Am. J. Pot Res (2010) 87:492–496 DOI 10.1007/s12230-010-9151-6
Evaluation of Verticillium Wilt Resistance in Russet Norkotah and Six Strain Selections Shelley H. Jansky & J. Creighton Miller Jr.
Published online: 7 July 2010 # Potato Association of America 2010
Abstract Strain selections of Russet Norkotah have been selected for enhanced vigor and high yield. In addition, they exhibit less severe expression of disease symptoms in the presence of Verticillium dahliae, a soil-borne fungal pathogen that causes Verticillium wilt. However, this apparent resistance may be due to later maturity in the strain selections. This study was designed to compare the levels of Verticillium wilt resistance in Russet Norkotah with that of six popular strain selections. In two years, trials were carried out on a V. dahliaeinfested field and an adjacent fumigated field. Comparisons were made between Russet Norkotah and its strains for maturity, symptom expression, stem colonization, and tuber yield. Compared to Russet Norkotah, the strains were later in maturity, exhibited fewer Verticillium wilt symptoms, and were higher yielding in the absence of V. dahliae. However, they were similar to Russet Norkotah in stem colonization and yield in the presence of the pathogen. Apparent resistance in the strain selections appears to be due to immature plant physiology rather than their ability to limit fungal growth and reproduction in stem tissues. Resumen Se han seleccionado líneas de Russet Norkotah para aumento de vigor y alto rendimiento. Además, presentan
expresiones menos severas de síntomas de la enfermedad en la presencia de Verticillium dahliae, un patógeno del suelo que causa marchites por Verticillium. No obstante, esta aparente resistencia pudiera deberse a madures tardía en las selecciones. Este estudio se diseñó para comparar los niveles de resistencia a la marchites por Verticillium en Russet Norkotah con la de seis selecciones comunes. En dos años los ensayos se llevaron a cabo en un campo infestado por V. dahliae junto a un campo fumigado. Las comparaciones se hicieron entre Russet Norkotah y sus líneas para madures, expresión de síntomas, colonización de tallo y rendimiento de tubérculo. En comparación con Russet Norkotah, las líneas fueron más tardías en madures, presentaron menos síntomas de marchites por Verticillium, y fueron superiores en rendimiento en la ausencia de V. dahliae. No obstante, fueron similares a Russet Norkotah en colonización del tallo y rendimiento en presencia del patógeno. La resistencia aparente en las líneas seleccionadas parece que se debe a la fisiología de planta inmadura más que a su habilidad a limitar el crecimiento y reproducción del hongo en los tejidos del tallo. Keywords Russet Norkotah . Strain selection . Potato early dying . Verticillium wilt
Introduction S. H. Jansky (*) USDA-ARS and Department of Horticulture, University of Wisconsin-Madison, 1575 Linden Drive, Madison, WI 53706, USA e-mail:
[email protected] J. C. Miller Jr. Department of Horticultural Sciences, Texas A&M University, College Station, TX, USA
Potato breeding efforts typically focus on selecting superior individuals following the hybridization of parental clones. Both an advantage and a disadvantage of this strategy is that large populations of genetically variable offspring are generated by crossing highly heterozygous tetraploids. It is advantageous because new combinations of genes and, therefore, phenotypes, are created, providing clones that
Am. J. Pot Res (2010) 87:492–496
may be selected as new cultivars. The disadvantage is that desirable combinations of genes are reshuffled with every sexual cycle. Often, a potato breeder would like to change only a few attributes of a highly desirable clone. For example, Russet Norkotah produces a large proportion of uniform attractive tubers, with resistance to hollow heart and second growth, and good storability (Johansen et al. 1988). However, it produces a weak vine and is susceptible to potato virus Y and Verticillium wilt (Miller et al. 1999). One strategy to improve Russet Norkotah is line selection, in which somatic variants for vine vigor are selected. Strain selection has been successful in the development of potato cultivars, including Russet Burbank, Cobbler, Norgold Russet Strain M, Red Triumph, Red Warba, Russet Sebago, Red Pontiac, and Red LaSoda (Lever et al. 1994; Miller 1954). A Russet Norkotah strain selection program was initiated in 1989, based on the identification of giant hill plants (Miller et al. 1999). In subsequent cycles, selection was based on tuber type and yield, rather than vine vigor. This effort has led to the development of several commercially successful Russet Norkotah strains. In the U.S. in 2009, more certified seed acres of Russet Norkotah strains were produced (2,408 ha) than certified seed acres of standard Russet Norkotah (1,837 ha). These clones are more vigorous and usually higher yielding than standard Russet Norkotah. In addition, many field observations have suggested that they might have improved resistance to Verticillium wilt. The objective of this investigation was to determine whether Russet Norkotah strain selections are more resistant to Verticillium wilt than the standard Russet Norkotah clone.
Materials and Methods Tubers were planted on May 5, 2008 and April 29, 2009 at the Hancock, Wisconsin, Agricultural Experiment Station. In both years, three trials were planted in a randomized complete block design with three replications for each of seven clones. The strain selections chosen for the study are the most commercially successful and, as such, have received plant variety protection (Miller et al. 2004). The clones included standard Russet Norkotah and six clonal selections (Russet Norkotah 112 [TXNS112], Russet Norkotah 223 [TXNS223], Russet Norkotah 278 [TXNS278], Russet Norkotah 296 [TXNS296], Russet Norkotah 3 [CORN3], and Russet Norkotah 8 [CORN8]). Trials 1 and 2 were planted on a V. dahliae-infested field (∼20 cfu/g soil), while Trial 3 was planted on an adjacent field that was fumigated in the fall of the previous year (
