2009 Annual Report 1a.Objectives (from AD-416) Apply tested ethylene molecular markers for ACS1 and AC01 in segregation populations in the WSU Apple Breeding Program to select for low ethylene production. Test and apply a reported apple fruit peel red color marker in the existing WSU segregation population for selection of red color development capacity. Identify potential candidate genes regulating apple firmness and crispness. Elucidate relationships between expression of apple AAT (alcohol acyl transferase) genes and cultivar differences in volatile ester production. 1b.Approach (from AD-416) Genomic, genetic and physiological methods will be employed to identify the genes and pathways regulating apple fruit firmness and crispness, using existing apple cultivars exhibiting distinct phenotype on these traits. Further validation and detailed functional analysis will be conducted by RT-PCR, real-time PCR, and/or RNA gel blot analysis. Candidate gene approach will be used to examine the alcohol acyl transferase gene family to understand the contribution of each member to the varietal difference on volatile ester production from ripening apple fruit. Current available molecular markers on ethylene production and peel red color will be applied in current apple breeding project. Documents SCA with WSU-Pullman. 3.Progress Report This project is related to objective 2 of the associated in-house project which is to identify the genetic factors regulating fruit quality. Apple fruit quality is determined by attributes that contribute to appearance and edibility. Two of these quality attributes, color and texture, are critical determinants of commercial success for any variety. Understanding the genetic control of color and texture will facilitate the development of tools breeders can use to develop new apple cultivars with superior color and texture attributes. During 2009, ARS scientists at the Tree Fruit Research Laboratory conducted genetic and physical analyses of two apple cultivars, ‘Pink Lady’ and ‘Honeycrisp’, which have distinct ripening behavior and texture attributes including crispness and firmness. Scanning electron microscope images of tissues prepared from fruits with similar stage of ripeness suggest that the cell wall thickness may contribute to the observed firmness and crispness phenotype. Genetic analysis indicated that many genes express differentially between cultivars and ripening stages. Some of these genes are known to be involved in cell wall and hormonal metabolism and other basic cellular functions that are relatable to fruit ripening and changes in texture. Additionally, a test of a DNA marker of apple fruit skin color was conducted with nearly 300 apple selections. Results indicate an approximate 80% predictability of this marker to predict apple fruit skin color. Detailed genetic analyses are continuing and results will be published and communicated to apple breeders. Monitoring Activities: Progress is monitored through annual submission of written and oral progress reports.