Narrow-Sense Heritability Estimates for Yield and Quality Characteristics in CSIRO's Table Grape Breeding Program

A diverse range of bi-parental progenies involving different combinations of 40 female and 60 male parents such that many complex pedigree relationships occurred has been produced in CSIRO’s breeding program over the last two decades. Yield and quality characteristics were measured for all (5,039) and a sub-sample (1,848) of grape-bearing hybrids in 1999 and 2000 respectively. Genetic parameters were estimated from data for each season separately and from data pooled over both years using restricted maximum likelihood (REML) statistical methods, which were used to account for pedigree information and unbalanced data sets. For yield characteristics, narrow-sense heritability (h2) estimates were similar between seasons for most characteristics except bunch number, which were 0.24 ± 0.06 and 0.51 ± 0.10 in 1999 and 2000 respectively. The values of h2 from pooled data analyses were 0.22 ± 0.05 for vine vigour, 0.18 ± 0.04 for fresh yield, 0.41 ± 0.08 for bunch number per vine, 0.23 ± 0.05 for bunch weight, 0.28 for bunch length and 0.14 ± 0.05for bunch compactness. Bunch size uniformity was only measured for the sub-sample of hybrids in 2000 and h2 was 0.14 ± 0.05. Quality characteristics were generally under strong additive genetic control and h2 estimates were higher than for yield characteristics. The values for h2 from pooled data were 0.63 ± 0.04 for berry weight, 0.69 ± 0.04 for berry width, 0.68 ± 0.04 for berry length, 0.58 ± 0.07 for seediness, 0.35 ± 0.03 for ripening date, 0.48 ± 0.06 for °Brix, 0.36 ± 0.08 for acidity and 0.10 ± 0.09 for the ratio of °Brix and acidity. Strong genetic correlations were shown for the different characteristics between harvests and indicated that genotype x season interactions were not an issue. Estimates of genetic parameters were similar for seedless and seeded sub-groupings and mirrored the estimates for the combined population.