Variations in salinity tolerance in wild pepper (Capsicum annuum L. var. glabriusculum) populations

The wild pepper (Capsicum annuum L. var. glabriusculum (Dunal) Heiser & Pickersgill) is a valuable genetic resource for agriculture and food. Around the world salinity is a significant environmental stress that limit and affect agriculture productivity. This work estimates the variation in salinity tolerance in six populations of wild pepper populations of the Northwest of Mexico at three salinity levels (without NaCl, 25 and 50 mM NaCl). The measured traits were height, stem development, foliar area, relative content of chlorophyll, dry weight of plant, root, stem, and leaves. Salinity tolerance was estimated with a stress tolerance index (STI) obtained by comparing values of traits between control treatment (without NaCl) and salinity treatments. Data were subjected to univariate and multivariate variance analysis of principal components. All measured traits were negatively and significantly affected by salinity. Univariate variance analysis and of principal components clearly differentiated the studied populations. At 50 mM NaCl, height, stem diameter, foliar area, stem and leaves dry weight correlated positively with electrical conductivity, and foliar area, relative content of chlorophyll, stem and leaves dry weight correlated with soil Na at the site of origin of the populations. Presa Oviachic showed a higher salinity tolerance in both NaCl treatments (1.17 and 0.99), followed by two more populations (Lo de Vega and Yecorato), each with each salinity treatment. Presa Oviachic presented the highest average STI in both treatments, 37.6% and 40.4% higher than Cosala and Mazocahui respectively. Root dry weight (0.427), stem diameter (0.419), leaf area (0.412), stem dry weight (0.407) and plant dry weight ( 0.345) were the most important traits in that order and Presa Oviachic was significantly superior to the rest of populations in STI at 50 mM NaCl. Plants of these populations could be a source of salinity resistance. The variation pattern observed in these traits suggests adaptation to the local edaphic conditions.