ABSTRACT
Oranges and mandarins account for 70% of the world’s total citrus production, which is a genetically varied collection of tree fruits. Citrus output and fruit quality are diminishing due to numerous stressors; however, elite varieties have been developed and climatic resilience has been increased by the use of germplasm with unique alleles in breeding operations. The cost-effective characterization, identification of QTLs, and candidate gene studies for traits related to stress tolerance and fruit quality are now possible because of modern breeding methods. The increased stress tolerance in polyploid cultivars highlights the possibility of ploidy management. Genes that protect against the tristeza virus, canker, and greening disease have been silenced using genome editing techniques, increasing plant tolerance. Genetically varied germplasm core collections that have been helped by markers are ideal and might be kept up to date affordably. Early hybrid screening has been successfully carried out using markers such as SSRs, Indels, and SNPs. Understanding of the genes linked to flowering pathways has improved by analysis of genetic resources with early flowering. While omics techniques have identified the core citrus species, next-generation sequencing (NGS) has simplified germplasm screening cycles. Only kinds with enhanced in vitro regeneration can be considered transgenic. It is necessary to strengthen germplasm exchange programs to fully utilize genetic resources for agricultural improvement. A comprehensive overview and prospects of the above-discussed aspects are elaborated in this chapter.
