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

[EN] 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 di erent 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 e ects of cultivar, treatment and their interactions were highly significant (p Phaseolus (Leguminosae): A Recent Diversification in an Ancient Landscape. Systematic Botany, 31(4), 779-791. doi:10.1600/036364406779695960Broughton, W. J., Hernández, G., Blair, M., Beebe, S., Gepts, P., & Vanderleyden, J. (2003). Beans (Phaseolus spp.) – model food legumes. Plant and Soil, 252(1), 55-128. doi:10.1023/a:1024146710611Rendón-Anaya, M., Montero-Vargas, J. M., Saburido-Álvarez, S., Vlasova, A., Capella-Gutierrez, S., Ordaz-Ortiz, J. J., … Herrera-Estrella, A. (2017). Genomic history of the origin and domestication of common bean unveils its closest sister species. Genome Biology, 18(1). doi:10.1186/s13059-017-1190-6Berglund-Brücher, O., & Brücher, H. (1976). The south American wild bean (Phaseolus aborigineus Burk.) as ancestor of the common bean. Economic Botany, 30(3), 257-272. doi:10.1007/bf02909734Arteaga, S., Yabor, L., Torres, J., Solbes, E., Muñoz, E., Díez, M. J., … Boscaiu, M. (2019). Morphological and Agronomic Characterization of Spanish Landraces of Phaseolus vulgaris L. Agriculture, 9(7), 149. doi:10.3390/agriculture9070149Molina, J. C., Moda-Cirino, V., Fonseca Júnior, N. S., Faria, R. T., & Destro, D. (2001). Response of Common Bean Cultivars and Lines to Water Stress. Cropp Breeding and Applied Biotechnology, 1(4), 363-372. doi:10.13082/1984-7033.v01n04a05Graham, P. H., & Ranalli, P. (1997). Common bean (Phaseolus vulgaris L.). Field Crops Research, 53(1-3), 131-146. doi:10.1016/s0378-4290(97)00112-3Singh, S. P. (2007). Drought Resistance in the Race Durango Dry Bean Landraces and Cultivars. Agronomy Journal, 99(5), 1219-1225. doi:10.2134/agronj2006.0301CUELLAR-ORTIZ, S. M., DE LA PAZ ARRIETA-MONTIEL, M., ACOSTA-GALLEGOS, J., & COVARRUBIAS, A. A. (2008). Relationship between carbohydrate partitioning and drought resistance in common bean. Plant, Cell & Environment, 31(10), 1399-1409. doi:10.1111/j.1365-3040.2008.01853.xMaas, E. V., & Hoffman, G. J. (1977). Crop Salt Tolerance—Current Assessment. Journal of the Irrigation and Drainage Division, 103(2), 115-134. doi:10.1061/jrcea4.0001137Zhumabayeva, B. A., Aytasheva, Z. G., Dzhangalina, E. D., Esen, A., … Lebedeva, L. P. (2019). Screening of domestic common bean cultivar for salt tolerance during in vitro cell cultivation. International Journal of Biology and Chemistry, 12(1), 94-102. doi:10.26577/ijbch-2019-1-i12Fess, T. L., Kotcon, J. B., & Benedito, V. A. (2011). Crop Breeding for Low Input Agriculture: A Sustainable Response to Feed a Growing World Population. Sustainability, 3(10), 1742-1772. doi:10.3390/su3101742Hurtado, M., Vilanova, S., Plazas, M., Gramazio, P., Andújar, I., Herraiz, F. J., … Prohens, J. (2014). Enhancing conservation and use of local vegetable landraces: the Almagro eggplant (Solanum melongena L.) case study. Genetic Resources and Crop Evolution, 61(4), 787-795. doi:10.1007/s10722-013-0073-2Szabados, L., & Savouré, A. (2010). Proline: a multifunctional amino acid. Trends in Plant Science, 15(2), 89-97. doi:10.1016/j.tplants.2009.11.009Verslues, P. E., & Sharma, S. (2010). Proline Metabolism and Its Implications for Plant-Environment Interaction. The Arabidopsis Book, 8, e0140. doi:10.1199/tab.0140Kapuya, J. A., Barendse, G. W. M., & Linskens, H. F. (1985). WATER STRESS TOLERANCE AND