Citrus Biotechnology

Citrus (Rutaceae family) are plants characteristic of the tropical and subtropical regions in the world. Although they produce fresh fruit that are highly nutritious and obtain good values in the fresh market, citrus are also grown for the food industry (juice, essential oils, etc.) and for ornamental purposes.

Biotechnology can help nurserymen and breeders by speeding up propagation, and by assisting breeders in developing new cultivars that have improved yield and fruit quality or that overcome new abiotic (e.g. climate change) and biotic (e.g. diseases and pests) stresses. Keeping in mind that the objectives for plant breeders change according to rootstock and scion goals, and the place and the time considered, citrus breeding is restricted by biological characters such as high heterozygosity, long juvenile period, nucellar polyembryony, sexual incompatibility, and large plant size. Citrus spp. are normally not recalcitrant to in vitro cell-to-plant regeneration and transformation. Several strategies applying in vitro techniques and biotechnology are being exploited worldwide. Various in vitro techniques have been developed to enhance this valuable genus, which have sufficiently standardized regeneration and transformation protocols, at least for the most notable cultivars, improving the efficiency and changing the genotype and the season.

Micropropagation, via shoot multiplication and rooting, and synthetic seeds technology, are some examples of biotechnological applications to citrus propagation.

New elite genetically improved cultivars have been created, thanks to biotechnology.

Embryo rescue has been used to regenerate zygotic embryos in polyembryonic cultivars and to better recover triploid plants.

Somaclonal variation has been employed to produce clones that have improved fruit quality and mature at different times. Somatic hybridization, through protoplast isolation and fusion, has been applied to produce inter-specific and inter-generic hybrids, overcoming self- and cross-incompatibility impediments.

Transformation or genetic modification by Agrobacterium has been established in citrus tissues and protoplasts, to introduce agronomically important genes into Citrus spp. Encouraging results have been obtained with transgenics for resistance to biotic stresses such as viruses and bacteria. Polyploids and ploidy manipulation can be used for citrus breeding. Haploidy can be obtained through gametic embryogenesis (gynogenesis or anther and isolated microspore culture).

Emerging technologies such as CRISPR gene editing will, in the future, affect progress in citrus breeding.

The Working Group Citrus Biotechnology operates under the Division Plant Genetic Resources, Breeding and Biotechnology and its main function is the organization and convening of symposia on citrus biotechnology, which provide the opportunity for all those interested in this topic to meet, hear about the latest research and technology, discuss ideas and network.