ASSESSING THE POSSIBLE CAUSES OF STRAWBERRY DRIED CALYX DISORDER

Abstract

Trials were performed in Huelva (Spain) during 2010 and 2011 crop cycles on strawberry (Fragaria x ananassa Duch.) cultivars. During 2010 crop cycle preliminary assays were conducted to characterize the symptom characteristics of 'strawberry dried calyx disorder' and tolerance to different types of salinity in the irrigation water in soilless growing system. At the end of 2010 crop cycle fruit from a wide range of sizes were harvested and taken to laboratory and stored at 4-5°C. Occurrence of calyx injury and the characteristic of the symptoms were observed periodically as determined by progression of symptoms. 'Camarosa', 'Festival' and 'Palomar' cultivars were planted on 20 October in polyethylene bags in rows under plastic high tunnels and in rows under high tunnels without plastic. Polyethylene bags were filled with three different growth media: perlite, coir fiber and rockwool. Three salinity levels were compared which induced different electrical conductivity (EC) levels (1, 2 and 3 mS cm-1) respectively. A split-split-plot design (3 treatments x 3 cultivars x 3 growth media x 2 replications) was used. The values of severity were analyzed in three different dates. Severity of dried calyx disorder was measured in calyx of fruit by a symptom scale, where 0 = plant with no symptoms, 1 = ≤50% brown speckles fruit calyx, 2 = more than 50% brown speckles fruit calyx and 3 = dead plant. The main effects of EC, cultivar and growth media on dried calyx disorder severity were evaluated. The results indicated that the symptoms appear to be associated with high EC of hydroponic solutions and there were significant differences between cultivars. 'Palomar' cultivar recorded the highest values of dried calyx disorder severity and showed the strawberry dried calyx disorder earlier and more severity than 'Camarosa' and 'Festival' cultivars.