Genetic Differences and Environmental Variations in Carotenoid Contents of Fruit Flesh in Parental Population Used in Citrus Breeding in Japan

ADDITIONAL INDEX WORDS. breeding strategy, broad-sense heritability, b-cryptoxanthin, mandarin, location effect ABSTRACT. To aid the breeding of citrus (Citrus sp.) for high carotenoid content, we assayed the fruit flesh of 48 cultivars and selections within a parental population consisting of both old and new cultivars and selections at two locations in Japan. The mean total carotenoid (CAR) content across all 48 cultivars and selections over the two locations was 26.59 mgg L1 fresh weight (FW). The most prominent carotenoid was b-cryptoxanthin (BCR (12.09 mgg L1 FW)) followed by violaxanthin (VIO (8.04 mgg L1 FW)), z-carotene (2.27 mgg L1 FW), phytoene (1.86 mgg L1 FW), and b-carotene (0.96 mgg L1 FW). Broad-sense heritabilities of CAR, BCR, and VIO were 0.80 or greater based onasampleoffivefruitononetreeperlocationinonetimesamplingfor1yearinalocation,whichwererevealedtobe large enough for gauging the genetic variation. The mean CAR and BCR contents in a cultivar and selection group in advanced generations were nearly the same as in the initial population, suggesting no or little selection pressure on carotenoid content in the citrus breeding so far. High carotenoid contents in cultivars and selections released or selectedrecently,whichhavehighfruitqualities,suggesttheirhighpotentialforcombininghighfruitqualityandhigh carotenoid content in breeding. We showed that the critical phenotypic value used in selecting hybrid seedlings can be determined from the estimate of environmental variance.