COMPARATIVE ANALYSIS OF THE RESPONSE OF THREE BULGARIAN VARIETIES OF SPRAY CARNATION TO DROUGHT STRESS, INDUCED BY POLYETHYLENE GLYCOL (PEG-6000)
NADEJDA ZAPRYANOVA1*, MARIYA YOVKOVA2, IVANKA IVANOVA1, BISTRA ATANASSOVA1
1-Institute of Ornamental and Medicinal Plants – Sofia, Negovan 1222
2- Insititute of Biodiversity and Ecosystem Research, BAS, 2 Gagarin Street, 1113 Sofia, Bulgaria
*Corresponding author: nadejda_zaprianova@abv.bg
Keywords: spray carnation, polyethylene glycol (PEG), growth, relative water content (RWC%), conductivity
Abstract: The response of the in vitro cultures to induced stress enables selection of plants in early stage that are tolerant to water deficit.
The model plants were three Bulgarian cultivars of spray carnation (Dianthus caryophyllus f. spray, Hort.:‘Biliana’, ‘Ira’ and ‘Rusalka’). Polyethylene glycol (PEG-6000) in different concentrations (10%, 20%, 30% and 40%) and for different time durations (1, 3 and 6 days) was used to simulate water deficit in in vitro conditions. The response to drought stress was studied using plant growth reactions, relative water content (RWC %), and electrolyte leakage (conductivity). Results showed that the growth of explants in all three cultivars decreased proportionally to the increasing PEG concentrations. For instance, at 30% and 40% PEG the growth decrease was approximately 50% compared to the control. The simulated drought at different concentrations of PEG (10%, 20%, 30% and 40%) induced changes in cell membranes of studied plants. Higher levels of electrolyte leakage on the first day were detected in ‘Ira’ cultivar (2633±521 μS/g fresh weight at 40% PEG). As a difference in the other 2 cultivars, the highest value was measured at the 6th day of 40% PEG stress (‘Biliana’ 1864±389.2 μS/g fresh weight and ‘Rusalka’ – 1712, 8±363 μS/g fresh weight). Relative water content in plant tissues was reduced according to the effect of PEG concentrations. Lowest values of RWC% were recorded at 40% PEG, as in ‘Ira’ cultivar it was measured on the first day of the experiment (28.52±5,2%), and for ‘Biliana’ and ‘Rusalka’ – on the 6th day (respectively 36,4±6,9% and 25,1±2,1%). After the different stress periods spray carnation explants were placed on MS medium for recovery. The results showed that the plant recovery was 100% after 1 day of drought stress and rooting was observed for all variants of PEG concentrations. On the 6th day, plant explants showed good adaptive response (average of 40%) at high level PEG concentrations (30% and 40%), but explants’ rooting was detected only in cultivar Rusalka.