In vitro selection for tolerance to osmotic and ionic stress in Brazilian guava (Psidium guajava L.)

Drought and salinity are two of the major problems limiting crop production worldwide. In vitro culture has been used to select plants tolerant to these two factors. Three commercial cultivars of Psidium guajava L. were evaluated for their tolerance to osmotic and ionic stresses using in vitro plant selection techniques. Plantlets of guava ‘Paluma’, ‘Cortibel Rugosa Média’, and ‘Cortibel Rugosa Grande’ were cultured on MS medium without stressors and with two concentrations of mannitol (12.26 g L⁻¹ and 24.52 g L⁻¹) or NaCl (5.9 g L⁻¹ and 11.8 g L⁻¹). The experiment followed a completely randomized design with a two-factor factorial arrangement. Morphological and biochemical traits were statistically analyzed, and anatomical features were observed for variations under the tested conditions. Guava cultivars exhibited greater reductions in plantlet size under NaCl-induced stress. Biochemically, guava ‘Paluma’ and ‘Cortibel Rugosa Média’ showed similar patterns in the accumulation of amino acids, proline, and phenolic compounds, particularly under saline conditions. The malondialdehyde content in these two cultivars was inversely related to the levels of these organic compounds. Additionally, saline conditions appeared to promote thicker cuticles and greater epicuticular wax deposition on the leaves of Psidium guajava L. ‘Paluma’. These findings demonstrated that ‘Paluma’ and ‘Cortibel Rugosa Média’ were tolerant to osmotic and ionic stress. The use of stressors for in vitro selection enabled the identification of Psidium guajava L. ‘Paluma’ and ‘Cortibel Rugosa Média’ as tolerant to osmotic and moderate ionic stresses.