Timing of flowering is a fundamental developmental transition that has great ecological and agricultural importance. For perennial plants, seasonal timing of bloom and anthesis, which is the ultimate stage of flowering, can be determined by the net effect of several preceding developmental steps: seasonal timing of floral initiation, rate and extent of floral development before winter dormancy, duration of dormancy, and rate of floral development after release from dormancy. In the domestic apple (Malus ×domestica), fruit production has generally favored cultivars that bloom relatively early in the season. However, floral tissues are easily damaged by freezing temperatures, and freeze injury is especially problematic in years when abnormally warm temperatures in early spring lead to rapid floral development. To facilitate identification of genes/alleles that govern bloom time, and that could add versatility to production systems for apple, we evaluated seasonal bloom time for accessions of M. ×domestica, wild apple species (Malus sp.), and Malus hybrids maintained in a large germplasm diversity collection.
Chris Gottschalk and Steve van Nocker
Nobuko Sugimoto, Steve van Nocker, Schuyler Korban and Randy Beaudry
A microarray containing over 10,000 gene fragments was used to link changes in gene expression with changes in aroma biosynthesis in ripening apple (Malus ×domestica Borkh). The microarray was probed with fluorescent-tagged cDNA derived from RNA extracted from `Jonagold' apple skin and cortex tissue representing eight distinct physiological stages spanning 70 days during ripening and senescence. The ripening stages, in chronological order, were: 1) early preclimacteric; 2) late preclimacteric and onset of trace ester biosynthesis; 3) onset of the autocatalytic ethylene and rapidly increasing ester biosynthesis; 4) half-maximal ester biosynthesis and engagement of the respiratory climacteric; 5) near maximal ester biosynthesis, peak in respiratory activity, and the onset of rapid tissue softening; 6) maximal ester biosynthesis prior to its decline, the conclusion of the respiratory climacteric, and the completion of tissue softening; 7) midpoint in the decline in ester biosynthesis and maximal ethylene biosynthesis; and 8) postclimacteric minimum in ester production. Patterns in gene expression reflecting the rise and fall in ester formation were found in some putative genes for beta-oxidation (acyl-CoA oxidase, enoyl-CoA hydratase, and acetyl-CoA acetyl transferase), ester formation (aminotransferase, alcohol dehydrogenase, and alcohol acyl transferase), and fatty acid oxidation (lipoxygenase), but not fatty acid biosynthetic genes. A marked decline coinciding with the onset of ester production was detected in several putative genes for ADH.
Carol A. Miles, Travis R. Alexander, Gregory Peck, Suzette P. Galinato, Christopher Gottschalk and Steve van Nocker
Hard cider, made by fermenting apple (Malus ×domestica) juice, was at one time the most widely consumed alcoholic beverage in America. Largely abandoned after Prohibition, within the past 2 decades the rise in popularity of craft beverages has led to the reemergence of hard cider as an alternative to beer, wine, and spirits. Today, hard cider represents one of the fastest growing sectors within the craft beverage industry. The recent interest in cider presents additional marketing opportunities for apple growers and businesses currently involved in, or considering entering, the apple cider or craft beverages industries. However, the lack of a strong history or experience in selecting, producing, and using cider apples poses a significant challenge to this emerging market. This article reviews the current state of research in cider apple production, including economic feasibility, mechanized management, and cultivar evaluation and improvement.