The effects of different polyamine applications on salt stress in strawberry in in vitro conditions

In recent years, the most important environmental problem in our country and in the world is seen as climate changes. Climate changes with global warming are most damaging to agricultural production. Particularly with the loss of yield and quality in plants, plant growth is significantly affected. For these reasons, agricultural researches were carried out in recent years are mostly on the adaptation mechanisms of plants against climate changes, at the same time studies with breeding purposes are carried out to obtain plants resistant to drought and salinity. Additionally, studies are carried out on applications and cultivation techniques to increase tolerance in in vitro and in vivo studies. Strawberry is in the category of berry fruits with the highest added value in our country. Strawberry, which can be grown in the open and under cover in very large areas in our country, is also rapidly affected by climate changes and is exposed to yield loss. For this reason, studies that can be transformed into practical applications that increase tolerance to abiotic stress conditions such as drought and salinity are speeding up. In the research conducted for this purpose, the effects of different polyamine types and concentrations at different salinity levels on some morpho-physiological and biochemical features of explants were investigated in vitro culture conditions on Festival strawberry cultivar. Propagated explants in vitro conditions were at three different salinity levels (1. Control; 2. %0.4 NaCl; medium salinity; 3. %0.8 NaCl; high salinity) and cultured in five different polyamine applications (1. Control; 2. 0.5 mg/l Spermine; 3. 1.0 mg/l Spermine; 4. 0.5 mg/l Putrescine; 5. 1.0 mg/l Putrescine) in the research. In the research, at the end of each subculture, morpho-physiological observations and analyses (shoot number, shoot length, shoot proliferation rate, wilting scale, shoot fresh weight, shoot dry weight, shoot dry matter ratio, membrane damage index) and biochemical analyses (malondialdehyde) -MDA and superoxide dismutase-SOD) were performed. As a result of the research, depending on the increase in salinity concentration, the number of shoots per explant, shoot length, shoot proliferation rate and wilting scale values decreased. In addition, all tried polyamine applications did not affect statistically the shoot proliferation rate, while increasing the number of shoots per explant, shoot length and wilting scale values compared to the control. In the control (0% NaCl) salinity application, the highest shoot number and shoot length values were determined at both concentrations of spermine (0.5 mg/l and 1.0 mg/l spermine). While in medium salinity (0.4% NaCl), the highest shoot number and shoot length were determined in the application of 1.0 mg/l spermine, all polyamine types and concentrations increased shoot number and shoot length compared to the control. Similarly, while polyamine treatments increased the wilting scale values, compared to the control, it did not affect the proliferation rate. At high salinity (0.4% NaCl), the highest shoot number, shoot length and wilting scale values were determined in the application of 1.0 mg/l spermine. In addition, depending on the increase in salinity concentration, while the effect on shoot fresh and dry weights and dry matter content decreased, the membrane damage index increased. When examined in terms of polyamine applications, it was seen that the application of 1.0 mg/l spermine came to the fore considering these criteria. Also in the experiment, the highest shoot dry weight and dry matter ratio were determined in the application of 1.0 mg/l spermine in control (0% NaCl), medium salinity (0.4% NaCl) and high salinity (0.8% NaCl) applications. In addition, all polyamine applications which were tried at medium and high salinity levels decreased the membrane damage index compared to the control. In the experiment, the MDA and SOD content of the explants increased due to the increase in the in vitro salinity concentration. Polyamine applications, had significant effects on MDA content, while all tested polyamine applications decreased MDA content compared to control, SOD content was not affected. In addition, MDA content decreased compared to the control in moderate salinity (0.4% NaCl) and high salinity (0.8% NaCl) applications in the experiment. Our research findings have shown that the use of polyamines in both medium and high salinity concentrations suppresses the effect of salt damage morpho-physiologically and biochemically. In particular, the use of 1 mg/l spermine contributed to the positive development of explants under all the stress conditions.