The role of supporting substrates in ex vitro acclimatization and growth of tissue cultured cassava plantlets

摘要

Tissue-cultured cassava plantlets were acclimatized on three different supporting substrates (agar matrix, river sand/sawdust and peat pellet/vermiculite) to determine their effect on growth and development of the plantlets. The in vitro-raised cassava roots were carefully washed with distilled water before planting with care onto sterile substrates in a humidity tent. To lower the relative humidity in the tent, holes were created on the sides of the tent starting from the third day to the fifth day in a stepwise fashion. Gradual increase in growth were observed after transfer to humidity tent for 2 weeks followed by accelerated growth between 4 to 6 weeks with values (13.22, 22.42 cm, 12.93 and 24.96 cm) for number of leaves and shoot heights on the supporting substrates (river sand/sawdust and peat pellet/vermiculite), respectively, compared to 10.43 (number of leaves) and 16.35 cm (shoot heights) produced on agar matrix. The most significant feature was the development of a dense mass of roots in both river sand/sawdust and peat pellet/vermiculite substrates suggesting that the porosity of these supporting substrates enhanced rooting and growth of these plantlets. The significance of the supporting substrates during acclimatization and their effects on the plantlets survival as well as the overall plant performance and environmental conditions during acclimatization of the TMS 98/0505 cassava variety are also discussed.