Genetic Variation and Covariation of Yield and Phytochemical Traits in a Red Raspberry Factorial Study

Breeding for high yield is a major objective of most small fruit breeding programs worldwide. In recent years, research associated with health benefits of berry fruit has resulted in some breeding programs looking for material with improved health properties with the goal of incorporating these into genotypes with high yield and other favorable agronomic characters. In this study, we estimated variance components, heritabilities, and phenotypic and genotypic correlations for yield components and phytochemicals [total phenolics (TPH), antioxidant activity (FRAP), and total anthocyanins (TACY)] from 828 genotypes in a red raspberry (Rubus idaeus) factorial mating design based on 42 full-sib families derived from seven female and six male parents harvested in one season in New Zealand. Narrow sense heritability estimates varied from moderately low [0.23 for percent budburst (PCBB)] to high [0.82 for mean berry weight (BWT)]. Highest genotypic correlations with total yield (TYLD) were found for mean cane length (0.60) followed by moderate correlations for PCBB (0.38), BWT (0.34) and fruit number per unit lateral (0.31). For these four components, the correlation between the product of the empirical breeding values (eBV) and TYLD was as good (0.67) as the correlation between the product of the seven yield components measured (0.68). Moderately high negative genotypic correlations were found between TYLD and TPH (–0.67), FRAP (–0.68), and TACY (–0.64), suggesting that breeding for high-yielding genotypes may result in reduced phytochemical levels. A pigment-deficient R. parvifolius x R. idaeus hybrid derivative parent (R. parv deriv) had the most influence on berry weight as a yield component. Removal of the R. parv deriv progeny from the analysis increased the contribution of berry weight to total yield. Heritability estimates were generally lower when the R. parv deriv crosses were omitted, particularly for number of canes BWT, TYLD, and the phytochemicals. Implications of R. parv deriv crosses on these results are discussed. Of the 828 genotypes, only five had an eBV for total yield greater than that of the best yielding parent, whereas 49 had larger berries than the best parent. None of the 828 genotypes had an eBV for yield components or phytochemicals less than that of the lowest parent, whereas 13 had a higher eBV associated with phytochemicals than that of the highest parent.