1a.Objectives (from AD-416):
Characterize the expression patterns of ACS3 genes among elite apple cultivars, and elucidate the relationship of ACS3 expression and effectiveness of MCP treatment as well as subsequent postharvest fruit quality.
1b.Approach (from AD-416):
1. Fruit tissues representing different developmental stages will be collected for 12-16 cultivars, starting 30 days after full bloom till commercial maturity. 2. Apple fruits harvested at commercial maturity will be treated with1-MCP and fruit firmness changes of stored fruit will be assessed for at least 3 months. 3. Total RNAs will be isolated from above-mentioned fruit tissues using established procedure. 4. Gene-specific primers will be utilized to examine the expression patterns and dynamics on major ethylene biosynthesis enzyme encoding genes by quantitative real-time PCR methodology.
This serves as a final report for project 5350-43000-006-06T which expired 8/14/2013. This project relates to objective 1 of the associated in-house project which seeks to identify factors that influence postharvest fruit quality and development of market limiting physiological disorders. Apple fruit ripening behaviors closely influence fruit quality such as firmness and postharvest firmness retention. Firmness retention during fruit storage is ultimately associated with industry profitability and sustainability. Ethylene plays an important role in apple fruit development and it is produced by the activity of several proteins. Apple gene MdACS3 encodes a protein which is responsible for the basal level of ethylene production in apple fruit before fruit initiate the ripening process. Assessment of the expression features for the MdACS3 gene during maturation of 12 apple cultivars indicates MdACS3 acts as a ripening “accelerator” causing apple varieties to begin to ripen at different rates during the fall. 1-methylcyclopropene (1-MCP) blocks ethylene action when applied to apple. The efficacy of 1-MCP treatment on fruit firmness retention is greater for most of the early ripening cultivars compared with late-ripening cultivars. For the field formulation of 1-MCP, its application efficacy is critically affected by fruit maturity. The results from this study could be utilized to develop tools for breeders to design new apple varieties with desired ripening characteristics, and also to enhance efficacy of pre-harvest 1-MCP application.