Proceedings of the XLVI Italian Society of Agricultural Genetics - SIGA Annual Congress

Giardini Naxos, Italy - 18/21 September, 2002

ISBN 88-900622-3-1

Poster Abstract - 4.24

FINE MAPPING OF THE BARLEY LEAF STRIPE RESISTANCE GENE RDG2A

GOVONI C.*, DALLAGLIO E.*, FACCINI N.*, HAEGI A.**, DELOGU G.*, VALE’ G.*

*) Experimental Institute for Cereal Research, I-29017 Fiorenzuola d’Arda (PC), Italy

**) Plant Pathology Research Institute, I-00156 Roma, Italy

barley, leaf stripe, fine mapping, synteny

A barley gene conferring resistance to the leaf stripe agent Pyrenophora graminea has previously been mapped on the telomeric region of the chromosome 1 (homeologous group 7H). This resistance gene, named as Rdg2a, confers resistance towards all the isolates of the pathogen tested with the exclusion of one isolate.

As a first step towards the map-based cloning of the gene, we have performed the fine mapping of Rdg2a. For this pourpose two molecular markers (ABG704 and Q9-700, two CAPS markers) which define an interval of about 8,5 cM, a chromosomal region where Rdg2a is included, have been used to screen an F2 population of 1400 plants (2800 gametes) segregating for resistance. A total of 109 recombinants between the two molecular markers have been identified; these recombinants thus represent our high resolution mapping population.

The phenotype at the resistance gene locus has then been verified by artificial inoculation of seeds of the F3 progenies obtained from the selfing of the F2 recombinant plants.

To saturate the Rdg2a chromosomal region with molecular markers, two approaches have substantially been used: 1) microsatellites and PCR-based markers derived from RFLP previously positionated in this region have been tested for polymorphisms between the resistant and susceptible parent and then mapped in the Rdg2a mapping population; 2) by exploiting the syntenic relationships between the telomeric regions of barley chromosome 7H and rice chromosome 6, rice ESTs and barley ESTs homologs to rice ESTs mapped to the telomeric region of the rice chromosome 6, have been used to generate PCR-based markers or RFLP markers and then mapped in the Rdg2a mapping population.

By using these approaches, molecular markers thighly linked to Rdg2a have been identified.