title: Fine Mapping for Identification of Citrus Alternaria Brown Spot Candidate Resistance Genes and Development of New SNP Markers for Marker-Assisted Selection.
abstract: Alternaria brown spot (ABS) is a serious disease affecting susceptible citrus genotypes, which is a strong concern regarding citrus breeding programs. Resistance is conferred by a recessive locus (ABSr) previously located by our group within a 3.3 Mb genome region near the centromere in chromosome III. This work addresses fine-linkage mapping of this region for identifying candidate resistance genes and develops new molecular markers for ABS-resistance effective marker-assisted selection (MAS). Markers closely linked toABSrlocus were used for fine mapping using a 268-segregating diploid progeny derived from a heterozygous susceptible × resistant cross. Fine mapping limited the genomic region containing theABSrresistance gene to 366 kb, flanked by markers at 0.4 and 0.7 cM. This region contains nine genes related to pathogen resistance. Among them, eight are resistance (R) gene homologs, with two of them harboring a serine/threonine protein kinase domain. These two genes along with a gene encoding a S-adenosyl-L-methionine-dependent-methyltransferase protein, should be considered as strong candidates for ABS-resistance. Moreover, the closest SNP was genotyped in 40 citrus varieties, revealing very high association with the resistant/susceptible phenotype. This new marker is currently used in our citrus breeding program for ABS-resistant parent and cultivar selection, at diploid, triploid and tetraploid level.
authors.affiliation: Centro de Citricultura y Producción Vegetal, Instituto Valenciano de Investigaciones Agrarias Valencia, Spain.
authors.forename: Jose
authors.initials: J
authors.lastname: Cuenca
authors.affiliation: Centro de Citricultura y Producción Vegetal, Instituto Valenciano de Investigaciones Agrarias Valencia, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Aleza
authors.affiliation: Centro de Citricultura y Producción Vegetal, Instituto Valenciano de Investigaciones Agrarias Valencia, Spain.
authors.forename: Andres
authors.initials: A
authors.lastname: Garcia-Lor
authors.affiliation: CIRAD, UMR AGAP Petit-Bourg, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Ollitrault
authors.affiliation: Centro de Citricultura y Producción Vegetal, Instituto Valenciano de Investigaciones Agrarias Valencia, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Navarro
keywords: Alternaria alternata; fungal disease resistance; gene mapping; mandarin; molecular markers