Articles
Identification of C. glauca domestication QTLs in the genome of a cultivated mandarin
Article number
1448_5
Pages
45 – 54
Language
English
Abstract
Complete resistance to Huanglongbing disease is rare but has recently been identified among Oceanian citrus species, notably C. glauca. Whilst this species has long been of interest to plant breeders because of many other useful traits, persistent efforts to cross it with Asian cultivated species has resulted in few surviving hybrids.
We partially overcame this barrier and produced a large C. glauca × mandarin population that subsequently showed strong segregation for vigour/field-survival.
Genotype-by-sequencing (GBS) data from this population was used to produce genetic maps of the two parents and to search for QTLs associated with vigour variability.
GBS libraries of 184 hybrids and their parents were prepared with Apek1 and pair-end sequenced.
Nine linkage groups were defined for both maps.
The C. glauca and mandarin maps include 1846 and 1411 SNPs and encompass 853 and 1101 cM, respectively.
They are highly syntenic and collinear.
Two vigour traits (trunk diameter and plant height) were assessed at two development stages.
The association analysis provided very similar results for all four stages-traits combinations, identifying two QTLs on chromosomes 3 (QTL3.1 and QTL3.2, same haplotype) and one on chromosome 7 (QTL7.1) of the mandarin genome and none on the C. glauca genome.
Remarkably, the QTL with the strongest effect on vigour (QTL3.1) is located very close to the Alternaria brown spot (ABS) susceptibility gene, in the same haplotype.
Indeed, the linkage-drag between these traits is so high that culling for ABS susceptibility during the nursery phase would have removed all hybrids capable of normal growth under field conditions.
The discovery of these C. glauca domestication QTLs in mandarin should prove useful in choosing parents, deferring ABS culling to subsequent generations, and improving the efficiency of introgressing useful genes from C. glauca into domesticated citrus in the battle against Huanglongbing.
We partially overcame this barrier and produced a large C. glauca × mandarin population that subsequently showed strong segregation for vigour/field-survival.
Genotype-by-sequencing (GBS) data from this population was used to produce genetic maps of the two parents and to search for QTLs associated with vigour variability.
GBS libraries of 184 hybrids and their parents were prepared with Apek1 and pair-end sequenced.
Nine linkage groups were defined for both maps.
The C. glauca and mandarin maps include 1846 and 1411 SNPs and encompass 853 and 1101 cM, respectively.
They are highly syntenic and collinear.
Two vigour traits (trunk diameter and plant height) were assessed at two development stages.
The association analysis provided very similar results for all four stages-traits combinations, identifying two QTLs on chromosomes 3 (QTL3.1 and QTL3.2, same haplotype) and one on chromosome 7 (QTL7.1) of the mandarin genome and none on the C. glauca genome.
Remarkably, the QTL with the strongest effect on vigour (QTL3.1) is located very close to the Alternaria brown spot (ABS) susceptibility gene, in the same haplotype.
Indeed, the linkage-drag between these traits is so high that culling for ABS susceptibility during the nursery phase would have removed all hybrids capable of normal growth under field conditions.
The discovery of these C. glauca domestication QTLs in mandarin should prove useful in choosing parents, deferring ABS culling to subsequent generations, and improving the efficiency of introgressing useful genes from C. glauca into domesticated citrus in the battle against Huanglongbing.
Publication
Authors
M.W. Smith, M. Miranda, D.L. Gultzow, M. Reid, J. Huie, P. Mournet, P. Ollitrault
Keywords
Citrus, Citrus glauca, HLB, interspecific hybrid, vigour, disease resistance, GBS, SNPs, genetic mapping, genetic association, linkage-drag
Groups involved
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