Effects of Ammonium Nitrate and Calcium Chloride Salts on Proliferation and Improvement of In Vitro Shootlets Quality of Vigorous Pear Rootstocks

The clonal propagation of vigorous pear rootstocks is possible by micropropagation, but in this condition many of them demonstrate low proliferation rate and produce short in vitro shootlets. To improve quality of in vitro shootlets, the effects of NH4NO3 and CaCl2, were investigated in pear rootstocks, Q1 (Pyrus communis L.), P. betulifolia, Konjuni (P. communis×P. ussuriensis Rehd.) and Dargazi seedling as control on QL medium. This objective was followed by adding NH4NO3 in 6.25 (control QL medium), 12.5 and 18.75 mM, and CaCl2 in 0 (control QL medium), 0.9 and 1.8 mM and evaluation of proliferation, shootlets quality and percentage of N and Ca absorption by shootlets. P. betulifolia normally expressed high growth and low proliferation, while Q1 had moderately higher proliferation in comparison with other rootstocks. Increasing of NH4NO3 reduced the proliferation but CaCl2 increasing improved the leaf expansion. N and Ca absorption in all rootstocks were higher than threshold levels of these elements in this species and NH4NO3 addition increased N absorption for P. betulifolia, Q1, Konjuni and Dargazi seedling to 7.58, 4.31, 5.78 and 6.24%, respectively. Contrarily to N absorption, the highest Ca absorption was observed for three rootstock, P. betulifolia, Q1 and Konjuni in lowest CaCl2 concentration. The presence of highest Ca contents in the lowest NH4NO3 concentration shows the negative effects of this salt on Ca absorption in pear rootstocks.