Effects of Hormone Concentration Combinations on Branch Elongation and Rooting in Mature Avocado
This experiment was conducted to investigate the suitable culture conditions for the elongation of mature oil pear explants by combining cytokinin(meta-tooling,MT)at different concentrations(0.1,0.5,1.0,1.0,and 1.5 mg·L-1)and gib-berellin(GA3)at various concentrations(0.1,0.5,1.0,and 1.5 mg·L-1)to study the culture conditions suitable for the elonga-tion of mature avocado explants to establish a fast breeding technology system for root rot-resistant mature oil pear rootstocks,and at the same time,rooting media with different concentrations(0.5,1.0,1.5,2.0,2.5,and 3.0 mg·L-1)of indole-3-butyric acid(IBA)were used to determine the optimal culture conditions for the rooting of avocado explants.We investigated the most suitable culture conditions for the rooting of avocado explants.The effects of the elongation test for 30 d(D30)on the increase in plant height and stem thickness of avocado explants were in the order of MT concentration×GA3 concentration>MT con-centration>GA3 concentration,and the effects on the increase in leaf blades of D30 were in the order of MT concentration>MT concentration×GA3 concentration>GA3 concentration.The most suitable hormone concentration combinations for elongation in the tested range of this study were 2 mg·L-1 MT and 0.5-1.0 mg·L-1 GA3,and no root growth was observed in any of the tested IBA concentration ranges.Microstructural observation revealed that the stem xylem of oil pear explants treated with an MT concentration of 1 mg·L-1(with a xylem thickness of 171.6 μm)grew better than that of plants treated with an MT con-centration of 0.1 mg·L-1(with a xylem thickness of 95.3 μm),indicating that MT had a positive effect on successful domesti-cation at a later stage.The results of this study can be helpful for future fast propagation systems for mature avocado estab-lishment.