Field and Greenhouse Response of Red Raspberry Genotypes to Root Rot

Abstract

<jats:p>Red raspberry genotypes (<jats:italic>Rubus idaeus</jats:italic> L.) were evaluated for resistance to root rot at two field sites in Washington state and in a greenhouse study. Thirteen raspberry genotypes were planted in two field sites naturally infested with <jats:italic>Phytophthora fragariae</jats:italic> var. <jats:italic>rubi</jats:italic> Wilcox and Duncan and evaluated over 3 years for growth and symptom expression. In greenhouse pot tests, 14 genotypes were inoculated with an isolate of <jats:italic>P. fragariae</jats:italic> var. <jats:italic>rubi</jats:italic> at three inoculum levels and evaluated for growth, root color, and symptom expression using a 1 to 4 rating scale. Eleven of the 14 cultivars were found to be susceptible or very susceptible to root rot in the field and greenhouse. ‘Summit’ and ‘Newburgh’ possessed high levels of resistance to the pathogen. ‘Cascade Bounty’ also showed high resistance to root rot in the greenhouse, but confirmation from a field study is needed. Subjective root ratings of greenhouse-grown plants correlated well with measurements of cane numbers and cane infection in the field. The greenhouse tests were useful in identifying resistant genotypes and very susceptible genotypes but did not always match field results. Observation of at least 3 years in the field was necessary to compare relative reaction with root rot among genotypes.</jats:p>

BC 90-19-34 and BC 93-16-43 Red Raspberries

“…Consistently, through the course of these screens, BC 93-16-43 was one of the top performers and had a similar rating of disease symptoms to 'Latham' (Table 2). It is worth noting that comparisons between field and greenhouse screenings for root rot in raspberry have varied between showing good (Hoashi-Erhardt et al, 2008) and poor (Graham et al, 2011) correlation to field results with mixed reports regarding which is likely to produce a more severe disease reaction (Graham et al, 2011;Hoashi-Erhardt et al, 2008;Pattison et al, 2004). Because of the myriad of reasons why greenhouse screenings may produce different results from field plantings, it is recommended that the performance of both selections be assessed locally on diseased field sites to be certain that the observed resistance is effective against local isolates and in other environments.…”

“…Since being selected in the mid-1990s, BC 90-19-34 and BC 93-16-43 have been rated subjectively, on a yearly basis, for incidence and severity of spur blight caused 2004and 2005and harvested in 2006and 2008 Plants were grown in hills with a spacing of 0.9 m between the plants and row spacing of 3 m (3588 plants/ha) and were pruned to six canes per hill and topped to a height of 1.5 m. y Weighted average based on mass of 50 randomly selected fruit at each harvest date.…”

Pathogenicity, Fungicide Resistance, and Genetic Variability ofPhytophthora rubiIsolates from Raspberry (Rubus idaeus) in the Western United States

“…Some red and black raspberry cultivars resistant to P. fragariae are susceptible to P. megasperma (37). The newly released processing variety 'Cascade Bounty' is resistant to P. rubi; the widely planted fresh market variety 'Tulameen' is susceptible; and the predominant processing cultivar 'Meeker' has an intermediate reaction (13). However, the reaction of these varieties to other Phytophthora spp.…”