Identification of distinctive physiological and molecular responses to salt stress among tolerant and sensitive cultivars of broccoli (Brassica oleracea var. Italica)

Background: Salt stress is one of the main constraints determining crop productivity, and therefore one of the main limitations for food production. The aim of this study was to characterize the salt stress response at the physiological and molecular level of different Broccoli (Brassica oleracea L. var. Italica Plenck) cultivars that were previously characterized in field and greenhouse trials as salt sensitive or salt tolerant. This study aimed to identify functional and molecular traits capable of predicting the ability of uncharacterized lines to cope with salt stress. For this purpose, this study measured different physiological parameters, hormones and metabolites under control and salt stress conditions. Results: This study found significant differences among cultivars for stomatal conductance, transpiration, methionine, proline, threonine, abscisic acid, jasmonic acid and indolacetic acid. Salt tolerant cultivars were shown to accumulate less sodium and potassium in leaves and have a lower sodium to potassium ratio under salt stress. Analysis of primary metabolites indicated that salt tolerant cultivars have higher concentrations of several intermediates of the Krebs cycle and the substrates of some anaplerotic reactions. Conclusions: This study has found that the energetic status of the plant, the sodium extrusion and the proline content are the limiting factors for broccoli tolerance to salt stress. Our results establish physiological and molecular traits useful as distinctive markers to predict salt tolerance in Broccoli or to design novel biotechnological or breeding strategies for improving broccoli tolerance to salt stress.

This work was funded by Grant RTC-2017-6468-2-AR (APROXIMACIONES MOLECULARES PARA INCREMENTAR LA TOLERANCIA A SALINIDAD Y SEQUíA DEL BRÓCOLI) funded by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe" by the European Union. S.C. is a recipient of grant FPU19/01977 from the Spanish Ministerio de Universidades. L.M. was supported by the Spanish MICINN (PTA2019-018094). L.M and A.V. activities were founded by Prometeu program (IMAGINA project, PROMETEU/2019/110). CEAM foundation is funded by Generalitat Valenciana.