In vitro tolerance of citrus rootstocks under saline stress

The search for citrus rootstocks that confer resistance and tolerance to biotic and abiotic factors is increasing. Among abiotic stresses, salinity is one of the main factors that significantly affect growth and development in this crop. Faced this situation, genetic improvement seeks, among other aspects, to generate rootstocks that are tolerant to salinity. In this sense, tissue culture constitutes an important tool for citrus improvement, as it helps in the pre-selection of genotypes that best express salinity tolerance. Thus, this work aimed to study the tolerance of 11 citrus rootstocks to saline stress in vitro, using different concentrations of sodium chloride (NaCl). For analysis of in vitro regeneration, 1 cm long stem apexes, originating from the in vitro cultivation of rootstocks, were introduced in basal WPM medium and supplemented with 0.64, 1.28, 1.92, 2.56 and 3.20 g L-1 of NaCl. After 120 days in a growth room, the plants were evaluated and the data were analyzed using the R statistical program. The genotypes showed different behaviors depending on the interaction between the studied factors. There was a reduction in most of the in vitro development variables of rootstocks grown in culture medium supplemented with NaCl. The 'Riverside' citrandarin genotypes, HTR 051, LRF (LCR x TR) - 005, BRS Bravo, TSK x TRBK - Colombia and BRS H Montenegro, were more tolerant to salinity, while TSKC x CTSW - 028, the mandarin 'Sunki Tropical' and BRS Santana were the most sensitive. In this study, we identified genotypes of citrus rootstocks with different levels of salinity tolerance through tissue culture, contributing to genetic improvement and enhancement of citrus production.