Plant Biotechnology

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Influence of carbon source on in vitro tuberization and growth of white yam (Dioscorea rotundata Poir.)

The response of white yam (Dioscorea rotundata Poir.) nodal cuttings to eight different carbon sources (sucrose, glucose, mannose, maltose, galactose, fructose, lactose, and sorbitol) at two concentrations (3 and 5%) in modified Murashige and Skoog medium was investigated. The number of nodes per plant (NNP), plantlet fresh weight, number of leaves per plant (NLP), percentage tuberization, number of micro-tubers per plant (NTP), and micro-tuber weight per plant (TWP) were significantly different among the carbon sources (P < 0.01). There were no significant differences in terms of micro-tuber weight per tuber and plant dry matter content. In terms of NNP and NLP, fructose, glucose, mannose, and sucrose at 3 and 5%, and sorbitol at 5% were comparable. However, nodal cuttings were unable to produce tubers in media containing sorbitol. All the explants cultured in 5% sucrose, 5% fructose, and 3 and 5% mannose produced micro-tubers. The NTP ranged from 0.9 (3% mannose) to 1.8 (5% sucrose), while 5% glucose gave the highest TWP, followed by 5% sucrose. The best carbon sources for in vitro tuberization were sucrose and fructose

Effects of DNA extraction procedures on the characterization of a minor tuber crop 'Rizga' (Plectranthus esculentus N. BR.)

Effects of DNA extraction procedures on the characterization of a minor tuber crop 'Rizga' (Plectranthus esculentus N. Br) was demonstrated. Result indicated that evaluation of DNA extraction procedures was necessary in developing a standard protocol that would be suitable for the DNA fingerprinting of P.esculentus clones. Whereas DNA polymorphism was observed in clones under evaluation when extraction procedure Dex 1 was used, there was non observed in the case of Dex2. Furthermore, the estimation of the genetic distances and similarities between some clones of P.esculentus using RAPD profiles obtained from DEx1 procedure indicated that clones VTH and VTHc were similar with a coefficient of 0.83. Clones LK and VTJ had a coefficient of 0.67 followed by VTB and LM with a coefficient of 0.57 as also VTA and VTF with a coefficient of 0.57. Coefficients of the other clones under study are further discussed. Key Words : Characterization, RAPD, tuber, Plectranthus esculentus [Global Jnl Agric Sci Vol.1(1) 2002: 33-40

Callus initiation and regeneration in a minor tuber crop 'Rizga' (Plectranthus esculentus N. BR.)

Calli were initiated from tuber cuttings, internodes and leaf disc explants of P.esculentus. From tuber cutting, calli were formed when explants were cultured on MS basal salts supplemented with differing regimes of either 2, 4-D and NAA separately or in combination with 0.5mgl-1 BAP. Initiation of callus was best when cultures were incubated on 2, 4-D containing media. 2, 4-D at a concentration of 1mgl-1 and culture condition of total darkness/25oC gave maximum calli fresh weight of 541.5 ± 43.9mg. In the case of internodes, maximum callus (82.3 ± 18.4mg) was obtained when explants were incubated on MS medium supplemented with 50gl-1 sucrose and 1mg-1 2, 4-D. Leaf disc explants gave maximum calli fresh weights of 2,462.8 ± 279.7 and 1,688.8 ± 350.9 mg at sucrose concentration of 50 and 60gl-1, respectively. Histological assessment of calli initiated from explants cultured on MS basal salts supplemented with 50gl-1 sucrose and 1mgl-1 2, 4-D and CP -a cytokinin, suggested caulogenesis and somatic embryogenesis might have occurred on CP and 2, 4-D containing media, respectively. Key words: Callus, regeneration, tuber, Plectrantus esculentus [Global Jnl Agric Sci Vol.1(1) 2002: 55-62

A Preliminary Evaluation of Cell and Tissue Culture Methods Suitable for Screening Anthrocnose Disease Reactions in Tropical Yams.

