Plant & Animal Genome VI Conference

W82

MOLECULAR ANALYSIS OF THE CHICKPEA GENOME: MICROSATELLITES, MICROSATELLITE-BASED MARKERS, AND CANDIDATE RESISTANCE GENES

1. Plant Molecular Biology, Biocentre, University Frankfurt, Marie-Curie-Str.9, D-60439 Frankfurt, Germany
2. ICARDA, Aleppo, Syria
3. Agricultural University Faisalabad, Faisalabad, Pakistan
4. Universidad Autonoma de Mexico, Mexico D.F., Mexico
5. USDA-ARS, 303 Johnson Hall, Washington State University, Pullman, WA , 99164-6434, USA

As a result of obligatory self-pollination and thousands of years of selection the genome of chickpea (Cicer arietinum L.) has been streamlined and became extensively monotonous. Therefore, little or no genetic variability can be detected using isozymes, RFLPs or RAPDs. However, there exists an unexpected fluidity in the repetitive portion of the genome, which encompasses retroelements, clustered satellites, dispersed repeat sequences, and especially microsatellites. Microsatellites in fact are a rich source of polymorphisms, and therefore have been exploited to (1) detect genetic diversity in otherwise homogeneous chickpea materials, (2) generate more than 120 allele-specific STMS markers to screen chickpea germplasm world-wide, (3) establish a first codominant STMS marker map with landmarks covering about 600 cM of the genome. This core map is presently being extended and further supported by AFLPs to increase its density. Whereas no tight tagging of e.g. R genes has yet been possible, a candidate gene approach using degenerate primers complementary to conserved transmembrane domains and nucleotide-binding sequences (NBS), or two NBS domains of known R genes detected several distinct classes of presumptive R genes of chickpea. Attempts are presently being made to map these genes on populations segregating for R-genes for Ascochyta rabiei and Fusarium oxysporum, the most devastating fungal pathogens of chickpea.