Abstract
Polyploid evolution is evident in several important taxonomic series of the tuber-bearing Solanums. Polyploids can result from the functioning of 2n gametes following both intra and inter-ploidy matings. The bilateral and unilateral sexual polyploidizations (BSP and USP, respectively) are greatly facilitated by the existence of genetically determined 2n gametes. Many species, in series containing polyploids, have individuals with 2n gametes. The genetic basis of 2n pollen formation has been established in Phurejahaploid Tuberosum hybrids, and the genetic basis of 2n egg formation is being investigated in these hybrids andS. chacoense. Preliminary results indicate that relatively few genes may be involved. FDR and to a lesser extent SDR 2n gametes avoid the inbreeding in the polyploid that is maximal with somatic doubling. The vigor, fertility and competitive ability of a founder polyploid are dependent on minimizing inbreeding depression. Even more important, polyploids, particularly from FDR 2n gametes, inherit the beneficial epistatic interactions of the parent(s). Genetically determined 2n gametes make systematic sexual polyploidization a recurring phenomenon in two ways. For example, initial BSP of two diploids gives rise to a tetraploid, and thereafter USP ensures continuing contact between ploidy levels resulting in unidirectional introgression. Triploids can also be involved in polyploid evolution if they produce 2n gametes by FDR. Artificial hybridizations indicate that 2n gametes, by overcoming crossing barriers between various ploidy levels, provide the opportunity for continuous gene flow.
Resumen
La evolución poliploide es evidente en diversas series taxonómicas importantes de los Solanum tuberíferos. Los poliploides pueden resultar del funcionamiento de gametos 2n como consecuencia de apareamientos intra é inter niveles de ploidía. La existencia de gametos 2n genéticamente determinados facilita grandemente la poliploidización sexual unilateral y bilateral (U.S.P. y B. S. P.), respectivamente. Muchas especies, en series que contienen poliploides tienen individuos con gametos 2n. La base genética de formación de polen 2n ha sido determinada en híbridos Phureja-tuberosum haploide y la base genética de la formación de huevos 2n está siendo investigada en dichos híbridos y enS. chacoense. Los resultados preliminares indican que relativamente pocos genes pueden estar involucrados. Los gametos 2n producidos por FDR y en menor extension SDR evitan la endocria en el poliploide mientras que es máxima con un doblamiento somático. El vigor, la fertilidad y habilidad competitiva del poliploide original dependen de la minimización de la endocría. Aún más importante, los poliploides particularmente aquellos provenientes de gametos 2n FDR, heredan las interacciones epistáticas beneficiosas del progenitor o progenitores. Los gametos 2n genéticamente determinados hacen de la poliploidización sexual sistemática, un fenómeno recurrente en dos maneras. Por ejemplo, una poliploidización sexual bilateral inicial de dos diploides dá lugar a un tetraploide, y en adelante la poliploidización sexual unilateral asegura el contacto contínuo entre niveles de ploidía dando como resultado una introgresión unidireccional. Los triploides pueden también estar involucrados en la evolución de los poliploides si es que producen gametos 2n via FDR. Las hibridizaciones artiflciales indican que los gametos 2n al superar barreras de cruzamiento entre varios niveles de ploidía, proporcionan oportunidad para un continuo flujo de genes.
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Paper No. 2065 of the Laboratory of Genetics. Research supported by The College of Agricultural and Life Sciences, a gift from Frito-Lay, Inc., and grants from NIH (GM 15422) and the International Potato Center.
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Den Nijs, T.P.M., Peloquin, S.J. Polyploid evolution via 2n gametes. American Potato Journal 54, 377–386 (1977). https://doi.org/10.1007/BF02852758
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DOI: https://doi.org/10.1007/BF02852758