Genetic differences in and inheritance of changes in organic acid content in citrus cross-breeding population in Japan

Abstract

The organic acid content of the flesh of Citrus spp. fruit decreases during fruit growth. Citric acid is responsible for most of the decrease in many cultivars. The pattern of decrease of citric acid depends on genotype, but the inheritance of the trait is unclear. We investigated the pattern of decrease of citric acid during fruit growth of 100 cultivars and selections used as parents in citrus breeding in Japan and classified them by hierarchical cluster analysis. We also estimated the heritability of the pattern using data from 581 seedlings in 39 families. The accessions were classified into 4 clusters according to the pattern of decrease of citric acid from the early to the late fruit growing stages: Cluster 1, content decreased from very high to medium; Cluster 2, content decreased from high or medium to low; Cluster 3, content remained high; and Cluster 4, content remained low or medium. The heritability (±SE) of the citric acid content was 0.38±0.11 at the early stage and 0.60±0.09 at the late stage, and that of the rate of decrease was 0.67±0.12. These results suggest that selecting parents with a high rate of decrease of citric acid content from Cluster 2 will allow the development of new early-maturing cultivars.