Shoot location and collection time effects on meristem tip culture of some apple rootstocks

Abstract

The aim of this study was to determine the effects of explant source and collection time on meristem tip culture from M9, MM106, and MM111 clonal apple rootstocks. Meristem tips were collected on 3 different times, from the terminal and lateral shoots of 1-2 year old potted plants. After surface sterilization of the explants, the meristem tips were excised and placed in tubes containing MS (1/2xNH(4) NO(3) and K NO(3)) medium supplemented with 0.5 mg /l BAP, 0.1 mg/l GA(3) and 0.1 mg/l IBA. The multiplication medium consisted of MS, supplemented with 1 mg/l BAP, 0.5 mg/l GA(3) and 0.1 mg/l IBA. After two consecutive sub culture the shootlets were excised and transferred to the rooting medium containing MS supplemented with 0.5 mg/l IBA.

Shoot formation ratios from the meristem tips were good for the rootstocks, but the collection time and source of the meristem affected these ratios. Higher shoot formation was 95.4% for the M9 from terminal shoots collected on June the 8(th), 93.3% for the MM106 from lateral shoots and 81.2% for the MM111 from terminal shoots collected on June the 16(th). The optimum explant collection time was the time when the shoots tend to decrease their growth rate. One of the main problems during shootlet formation and multiplication steps was vitrification especially for M9 rootstock. Tissue browning in the explants immediately after establishment in the medium or during early stage of development of the shootlets was also higher especially for MM111 rootstock. General averages of the multiplication coefficients for the rootstocks were as follow: 4.16 for M9, 5.33 for MM106, and 5.74 for MM111. Rooting ability of the shootlets was higher (62.5-90.3%) for MM106, medium (53.6-66.6%) for M9, and low (12.1-40.0%) for MM111. We found that meristem tip culture are difficult with M9 and MM111 but feasible with MM106 rootstock.