Single nucleotide polymorphisms from Theobroma cacao expressed sequence tags associated with witches' broom disease in cacao

In order to increase the efficiency of cacao tree resistance to witches¿ broom disease, which is caused by Moniliophthora perniciosa (Tricholomataceae), we looked for molecular markers that could help in the selection of resistant cacao genotypes. Among the different markers useful for developing marker-assisted selection, single nucleotide polymorphisms (SNPs) constitute the most common type of sequence difference between alleles and can be easily detected by in silico analysis from expressed sequence tag libraries. We report the first detection and analysis of SNPs from cacao-M. perniciosa interaction expressed sequence tags, using bioinformatics. Selection based on analysis of these SNPs should be useful for developing cacao varieties resistant to this devastating disease. (Résumé d'auteur

A protocol for large scale genomic DNA isolation for cacao genetics analysis

Advances in DNA technology, such as marker assisted selection, detection of quantitative trait loci and genomic selection also require the isolation of DNA from a large number of samples and the preservation of tissue samples for future use in cacao genome studies. The present study proposes a method for the preservation of sample tissues for DNA extraction and for manual extraction of large number of samples using spheres. The integrity and concentration of the DNA by these methods were assessed and compared with conventional method using mortar. The best parameters in order to obtain a fine powder using spheres was the use of 4 lyophilized leaf disks (50 mg), a single steel ball of 6 mm in diameter, followed by 30 s of manual maceration. The quantity of DNA obtained was four times higher than the conventional method. The purity of the DNA obtained was satisfactory and proved to be amplifiable by PCR using SSR primers. The present approach is a reliable, rapid, simple and consistent DNA isolation method for cacao, compared to the conventional methods. The protocol greatly increases the efficiency of extraction and suggests an inexpensive and practical way of DNA isolation of cacao for large scale.Keywords: DNA extraction, cacao, spheres, lyophilized