Resistance to Fusarium sambucinum in Wild and Cultivated Solanum Species

American Journal of Potato Research,  Nov/Dec 2003  by Lynch, D R,  Kawchuk, L M,  Chen, Q,  Kokko, M

• E-mail
• Print
• Link

ABSTRACT

Several species of Fusarium cause both dry rot in storage and seedpiece decay in the field, which results in severe losses in all major potato-growing regions. In temperate climates two Fusarium species are the principle causes of tuber dry rot-F. sambucinum and F. coeruleum. Resistance to F. sambucinum was identified in cultivated and wild Solanum species. Relatively high levels of resistance exist in the following 2EBN species: S. boliviense (PI#'s 265860, 310975, 310974, 545853, 545889, 545964), S. gourlayi ssp. gourlayi (PI#'s 473344, 545865), S. microdontum (PI#'s 310979, 473171), S. sancta-rosae (PI# 498392), S. kurtzianum (PI# 472930), S. fendleri ssp. fendleri (PI# 262895), S. gandarillasii (PI#'s 265866, 283076), S. oplocense (PI# 498281) and S. vidaurrei (PI# 498332). The resistance is highly heritable but appears, at least in some of the species, to be associated with recessive alleles.

RESUMEN

Muchas especies de Fusarium causan tanto pudricion seca durante el periodo de almacenamiento como deterioro del tuberculo semilla en el campo, lo cual da como resultado perdidas severas en las mas importantes regiones de cultivo de papa. En climas templados, son dos las principales especies de Fusarium que causan la pudricion seca del tuberculo: F. sambucinum y F. coeruleum. Se ha identificado resistencia a F. sambucinum en especies cultivadas y silvestres de Solanum. Existen niveles de resistencia relativamente altos en las siguientes especies 2 EBN: S. boliviense (PI#'s 265860, 310975, 310974, 545853, 545889, 545964), S. gourlayi ssp. gourlayi (P#'s 473344, 545865), S. microdontum (P#'s 310979, 473171), S. sancta-rosae (P#'s 265866, 283076), S. oplocense (PI# 498281) y S. vidaurrei (PI# 498332). La resistencia es altamente hereditaria, pero parece, al menos en algunas especies estar asociada con alelos recesivos.

Accepted for publication 30 July 2003.

ADDITIONAL KEY WORDS: potato, S. boliviense, S. gourlayi, S. microdontum, S. sancta-rosae, S. kurtzianum, S. fendleri, S. gandarillasi, S. oplocense, S. vidaurrei.

INTRODUCTION

Several species of Fusarium cause both dry rot in storage and seedpiece decay in the field, which results in severe losses in all major potato-growing areas (Booth 1971). In temperate climates two Fusarium species are principal causes of tuber dry rot-F. sambucinum (F. roseum Lk. ex Fr. f. sp. sambucinum or F. sulphureum Schlect) and F. coeruleum (F. solani var. coeruleum (Sacc.) Booth). Infected potatoes develop dry discolored tissue often surrounding an internal cavity that may contain mycelium (Boyd 1972; Theron and Holz 1987). Since infection occurs through a wound in the periderm, contaminants on tuber surfaces and in the soil, Erwinia species in particular, often occur in combination with fusarium dry rot (Staghellini and Russell 1971; Davis et al. 1983; Corsini and Pavek 1986).

Resistance to the major Fusarium species is controlled by independent genetic mechanisms (Corsini and Pavek 1986; Wastie et al. 1989; Huaman et al. 1989) which complicate breeding for resistance. Several studies have identified heritable sources of resistance within North American and European breeding populations (Leach and Webb 1981; Corsini and Pavek 1986; Wastie and Bradshaw 1993; Lees and Bradshaw, 2001). In some instances this could be traced back to S. tuberosum ssp. andigena (Corsini and Pavek 1986). Huaman et al. (1989) also identified genotypes within S. tuberosum, ssp. andigena that combine resistance to species of both Erwinia and Fusarium. Resistance in the wild Solanum species (S. ehrenbergii, S. spegazzinii, S. chacoense, and S. vernei) was reported by Wojciechowska-Kot (1981). However, a comprehensive screening of the Solanum species for sources of resistance is not reported in the literature, and the nature of the inheritance remains unresolved. This research was undertaken to address these important issues.

MATERIALS AND METHODS

Experiment #1

Plant material: In 1996 botanical seed of one to three accessions of 31 wild and cultivated Solanum species was received from the USDA Potato Introduction Station (Sturgeon Bay, WI, USA) (Table 1). The seed was treated with gibberellic acid (GA^sub 3^; 1.5 g liter^sup -1^; Sigma-Aldrich Ltd. Ontario, Canada) and planted in seedling flats containing Cornell Mix (Boodley and Sheldrake 1977). After 14 days (four-leaf stage) the seedlings were transplanted into Cornell Mix contained in 15-cm plastic pots and placed in a greenhouse with a 22/18 C day/night temperature regime and a 16-h photoperiod. Greenhouse-grown seedling tubers were harvested from tuber-bearing genotypes (ranged from one to seven genotypes per plant introduction [PI]) 4 months after transplanting. Following at least 6 wk of post-harvest storage at 4 to 6 C, unblemished tubers were selected from each genotype. The tubers were washed with tap water to remove all greenhouse mix, disinfected for 5 min in 0.5% sodium hypochlorite, rinsed thoroughly, and allowed to dry prior to inoculation. Russet Burbank was used as a control in both the inoculated and non-inoculated (sterile water) treatments.