2019 ASHS Annual Conference

UCB-1 is a hybrid pistachio rootstock (P. atlantica x P. integerrima) that is commonly used in commercial Pistachio production. Typically, growers use seedling UCB-1 rootstock; however, many orchards are grafted onto clonal UCB-1. It is wise replace these clones regularly because somaclonal variation may increase over time with micropropagated UCB-1 clones. Field-grown UCB-1 trees contain endophytes, therefore, new seeds must be introduced into sterile culture to produce aseptic clones. This study was to quantify the in vitro performance of 119 UCB-1 clones. Seeds were removed from the pericarp, surface disinfested in NaDCC, then placed on DKW media modified with 5µM BA and 80µM FeNaEDDHA with 30g of Sucrose and 6g of A111 agar. Data were collected every 4 weeks at transfer on shoot number and length, and callus volume on each of the 4 shoot reps/clone. At transfer, shoots were excised to reduce each culture vessel to a single shoot. There was substantial variation for in vitro growth among the seedling lines. Most clonal lines (70/120) elongated a single shoot; however, 2 clones produced at least two shoots (one primary and one axillary shoot) each month, which doubles the production rate of most clones. Likewise, most shoots were shorter than 2 cm tall after each month in vitro; however, 8 clones were ≥ 2 cm tall and 1 clone consistently grew to be over 3 cm tall at the end of each month. Ability to micropropagate efficiently, as seen with some seedling clones, is important for efficient commercial micropropagation.