Polygene Mapping as a Tool to Study the Physiology of Potato Tuberization and Dormancy

American Journal of Potato Research, Jul/Aug 2004 by Ewing, E E, Simko, I, Omer, E A, Davies, P J

ABSTRACT

Efforts to breed for the ability to tuberize under long days or for the length of tuber dormancy should benefit not only from information on the location of genes associated with these traits, but also from an understanding of the hormones the genes control. Understanding the role of the respective genes is a logical step in developing the best breeding strategy, both for conventional breeding and for gene transfer using molecular techniques. Polygene mapping affords a way to achieve such understanding and is also a tool to study the physiology of potato tuberization and potato tuber dormancy. The addition of DNA markers to a plant population facilitates the mapping of polygenes that control quantitatively inherited traits segregating in the population. A quantitative trait locus denotes a region of chromosome that is linked to the marker gene and which has a significant effect on the quantitative trait under study. Our approach has been to find the quantitative trait loci associated with tuberization and tuber dormancy in a segregating diploid population, and then to map the population for quantitative trait loci associated with levels of hormones implicated in the control of these two traits. We are using a population derived from a hybrid between haploid Solanum tuberosum and S. berthaultii that was backcrossed to a different haploid S. tuberosum. We have found ten quantitative trait loci for the ability to tuberize under long days and eight quantitative trait loci for tuber dormancy. In the same population we have found one or more quantitative trait loci for polyamines, abscisic acid, tuberonic acid, tuberonic acid glucoside, zeatin riboside, and gibberellin A1. Some of the hormone quantitative trait loci have coincided with quantitative trait loci for tuberization or dormancy. Implications of such commonality are discussed, along with the usefulness and limitations of the methods.

RESUMEN

Todo lo que se haga para mejorar l a habilidad de tuberizar bajo d�as largos o para la duraci�n de la latencia deber�a servir no s�lo como informaci�n sobre la localizaci�n de los genes asociados con estos caracteres, sino tambi�n para comprender el control que ejercen los genes sobre las hormonas. El conocimiento del rol de los respectives genes es un paso l�gico para desarrollar una mejor estrategia, tanto para el mejoramiento convencional como para la transferencia de genes por medio de t�cnicas moleculares. El mapeo polig�nico proporciona una forma de desarrollar dicho conocimiento y tambi�n constituye una herramienta para estudiar la fisiolog�a de la tuberizaci�n y la latencia del tub�rculo de papa. Anadir marcadores de ADN a una poblaci�n de plantas facilita el mapeo de los poligeiies que controlan cuantitativamente los caracteres segregantes heredados en una poblaci�n. Un locus de caracteres cuantitativos se�ala una regi�n del cromosoma que est� ligada al gen marcador, el cual tiene un efecto significativo sobre el car�cter cuantitativo en estudio. Nuestro enfoque ha sido ubicar los locus de caracteres cuantitativos asociados a la tuberizaci�n y latencia del tub�rcule en una poblaci�n diploide segregante y luego hacer un mapeo de la poblaci�n para ubicar los locus de caracteres cuantitativos asociados con los niveles de hormonas implicadas en el control de estos dos caracteres. Estamos utilizando una poblaci�n derivada de un h�brido entre Solanum tuberosum haploide y S. berthaultii que fue retrocruzado a un haploide diferente de S. tuberosum. Hemos encontrado diez locus de caracteres cuantitativos para habilidad de tuberizaci�n bajo d�as largos y ocho para latencia. En la misma poblaci�n hemos encontrado uno o m�s locus de caracteres cuantitativos para poliaminas, �cido absc�sico, �cido tuber�nico, gluc�sido de �cido tuber�nico, zeatina rib�sido y giberelina A^sub 1^. Algunos de los locus para caracteres cuantitativos de hormonas coincidieron con los locus de caracteres cuantitativos para tuberizaci�n o para dormancia. Se discuten las implicancias de tales hechos comunes, to mismo que la utilidad y limitaciones de taies m�todos.

Accepted for publication 6 February 2004.

ADDITIONAL KEY WORDS: QTL, Solanum tuberosum, Solatium berthaultii, hormone, review

This paper was originally presented as part of a symposium entitled "Recent Advances in the Physiology of Tuberization and Tuber Dormancy." The symposium was held on 11 August 2003, by the Potato Association of America, in Spokane, WA.

ABBREVIATIONS: ABA, abscisic acid; QTL, quantitative trait locus; RFLP, restriction fragment length polymorphism; SAMdc, docarboxylated S-adenosylmethionine

INTRODUCTION

In recent years our principal research effort has been the study of tuberization and tuber dormancy through polygene mapping. Our aim is to use mapping as a tool to dissect the hormonal regulation of these phenomena (Davies et al. 1999a). It may be helpful to compare this approach to a much more familiar one, namely the study of qualitative traits-phenotypical changes produced by single gene mutations.