An investigation to estimate genetic parameters in CSIRO's table grape breeding program. 2. Quality characteristics

Genetic parameters for table grape quality characteristics, including ripening date, berry size (weight, width and length) and uniformity, seediness, ^°Brix, acidity and the ratio of ^°Brix and acidity, were estimated based on two seasons' evaluations. Data were collected from a total of 5039 vines in 1999 and 1848 vines in 2000 and individual vine mixed models using the restricted maximum likelihood approach were used to account for all pedigree information. The results showed that quality characteristics were generally under strong additive genetic control; narrow-sense heritability estimates were 0.35 for ripening date, 0.63 for berry weight, 0.69 for berry width, 0.68 for berry length, 0.58 for seediness, 0.48 for ^°Brix, 0.36 for acidity and 0.10 for the ratio of ^°Brix and acidity. Berry size components (berry weight, width and length) were correlated strongly and positively with each other (r _g = 0.88 ∼ 0.96), and correlated negatively with ^°Brix and acidity (–0.19 ∼ –0.62), but positively with the ratio of ^°Brix: acidity (0.05 ∼ 0.33). ^°Brix was also favourably associated with acidity (0.41). Vine vigour was associated with ^°Brix (–0.05) and acidity (0.30) without an unfavourable impact on berry size. Thus, low vigour vines may potentially produce high quality table grapes. Ripening date was generally independent of most quality characteristics. Heritability estimates derived from seedless and seeded populations were similar to each other and mirrored the estimates for the combined population. The implications of these estimates for table grape breeding are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.