Seasonal influence on axillary bud sprouting and micropropagation of elite cultivars of mulberry

Abstract

High frequency of sprouting from axillary buds was observed during summer in all four cultivars in field and in vitro conditions. In the China White cultivar, sprouting was asynchronous and at the end of 60 days only 23.3% of the nodal cuttings established into plants in summer in field conditions. Under in vitro conditions, a high frequency of sprouting was induced in M-5 and S-36 cultivars on medium supplemented with 1.36 μM 2,4-D. In the S-13 cultivar, the axillary buds collected during summer sprouted with the same frequency of 73.3% on medium supplemented individually with 2,4-D and KN at 1.36 and 1.39 μM concentrations, respectively, whereas in the China White cultivar, a high frequency of axillary bud sprouting was induced on KN (9.29 μM) supplemented medium. Shoot multiplication was achieved in all four cultivars by culture of shoot tips on MS medium with BAP (2.22 μM). Addition of fructose instead of sucrose in the multiplication medium increased the shoot number and also the growth of the shoots was vigorous. In vitro differentiated shoots of all cultivars rooted with a high frequency on medium supplemented with 4.52 μM 2,4-D. Micropropagated plants were successfully established in soil in field conditions with a survival frequency of 85–90%.