Development and Evaluation of Potato Breeding Lines with Introgressed Resistance to Columbia Root-Knot Nematode (Meloidogyne chitwoodi)

American Journal of Potato Research,  Jan/Feb 2006  by Brown, C R,  Mojtahedi, H,  James, S,  Novy, R G,  Love, S

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ABSTRACT

Columbia root-knot nematode (Meloidogyne chitwoodi) (CRN) is a serious pest of potato in the Pacific Northwest of the USA. Because this nematode can reproduce rapidly within a single growing season, small initial populations are capable of causing crop loss in the Columbia Basin of Washington or Oregon. Presently, soil fumigation is the main treatment for controlling CRN on potato. Developing potato varieties with resistance to CRN is highly desirable to reduce the cost of control and to alleviate concerns about the effects of fumigants on the environment. Resistance to CRN race 1 was found in two wild Solanum species. Resistance from S. bulbocastanum was introduced via protoplast fusion and from S. hougasii via sexual hybridization. Subsequent breeding consisted of repeated backcrossing and selection. The dominant monogenic inheritance was expressed in undiminished fashion across several backcross generations. When tested in replicated trials in three locations, selected resistant clones from the BC^sub 4^ and BC^sub 5^ of the S. bulbocastanum introgression populations had total marketable yields and yields of >113-g (4 oz) tubers as good or better than standard potato varieties tested in replicated yield trials in three locations. Percentage of tubers weighing more than 113 g in the highest yielding clones was not significantly different from commercial standards. The resistance phenotype, typified by failure of the nematode to reproduce on the root systems, was sufficiently effective to prevent economic damage in a field exposure. All CRN-resistant clones are pollen sterile. Germplasm listed is available upon request.

RESUMEN

El nematodo del nudo de Columbia (Meloidogyne chitwoodi) (CRN), es un parásite serio de la papa en la zona del Pacífico noroeste de los EUA. Poblaciones iniciales pequeñas son capaces de ocasionar la pérdida del cultive, debido a la habilidad de este nematodo a reproducirse rápidamente dentro de un mismo période de cultivo en los valles de Columbia de Washington u Oregon. Actualmente, la fumigación del suelo es el principal método de control del CRN de la papa. El desarrollo de resistencia al CRN es muy deseable para reducir los costos de control y la preocupación que se tiene de los fumigantes sobre el medio ambiente. Se encontró resistencia a la traza 1 del CRN en dos especies silvestres de Solarium spp. La resistencia de S. bulbocastanum se introdujo por fusión de protoplastos y la de S. hougasii por hibridación sexual. Las siguientes pruebas de mejoramiento consistieron en retrocruzas repetidas y selección. La herencia monogénica dominante fue expresada a lo largo de varias generaciones de retrocruza. Cuando se hicieron pruebas multiples en tres localidades, los clones resistentes seleccionados de BC^sub 4^ y BC^sub 5^ de la población de introgresión de S. bulbocastanum tuvo un rendimiento total comerciable de tubérculos por encima de los 113g (4 onzas), tan bueno o mejor que las variedades estándar de papa evaluadas en pruebas de rendimiento con repeticiones en tres localidades. El porcentaje de tubércules con pesos mayores a los 113 gramos en el clon de mayor rendimiento, no mostró diferencia significativa en comparación con los estándares comerciales. La resistencia del fenotipo, tipificado por la, falta de reproducción del nematodo en los sistemas de raíces, fue suficientemente efectiva para prevenir el daño económico en la exposición de campo. Todos los clones resistentes CRN son de polen estéril. El germoplasma incluido en la lista está disponible para quien lo solicite.

Accepted for publication 3 June 2005.

ADDITIONAL KEY WORDS: breeding, germplasm, nematode resistance, Solatium bulbocastanum, Solanum hougasii, Solarium tuberosum, Meloidogyne chitwoodi

INTRODUCTION

Columbia root-knot nematode (Meloidogyne chitwoodi, Golden et al. 1980) (CRN) is a serious pest of potato, causing galling of the tubers and blemishes in the tuber flesh. The nematode penetrates the roots, establishes a feeding site, and passes through several molts before producing an egg mass that is extruded into the soil medium. Upon eclosion, J2 larvae re-infest roots or enter tubers at 900-degree days accumulated post-planting (base temperature of 6 C) when lenticels are developed on tubers (Pinkerton et al. 1991). The nematodes mature, producing egg masses, which in turn cause visible small brown dots in the tuber flesh. Accompanying this is the formation of galls on the tuber surface. Columbia root-knot nematode can reproduce up to five reproductive cycles on potato root system in the long, warm growing season of the Columbia Basin during which invasion of bulking tubers is continuous. The most common rotation crops (e.g., wheat, corn, and carrot) are good hosts for CRN and will not depress the field population. Due to activity at lower temperatures, very small initial populations of CRN (one second-stage juvenile/250 cm^sup 3^ soil at planting) are sufficient to damage a potato crop in the Pacific Northwest of the United States (PNW) (Santo et al. 1981). Thus the only defenses against CRN are to use effective chemical fumigants, or to develop resistant potato varieties through breeding.