Marker-assisted recurrent selection for drought tolerance (G7009.09/G7010.01.03)

Although cassava produces more energy per unit area compared to other crops under harsh conditions such as limited rainfall (less than 500mm per year) or extended dry seasons (5–6 months), yield potential under drought varies widely in the gene pool.

Previous work revealed certain varieties from Africa are drought-tolerant, and this germplasm is the basis of an innovative molecular-breeding scheme based on marker-assisted recurrent selection (MARS) that seeks to deploy drought-tolerant hybrids more widely in cassava gene pools of the major cassava-growing agroecologies of West Africa.

The scheme employs a two-pronged approach: first, a drought tolerant genotype identified using phenotypic information will be used in crosses with a commonly grown elite lines, and the progeny used for QTL mapping. Secondly, marker-assisted breeding through MARS will be employed to improve the efficiency of producing elite germplasm with exceptional performance under drought by identifying useful allele (ie, quantitative trait loci or QTL) combinations and pyramiding (and fixing) multiple sources of genes for drought tolerance into a set of new progenitors.

Genotypic information will be generated by a high-throughput single nucleotide polymorphism (SNP) marker genotyping platform based on SNP marker resources currently being developed.

Objectives

1. To develop mapping populations
2. To identify QTLs associated with drought and yield performance
3. To recombine useful QTLs (genes) through MARS
4. To identify useful allele combinations for selection of elite drought-tolerant genotypes in MARS breeding schemes
5. To develop a new generation of top-performing and drought-tolerant elite lines