Abstract
A number of experiments in relation to production and breaking of dormancy of potato microtubers were conducted at the tissue culture laboratory, Tuber Crops Research Centre (TCRC), Bangladesh Agricultural Research Institute (BARI) during 2000-2003. Five levels of nitrogen (30, 45, 60, 75 and 90 mM) with different levels of CCC (0, 300, 500 and 700 mg/1), coumarin (0, 30, 50 and 70 mg/1), BAP (0, 2.5, 5.0, 7.5 and 10.0 mg/t) and sucrose (4, 6, 8 10 and 12%) either singly or in combination were used for production of microtubers of potato cv. Diamant. The most effective doses of N, BAP and sucrose were tested for production of microtuber in potato cv. Dheera. Experiments were carried out to break dormancy of freshly harvested microtubers by soaking intact or slightly peeled microtubers in solutions of GA3 ( 0, 5.0, 10.0 and 15.0 mg/1 or 0, 0.1, 0.5 and 1.0 mg/l), IAA (0, 0.1, 0.5 and 1.0 mg/1) and Kinetin (0.1, 0.5, 1.0 and 2.0 mg/1 or Kinetin 0.01, 0.05 and 0.10 mg/1) for variable time (1, 5, 25 and 50 min). The intact microtubers after treatment with GA3 ( 0, 5.0, 10.0 and 15.0 mg/I) were stored under room temperature (29±3°C), controlled temperature (22±2°C ) and refrigerator's environment (6±1°C). While slightly peeled (3 x 3 sq. mm periderm) niicrotubers after treatment with GA3 ( 0, 0.1, 0.5 and 1.0 mg/1), IAA (0.1, 0.5 and 1.0 mg/1) and Kinetin (0.01, 0.05 and 0.10 mg/) or slightly peeled microtubers after treatment with the above stimulators followed by suberisation for 48 hrs were put in petriplates containing water soak ed cotton pad and stored under controlled temperature (22±2°C ). Nitrogen at 45 and 60 mM was found very effective to produce microtubers. These N levels with 300-500 mg/1 CCC or 30-50 mg/1 coumarin produced higher proportion of large (>200 mg) microtuber (>20% and >40% by number of >200 and 100-200 mg, respectively) after 105 days, while BAP at 5.0 mg/1 produced heavier microtubers within 90 days of culture period (>25% and >50% by number of >200 and 100-200 mg, respectively) though BAP of 2.5 mg/1 was also effective. The nitrogen levels at 45 and 60 mM with relatively higher dose of sucrose (10%) also produced higher microtuber yield. But nitrogen at 45 mM with 5 mg/1 BAP and 10% sucrose proved to he the best for producing microtubers with 90 days culture period. Treatment of intact microtuber with GA3 (0, 5, 10 and 15 mg/1) did not show any significant effect on dormancy breaking, while treated of slightly peeled microtuber with 0.1-1.0 mg/1 GA3 , 0.1 to 1.0 mg/1 IAA and 0.01 to 0.1 mg/lKin for 1 to 25 min showed >90% sprouting within 7 days. Ambient situation had >25% rot tubers compared to 3-5% in controlled and 1-3 % under refrigerator's environment. Mature microtubers sprouted earlier than immature ones. Direct planting of microtubers after having treated with GA3 and IAA had >90% emergence within 15 days in sand trays. The size of microtubers or of inducers used in the media did not have any distinguishable effect on sprouting. Suberisation of slightly peeled microtubers after treatment had no effect on sprouting, but was safe from rot. There was no rot of microtuber while handling aseptically.