In vitro microtuber production and dormancy as affected by some cultural factors

Scarcity of planting materials, pest and diseases are major constraints to yam production. The tissue culture techniques, meristem culture combined with heat therapy has been used to produce high yielding virus-tested plantlets of root crops, which are later multiplied through micropropagation. This procedure, however has low regedaration and multiplication rates in yam. We investigated effects of different plant growth regulators on rate of growth of yam plantlets when applied at different growth phases. Three concentrations each of uniconazole-p (UP), gibberellic acid (GA3), jasmonic acid(JA) and naphthalene acetic (NAA) acids were applied at single node and primary nodal complex (PNC) formation phases in a split-plot design using two genotypes each of white and water yam. Number of nodes per plantlet was recorded after 16 weeks. Results showed that number of new nodes varied significantly with genotype by growth phase interaction and the main effect of PGRs. After 16 weeks, the control, 1.7 μM UP and 0.03 μM JA showed highest means of 7, 9 and 8 nodes per plantlet respectively compared to 2-3 nodes in the GA treatments. We demonstrated that 4900, 8100 and 6400 plantlets could be obtained in one year using 100 nodes by sub-culturing them four times. Addition of PGRs at PNC doubled the number of nodes per plantlet. However the effect of stage of treatment varied with genotypes. The GA and its inhibitor, UP influenced the multiplication rate of yam.

种用种苗材料匮乏、病虫害是制约山药生产的主要瓶颈。茎尖培养结合热处理脱毒的组织培养技术，已被用于培育高产脱毒块根作物组培苗，后续通过微型繁殖扩大种苗种群。然而该技术应用于山药时，再生效率与繁殖倍率均较低。本研究探究了不同植物生长调节剂在不同生长阶段施加后，对山药组培苗生长速率的影响。试验采用裂区设计，以白山药（white yam）与大薯（water yam）各2个基因型为供试材料，分别在单节段及初生节复合体（PNC）形成阶段，施加3种浓度的烯效唑-p（UP）、赤霉素（GA3）、茉莉酸（JA）与萘乙酸（NAA）。于接种16周后统计每株组培苗的节数。结果显示，新生节数在基因型与生长阶段的交互作用，以及植物生长调节剂的主效应下均存在显著差异。接种16周后，对照组、1.7 μM烯效唑-p组与0.03 μM茉莉酸组的节数均值最高，分别为每株苗7节、9节与8节，而赤霉素处理组的节数仅为2-3节。本研究证实，以100个节段为起始材料，经4次继代培养后，一年内可获得4900、8100与6400株组培苗。在初生节复合体形成阶段添加植物生长调节剂，可使每株组培苗的节数翻倍。不过施加阶段的效应因供试基因型不同而存在差异。赤霉素及其抑制剂烯效唑-p对山药的繁殖倍率具有显著调控作用。