The long-term goal of this project is to develop tools for quality management of deciduous tree fruits. Specifically, during the next five years we will focus on the following objectives. Objective 1: Resolve production and post-harvest environmental and genetic regulation of apple, pear, and sweet cherry quality. [NP306, C1, PS1A] Sub-objective 1A: Identify if interactions among storage temperature protocol, controlled atmosphere establishment date, and inhibition of ethylene action impact apple and pear fruit market quality and development of physiological disorders. Sub-objective 1B: Determine if dynamic control of controlled atmosphere (CA) oxygen concentration can enhance apple fruit post storage volatile production without fruit quality loss. Sub-objective 1C: Determine relationship between sweet cherry cutin composition, gene expression, and surface defects caused by sun stress following harvest. Objective 2: Use of biomarkers to enhance/assist commercial apple and pear management strategies. [NP306, C1, PS1A] Sub-objective 2A: Determine metabolic and genomic changes related to apple and pear fruit maturation and postharvest chilling. Sub-objective 2B: Identify metabolic and genomic changes linked with fruit quality loss and physiological disorder development during cold storage.
Fruit from commercial orchards will be harvested then stored at ARS-Wenatchee in controlled atmosphere (CA) chambers. Fruit quality, metabolites, and RNA will be characterized at harvest and after storage using standard methods. Hypothesis 1A: The manner in which postharvest technologies are imposed results in additive, synergistic, and antagonistic effects on fruit quality and disorder development. Apple and pear fruit from commercial orchards will be stored continuously at 0.5°C or at 10°C for 7 days, then at 0.5°C. Fruit will be exposed to 0 or 1 µL L-1 1-MCP for 16 hours, then in air or a CA initiated 1 or 9 days after harvest. Following 6 to 8 months, fruit will be removed from storage and held 7 days at 20°C to allow post-storage quality loss and disorder development to occur. Hypothesis 1B: The manner in which postharvest technologies are imposed results in additive, synergistic, and antagonistic effects on apple firmness and related gene expression. Tissues from ‘Gala’ apples stored at various temperatures, in air or CA, with or without 1-MCP treatment will be collected over time. Fruit firmness will be assessed at the same time as tissue harvest for transcriptome analysis plus after 7 at 20°C. Hypothesis 1C: Reciprocity is valid for mean oxygen concentration during CA storage and apple fruit post-storage volatile production and quality. Honeycrisp’ apples will be CA stored continuously at 5.1% O2 as well as at 2.5% O2 with repeated periods in air to average 5.1% O2 over the storage period. Control fruit will also be held continuously in air. Fruit removed from storage after 4 and 8 months will be assessed for external disorders on the day of removal, then will be held 7 days at 20°C in air. On day 7, volatile compounds emitted from intact fruit will be collected and analyzed. Hypothesis 1D: Cuticle composition and gene expression will be impacted by sunlight exposure. Sweet cherries will be harvested from the tree periphery and interior or following shading with black cloth. Fruit peel will be assessed for microcracks using microscopy. RNA will be collected from peel sections with contrasting cutin deposition patterns using laser microdissection. Hypothesis 2A: Changes in molecular phenotypes (metabolites and gene activity) can be linked with progression of fruit maturation and low temperatures during storage. Apple and pear cultivars will be harvested over 12 weeks bracketing horticultural maturity. Fruit maturity, metabolite and RNA content will be assessed using standard methods. Maturity dependent responses to abiotic stress will consist of holding fruit at 20 or 1°C for 48 hours. Hypothesis 2B: Specific changes in apple and pear cell membrane components are provoked by high carbon dioxide, low oxygen CA leading to higher risk of developing carbon dioxide related storage disorders. Apples treated or not with DPA will be stored in CA at 0.5% O2 and up to 5% CO2. Fruit quality and disorders will be assessed after storage as will fruit metabolites and RNA.
This project is linked to the expired project 2094-43000-007-00D, “Developmental Genomics and Metabolomics Influencing Temperate Tree Fruit Quality” and has successfully completed NP306 OSQR review. This is a replacement project that began 05/04/2020. Initial research for Objectives 1 and 2 is underway.