Shoot regeneration from organogenic callus of sweet cherry (Prunus avium L.)

A complete method to regenerate adventitious shoots and to produce field-ready trees from three commercial cultivars of sweet cherry (Prunus avium L.) is described. The effects of explant types, pre-treatments, basal media, and phloroglucinol on cultivars Bing, Sweetheart, and Lapins were investigated. Callus developed on four explant types: apical shoot tips isolated from orchard trees; and punctured shoot tips, stem sections, and shoot bases of in vitro shoot cultures. Callus formed on Bing (5%), Sweetheart (8%), and Lapins (20%) shoot tips from orchard trees after 4 months on Murashige and Skoog medium (MS) at half-strength with 3 μM benzylaminopurine (BA). In vitro-derived explants formed callus after 3 months on Woody Plant Medium with 3 μM BA (W3B): punctured shoot tips (Sweetheart and Lapins 67%), stem sections (Sweetheart 31%, Lapins 27%), and shoot bases (Sweetheart 10%, Lapins 17%). Pre-treatment of shoot cultures on MS with 3 μM BA and 1 mM phloroglucinol increased callus formation three-fold on shoot base explants. Callus was separated from parental explants and maintained on MS with 3 μM BA. Shooting was induced by transferring callus to W3B. At 2 weeks, shoot development approached 100%. By 4 weeks, 7–17 shoots had formed on each explant. Callus was maintained for 1.5 years with no decrease in shoot production. Shoots were grafted onto Mazzard (P. avium) rootstocks with 54% (Sweetheart), 57% (Lapins), and 21% (Bing) success after 5 weeks.