PROLINE ACCUMULATION IN PHASEOLUS VULGARIS L. Acta Botanica Neerlandica, 34(3), 293-300. doi:10.1111/j.1438-8677.1985.tb01921.xMisra, N., & Gupta, A. K. (2005). Effect of salt stress on proline metabolism in two high yielding genotypes of green gram. Plant Science, 169(2), 331-339. doi:10.1016/j.plantsci.2005.02.013C醨denas-Avila, ML, Verde-Star, J., Maiti, R., Foroughbakhch-P, R., G醡ez-Gonz醠ez, H., … Morales-Vallarta, M. (2006). Variability in accumulation of free proline on in vitro calli of four bean (Phaseolus vulgaris L.) varieties exposed to salinity and induced moisture stress. Phyton, 75(1), 103-108. doi:10.32604/phyton.2006.75.103WANG, Q. (2019). EFFECTS OF DROUGHT STRESS ON ENDOGENOUS HORMONES AND OSMOTIC REGULATORY SUBSTANCES OF COMMON BEAN (PHASEOLUS VULGARIS L.) AT SEEDLING STAGE. Applied Ecology and Environmental Research, 17(2), 4447-4457. doi:10.15666/aeer1702_44474457Jiménez-Bremont, J. F., Becerra-Flora, A., Hernández-Lucero, E., Rodríguez-Kessler, M., Acosta-Gallegos, J. A., & Ramírez-Pimentel, J. G. (2006). Proline accumulation in two bean cultivars under salt stress and the effect of polyamines and ornithine. Biologia plantarum, 50(4), 763-766. doi:10.1007/s10535-006-0126-xAl Hassan, M., Morosan, M., López-Gresa, M., Prohens, J., Vicente, O., & Boscaiu, M. (2016). Salinity-Induced Variation in Biochemical Markers Provides Insight into the Mechanisms of Salt Tolerance in Common (Phaseolus vulgaris) and Runner (P. coccineus) Beans. International Journal of Molecular Sciences, 17(9), 1582. doi:10.3390/ijms17091582Morosan, M., Hassan, M. A., Naranjo, M. A., López-Gresa, M. P., Boscaiu, M., & Vicente, O. (2017). Comparative analysis of drought responses in Phaseolus vulgaris (common bean) and P. coccineus (runner bean) cultivars. The EuroBiotech Journal, 1(3), 247-252. doi:10.24190/issn2564-615x/2017/03.09Bates, L. S., Waldren, R. P., & Teare, I. D. (1973). Rapid determination of free proline for water-stress studies. Plant and Soil, 39(1), 205-207. doi:10.1007/bf00018060Arteaga, S., Al Hassan, M., Chaminda Bandara, W., Yabor, L., Llinares, J., Boscaiu, M., & Vicente, O. (2018). Screening for Salt Tolerance in Four Local Varieties of Phaseolus lunatus from Spain. Agriculture, 8(12), 201. doi:10.3390/agriculture8120201Andrade, E. R., Ribeiro, V. N., Azevedo, C. V. G., Chiorato, A. F., Williams, T. C. R., & Carbonell, S. A. M. (2016). Biochemical indicators of drought tolerance in the common bean (Phaseolus vulgaris L.). Euphytica, 210(2), 277-289. doi:10.1007/s10681-016-1720-4Bacha, H., Tekaya, M., Drine, S., Guasmi, F., Touil, L., Enneb, H., … Ferchichi, A. (2017). Impact of salt stress on morpho-physiological and biochemical parameters of Solanum lycopersicum cv. Microtom leaves. South African Journal of Botany, 108, 364-369. doi:10.1016/j.sajb.2016.08.018Sen, A., Ozturk, I., Yaycili, O., & Alikamanoglu, S. (2017). Drought Tolerance in Irradiated Wheat Mutants Studied by Genetic and Biochemical Markers. Journal of Plant Growth Regulation, 36(3), 669-679. doi:10.1007/s00344-017-9668-8Koźmińska, A., Wiszniewska, A., Hanus-Fajerska, E., Boscaiu, M., Al Hassan, M., Halecki, W., & Vicente, O. (2019). Identification of Salt and Drought Biochemical Stress Markers in Several Silene vulgaris Populations. Sustainability, 11(3), 800. doi:10.3390/su11030800Verbruggen, N., & Hermans, C. (2008). Proline accumulation in plants: a review. Amino Acids, 35(4), 753-759. doi:10.1007/s00726-008-0061-6Parvaiz, A., & Satyawati, S. (2008). Salt stress