild species has been related to a greater expression or better functioning under stress conditions of the enzyme pyrroline-5-carboxylate synthetase, which has a fundamental role in the biosynthesis pathway of proline [62].…”