Ex Vitro Propagation of Rubber Tree (Hevea Brasiliensis) using Stem Cuttings

Stem cutting propagation preserves the genetic traits and leads to transfer of superior and genetically similar traits of parent plants to progenies. This method is also used to propagate recalcitrant, nonviable and difficult to germinateseeds. Stem cutting in tree species is used to address phenological and intraclonal problems. The use of rubber cuttings as planting material is a feasible option, worthy of investigation. There has been little or no research studies into the USAge of Hevea brasiliensis stem cuttings as an alternative vegetative propagation method for an in vivo propagation of rubber tree in Ghana. Propagation of H. brasiliensis by stem cutting techniques was used to study alternative procedures for mass production of rubber planting materials. Brown and green rubber stem cuttings of Clone I and Clone II were soaked for 6 hours in 0.0-22.5g/L Naphthalene Acetic Acid (NAA) followed by propagation in a nursery bag filled with nutrient-rich soil. Only the brown stem cuttings of H. brasiliensis survived. The percent survival, length of shoots, number of roots as well as length of roots of Clone II was significantly (

Analysis of conserved microRNAs in floral tissues of sexual and apomictic Boechera species

<p>Abstract</p> <p>Background</p> <p>Apomixis or asexual seed formation represents a potentially important agronomic trait whose introduction into crop plants could be an effective way to fix and perpetuate a desirable genotype through successive seed generations. However, the gene regulatory pathways underlying apomixis remain unknown. In particular, the potential function of microRNAs, which are known to play crucial roles in many aspects of plant growth and development, remains to be determined with regards to the switch from sexual to apomictic reproduction.</p> <p>Results</p> <p>Using bioinformatics and microarray validation procedures, 51 miRNA families conserved among angiosperms were identified in <it>Boechera</it>. Microarray assay confirmed 15 of the miRNA families that were identified by bioinformatics techniques. 30 cDNA sequences representing 26 miRNAs could fold back into stable pre-miRNAs. 19 of these pre-miRNAs had miRNAs with <it>Boechera</it>-specific nucleotide substitutions (NSs). Analysis of the Gibbs free energy (ΔG) of these pre-miRNA stem-loops with NSs showed that the <it>Boechera</it>-specific miRNA NSs significantly (p ≤ 0.05) enhance the stability of stem-loops. Furthermore, six transcription factors, the Squamosa promoter binding protein like SPL6, SPL11 and SPL15, Myb domain protein 120 (MYB120), RELATED TO AP2.7 DNA binding (RAP2.7, TOE1 RAP2.7) and TCP family transcription factor 10 (TCP10) were found to be expressed in sexual or apomictic ovules. However, only SPL11 showed differential expression with significant (p ≤ 0.05) up-regulation at the megaspore mother cell (MMC) stage of ovule development in apomictic genotypes.</p> <p>Conclusions</p> <p>This study constitutes the first extensive insight into the conservation and expression of microRNAs in <it>Boechera </it>sexual and apomictic species. The miR156/157 target squamosa promoter binding protein-like 11 (SPL11) was found differentially expressed with significant (p ≤ 0.05) up-regulation at the MMC stage of ovule development in apomictic genotypes. The results also demonstrate that nucleotide changes in mature miRNAs significantly (p ≤ 0.05) enhance the thermodynamic stability of pre-miRNA stem-loops.</p

Enhancing the potency of vegetable oils by combining with pirimiphos-methyl for protection of stored cowpea against infestation by Callosobruchus maculatus (Fab.)

The cowpea beetle Callosobruchus maculatus (Fab.) is a major insect pest of stored cowpea in Ghana. The efficacy of coconut, groundnut and soybean oils applied at 1, 2, 5 and 10 ml kg-1 and pirimiphos-methyl at 2.5, 5.0 and 10 ml active ingredient in 2 ml of water kg-1 of grain (1/16, 1/8 and 1/4 of the recommended dose) alone or in combination to adults and immature stages of C. maculatus and the persistence of the treatments in cowpea grain were evaluated in the laboratory. All the treatments caused significant mortality compared to untreated controls. Lower dosages of the oils and pirimiphos-methyl when combined were highly toxic to C. maculatus. The mixtures also completely inhibited the development of immature stages of the beetle. Only pirimiphos-methyl and the mixtures remained effective 60 days after application. Pirimiphos-methyl can be used at reduced rates if combined with lower dosages of vegetable oils to control the infestation of C. maculatus in stored cowpea. SINET: Ethiopian Journal of Science Vol. 23, No. 2 (December 2000), pp. 263-272 Key words/phrases: Callosobruchus maculatus, cowpea, mortality, pirimiphos-methyl, potenc

Genetic diversity in cocoyam as revealed by random amplified polymorphic DNA

Forty-eight accessions of cocoyam (Xanthosoma sagittifolium) were evaluated for genetic diversity using random amplified polymorphic DNA (RAPD) analysis. Out of 50 primers screened, 10 were able to amplify the genomic DNA giving reproducible amplification patterns with individual fragments that stained intensely. Two of the primers OPA-05 and OPE-09 were considered highly informative because they amplified one or more polymorphic bands that distinguished between accessions. RAPDs showed higher genetic diversity in the accessions from Kade than those from Bunso, where the nation’s germplasm is maintained. UPGMA cluster analysis of genetic similarity estimates (Jaccard’s coefficient), separated the accessions into 5 main groups, 2 of which were one member groups. The primers will be useful for further genetic analysis and provide cocoyam breeders with suitable genetic marters for the selection of parents for crop improvement and germplasm conservation. Polymorphic markers identified in the DNA fingerprinting will also be useful in the study of mutant populations, which are currently being studied in our laboratory