Fruit Resistance toColletotrichum acutatumin Strawberries

Abstract

Evaluation of strawberry resistance to anthracnose is generally limited to the crown rot phase of the disease. The major objective of this study was to develop a screening test for resistance to anthracnose fruit rot (Colletotrichum acutatum) using detached strawberries under controlled-environment conditions. Inoculation was carried out on detached fruits harvested at the stage when they were turning white-pink. Lesion diameter and percentage of diseased fruits (disease incidence) were measured. An incubation temperature of 18°C allowed a better discrimination between resistant and susceptible genotypes than 25°C. At 18°C and 8 days after inoculation, 26 genotypes differed greatly in susceptibility to anthracnose fruit rot, and lesion size ranged from 0 to 17 mm with disease incidence of 10 to 100%. A relationship between lesion size and disease incidence was established. The 26 genotypes were classified into three groups of susceptibility according to lesion size and percentage of diseased fruits. The susceptible group included nine genotypes with lesion sizes of 8.2 to 14.4 mm and 81 to 100% diseased fruits. In this group, Pajaro and Elsanta were the most susceptible. The four genotypes belonging to the resistant group, Dover, Capitola, US159, and US438, showed small fruit lesion sizes of 0.4 to 1.0 mm and a limited disease incidence (10 to 17%). The resistance of two genotypes to anthracnose fruit rot was evaluated under field conditions (plastic tunnel). The relatively resistant genotype, Sequoia, displayed reduced incidence of anthracnose fruit rot in the sections closest to the source of inoculum compared with the susceptible genotype Elsanta.

Isolation and pathogenicity of Colletotrichum spp. causing anthracnose of strawberry in south west Spain

“…Ureña-Padilla et al (2001) have also studied this difference, reporting that C. acutatum isolated from diseased fruit was not able to induce symptoms when inoculated into strawberry crown tissue, and C. gloeosporioides strains isolated from infected plant material were not pathogenic when re-inoculated onto fruit or leaf tissue. These results suggest that the relationship between host and pathogen is dependant on the infected tissue (Denoyes-Rothan et al 1999).…”

“…All three species can be found on all parts of the plant; however crown rot and fruit rot are the most economically damaging. The late onset of fruit rot can cause serious and sudden losses both pre-and post-harvest (Denoyes-Rothan et al 1999). Colletotrichum acutatum was first reported in Europe causing anthracnose on strawberry plants in France in 1981. It is thought to have been introduced to Europe from California (USA) on infected runner material and rapidly established in mainland Europe by 1993 (Denoyes-Rothan and Baudry 1995).…”

Induction of a defense response in strawberry mediated by an avirulent strain of Colletotrichum

“…has been well documented and many compatible and incompatible interactions have been reported (Smith and Black, 1990;Denoyes and Baudy, 1995;Denoyes-Rothan et al, 1999. A large number of light and electron microscope studies have been published concerning the interaction of plants with fungal pathogens including Colletotrichum species (OÕConnell et al, 2000;Wharton et al, 2001;Curry et al, 2002;Kim et al, 2004).…”

In vitro response of strawberry cultivars and regenerants to Colletotrichum acutatum

“…Except for cultivar Delmarvel, the severity of infection (% leaf necrosis) on the cultivars, following in vitro inoculation with C. acutatum (Figure 2), corresponded to the fruit susceptibility classification under field conditions (Chandler et al, 1997;Smith et al, 1998;Denoyes-Rothan et al, 1999;Galletta, personal communication). Although 'Delmarvel' was evaluated previously as a resistant cultivar (Galletta et al, 1995), our results clearly show 'Delmarvel' with 86% leaf necrosis ( Figure 2, Table 1), to be susceptible to C. acutatum.…”

“…Galletta, personal communication), Chandler (Smith et al, 1998), Honeoye (Denoyes-Rothan et al, 1999)], and three anthracnose fruit-or runner-resistant cultivars [Delmarvel (Galletta et al, 1995), Sweet Charlie (Chandler et al, 1997), and Pelican (Smith et al, 1998)] were obtained from Dr. G. Galletta, USDA/ARS, Fruit Laboratory, Beltsville, MD. These shoots were maintained on shoot proliferation medium containing MS salts (Murashige and Skoog, 1962), nicotinic acid (50 mg l )1 ), pyridoxine-HCl (50 mg l )1 ), glycine (200 mg l )1 ), thiamine-HCl (10 mg l )1 ), myo-inositol (1 mg l )1 ), 5.7 lM IAA, 4.4 lM BA, 0.03 lM GA 3 , 87.6 mM sucrose and 0.8% (w/v) Bacto agar.…”