and phyto-biochemical responses of plants – a review. Plant, Soil and Environment, 54(No. 3), 89-99. doi:10.17221/2774-pseHayat, S., Hayat, Q., Alyemeni, M. N., Wani, A. S., Pichtel, J., & Ahmad, A. (2012). Role of proline under changing environments. Plant Signaling & Behavior, 7(11), 1456-1466. doi:10.4161/psb.21949KAVI KISHOR, P. B., & SREENIVASULU, N. (2013). Is proline accumulationper secorrelated with stress tolerance or is proline homeostasis a more critical issue? Plant, Cell & Environment, 37(2), 300-311. doi:10.1111/pce.12157Al Hassan, M., López-Gresa, M. del P., Boscaiu, M., & Vicente, O. (2016). Stress tolerance mechanisms in Juncus: responses to salinity and drought in three Juncus species adapted to different natural environments. Functional Plant Biology, 43(10), 949. doi:10.1071/fp16007Al Hassan, M., Pacurar, A., López-Gresa, M. P., Donat-Torres, M. P., Llinares, J. V., Boscaiu, M., & Vicente, O. (2016). Effects of Salt Stress on Three Ecologically Distinct Plantago Species. PLOS ONE, 11(8), e0160236. doi:10.1371/journal.pone.0160236Plazas, M., Nguyen, H. T., González-Orenga, S., Fita, A., Vicente, O., Prohens, J., & Boscaiu, M. (2019). Comparative analysis of the responses to water stress in eggplant (Solanum melongena) cultivars. Plant Physiology and Biochemistry, 143, 72-82. doi:10.1016/j.plaphy.2019.08.031Chen, Z., Cuin, T. A., Zhou, M., Twomey, A., Naidu, B. P., & Shabala, S. (2007). Compatible solute accumulation and stress-mitigating effects in barley genotypes contrasting in their salt tolerance. Journal of Experimental Botany, 58(15-16), 4245-4255. doi:10.1093/jxb/erm284Kozminska, A., Al Hassan, M., Hanus-Fajerska, E., Naranjo, M. A., Boscaiu, M., & Vicente, O. (2018). Comparative analysis of water deficit and salt tolerance mechanisms in Silene. South African Journal of Botany, 117, 193-206. doi:10.1016/j.sajb.2018.05.022Rosales, M. A., Ocampo, E., Rodríguez-Valentín, R., Olvera-Carrillo, Y., Acosta-Gallegos, J., & Covarrubias, A. A. (2012). Physiological analysis of common bean (Phaseolus vulgaris L.) cultivars uncovers characteristics related to terminal drought resistance. Plant Physiology and Biochemistry, 56, 24-34. doi:10.1016/j.plaphy.2012.04.007Sánchez, E., López-Lefebre, L. R., García, P. C., Rivero, R. M., Ruiz, J. M., & Romero, L. (2001). Proline metabolism in response to highest nitrogen dosages in green bean plants (Phaseolus vulgaris L. cv. Strike). Journal of Plant Physiology, 158(5), 593-598. doi:10.1078/0176-1617-00268Mackay, C. E., Christopher Hall, J., Hofstra, G., & Fletcher, R. A. (1990). Uniconazole-induced changes in abscisic acid, total amino acids, and proline in Phaseolus vulgaris. Pesticide Biochemistry and Physiology, 37(1), 74-82. doi:10.1016/0048-3575(90)90110-nAbdelhamid, M. T., Rady, M. M., Osman, A. S., & Abdalla, M. A. (2013). Exogenous application of proline alleviates salt-induced oxidative stress inPhaseolus vulgarisL. plants. The Journal of Horticultural Science and Biotechnology, 88(4), 439-446. doi:10.1080/14620316.2013.11512989Gürel, F., Öztürk, Z. N., Uçarlı, C., & Rosellini, D. (2016). Barley Genes as Tools to Confer Abiotic Stress Tolerance in Crops. Frontiers in Plant Science, 7. doi:10.3389/fpls.2016.01137Yoshida, J., Tomooka, N., Yee Khaing, T., Shantha, P. G. S., Naito, H., Matsuda, Y., & Ehara, H. (2019). Unique responses of three highly salt-tolerant wild Vigna species against salt stress. Plant Production Science, 23(1), 114-128. doi:10.1080/1343943x.2019.169896

