Male and female inheritance patterns in tetraploid ‘Moncada’ mandarin

Abstract

Key message Tetraploid `Moncada´ mandarin, used as male and female in interploidy hybridizations, displays mainly tetrasomic inheritance for most LGs, with slight variations according to the direction of the crossing. Abstract Triploid-breeding programs in citrus are key tool to develop seedless cultivars. Obtaining triploid citrus hybrids may be achieved through different strategies, such as the exploitation of female unreduced gamete in crosses between diploid parents and diploid by tetraploid sexual hybridizations, in which tetraploid genotypes can be used as male or female parents. Genetic configuration of triploid populations from interploid crosses greatly depends on the chromosomic segregation mode of the tetraploid parent used. Here, we have analyzed the inheritance of the tetraploid 'Moncada' mandarin and compared the genetic structures of the resulting gametes when used as male and as female parent. The preferential chromosome pairing rate is calculated from the parental heterozygosity restitution (PHR) of codominant molecular markers, indicating the proportion between disomic and tetrasomic segregation. Tetraploid 'Moncada' both as female and male parent largely exhibited tetrasomic segregation. However, as female parent, one linkage group (LG8) showed intermediate segregation with tendency towards tetrasomic inheritance, while another linkage group (LG4) evidenced a clear intermediate segregation. On the other hand, when used as male parent two linkage groups (LG5 and LG6) showed values that fit an intermediate inheritance model with tetrasomic tendency. Significant doubled reduction (DR) rates were observed in five linkage groups as female parent, and in six linkage groups as male parent. The new knowledge generated here will serve to define crossing strategies in citrus improvement programs to efficiently obtain new varieties of interest in the global fresh consumption market.

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

“…The inheritance patterns of molecular markers are powerful tools for determining meiotic behavior in polyploid species. They have been successfully used in citrus for doubled diploids [47,57,58,87] and somatic hybrids [46,73,88]. Indeed, the genetic structure of diploid gamete populations produced by tetraploid parents and particularly parental heterozygosity restitution depends on preferential chromosome pairing and on the double reduction rate with two extreme models, disomic and tetrasomic [42,44,89].…”

“…maxima gene pool revealed preferential tetrasomic inheritance. This was the case of doubled diploids of clementine [57] and 'Moncada' mandarin [87] as well as for a somatic hybrid between 'Nova' tangelo and 'HB' pummelo [88]. Rouiss et al [47] suggested that the PP rate, and more generally meiotic behavior, is determined by the phylogenomic structure of the tetraploid parents.…”

Pollen Development and Viability in Diploid and Doubled Diploid Citrus Species

“…In the framework of our triploid breeding program, we obtained a large number of doubled diploid plants from non-apomictic genotypes using antimitotic chemicals, and it is important to point out differences in pollen performance and viability between them. For example, stable doubled diploid plants of “Chandler” pummelo and “Moncada” ( Garavello et al, 2020 ), “Temple,” and “Encore” mandarins have good pollen performance, whereas other doubled diploid mandarin varieties like “Wilking,” “Marisol,” and “Fina” clementines display less pollen performance. In other crop species like flax, sunflower, barley, and cotton ( Luckett, 1989 ; Yemets and Blume, 2008 ; Ahmadi and Ebrahimzadeh, 2020 ), it has been observed that colchicine can cause chromosome loss or rearrangement and gene mutations, which could affect the viability of pollen grains.…”

Genotyping of polyploid plants using quantitative PCR: application in the breeding of white-fleshed triploid loquats (Eriobotrya japonica)

“…There are several methods for estimating polyploid allele dose, among which KASPar technology [ 39 , 43 ] and QF-PCR [ 44 , 45 ] are widely applicable. KASPar technology is similar to TaqMan technology, and this method requires a high-density SNP database and genome-wide association analysis [ 46 ].…”

“…In the preferential pairing of homologous chromosomes, the transmission of parental heterozygosity decreases as the tetrasomy rate (τ) increases [ 80 ]. Garavello et al [ 45 ] found that the Parental heterozygosity restitution (PHR) of tetraploid ‘Moncada’ female gametes was higher and that the progenies of tetraploid female parents presented higher genotype consistency with the parent. Accurate assessment of preferential pairing and multivalent formation in tetraploids can accelerate the accumulation of rare but advantageous alleles through MAS [ 46 , 48 ].…”