Sensory evaluation and quantitative genetics of
fruit texture traits in apple (Malus pumila Mill.)
Steven J. McKay1,
James J. Luby1, James M. Bradeen2, and Ruth G. Shaw3
1Department of Horticultural Science
2Department of Plant Pathology
3Department of Ecology and Evolutionary Behavior
University of Minnesota
St. Paul, MN 55108
The large tree size, delayed maturity, high levels of heterozygosity, and vulnerability to inbreeding depression has inspired considerable interest in the applicability of marker-aided or marker-assisted selection in apple. The apple cultivar ÔHoneycrisp,Õ a University of Minnesota release, is widely recognized for its crisp fruit, and the heritability of this crispness is of great interest for future apple breeding programs. Before heritability can be estimated, however, accurate phenotypic values must be estimated. Additionally, inter-annual repeatability of fruit texture traits must be confirmed in advance of a marker-aided selection program.
Fruit from five full-sib progenies with ÔHoneycrispÕ as a common parent were harvested for two years. Multiple harvest dates spanned several weeks in each year, which allowed for a uniform harvest criterion to be applied. Evaluation panels were held weekly, with sensory data being collected using a labeled magnitude scale. Apples were distributed among panelists according to a randomized incomplete block design. Individual panelist effects were estimated and removed by means of mixed-effects modeling. Subsequent analysis revealed phenotypic differences between progenies and between trees within progenies, as would be expected for polygenic traits in a highly heterozygous species. Unexpectedly, modest maternal effects were suggested as well for one of the three texture traits evaluated. Results were consistent across the two yearsÕ data.