Exposure of Common Bean Seeds to Liquid Nitrogen Modifies Mineral Composition of Young Plantlet Leaves

Many publications describe cryopreservation techniques but only a few studies have focused on the biochemical and physiological changes occurring in plants regenerated from seeds exposed to liquid nitrogen. This paper aims at describing the effect of common bean seed cryostorage on mineral nutrition of young plantlets. The following elements were measured on leaves of 10-day-old plantlets from non-cryopreserved and cryopreserved seeds: Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, S, Se, Sr and Zn. At 10 days after sowing, both treatments (control and cryopreserved seeds) showed 100% seed germination without any visual phenotypic difference. However, contents of several elements in the leaves were different. Exposure of seeds to liquid nitrogen decreased Cu, Cd and Na uptake and increased absorption of B and Al. Further studies are required to understand the mechanisms underlying the relationship between seed exposure to liquid nitrogen and mineral nutrition during the early stages of plantlet growth.DAADLeibniz University of HannoverUniversity of Ciego de Avila, Cub

Histology of maize seeds and young germinating embryos after liquid nitrogen exposure

[EN] Maize represents a staple food crop and is the second most important agricultural commodity globally. Considering the important role of maize for food security, the long-term conservation of valuable germplasm is critical to ensure that high levels of genetic diversity are available for breeding superior cultivars to face future challenges. Cryopreservation is regarded as the most appropriate tool for long-term germplasm preservation and has been investigated in different crops. This short communication adds to the existing knowledge on maize cryopreservation by describing histological changes observed in maize seeds and young germinating embryos after liquid nitrogen (LN) exposure. Plants were examined immediately after recovery from LN (day zero) and following 3 days of germination. At day 3, seeds exposed to LN showed lower germination rates than non-cryostored seeds, i.e., 60.7% vs. 83.3%. Histological evaluation at day 3 revealed that the thickness of the conical endosperm and the scutellum did not show any statistically significant differences between control and cryopreserved seeds. In contrast, for the other histological evaluations made, mostly regarding the thickness of mesocarp, mealy endosperm, plumule, radicle and the epidermis, significant differences were observed between control and cryostored seeds with the former consistently displaying higher average values than the latter.Villalobos-Olivera, A.; Pereira, R.; Gómez, D.; Martínez, J.; Escalante, D.; Martínez-Montero, ME.; Hajari, E.... (2021). Histology of maize seeds and young germinating embryos after liquid nitrogen exposure. Romanian Biotechnological Letters. 26(4):2855-2861. https://doi.org/10.25083/rbl/26.4/2855.28612855286126

Mutagenic effects of sodium azide on pineapple micropropagant growth and biochemical profile within temporary immersion bioreactors

Sodium azide (NaN3) is widely used to induce mutagenesis within in vitro plant systems. However, since this mutagenesis is undirected, its unintended effects demand characterization. This study investigated the mutagenic effects of sodium azide (0-0.45 mM) on selected growth (shoot multiplication rate and shoot cluster fresh weight) and biochemical (aldehydes, chlorophylls, carotenoids and phenolics) parameters in pineapple micropropagants within temporary immersion bioreactors (TIBs). The content of soluble phenolics in the culture medium was also evaluated. Irrespective of the concentration NaN3 decreased shoot multiplication rate (by 87% relative to the control at 0.45 mM) and fresh weight (by 66% relative to the control at 0.45 mM). Levels of chlorophyll a and b, and soluble phenolics in the culture medium were also negatively correlated with NaN3 concentration. Interestingly, NaN3 application increased shoot carotenoid and soluble phenolic levels but had no significant effect on a range of established plant stress biomarkers: cell wall-linked phenolic levels, malondialdehyde and other aldehydes. Given that 0.19 mM NaN3 decreased shoot multiplication rate by 50% and resulted in propagants that displayed no morphologically abnormalities, increased levels of photoprotective pigments (relative to the control) and no significant increase in lipid peroxidation products, the mutagen can be used at this concentration to induce pineapple mutagenesis in TIB based studies aimed at producing agriculturally-useful mutants

