| Apple tree is currently the world's major cultivated fruit trees, and enjoys the largest cultivated area in China. In drought and semi-arid region of northwest China, water stress is the key factor to limit its output and quality. Drought resistance of rootstocks has a direct impact on the yield and quality of apple. So, correct choice of rootstock can enhance the resistance and adaptability of apple trees and improving the production and quality. In this study, five kinds of apple rootstocks were used as the material; we tend to research on Tissue Culture and PEG-6000 stress on the indicators of the external morphology, cell membrane, enzymatic activity of apple rootstock via plant tissue culture. According to the changes in the value of each index, we employed the drought resistance of fuzzy membership function to make comprehensive evaluation. The objective of this study is to provide efficient methods for present several common breeding stocks and provide a theoretical basis for apple rootstocks. The main results were as follows:1.For all this 5 apple rootstocks, the medium of MS+6-BA1.0mg·L-1 +NAA0.1 mg·L-1 is the best when their shoots cultivated in vitro.For M9 and M26, the optimum enrichment medium and the optimum rooting medium were MS+6-BA 1.0 mg·L-1 +IBA 0.1 mg·L-1 and 1/2MS+IBA0.3 mg·L-1 +NAA0.1 mg·L-1, respectively. The rooting rates were 70.6% and 69.6%, respectively.To Malus micromalus Mak,Malus hupenensis Rehd and M. sieversii Roem the optimum subcultured medium and the optimum rooting medium were MS+6-BA1.0 mg·L-1+IBA0.3 mg·L-1 and 1/2MS+IBA0.3 mg·L-1, respectively. All of the rooting rates were over 80%.The nursery substrate treatment with 0.5% FeSO4 made the survive rate of the root regeneration plant above 90%.2. Different concentrations of PEG-6000 stress has some restrictive effect on the height growth of tissue culture stock, with the stress concentration increased, growth of seedlings decreased. Under the same conditions, the leaves of stock suffered different hurt with the stress concentration increased. Compared with M9, M26 leaves, Malus micromalus Mak, Malus hupenensis Rehd and M. sieversii Roem leaves were damaged minorly. Meanwhile,the proliferation number of leaves of the 5 kinds of stock decreased gradually with the concentration increased .3. Under the PEG-6000 stress, the various physiological changes in leaves of trend.①.The chlorophyll content of different varieties exhibited a declining trend overall. Compared with M9, M26 and Malus micromalus Mak, the chlorophyll content of Malus hupenensis Rehd and M. sieversii Roem decreased minorly at the highest concentration of stress.②.The relative conductivity and MDA of different apple rootstocks leaves increased gradually with the concentration of PEG-6000 increased. With the concentration of PEG-6000 increased,the trend of MDA content is same between transplant apple stocks and in vitro culture.③.In the whole process of the stress, the protein content in leaves of apple rootstocks increased with the increase of stress concentration and showing an increasing trend with the stress time increased, and the protein content in leaves of apple stocks also reached a maximum. With the increase of stress concentration, the protein content in leaves of 3 kinds of transplant apple stocks shows an obvious increasing.④.SOD activity first increased and then decreased with the PEG-6000 stress concentration increased. At 20% PEG Stress, SOD have reached the maximum. The POD activity showed an increasing tend.While, both SOD and POD activity are performing for increasing tend in transplant seeding4. Through the analysis of membership function value, under PEG-6000 outdoor simulation of drought stress, the order of drought resistance of 5 apple rootstocks was M. sieversii Roem > Malus hupenensis Rehd > Malus micromalus Mak > M26> M9.The concentration of 25% PEG-6000 as suitable concentration of Apple rootstock in vitro drought resistance identification... |
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