EVALUATION OF DROUGHT TOLERANCE IN ALFALFA (Medicago sativa) GENOTYPES IN THE CONDITIONS OF OSMOTIC STRESS

Abstract

The aim of the study was to evaluate alfalfa material on drought tolerance to distinguish the genotypes, which are resistant to water deficit at early stages of growth. The study was carried out during 2016-2018 in laboratory conditions at the Institute of Irrigated Agriculture of NAAS (Ukraine) using alfalfa seeds of different genotypes were subjected to germination in sucrose osmotic solutions with a pressure of 0.3, 0.5, 0.7 MPa within 7 days in the thermostat at the temperature 20 ± 2ºC. The control variant - purified water. The highest germination rate of alfalfa seeds was observed in the purified water - 82.0-96.1%. The increase of osmotic pressure in sucrose solutions decreased germination rate of seeds. Root length and hypocotyl length reached the highest values in the purified water – 24.1-33.9 and 26.1-34.1 mm, respectively. Sucrose osmotic solution with the pressure of 3.04 bar oppressed the growth of root length and hypocotyl length, which at this variant reached 11.4-19.9 and 13.8-21.9 mm, respectively. Besides, different alfalfa genotypes showed different reaction to the osmotic stress. The highest values of vegetation growth intensity (VI) in the osmotic solution with the pressure of 0.3 MPa were recorded for genotypes MgP and Unitro - 31.7 and 34.1, respectively. The values of the index at 0.5 MPa decreased in the genotypes to 19.4 and 17.6, respectively. Particular attention should be paid to the genotypes Kazachka No.2 and Pr, which are characterized with a gradual decrease in VI with the increase of osmotic pressure from 0.3 MPa to 0.7 MPa in the solution: 20.3, 13.1, 10.5 and 25.1, 19.9, 7.3, respectively. The genotypes Kazachka No.2, Pr, Unitro had the best indices of germination rate, root, and hypocotyl length, VI values, and are recommended as the most prospective in alfalfa breeding for drought tolerance.