Approaching chickpea quantitative trait loci conditioning resistance to Ascochyta rabiei via comparative genomics

This paper reports on the strategy being used to study chickpea ( Cicer arietinum) quantitative trait loci ( QTL) conferring resistance to the necrotrophic fungal pathogen Ascochyta rabiei. The three chickpea linkage groups ( LG), harbouring six QTL conditioning resistance against A. rabiei, were compared with the most comprehensive chickpea map ( W-Ca-LG) and to the orthologous pseudochromosomes of the legume model plant Medicago truncatula. QTL1 was located in the subcentromere region of the chickpea W-Ca-LG3 ( chromosome C) and on the short arm of the M. truncatula pseudochromosome 7. QTL2 and QTL3 were located on the long arm of the W-Ca-LG8 ( chromosome H) and on the short arm of the M. truncatula pseudochromosome 5. QTL4, QTL5 and QTL6 were located in the subcentromere region of the W-Ca-LG4 ( chromosome B) and in a similar location of the M. truncatula pseudochromosome 1. To further delimit the genomic regions where the QTL were located, 25 legume expressed sequence tags ( ESTs), which were shown to be upregulated in resistant chickpea accessions challenged with A. rabiei, were selected and BLASTed against M. truncatula genome sequences using a chromosome visualisation tool. Eleven of the 25 ESTs were mapped in silico on the nine M. truncatula pseudochromosomes with 1-4 copies. The association of mapped ESTs with chickpea resistance to A. rabiei requires further characterisation.