Ploidy Manipulation for Citrus Breeding, Genetics, and Genomics

Intermediate Inheritance with Disomic Tendency in Tetraploid Intergeneric Citrus × Poncirus Hybrids Enhances the Efficiency of Citrus Rootstock Breeding

“…Such value is based on dominant inheritance in full intergeneric heterozygous structures. Taking advantage of spontaneous chromosome doubling in nuclear cells, doubled diploid lines were selected for the most interesting intergeneric citrange, citrandarin and citrumelo [11,35]. To further optimize breeding using these intergeneric tetraploids as sexual parents (tetrazyg strategy; [30]), it is therefore essential to transmit a large part of the parental intergeneric heterozygosity to the progenies in order to prevent overall breakage of the favorable complex multilocus genotypic structure selected at the diploid level.…”

“…Interestingly, in citrus, polyploidy has been reported to improve adaptation to different types of stress and to promote resilience [11]. Under salinity stress or water deficit, tetraploid seedlings were shown to be more tolerant than their parental diploid counterparts [12][13][14][15][16][17].…”

Unreduced Megagametophyte Formation via Second Division Restitution Contributes to Tetraploid Production in Interploidy Crosses With 'Orah' Mandarin (Citrusreticulata)

“…In addition, the mechanisms underlying 2n gamete formation affects the breeding efficiency for particular traits and is related to both the genetic distance between centromeres and the major locus controlling the particular trait [35] . The 2n gametes produced by the SDR mechanism transmits about 40% PHR to the progeny [4] . The genotypes of progeny produced by interploidy crosses that utilize 'Orah' mandarin as the female parent may show great variation and be expected to be useful for breeding new elite cultivars.…”

“…Although self-incompatibility and parthenocarpy have led to the production of seedless citrus fruit, most citrus cultivars still produce fruits with seeds because of cross-pollination [3] . Thus, ploidy manipulation for developing triploid progeny has become an important component of citrus breeding programs because triploid seedless fruits are more competitive in the citrus fresh fruit market [4] . Diploid × tetraploid hybridization is the most common strategy used for breeding seedless citrus [5] .…”

“…The 2n gametes produced by FDR and SDR transmit about 80% and 40% PHR to the progeny, respectively. The 2n gametes derived from PMD possess full homozygosity due to an extra round of genome duplication that occurs after the formation of the haploid gametes [4] . The differences in the transmission of PHR in the different types of 2n gametes can greatly impact the gametic structures and thus the efficiency of a particular breeding strategy.…”