Crown rot (Phytophthora cactorum) causes significant economic losses in strawberry production. The best control strategy would be to use resistant cultivars, but polygenically inherited resistance makes the breeding of the garden strawberry (Fragaria × ananassa) challenging. The diploid wild strawberry Fragaria vesca Hawaii 4 genotype was shown previously to have resistance against crown rot. To explore the resistance mechanisms, we inoculated the roots of Hawaii 4 with P. cactorum in a novel in vitro hydroponic system to minimize interference caused by other microbes. Major reprogramming of the root transcriptome occurred, involving 30% of the genes. The surveillance system of the plant shifted from the development mode to the defense mode. Furthermore, the immune responses as well as many genes involved in the biosynthesis of the defense hormones jasmonic acid, ethylene and salicylic acid were up-regulated. Several major allergen-like genes encoding PR-10 proteins were highly expressed in the inoculated plants, suggesting that they also have a crucial role in the defense responses against P. cactorum. Additionally, flavonoids and terpenoids may be of vital importance, as several genes involved in their biosynthesis were up-regulated. The cell wall biosynthesis and developmental processes were down-regulated, possibly as a result of the down-regulation of the key genes involved in the biosynthesis of growth-promoting hormones brassinosteroids and auxin. Of particular interest was the expression of potential resistance genes in the recently identified P. cactorum resistance locus RPc-1. These new findings help to target the breeding efforts aiming at more resistant strawberry cultivars.

No abstract

Morphological and molecular identification methods were developed for R. arcticus. The best morphological characteristics were the length-to-width ratio of the middle leaflet and leaf margin serration. A particular characteristic, fingertip touch, was shown by electron microscopy to be related to the density and quality of the leaf hairs. Red raspberry SSR marker no. 126 proved to be applicable for differentiation of the eight arctic bramble cultivars tested. These identification methods are critical to secure the maintenance and management of R. arcticus. However, the challenges faced and approaches taken are equally applicable to other species with similar biology.

The goal of this work was to develop improved tools for the detection of Phytophthora ramorum and P. kernoviae for field and the laboratory use. ImmunoStrip ® and ELISA were selected as the test formats for development. Presently, the diagnosis of sudden oak death (SOD) in the national survey of P. ramorum depends on the use of ELISA to pre-screen samples, and then confirms results with PCR and morphological identification. This approach has some disadvantages because the ELISA has a wide spectrum reaction with Phytophthora spp. and cross-reacts with Pythium spp. A faster and more specific serological test to detect P. ramorum would be very useful in the survey of this pathogen. P. kernoviae was first detected in rhododendron in Cornwall in 2003 during surveys for P. ramorum, and the pathogen has been found in New Zealand. P. kernoviae has not been reported in the U.S. However,

Downy mildew, inflicted by Peronospora sparsa, causes yield losses in arctic bramble (Rubus arcticus ssp. arcticus), boysenberry (Rubus spp. hybrid) and blackberry (Rubus fruticosus), and is a serious threat to the cultivation. Arctic bramble is a high‐value crop but its commercial potential is not realisable partly due to downy mildew. Although P. sparsa has been associated with yield losses in arctic bramble, this has not been experimentally proven, nor have the downy mildew symptoms in arctic bramble fruits been described in a controlled experiment. In this study, downy mildew was found to affect the fruits and reduce the yield of arctic bramble. There was a direct correlation between the number of infected leaves and hard fruits resulting from the infection. Owing to the new pesticide legislation in the European Union, it is important to find alternatives to fungicides in the control of downy mildew. The products ALIETTE (fungicide), PHOSFIK (leaf fertiliser) and BION (pathogen defence elicitor) were effective in downy mildew control, Aliette and Phosfik being more effective than Bion especially in preventing yield losses. No arctic bramble cultivars known to be resistant to downy mildew are available. Evaluation of cultivars Alli, Mesma and Pima in the field showed that Mesma is more resistant to downy mildew than are Alli and Pima. Currently the main cultivar grown in Finland, Pima, was the most susceptible variety. The results of this study suggest that the yields and profitability of arctic bramble production could be improved by selecting more resistant varieties, combined with the application of agrochemicals that can suppress the development of downy mildew.