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Field performance of microtubers with or without coating was compared with that of conventional seed potatoes. Microtubers produced more tubers, but their yield on a plant basis was 79% with Superior and 55% with Dejima compared with conventional seed potatoes when grown in a green-house. The effect of coating microtubers on subsequent growth varied with the stage of tuber development. Yields per plant were compared between microtubers with their sprouts intact and those with their sprouts removed and then coated in TI-5 medium. Removal of the sprouts and the coating did not affect yield as long as microtubers were greater than 1 ㎝ in diameter. Tuber number and their weights increased when they were coated in TI-5 medium compared with those in distilled water. Microtubers coated in TI-5 medium produced more tubers per plant than conventional seed potatoes. On the other hand, conventional seed potatoes showed higher total tuber weights per plant than coated microtubers. With microtubers sprouted about 10%, field test showed that number of tubers and their weights increased when they were coated with medium compared with those in distilled water. Pretreatment of microtubers with GA₃ enhanced the coating effect further. Microtubers coated with TI-5 medium (without sucrose) in combination with GA₃ pretreatment yielded the most number of tubers with the highest tuber weight. This was followed by the coating microtubers with TI-5 medium containing 3% sucrose, non-coated, those without sucrose, and those with distilled water, in that order. No significant differences in tuber numbers and tuber weights were observed by foliar application of BAP and various concentrations of NaCl. However, the yield was the highest by a combined treatment of BAP and NaCl.
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