How the specificities of citrus reproductive biology drive the strategies for the selection of seedless varieties?
The length of the juvenile phase (4-8 years), gametophytic self-incompatibility and apomixis are reproductive traits of citrus that hamper the breeding by genealogic selection. These reproductive characteristics and the high interspecific heterozygosity of some of the most important horticultural groups of citrus such as sweet oranges, grapefruits or lemons resulting from natural interspecific crosses do not allow the use of sexual recombination within groups for their improvement. Indeed, it would generate too much phenotypic diversity and the loss of the initial ideotype. Intraspecific crosses are used for varietal diversification in the mandarin group, but with a limited number of generation and recombination events. The fresh fruit market requires the production of citrus seedless fruit. Sterility or gametophytic self-incompatibility (e.g. clementine) associated with parthenocarpy makes it possible to achieve this objective. The sterility can result from spontaneous or induced mutations (e.g. grapefruits, sweet oranges), cytoplasmic male sterility (e.g. Satsuma mandarin) or polyploidy (e.g. Tahitian lime is a spontaneous triploid genotype). This presentation gives an overview about the strategies used by different laboratories at the international level to obtain sterile varieties, taking into account the particularities of citrus reproduction and adapting the breeding method to the genetic status of the crop.
Luro, F., Froelicher, Y. and Ollitrault, P. (2022). How the specificities of citrus reproductive biology drive the strategies for the selection of seedless varieties?. Acta Hortic. 1342, 149-158
parthenocarpy, self-incompatibility, apomixes, juvenile phase, heterozygosity, sterility, polyploidy