MECHANISMS OF TOLERANCE TO SALINITY IN BANANA: PHYSIOLOGICAL, BIOCHEMICAL, AND MOLECULAR ASPECTS

In the northeastern region of Brazil, saline soils are constraints to banana production, becoming necessary to understand the mechanisms of salt tolerance. Two bananas genotypes, Tap Maeo, tolerant, and Berlin, sensitive, were subjected to treatment with 50 mol m(-3) NaCl or without salt. This study evaluated the effects of salt on the following physiological aspects: leaf area, content and distribution of Na+, membrane integrity, proton AT Pase activity. Besides, a search for differentially expressed genes was performed using the Differential Display technique. Tap Maeo genotype showed the smallest reduction in leaf area, smaller accumulation of Na+ and malondialdehyde (MDA), and higher activity of proton AT Pase activity. Two sequences differentially expressed in the tolerant genotype, (Musa 07, Musa 23), shared a high degree of identity with the amino acid sequences of the genes SOS1 and SOS2, respectively. The clone Musa 10 was highly similar to amino acid sequence of the ascorbate peroxidase gene, and Musa 26, encodes the enzyme betaine aldehyde dehydrogenase. These significant biological markers indicate that salinity tolerance in banana involves at least two simultaneous mechanisms: the activation of the SOS pathway, increasing the extrusion of Na+, and the activation of antioxidative system, increasing the synthesis of APX and betaine aldehyde dehydrogenase enzyme.