The objectives of this study were to determine the viability of in vitro culture of mature avocado (Persea americana Mill.) embryos as a strategy to select rootstocks for their tolerance to excess chloride, as well as to evaluate genotypic differences between embryos of the Mexican (var. drymifolia) and West Indian (var. americana) avocado races. Mature embryos excised from seeds of the two avocado races were cultured in Murashige and Skoog medium supplemented with 2 mg·liter-1 of glycine, 10 mg·liter-1 of myo-inositol, 4 mg·liter-1 of thiamine-HCl, 30 g·liter-1 of sucrose and 7.5 g·liter-1 of agar. Furthermore salts of NaCl, CaCl2·2H2O and the mixture of NaCl + CaCl2·2H2O (ratio 1:1) in concentrations from 0.1 to 1.0 %, at 0.1 % increments, were added. Excised embryos were incubated at 27 ± 1 ºC for 21 d in darkness followed by 65 d of 18 h day and 6 h night. Percentage of germination and survival were greater for the West Indian race (24 and 11 %, respectively) than for the Mexican race (21 and 6 %, respectively). In general, water potential as well as osmotic potential were reduced as the concentration of salts increased, while the turgor potential increased. The results suggest that the avocado has some degree of osmotic adjustment.

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