Abstract

‘Hass’ is the main avocado cultivar commercialized worldwide. The extended flowering period, very low percentage of fruit set and inability to ripen on the tree renders the product heterogeneous and unpredictable during postharvest management. The growing ‘ready to eat market’ for Hass avocadoes is being impacted due to the variable postharvest ripening or ripening heterogeneity of this fruit which creates severe logistical problems for marketers and inconsistent quality delivery to consumers. Dry matter content, the gold standard avocado harvest index that correlates very well with oil content has been extensively used to harvest Hass avocadoes to comply with the minimum standards to guarantee good eating quality. However, previous works and empirical experience demonstrate that dry matter does not correlate with time to reach edible ripeness. Several pre-harvest factors related to environmental, growing conditions and crop management as well as postharvest technology strategies influence the variable postharvest ripening. Preliminary work carried out by the principal investigator demonstrated differences at the metabolite levels between very slow ripening and very fast ripening ‘Hass’ avocadoes. Metabolites involved in key pathways such as amino acids, fatty acids and cell wall constituents were responsible of this phenotype difference. It has been observed that postharvest abiotic treatments such as cold and modification of the air atmosphere was able to partially synchronize postharvest ripening. Thus, this postharvest ripening heterogeneity is the sum of pre-harvest factors and post-harvest stresses. Hass avocado ripening is a complex process that requires the synthesis of a full machinery of enzymes to render the fruit capable of triggering all these processes. Thus, we hypothesize that ripening can be synchronized by applying hierarchical post-harvest treatments. The specific goals are (i) to fingerprint at the proteome and metabolite level the differences between very slow and very fast ripening avocadoes at harvest and after cold and controlled atmosphere (CA) storage and (ii) to study the mechanisms involved in the synchronization of ripening due to cold and CA storage. We will use for the first time an integrative approach based on a combination of post-genomics platforms such as gel free proteomics (nano LC-MS/MS), profiling and targeted metabolite (GC-FID and GC-MS) analysis, targeted cell wall enzymatic analysis and classical quality evaluations. In addition, this approach is based on a semi-destructive biopsy sampling of individual fruits at harvest and following non-destructively fruit ripening in each individual fruit. We also propose the introduction of an index to quantify and compare statistically postharvest ripening heterogeneity. The results of this study not only will provide more foundation into the biochemical and molecular ripening heterogeneity of ‘Hass’ avocados but also provide potential ‘biomarkers’ involved in postharvest ripening heterogeneity, which may help to implement non-destructive tools or postharvest protocols to reduce heterogeneity in practice. This project will generate scientific and academic publications, extension and training of young researchers and will strengthen the network with our international key partners.