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

Abstract

the linkage drag caused by the limited interspecific recombination associated with the predominant disomic inheritance.

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

“…Among them, 192 markers were selected according to their dispersion over the genome, their location on a gene and the absence of additional polymorphism closer than 50 bases. This selection produced 82.8% (159) successful markers, i.e., similar to the 83.6% obtained by Ahmed et al [58] using the same strategy for C. micrantha DSNPs. Among the 159 efficient markers, eight displayed apparent homozygosity in some intergeneric hybrids whereas they fully distinguished Citrus from Poncirus accessions, revealing the existence of null allele in heterozygosity in some Poncirus or Citrus parents of the intergeneric hybrids.…”

“…Considering the tetrasomic parameter (τ = 1 − PP) that defines the proportion of gametes resulting from random meiotic chromosomal pairing used in several previous studies of meiotic behavior of tetraploid citrus [44,46,47,57,58,73] the probability of the three possible diploid gametes produced for a A1A1A2A2 duplex marker can be calculated using the following formulae:…”

“…With the development of next-generation sequencing, SNPs have become the most important resources for developing citrus molecular markers from transcriptomic [58,74] and genomic data [37,38,75]. An efficient SNP genotyping method was developed for scalable experiments using competitive allele amplification (KASPar© technology) [53,76].…”

“…Curk et al [39,78] developed a set of KASPar SNP markers specific to four ancestral taxa of cultivated Citrus (C. maxima, C. micrantha, C. medica, and C. reticulata). The set was expanded for C. micrantha with 158 SNPs mined from GBS data to analyze the meiotic behavior of the tetraploid 'Giant Key' lime and to establish its genetic map [58]. Before the present work, only a few P. trifoliata dSNPs have been developed to distinguish zygotic from nucellar seedlings of intergeneric rootstocks [69].…”

“…The inference of diploid gamete structure from progeny analysis requires genotyping methods that identify the allelic doses in the polyploid hybrids. Cuenca et al [53] demonstrated the efficiency of the KASPar single-nucleotide polymorphism (SNP) genotyping technique in assigning heterozygous allelic configurations within polyploid citrus populations and the method was successfully used to analyze the genetic structure and origin of 2n gametes [53][54][55][56] and to perform tetraploid meiosis analyses [46,47,57,58]. Doubled diploid lines developed from these rootstocks can be therefore considered as allotetraploids resulting from the merger of the genomes of two divergent species.…”