Shoot and plantlet regeneration from meristems of Dioscorea rotundata Poir and Dioscorea alata L.

In vitro culture media capable of regenerating moderate to high shoots and/or plantlets from meristems of two yam species - Dioscorea rotundata and Dioscorea alata within comparable duration of 10 weeks as commonly obtained in other monocots and root and tuber crops were investigated. The study comprised 125 phytohormone combinations investigated in three factorial experiments each consisting of an auxin (NAA) and a cytokinin (BAP or kinetin), or two cytokinins only. The frequency of direct plantlet regeneration, though significantly (P < 0.05) higher for D. alata than for D. rotundata, was low and ranged from 0 to 10% at 3 weeks after culture (WAC) and 0 to 35% at 8 WAC. At 8 WAC, shoot regeneration of 42-75% was obtained in D. rotundata in MS medium supplemented with 0.1 M NAA + 0.20 M BAP, and shoot + plantlet regeneration of 60-82% obtained in media containing 0.05 M + 0.20 M BAP or 0.46 M BAP + 0.50 M kinetin in D. alata. Both shoot induction and plantlet regeneration were species-dependent. Induced shoots were successfully rooted in MS medium within 3 to 4 weeks, bringing time taken for plantlet regeneration to 11 to 12 weeks. Regenerants were morphologically similar to the mother plants. Results of the present study will facilitate regeneration of plantlets via meristem in D. rotundata and D. alata

Stable gene transformation in cowpea (Vigna unguiculata L. Walp.) using particle gun method

We investigated the possibility of transforming and obtaining transgenic cowpea (Vigna unguiculata L Walp) plants using the particle bombardment process. Meristematic explants that could give rise to whole fertile plants were used in transformation experiments with reporter and selectable marker genes driven by a 35S CaMV promoter. Conditions for optimal delivery of DNA to explants were established based on transient gus expression assays two days after bombardment. The size of microcarriers, microflight distance and helium pressure significantly affected transient expression of reporter genes. A total of 1692 explants were bombarded with DNA-coated particles and placed on 3 mg/l bialaphos selective medium. Only 12 regenerated shoots produced seeds eventually, and all were Gus negative even though 7 gave positive PCR signals with the bar primer. Eight out of 1400 seeds from To plants were GUS positive. DNA from eight of the GUS positive seedlings were amplified with both the gus and bar primers in PCR analysis but only two gave a positive Southern signal. Only two of the 3557 T2 seedlings obtained were GUS positive. However, 3 seedlings survived Basta spray. The two GUS positive and 3 Basta surviving seedlings gave positive Southern hybridisation signals. Twelve T3 seedlings from these were GUS positive and also gave positive Southern hybridisation signals. The positive reaction of T1, T2 and T3 seedlings under Southern analysis confirms the stable integration of introduced genes and the transfer of such genes to progenies. However, the level of expression of introduced genes in cowpea cells is very low and this accounted for the high mortality rate of progenies under Basta spray

Cloning and sequence analysis of the nucleotide-binding domain of an α-glucan, water dikinase gene from cassava (Manihot esculenta Crantz)

A

Effect of cultivar and explants type on tissue culture regeneration of three Nigerian cultivars of tomatoes (Solanum lycopersicon)

&lt;p&gt;In order to assess the suitable explant(s) for &lt;em&gt;in-vitro&lt;/em&gt; regeneration of three local cultivars of Nigerian tomatoes, Ibadan local (IbL), Ife and JM94/46, cotyledon, hypocotyls and radicle explants were cultured in shoot regeneration medium consisting of&lt;strong&gt; &lt;/strong&gt;MS containing 30 g L&lt;sup&gt;-1&lt;/sup&gt; sucrose and 8 g L&lt;sup&gt;-1 &lt;/sup&gt;agar with no exogenous plant growth hormones. Forty-five of each explant type was cultured on the medium in triplicate experiments and results showed varied percentage survival and shooting for the various explants. Hypocotyl explants had the highest percentage of shooting explants at 13.3% for IbL; 6.67% for Ife and 20% in JM94/46. IbL cotyledon explants had 4.44% of shooting explants with no shoots recorded in Ife and JM94/46 cotyledon explants. IbL radicle explants had 2.22% shooting explants and no shoots recorded in Ife and JM94/46. Student Neuman Keuls (SNK) statistical analysis of cultivar-media interaction showed there was no significant difference (P &amp;gt; 0.05) among the three cultivars in number of calli and shooting calli. There was however significant difference among the cultivars in the number of shoots recorded. SNK values for explants-media interaction showed that cotyledon and radicle explants were significantly different (P &amp;lt; 0.05) from hypocotyl explants in the number of shoots produced.&lt;/p&gt;</jats:p