Factors affecting the in-vitro establishment of Jamaican yams (Dioscorea spp) from nodal pieces

Factors such as inorganic ammonium, growth regulator supplements, propagule type and subculture period affecting the in-vitro establishment of Dioscorea cayenensis and D trifida have been examined. The results indicate that for D cayenensis, transfer of whole plantlets to fresh initiation media prior to cutting into nodal segments and transfer to establishment media was beneficial. Addition of 800 mg litre^?1 NH₄NO₃ to basal medium (BM) containing 0.5 mg litre^?1benzylamino purine (BAP) caused a significant improvement in nodal numbers and resulted ir. 11.8 propagules per original explant after 8 weeks or 184.1 propagules after 16 weeks in-vitro. Rapid establishment of D trifida cv Short Neck Yampie depended on the original explant source. Explants obtained from small tuber vines grew faster on establishment than those obtained from leafy cuttings. Initiation on BM supplemented with 0.5 mg litre^?1 kinetin (BM0.5K) and establishment on BM supplemented with 0.5 mg litre^?1 BAP (BM0.5BAP) produced the optimum result for the vines obtained from small tubers (24.0 propagules after 8 weeks of culture). For explants obtained from leafy cuttings, initiation on BM0.5BAP and establishment on BM0.5K gave optimum results (15.8). Quick establishment of initiated plantlets shown by increased shoot response and high multiplication rates were achieved in this study.     

Iron,nickel, copper,zinc and cadmium content of two cultivars of white yam (Dioscorea rotundata) and their source soils

The determination by atomic absorption spectroscopy of the iron, nickel, copper, zinc and cadmium content of two cultivars of white yam (Dioscorea rotundata Pair) and their source soil from three farms, and also of random samples of the cultivars from five geographical areas in Kaduna and Plateau states of Nigeria, is reported. The analyses show all the metals except Fe to be in trace amounts in the tissues of both cultivars; the barks contain two to four times more. The iron content was found to be about 20 times higher in the bark than in the tissue. Less than 0.7% of the metals present in the soil could be extracted with NH₄NO₃ solution. Yam bark, which contains reasonable amounts of the above metals, could be useful as cattle feed. Yam tissue, having a high content of Zn compared with Cd, could be recommended for the diet of hypertensive patients.     

Effects of growth hormones and maturity of the fruits on the callus culture of guava (Psidium guajava) fruits using response surface methodology

Guava, a tropical fruit, is valued for its aroma and is used in many fruit products. Earlier work from this laboratory has shown that the expression of the flavour as a secondary metabolite through tissue culture in vitro is possible. In the present study an attempt has been made to maximise the callus culture growth through optimisation of the hormonal combinations of indole acetic acid (IAA), 2,4-dichlorophenoxy acetic acid (2,4D) and kinetin (Kn). The effect of using fruits of different maturity was also assessed. The study of the complex interactions of the growth hormones and the identifications of the optimal hormonal levels have been carried out using appropriate design of experiments which are specially framed for such purposes. Simplex optimisation techniques were used to obtain the optimum levels of these hormones for highest relative growth in the experimental region. The results indicate that callus culturing with fruits before reaching climacteric with MS medium supplemented with 0.01 mg litre^?1 of IAA and 2,4D and 2.87 mg litre^?1 of Kn results in a high relative growth of 8.97 for the callus.