Abstract

Apple production in Chile is highlighted as one of the national fruit production chains that evolved the most in last decades. Although the whole production process has achieved a good performance, the Chilean apple production chain requires new technological solutions to enable at least the maintenance of current production, reduction of costs and improve fruit quality. Despite apple cultivation allowing the maximum preservation of natural resources while maintaining productivity and succeed of farmers, the biological and physiological disorders pose the highest risks for apple production in this country. Apple fruit can be susceptible to many different physiological disorders that can affect the skin, cortex and core areas alone or in combination. These disorders result in significant commercial losses to growers and storage operators. The type of disorder that is expressed is often a function of the variety, as most, if not all, disorders appear to be affected by the genetic makeup of the fruit. Harvest date is also an important factor as fruit maturity, usually in relation to the increase of ethylene production and the associated respiratory rate, which can greatly affect the susceptibility of fruit to disorder development. An additional factor is climate during the growing season and specific temperatures that fruits are sometimes experiencing in the orchard in the month or so before harvest. In order to overcome physiological disorders problems, several works have been accomplished for example nutrient applications preharvest and temperature regulation postharvest. However, none of these strategies are fully effective under the diverse environmental conditions where fruit grows and current climate change. Therefore, a well-focused approach combining the molecular, physiological, biochemical and metabolic aspects of oxidative tolerance is essential to improve productivity. Exploring suitable ameliorants or stress alleviant is one of the tasks of plant biologists. In recent decades, exogenous protectant such plant phytoprostanes is a promising option and have been found effective in mitigating oxidative stress-induced damage in plant. Currently, our knowledge of phytoprostanes quantification, identification and their roles can be found in many plants but apples, where it could be of scientific and practical interest. As working hypothesis in this project we conjecture that phytoprostanes may play an important role triggering antioxidant defense mechanisms in apple fruit under abiotic stress; therefore, the exogenous application of phytoprostanes can increase apple stress tolerance by decreasing physiological disorders on fruit, associated to high light and elevated temperature preharvest and low temperature postharvest. Apples cvs. Granny Smith and Cripps Pink grown under commercial conditions in orchards located in VII Region, Chile will be used to carry out all the experiments. Three experiments will be conducted: 1: characterization de phytoprostanes on apple fruit under high light and elevated temperature in the field. For this, apples with different light exposure will be tagged in the tree and sampled periodically in order to determine phytoprostane content (chromatographically). 2: evaluation of the capacity of phytoprostanes as oxidative stress marker. Phytoprostanes content in the tissue will be correlated with sunburn development in the field, and sunscald, superficial scald, and internal browning during cold storage. 3: evaluation of the performance of external applications of phytoprotanes on superficial scald, sunscald, and internal breakdown development postharvest. For this, exogenous application of phytoprostanes (100, 200, 300 umol) will be applied on apples in the field prior environmental conditions suitable to sunburn development appear. The same concentrations will also be applied at harvest to evaluate sunscald on Granny Smith and internal browning on Cripps Pink development postharvest. In addition, laboratory determinations will include: Ascorbate and Gluthatione determinations, antioxidant enzymes activities, as well as other maturity indices commonly used on apples.