title: Genetically based location from triploid populations and gene ontology of a 3.3-mb genome region linked to Alternaria brown spot resistance in citrus reveal clusters of resistance genes.
abstract: Genetic analysis of phenotypical traits and marker-trait association in polyploid species is generally considered as a challenge. In the present work, different approaches were combined taking advantage of the particular genetic structures of 2n gametes resulting from second division restitution (SDR) to map a genome region linked to Alternaria brown spot (ABS) resistance in triploid citrus progeny. ABS in citrus is a serious disease caused by the tangerine pathotype of the fungus Alternaria alternata. This pathogen produces ACT-toxin, which induces necrotic lesions on fruit and young leaves, defoliation and fruit drop in susceptible genotypes. It is a strong concern for triploid breeding programs aiming to produce seedless mandarin cultivars. The monolocus dominant inheritance of susceptibility, proposed on the basis of diploid population studies, was corroborated in triploid progeny. Bulk segregant analysis coupled with genome scan using a large set of genetically mapped SNP markers and targeted genetic mapping by half tetrad analysis, using SSR and SNP markers, allowed locating a 3.3 Mb genomic region linked to ABS resistance near the centromere of chromosome III. Clusters of resistance genes were identified by gene ontology analysis of this genomic region. Some of these genes are good candidates to control the dominant susceptibility to the ACT-toxin. SSR and SNP markers were developed for efficient early marker-assisted selection of ABS resistant hybrids.
authors.affiliation: Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias. Moncada, Valencia, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Cuenca
authors.forename: Pablo
authors.initials: P
authors.lastname: Aleza
authors.forename: Antonio
authors.initials: A
authors.lastname: Vicent
authors.forename: Dominique
authors.initials: D
authors.lastname: Brunel
authors.forename: Patrick
authors.initials: P
authors.lastname: Ollitrault
authors.forename: Luis
authors.initials: L
authors.lastname: Navarro
mesh_terms: D000528:Alternaria / Q000378:metabolism* / Q000502:physiology; D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics; D002957:Citrus / Q000235:genetics* / Q000382:microbiology; D003433:Crosses, Genetic; D060467:Disease Resistance / Q000235:genetics; D063990:Gene Ontology; D017343:Genes, Plant / Q000235:genetics; D005819:Genetic Markers / Q000235:genetics; D018745:Genome, Plant / Q000235:genetics*; D005838:Genotype; D054884:Host-Pathogen Interactions; D005810:Multigene Family; D009183:Mycotoxins / Q000378:metabolism; D010641:Phenotype; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D018515:Plant Leaves / Q000235:genetics / Q000382:microbiology; D020641:Polymorphism, Single Nucleotide; D011123:Polyploidy; D057885:Triploidy
chemical_list: D005819:Genetic Markers; D009183:Mycotoxins