Moderate and severe water stress effects on morphological and biochemical traits in a set of pepino (Solanum muricatum) cultivars

Abstract The pepino (Solanum muricatum) is a neglected crop from the Andean region with potential for expansion to many areas of the world. However, there is a lack of studies in pepino related to its response to water stress. In this study, we have subjected plantlets of seven pepino cultivars (Mur1-Mur7) to three treatments consisting of a fully irrigated control (C), a moderate water stress (WS-M), and a severe water stress (WS-S). Thirty-one traits related to growth, photosynthetic pigments, mono and divalent ions, osmolytes and antioxidants were measured. Significant differences were found among cultivars for most traits. The WS-M treatment did not affect most growth and biochemical parameters, while large differences with respect to the control were observed with the WS-S treatment. In general, the WS-S treatment induced an inhibition of the growth parameters, mainly the reduction of the fresh weight of leaves, stems and roots, as well as their water content. A principal component analysis (PCA) performed on the relative values of growth traits, together with the ANOVA for the traits for which significant interaction cultivar × treatment was detected, showed that cultivars Mur2 and Mur4 are the most tolerant to water stress. Although no clear-cut differences were observed among cultivars, the water-stressed plants of Mur2 and Mur4 displayed less variation with respect to the control than the other cultivars for the physiological and biochemical traits measured. Overall, photosynthetic pigments, malondialdehyde and total flavonoids decreased under severe water stress, while proline, Na+ and K+ contents increased significantly. The results obtained provide relevant information on the response to drought of pepino and have allowed identifying two cultivars better adapted to water stress that could be useful in breeding pepino for drought tolerance.