Promene u enzimatskoj aktivnosti i antioksidantnom kapacitetu plodova trešnje (Prunus avium L.) izazvane biotičkim stresom

Brown rot (the causal agent: Monilinia laxa Aderh. and Ruhl.) is one of the most common and most destructive diseases among stone fruit, sweet cherries in particular. The objective of this paper was to determine different responses to brown rot among nine sweet cherry genotypes grown under the field conditions of infection in open field. In terms of enzyme and antioxidant activity occurring under infection, the studied genotypes showed significant differences in comparison with healthy fruits. However, at the biochemical level, soluble proteins (SP), superoxid dismutase activity (SOD), guaiacol peroxidase activity (GPX), pyrogallol peroxidase activity (PPX), lipid peroxidation (LP) and antioxidant activity (ABTS and TRC assays) in sweet cherry fruits was significantly affected by genotype, plant disease and interaction of these two factors. Significant differences between studied parameters of healthy and infected fruits were recorded in genotypes Junska rana, Merchant, Sue and III/VAL. The parameters studied can be used as a method of assessment of resistance to brown rot among sweet cherry cultivars.Mrka trulež (uzročnik: Monilinia laxa Aderh. i Ruhl.) je jedna od najčešćih i najdestruktivnijih bolesti koštičavih voćaka, naročito trešnje. Cilj ovog rada je bio da se utvrde različiti odgovori na mrku trulež ploda između devet genotipova trešnje, uzgajanih u uslovima prirodne infekcije na otvorenom polju. U pogledu enzimatske i antioksidativne aktivnosti koja se javila u uslovima infekcije, ispitivani genotipovi su pokazali značajne razlike u odnosu na zdrave plodove. Na razlike u biohemijskom pogledu uticali su: genotip, prisustvo biljne bolesti kao i interakcija ova dva faktora. Biohemijski parametri koji su pokazali razlike u uslovima infekcije su: sadržaj rastvorljivih proteina (SP), aktivnost supereksid dismutaze (SOD), aktivnost gvajakol peroksidaze (GPX), aktivnost pirogalol peroksidaze (PPX), lipidna peroksidacija (LP) i antioksidativna aktivnost (ABTS i TRC testovi). Značajne razlike između ispitivanih parametara zdravih i zaraženih plodova zabeležene su u genotipovima Junska rana, Merchant, Sue i III/VAL. Ispitani parametri se mogu koristiti kao metoda procene otpornosti na mrku trulež izmedju genotipova trešnje

Postharvest changes in primary and secondary metabolites of sweet cherry cultivars induced by Monilinia laxa

The aim of the study was to evaluate in which way nine cultivars of sweet cherry fruit cope with postharvest, artificial inoculation with Monilinia laxa pathogenic fungus through changes in sugars, organic acids and polyphenolic compounds, as well as which phenolics compounds are crucial participants in coping with the disease. Contents of sugars in this study were (g kg(-1) dry weight): glucose 205-439 and 268-443, fructose 175-398.9 and 208.6-365.8 and sucrose 20-47.6 and 19.2-38.6 in healthy and infected fruit, respectively. Organic acids detected in sweet cherry cultivars were citric, malic, quinic, shikimic and fumaric acid and their content varied depending on cultivar and treatment. Only 'Burlat' accumulated tartaric acid after the infection. Of all phenolic acids, which content decreased in infected fruit, it is clear that only the more tolerant genotypes 'Merchant', 'Lionska', and 'Sue' enhanced content of 3-feruloylquinic acid (in healthy up to 93 and in infected fruit 105.3-139.1 mg kg(-1)). The most abundant anthocyanins were cyanidin derivatives (80-266.1 and 10-3700 mg kg(-1) in healthy and infected fruit, respectively). 'Burlat', 'Junska rana', 'Merchant' and 'Summit' dominantly had cyanidin-glucoside, while only infected fruit of 'Priusadebnaja' and 'Asenova rana' accumulated cyanidin-glucoside. 'Priusadebnaja', 'Asenova rana' and 'Lionska' had cyanidin-rutinoside. 'Lionska', 'Sue' and 'Asenova rana' had higher cyanidin and peonidin derivative contents in infected fruit (1.2 to 3-fold higher). Peonidine derivatives (peonidin glucoside and rutinoside), 5-carboxypyrano-cyanidin-rutinoside content mostly decreased after the infection (14.9-97.7 %). Bearing in mind obtained results, 3-feruloylquinic acid, flavonols and anthocyanins could be proposed as crucial participants in coping with the disease