GROWTH INHIBITORS IN POTATO in vitro. II. ALAR AND PACLOBUTRAZOLE

Abstract

Stem segments from in vitro grown potato (Solanum tuberosum L.) seedlings clone 750658 were transferred to liquid or solid media containing either Alar (B-9) or Paclobutrazole (Bonzi) at 10, 50, 125, 250, or 500 mg L-1 (active ingredient) and autoclaved or filter-sterilized. After a four month growing period Alar, at relatively low dosages (10 to 125 mg L-1) did not affect vegetative growth in most treatments but in autoclave semi-solid media. Similar effect was observed when plantlets were grown on autoclaved liquid medium containing 10 to 125 mg L-1 Paclobutrazole. On the other hand, both chemicals induced slow growth at 250 mg L-1. Nevertheless, when plantlets were transferred to a medium without inhibitors no differences on growth were observed, except for those plants from a previous medium with 500 mg L-1 of either product. Such plants did not grow or did not survive the in vitro treatments. Adding either compound at 250 mg L-1 to a solid autoclaved medium, potato plantlets in vitro were kept for a longer period, and the inhibitory effect was not observed when transferred to a similar medium without the chemicals. Survival and tuberization in vivo were not affected either.