Bibliography

Cassava is one of the most important sources of carbohydrates for over 500 million people in the tropics and subtropics. Cassava can be cultivated under conditions considered marginal for most other staple crops and has the added advantage of being utilized as an industrial crop for producing starch and derived products. Thus, cassava appeals to resource-limited, small-scale farmers as well as commercial farming systems. Due to high levels of heterozygosity and low flowering, breeding of cassava is arduous and advances in biotechnology could complement conventional breeding programs. However, as an orphan crop, tools for biotechnology-mediated improvement of cassava are currently limited. To enhance available genomics resources for cassava, we generated and characterized an 18,166 Expressed Sequence Tag (EST) dataset enriched for drought responsive genes. This dataset contains 8,577 unigenes comprised of 3,194 clusters and 5,383 singletons. About 63% of these ESTs could be annotated, while 11% were homologous to hypothetical genes with unknown function. The remaining 26% were not significantly homologous to sequences in public databases. To increase the repertoire of markers for molecular genetic applications, we identified Simple Sequence Repeats (SSRs) from this EST resource and validated these using a diverse cassava panel. We also utilized this EST resource, as well as publicly available sequences, to develop a 60-mer oligo DNA microarray: a total of 35,785 ESTs were assembled into 5,230 contigs and 8,838 singletons and used to design an array with ~11,000 probes for transcriptome analysis. Progress in these areas will be presented.