Screening for Salt Tolerance in Four Local Varieties of Phaseolus lunatus from Spain

[EN] This study assessed the responses of four local Spanish cultivars of Phaseolus lunatus (lima bean) to moderate salinity. For three weeks, plants were exposed to increasing salinity (50-150 mM NaCl) under greenhouse conditions. At the end of the experiment, several growth and biochemical parameters were determined. Salt stress reduced the fresh weight of aerial organs, allowing us to rank the four genotypes according to their tolerance to salinity. The concentration of most photosynthetic pigments remained unaltered, except carotenoids that were reduced in the least salt-tolerant cv. (cultivar) VPH-79. Leaf Na+ and Cl- concentrations increased with increased salt concentration of irrigation water, but K+ either remained constant, as in the most tolerant 'BGV-15410', or increased in the other cultivars, resulting in an unchanged K+/Na+ ratio under stress in two of the selected cultivars. Moreover, proline increased in all cultivars, most notably in cv. VPH-79, with the highest absolute concentrations registered in the more salt tolerant cultivars. Interestingly, these cultivars already had a relatively higher proline concentration in non-stressed plants. These findings indicate that P. lunatus is moderately salt tolerant and that its main mechanisms to adjust to salinity stress are the maintenance of high concentrations of K+ and proline accumulation in leaves.Arteaga-Castillo, SM.; Al Hassan, M.; Bandara, WMC.; Yabor, L.; Llinares Palacios, JV.; Boscaiu, M.; Vicente, O. (2018). Screening for Salt Tolerance in Four Local Varieties of Phaseolus lunatus from Spain. Agriculture. 8(12). https://doi.org/10.3390/agriculture8120201S81

Cryopreservation of sorghum seeds modifies germination and seedling growth but not field performance of adult plants

Climate change poses risks to both wild and crop plant biodiversity, which can be mitigated by cryopreservation (usually at -196 °C in liquid nitrogen [LN]) of crop germplasm. Cryopreservation is widely regarded as a reliable method for the ex situ conservation of plant genetic resources but its effects on subsequent field performance of popular crop species such as sorghum are largely unknown. This hampers the large-scale implementation (i.e. germplasm banks) of cryostorage for such species. This short communication describes the early stages of germination and field performance of plants derived from cryopreserved sorghum seed. Compared with the control, cryopreservation significantly increased seed electrolyte leakage and from 24 to 120 hours, percentage of germination of the control was ~2.6 folds higher than cryopreserved seeds. At 0 days, chlorophyll a/b rate was ~1.7 folds higher in the control and at 7 and 14 days, chlorophyll a level (~1.5 folds) and chlorophyll a/b rate (~1.8-1.9 folds) were higher in the control. Contrastingly, at 7 days, seedlings derived from cryopreserved seeds (treatment seedlings) showed ~1.5 folds more superoxide dismutase activity and ~1.9 folds more peroxidase activity. In contrast, treatment and control adult plants were statistically comparable in terms of chlorophylls, proteins, superoxide and peroxidase activities, plant architecture, and yield components. The fact that differences in biochemical indicators observed between control and treatment seedlings did not persist in adult plants validates the use of seed cryopreservation for the conservation of sorghum genetic resources

Identification of discriminant factors after exposure of maize and common bean plantlets to abiotic stresses