Effect of different temperatures (15, 19, 25 and 29 °C), media type (PDA and Czapek Dox agar) and light on sporulation of a Caribbean pathovar of Colletotrichum gloe-osporioides f.sp. dioscoreae were studied. Czapek Dox agar and temperature of 25 °C were found to be best conditions for supporting growth and sporulation of this organism. Long-term fungal cultures (2 years axenic culture) did not sporulate effectively under the above conditions unless they were first brought into contact with living tissues of Dioscorea. Methods for inoculation of yams with conidiospores of C. gloeosporioides were developed at the plant, mi-croplant and cell levels. In vitro shoot culture clones showed a similar range of disease reactions to the pathovar as field-grown plants. D. alata showed marked sensitivity to the disease while D. esculenta was the most tolerant species followed by D. composita and D. cayenensis. Dioscorea protoplasts responded differently when cultured in the presence of mycelial culture filtrates and Czapek Dox liquid medium. Glasshouse-raised plants developed anthracnose symptoms only after wounding.Made available in DSpace on 2011-04-09T12:13:38Z (GMT). No. of bitstreams: 1 pab11nov93.pdf: 623310 bytes, checksum: af3820a3d7e811ab9dc40f1b0842925d (MD5) Previous issue date: 2001-08-22199

A Preliminary Evaluation of Cell and Tissue Culture Methods Suitable for Screening Anthrocnose Disease Reactions in Tropical Yams.

Effect of different temperatures (15, 19, 25 and 29 °C), media type (PDA and Czapek Dox agar) and light on sporulation of a Caribbean pathovar of Colletotrichum gloe-osporioides f.sp. dioscoreae were studied. Czapek Dox agar and temperature of 25 °C were found to be best conditions for supporting growth and sporulation of this organism. Long-term fungal cultures (2 years axenic culture) did not sporulate effectively under the above conditions unless they were first brought into contact with living tissues of Dioscorea. Methods for inoculation of yams with conidiospores of C. gloeosporioides were developed at the plant, mi-croplant and cell levels. In vitro shoot culture clones showed a similar range of disease reactions to the pathovar as field-grown plants. D. alata showed marked sensitivity to the disease while D. esculenta was the most tolerant species followed by D. composita and D. cayenensis. Dioscorea protoplasts responded differently when cultured in the presence of mycelial culture filtrates and Czapek Dox liquid medium. Glasshouse-raised plants developed anthracnose symptoms only after wounding

Endophytic Bacteria Expressing β-glucuronidase Cause False Positives in Transformation of Dioscorea Species

False positive transformants obtained during plant transformation experiments on species of the monocotyledonous genus Dioscorea (yam) are described. The false positive results were found to be due to endophytic bacteria which exist within aseptically micropropagated shoot cultures and which express -glucuronidase (GUS). The bacteria were isolated and identified as two species of Curtobacterium. The expression of GUS in these organisms was found to be induced by a variety of glucuronide substrates. The induction of GUS activity in the bacteria can be inhibited by chloramphenicol, tetracycline, ticarcillin and sodium azide. Implications of these results for use of the gus gene in plant transformation work are discussed

Stable Transformation of the Food Yam Dioscorea alata L. by Particle Bombardment

A biolistic particle gun was used to deliver genetic material into intact yam cells. Cultured suspension cells of D. alata were bombarded with microprojectiles coated with pBI221.2 DNA and histochemical assays were carried out to show transient GUS expression in bombarded cells. Stably transformed D. alata cells were recovered from cultured cells after bombardment with microprojectiles coated with pRT99gus harbouring both the nptII and uidA genes. Bombarded cells were selected on a medium containing geneticin (G418). Two months after bombardment, calli resistant to G418 were assayed for GUS expression. There was a 100% correlation between resistance to G418 and GUS expression. From these calli, four cell lines were established and GUS activity in each line was determined fluorometrically. The use of a specific GUS inhibitor showed that the GUS activity was due to the introduced uidA gene rather than to any intrinsic GUS-like activity originating from the plant. Incorporation of the introduced DNA into the plant genomic DNA was confirmed by Southern analysis