Micropropagation of almond cultivars Nonpareil and Ne Plus Ultra and the hybrid rootstock Titan×Nemaguard

Abstract

Shoot multiplication was successfully achieved from two paper-shell almond cultivars (Nonpareil 15-1 and Ne Plus Ultra) and an almond/peach hybrid rootstock (Titan×Nemaguard) by culturing shoot tips, about 0.7 cm long with 3–5 leaves, on appropriate shoot multiplication media. For Nonpareil 15-1, AP medium with 0.049 μM IBA, 3 μM BAP, 0.058 M sucrose, and 0.7% agar at pH 5.7 was effective, whereas MS medium with 0.049 μM IBA, 5 μM BAP, 0.088 M sucrose, and 0.7% agar at pH 5.7 was suitable for Ne Plus Ultra. For the hybrid Titan×Nemaguard, MS medium supplemented with 10 μM BAP, 0.088 M sucrose, and 0.7% agar provided the best shoot proliferation. Shoots of the rootstock, about 2 cm long, were rooted after one week in the dark and 2 weeks in the light on half strength MS medium supplemented with 2.4 μM IBA, 0.088 M sucrose and 0.7% agar at pH 5.7, with 88.0% rooting efficiency. When almond scions, about 1.5 cm long, were micrografted on rootstock stems and cultured on rooting medium, the survival was 50 and 65% for Nonpareil 15-1 and Ne Plus Ultra, respectively. Rooted rootstocks and rooted micrografted plantlets were successfully acclimatised and transferred to potting mix with 92% survival.