A Standardized RNA Isolation Protocol for Yam (Dioscorea alata L) cDNA Library Construction

For the purpose of constructing yam cDNA libraries, attempts to isolate high quality RNA using several previously reported protocols were unsuccessful. Therefore a protocol was standardized for yam total RNA isolation by using guanidium buffer at the Department of Biology, Virginia State University. The RNA isolated using this standardized protocol was high in quality and led to successful good quality cDNA library construction and identification of functional ESTs in yam

The use of DNA markers for rapid improvement of crops in Africa

Genetic engineering and biotechnology are providing new tools for genetic improvement of food crops. Molecular DNA markers are some of these tools which can be used in various fields of plant breeding and germplasm management. For example, molecular markers have been used to confirm the identity of hybrids in breeding programmes. Another application of molecular markers is in determining phylogenetic relationships in related species. Information on phylogenetic relationships is useful in facilitating introgression of desirable traits from wild relatives to cultivated crop species. Molecular markers are also being used to construct genetic maps. A genetic map is a collection of genetic markers that have been grouped according to their linkage. Breeders can use DNA maps to carry out marker-assisted selection. This technique enables plants carrying desirable traits such as pest and disease resistance to be selected while still in the seedling stage. Ultimately, this enables the cloning of the genes to be used for crop improvement. The polymerase chain reaction (PCR) has become a popular technique for molecular genome mapping and the diagnosis of plant pathogens. The technique ensures amplification of specific DNA sequences by the use of primers and the enzyme Taq DNA polymerase. Restriction Fragment Length Polymorphisms (RFLPs), Random Amplified Polymorphic DNAs (RAPDs), microsatellites and Amplified Fragment Length Polymorphism (AFLP) are some of the most useful molecular markers for DNA fingerprinting. For viral, fungal and bacterial DNA fingerprinting and diagnosis as well as strain differentiation of rhizobia, PCR-RAPD and cDNA probes can be applied alongside with monoclonal antibodies. Key Words: Crop improvement, DNA polymorphism, marker-assisted selection (African Crop Science Journal 2000 8(1): 99-108

Ploidy level of the cultivated yams (Dioscorea cayenensis/D. rotundata complex) from Benin Republic as determined by chromosome counting and flow cytometry

The ploidy levels of ninety Guinea yam (Dioscorea cayenensis/D. rotundata complex) cultivars identified within Benin were determined by both chromosome counting from root tip cells and flow cytometry. Three different ploidy levels (4x, 6x, 8x) were detected among the samples. Eighty cultivars were tetraploid, five were hexaploid, three were octoploid and two cultivars, 'Tam-Sam' and 'Youbé' were mixoploid with both 4x and 8x ploidy levels. Chromosome counts were in agreement with data from flow cytometry that provides an easier assay for ploidy analysis. Flow cytometry was found to be a reliable tool for rapid determination of ploidy level in yam. (African Crop Science Journal 8(4) 2000: 355-364

Identification and differentiation of isolates of Colletotrichum gloeosporiodes from yam by random amplified polymorphic DNA markers

(African Crop Science Journal: 1999 7(2): 195-206