The citrus industry is an important source of incomes for both individual growers and producing countries. Therefore, breeding for quality especially seedlessness has a pivotal role for the market, since consumers demand seedless fruits. Recovery of triploid hybrids through ploidy manipulation is a very valuable methodology to recover seedless citrus varieties. Citrus triploid hybrids can be recovered through 2x x 2x taking advantage of the unreduced (2n) gametes formation. 2x x 4x and 4x x 2x sexual hybridizations are also widely exploited. Underlying the production mechanisms and genetic structures of diploid gametes is a key for optimizing polyploid breeding strategies. Two main mechanisms have been found in angiosperm for production of unreduced gametes: First Division Restitution (FDR) and Second Division Restitution (SDR). On the other hand, although tetraploid rootstocks display promising agronomic traits, their meiotic behavior and their segregation analysis is still mostly unknown in citrus. Disomic and tetrasomic models were defined as extreme models for tetraploid segregation, however, an intermediate inheritance model has been described for several crops. In this framework, this thesis aimed to study three main aspects: (i) the mechanisms underlying unreduced pollen gamete formation in the diploid 'CSO' tangor hybrid used as male parent in 4x x 2x triploid breeding programs, (ii) the frequencies and mechanism s involved in the unreduced 2n female gametes production for 'Eureka Frost' and 'Fino' lemon genotypes, and (iii) the interspecific recombination and the resulting diploid gamete structures of doubled-diploid 'Mexican' lime to evaluate the possibility that natural interploid hybridization maybe the origin of C. latifolia ('Tahiti' lime type) and C. aurantifolia ('Tanepao' lime type) triploid varieties. The production of 54 tetraploid hybrids from 4x x 2x sexual hybridizations allowed the analysis of the mechanisms underlying unreduced pollen gamete