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

The results revealed several disease resistance genes along and at the extremes of the analysed region, so the analysis was extended 1.5 Mb down from the TTC8 marker and 1.7 Mb up from the CiC3248-06 marker

José Cuenca; Pablo Aleza; Antonio Vicent; Dominique Brunel; Patrick Ollitrault; Luis Navarro

2013

Scholarcy highlights

  • Alternaria brown spot is a serious disease that induces necrotic lesions on fruit and young leaves, defoliation and fruit drop in susceptible citrus genotypes
  • Segregation of ABS resistance in various triploid progeny arising from sexual polyploidisation and interploid crosses
  • Symptoms of ABS were evaluated for all parental accessions and hybrids both from visual inspection of the trees grown at orchards and by in vitro inoculations with a conidial suspension of the pathogen
  • Total concordance between field and in vitro evaluations was observed for all evaluated populations with the exception of ‘Clemenules’ × ‘Orlando 4x’, where it was over 97%
  • The monolocus inheritance and recessivity of ABS resistance was confirmed in citrus triploid progeny, and the ABS resistance locus locus was mapped in the chromosome III genetically close to the centromere
  • Our results confirm the potential for raw location of major genes involved in phenotypic trait variability by coupling BSA strategies with genomic scanning, as previously proposed by previous research, and demonstrate that it can be successfully applied in a polyploid segregating population. This genomic region was further examined for additional SSR and single nucleotide polymorphisms markers, which were used for de novo mapping of the area by Half-Tetrad Analysis of 2n gamete inferred from triploid hybrid genotypes
  • The 39% and 19% of resistant triploid hybrids produced when crossed with resistant or heterozygous susceptible genotypes, respectively, are acceptable if combined with early selection by controlled inoculation phenotyping or marker-assisted selection

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