EFFECT OF PHYSIOLOGICAL AGE OF MOTHER TUBER AND NUMBER OF SUBCULTURESON IN-VITRO TUBERISATION OF POTATO (SOLANUM-TUBEROSUM L)

The physiological age of mother tubers (Solanum tuberosum L. cv. Kenne bec) used as a source of material influenced kinetin-induced in vitro tuberisation. Tuberisation significantly increased with physiological age. Kinetin- or ancymidol-induced tuberisation, plantlet and microtub er dry weight decreased with increasing number of subcultures. Single- node segments obtained from tubers stored for more than 9.5 months at 4 degrees C showed increased kinetin-induced tuberisation rates and ea rlier tuberisation than those obtained from younger tubers. For any ph ysiological age, material may be safely multiplied using node propagat ion until the third subculture and bioassayed for tuberisation without variation in the response.