Horticulture, University of Wisconsin-Madison, a mentor, friend and colleague, in recognition of the enormous contributions he has made to this area and for his enthusiasm for and stimulation of others to an awareness of the importance of its application to plant improvement.Additional keywords: 2n gametes, synaptic mutants, stylar barriers, Endosperm Balance Number, EBN, interspecific hybridization, introgression, imprinting, Solarium spp. SummaryHaploidy, 2n gametes, synaptic mutants, stylar barriers, endosperm barriers. Endosperm Balance Number (EBN) and its relationship to 2n gametes, stylar barriers and disomic genetics are a part of the reproductive biology of potato. Also all are tools for isolation and preservation of a species identity. Haploidy and 2n gametes allow for interploidy gene transfer. "Parallel spindles and synaptic mutants permit the transfer of entire parental genomes intact and are powerful tools in potato breeding. Stylar barriers provide a mechanism for interspecific isolation via unilateral incompatibility. Incongruity has also been invoked. Endosperm barriers have been discussed in terms of EBN which requires a 2 maternal:l paternal ratio in the endosperm for successful seed development. Genetic models suggesting three unlinked genes in a threshold-like system and a two gene system have been proposed. A relationship may exist between EBN and stylar barriers. The use and manipulation of 2n gametes, stylar barriers and EBN have been used effectively in germplasm transfer from species to cultivated potato.

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