Genotypic variation of rind colour in citrus tangor ‘Kiyomi’ progenies

Rind colour is the most important characteristic contributing to a fruit’s appearance and therefore theimprovement of rind colour has been a longstanding aim of citrus breeding programmes. However, due to thelack of information on the inheritance of rind colour in citrus, the breeder faces a difficult task when planningcrosses for breeding new cultivars. By quantifying the variation in a population the breeder can study therelationships between the hybrids and parents and gain an understanding of how certain characteristics areinherited. Therefore a study was undertaken to investigate the variation in rind colour, as chroma coordinatesL*, a* and b*, in six mandarin families, where female parent ‘Kiyomi’ tangor (Citrus unshiu x Citrus sinensis)was crossed with male parents ‘Dancy’, ‘Hansen’, ‘Rishon’, ‘Roma’, ‘Shani’ and ‘Sunburst’ mandarins (Citrusreticulata). A significant level of variation was found between both the parents and the families for all thecolour coordinates. A greater variation was found within the families than between the families, indicating ahigh level of genetic variation within the families, while the within tree variation was lower than the withinfamily variation. All the families showed an improvement in the population for rind colour over the femaleparent ‘Kiyomi’ for L* and b*, while all the families except for the ‘Kiyomi’ x ‘Dancy’ family showed animprovement for a*. The ‘Kiyomi’ x ‘Dancy’ and ‘Kiyomi’ x ‘Roma’ families were found to have a populationwith a lighter, more yellow-orange rind colour, while the ‘Kiyomi’ x ‘Hansen’, ‘Kiyomi’ x ‘Rishon’, ‘Kiyomi’ x ‘Shani’ and ‘Kiyomi’ x ‘Sunburst’ families had a population with a deeper, more orange-red rind colour. The intraclass correlation coefficient relevant to selection within the families was fairly low, indicating thevariation was only partly genetic and the environment contributed to the phenotypic variation. Therefore amean performance of multiple year’s data should be used for eff