Adverse environmental conditions limit crop yield and better understanding of plant response to stress will assist the development of more tolerant cultivars. Maize and common bean plantlets were evaluated under salinity, high temperature, drought and waterlogged conditions to identify biochemical markers which could be useful for rapid identification of putative stress tolerant plants. The levels of phenolics (free, cell wall-linked, total), aldehydes including malondialdehyde and chlorophylls (a, b, total) were measured on stressed plantlets. Only two indicators were statistically non-significant: chlorophyll b in maize plantlets stressed with sodium chloride and malondialdehyde content in drought stressed maize. The most remarkable effects of abiotic stresses can be summarized as follows: (i) salinity increased levels of free phenolics in maize plantlets and chlorophylls (a, b, total) in common bean; (ii) high temperature (40 °C) elevated levels of chlorophylls (a, b, total) in maize but decreased chlorophylls (a, b, total) and free phenolics in common bean; (iii) drought increased phenolics and decreased chlorophylls (a, b, total) in maize and increased chlorophyll pigments (a, b, total) in common bean; (iv) waterlogging increased free phenolics and decreased chlorophylls (a, b, total) in maize and increased chlorophyll (a, total) in common bean. Free phenolics and chlorophylls, especially a, were the most responsive indicators to stress and can, therefore, be considered putative biochemical markers for abiotic stress tolerance in maize and common bean. The use of Fisher s linear discriminant analysis to differentiate non-stressed and stressed plants in breeding programs is also a novel aspect of this report. Fisher s linear discriminant functions classified correctly 100% of non-stressed or stressed originally grouped plants.Hernández, L.; Loyola González, O.; Valle, B.; Martínez, J.; Díaz López, L.; Aragón, C.; Vicente Meana, Ó.... (2015). Identification of discriminant factors after exposure of maize and common bean plantlets to abiotic stresses. NOTULAE BOTANICAE HORTI AGROBOTANICI. 43(2):589-598. doi:10.15835/nbha4329916S58959843

Salinity induces specific metabolic changes in sugarcane shoot explants in temporary immersion bioreactors

There is a great demand of salt-tolerant sugarcane planting material in Cuba. Temporary immersion bioreactors (TIB) are effective to significantly increase sugarcane in vitro shoot proliferation rate from 1:4 in conventional containers to about 1:35. Sugarcane micropropagation in TIBs under NaCl stress may help screen mutants with salinity tolerance. We developed the experiment shown here to identify a NaCl concentration able to stress shoot in TIBs. At 30 days of culture initiation with different NaCl levels (0 - 200 mM), explant multiplication rate, shoot cluster fresh mass, and levels of aldehydes, chlorophylls, carotenoids and phenolics were determined in the plant material. Content of soluble phenolics in the culture medium was also evaluated. Addition of NaCl decreased shoot multiplication rate and fresh mass. Other statistically significant differences were recorded but the most important were noted in the increased contents of carotenoids, malondialdehyde, other aldehydes and soluble phenolics in the plants, and in the soluble phenolics in the culture medium. This research may be useful for future experiments of in vitro selection of new sugarcane genetic materials with NaCl tolerance. Fifty percent of multiplication rate was reduced with 89 mM NaCl which can be used to stress shoots during micropropagation in TIBs and eventually detect mutants with salt tolerance

Coefficient of Variation Can Identify the Most Important Effects of Experimental Treatments

Most agricultural experiments involve evaluation of multiple variables and at times it can be difficult to identify the biologically relevant effects of the experimental treatments after performing the traditional ANOVA, Tukey and t-tests. The coefficient of variation formula could be an important tool to focus ‘Result and Discussion ’ sections only on the most important changes produced by the experimental treatments. This short report is intended to exemplify the use of the coefficient of variation in three plant physiology experiments. The first one dealt with the effects of common bean plantlet exposure to high temperature under controlled conditions (levels: 28 and 40 °C). The second experiment was related to common bean seed exposure to liquid nitrogen during five different periods of time (levels: 0, 7, 14, 21 and 28 days). The third experiment was bi-factorial: factor 1 was the ‘type of plant material ’ (levels: pineapple plants genetically transformed and the untransformed control); and factor 2 was the ‘time of in vitro-plantlet hardening ’ (levels: 0, 15 and 30 days). Contents of phenolics, aldehydes, chlorophylls and proteins were determined. Percentage of seed germination, electrolyte leakage, peroxidase activity, plant height and weight were also measured. Experiments were monofactorial with two levels, monofactorial with five levels and bifactorial, respectively, with randomized design. The coefficient of variation showed that the most remarkable effects of high temperature were recorded in free phenolics and chlorophylls (a, b, total). Electrolyt

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

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