Differential metabolic rearrangements improve biomass and enhance the tolerance of two dwarf cashew (<i>Anacardium occidentale</i> L.) genotypes to salt stress

Abstract

Salinity is one of the abiotic stresses that affect crop productivity and plant development the most. We aimed to analyze the physiological and biochemical responses of dwarf cashew (A. occidentale L.) genotypes subjected to salt stress. The experiment was carried out in a greenhouse with a completely randomized design in a 5 × 2 factorial scheme, with five salinity levels (0, 25, 50, 75, and 100 mM NaCl) and 2 dwarf cashew genotypes (Embrapa51 and CCP76). There was no significant effect of salinity on plant height, leaf number, and stem diameter; however, the dry biomass was significantly reduced. Chlorophylls, starch, and total free amino acids decreased with salt stress, mainly with 75 and 100 mM NaCl. The CCP76 genotype salt-stressed increased carotenoids, anthocyanins, total soluble carbohydrates, reducing sugars, sodium, and potassium ions compared to Embrapa51. Free proline was increased in response to salt stress in dwarf cashew genotypes. Interestingly, sucrose declined in Embrapa51 and increased in CCP76 in response to salinity. When submitted to 75 and 100 mM NaCl, i.e., under severe stress, CCP76 presented more sucrose than Embrapa51. Our results indicated that sucrose accumulation plays an important role in the acclimation of CCP76 to salinity. This disaccharide induces metabolic rearrangements, mostly in the levels of soluble carbohydrates and amino acids, which contribute to rebalancing the osmotic potential and help to maintain favorable plant metabolism under salt stress. Overall, the dwarf cashew CCP76 was more tolerant to salinity than Embrapa51.

Keywords

• cashew genotypes
• chlorophylls
• salinity
• osmoprotectors