Evaluation of different levels of Sucrose, BAP and Photoperiod regimes for In-vitro Microtuber Production of Potato (Solanum tuberosum L.)

Abstract

Single-node stem cuttings of potato cv. “Desiree” were cultured on a multiplication medium^ containing MS basal elements supplemented with 0.5 mg X BAP, 0.01 mg X NAA and 0.4 mg X GAj for maintaining stock plantlets. The cultures were exposed to 25 ± 2°C temperature and 16/8 hrs. photoperiod with 75% relative humidity in a growth chamber. Six week-old plantlets from mother stock were treated with 10 ml MS liquid medium supplemented with four different levels of sucrose (100, 120, 140, 160 g X1) and four different levels of BAP (0, 2, 4, 6 mg X') in all possible combinations to promote microtuberization (Experiment 1). The cultures were maintained at 15±2°C temperature and 0/24 hrs photoperiod (total darkness). The treatment combination of 140 g X1 sucrose and 6 mg X1 BAP gave the highest micro tuber fresh weight (277.8 ±179.4 mg), highest micro tuber dry weight (58.4 ±33.4 mg), highest starch assimilation capacity of explant (605.8 ± 353.3 mg), highest cross sectional tuber area (66.7 ±29.1 mm2), maximum number of micro tubers per plantlet (3.32 ± 0.12) and the highest number of eyes per micro tuber (4.79 ± 0.06). The second experiment was designed to evaluate the effect of two different sucrose levels (120, 140 g X1) and three photoperiod regimes (0/24, 8/16, 16/8 hrs. light/dark) on microtuberization of potato. As in experiment 1 stock plantlets were maintained at same culture conditions and 10 ml of prepared two sucrose solutions were poured into six- weeks- old plantlets in all possible combinations to promote microtuberization. Growth regulators were not used in this MS liquid medium. The cultures were maintained at 15 ± 2 °C temperature. According to the results, most suitable treatment combination was 140 g X1 sucrose and 8/16 hrs photoperiod, which produced micro tubers with highest fresh weight (469.1 ±443.3 mg), highest dry weight (114.7 ± 113.8 mg), highest starch assimilation capacity per micro tuber (469.1 ± 443.3 mg), highest cross sectional tuber area (97.1 ± 63. 5 mm) and the highest number of eyes per micro tuber (16.1 ± 0.3). In conclusion, these results could be employed to adopt most optimum sucrose, BAP levels and photoperiod regime for effective micro tuber production of potato (cv. Desiree) based on the MS basal solution