Preferential Disomic Segregation and C. micrantha/C. medica Interspecific Recombination in Tetraploid 'Giant Key' Lime; Outlook for Triploid Lime Breeding

Dalel Ahmed (1) , Franck Curk (1) , Jean Charles Evrard (2, 3) , Yann Froelicher (2, 3) , Patrick Ollitrault (2, 3)

1 AGAP-Corse - Amélioration Génétique et Adaptation des Plantes méditerranéennes et Tropicales Corse - Antenne Corse
2 UMR AGAP - Amélioration génétique et adaptation des plantes méditerranéennes et tropicales
3 Cirad-BIOS - Département Systèmes Biologiques

The triploid 'Tahiti' lime (C. x latifolia(Yu. Tanaka) Tanaka) naturally originated from a merger between a haploid ovule of lemon (C. x limon(L.) Burm) and a diploid pollen from a 'Mexican' lime (C. x aurantiifolia(Christm.) Swing). The very limited natural inter-varietal diversity and gametic sterility ofC. latifoliarequires a phylogenomic based reconstruction breeding strategy to insure its diversification. We developed a strategy based on interploid hybridization between diploid lemon and the doubled diploid 'Giant Key' lime. This lime is a doubled diploid of 'Mexican' lime, itself a natural interspecific F1 hybrid betweenC. medicaL. andC. micranthaWester. For an optimized breeding program, we analyzed the meiotic behavior of the allotetraploid lime, the genetic structure of its diploid gametes, the interspecific recombination betweenC. medicaandC. micrantha, and constructed its genetic map. A population of 272 triploid hybrids was generated using 'Giant Key' lime as pollinator. One hundred fifty-eight SNPs diagnostic ofC. micrantha,regularly distributed throughout the citrus genome were successfully developed and applied. The genetic structure of the diploid gametes was examined based onC. micranthadoses along the genome. The diploid gametes transmitted in average 91.17% of the parental interspecificC. medica/C. micranthaheterozygosity. Three chromosomes (2, 8, and 9) showed disomic segregation with high preferential pairing values, while the remaining chromosomes showed an intermediate inheritance with a preferential disomic trend. A total of 131 SNPs were assigned to nine linkage groups to construct the genetic map. It spanned 272.8 cM with a low average recombination rate (0.99 cM Mb(-1)) and high synteny and colinearity with the reference clementine genome. Our results confirmed that an efficient reconstruction breeding strategy for 'Tahiti' lime is possible, based on interploid hybridization using a doubled diploid ofC. aurantiifolia. The tetraploid parent should be selected for favorable agronomic traits and its genetic value should be efficiently inherited by the progeny thanks to transmission of the high level of parental heterozygosity. However, it would require developing numerous progeny to overcome the linkage drag caused by the limited interspecific recombination associated with the predominant disomic inheritance.

Mots clés: polyploid; C. aurantiifolia; C. latifolia; meiosis; inheritance; crossing over; KASPar genotyping; single nucleotide polymorphism

Domaines: Reproduction sexuée; Amélioration des plantes; Génétique des plantes; Agronomie

Dalel Ahmed, Franck Curk, Jean Charles Evrard, Yann Froelicher, Patrick Ollitrault. Preferential Disomic Segregation and C. micrantha/C. medica Interspecific Recombination in Tetraploid 'Giant Key' Lime; Outlook for Triploid Lime Breeding. Frontiers in Plant Science, 2020, 11, pp.939. ⟨10.3389/fpls.2020.00939⟩. ⟨hal-02880427⟩