Utilization of somatic fusion techniques for the development of HLB tolerant breeding resources employing the Australian finger lime (Citrus australasica)

Comparative Analysis of Physicochemical Properties and Storability of a New Citrus Variety, Yellowball, and Its Parent

Although numerous citrus varieties have recently been developed to enhance their quality, information on their quality characteristics is limited. We assessed the quality characteristics of Yellowball, a novel citrus variety, by evaluating its appearance, storability, sensory properties, functionality, and metabolite profiles and then comparing these characteristics with those of its parent varieties, Haruka and Kiyomi. The metabolite profiles between the citrus varieties differed significantly, resulting in distinct physicochemical and functional qualities. The storability of Yellowball was significantly increased compared with that of its parent varieties owing to its strong antifungal activity and unique peel morphology, including the stoma and albedo layers. While we did not investigate the volatile compounds, overall functional activities, and detailed characteristics of each metabolite, our data provide valuable insights into the relationship between citrus metabolites, peel morphology, physicochemical properties, and storability, and demonstrate the potential of Yellowball as a promising variety in the citrus industry.

Overexpression of the salicylic acid binding protein 2 (SABP2) from tobacco enhances tolerance against Huanglongbing in transgenic citrus

Overexpression of the salicylic acid binding protein 2 (SABP2) gene from Tobacco results in enhanced tolerance to Huanglongbing (HLB; citrus greening disease) in transgenic sweet oranges. Huanglongbing (HLB), the most destructive citrus disease, is caused by Candidatus Liberibacter asiaticus (CaLas). Currently, no cure for this disease exists, and all commercially planted cultivars are highly susceptible. Salicylic Acid Binding Protein 2 (SABP2) is a well-characterized protein essential for establishing systemic acquired resistance (SAR) in tobacco. The constitutive over expression of SABP2 from tobacco (NtSABP2) in 'Hamlin' sweet orange resulted in the production of several transgenic lines with variable transcript levels. Transient expression of the NtSABP2-EGFP fusion protein in Nicotiana benthamiana plants demonstrated that NtSABP2 was cytosolic in its subcellular localization. In a long-term field study, we identified a SABP2 transgenic line with significantly reduced HLB symptoms that maintained a consistently low CaLas titer. Transcriptome analysis of this selected transgenic line demonstrated upregulation of several genes related to plant defense and SAR pathways. Genes, such as NPR family genes and those coding for monooxygenases and lipoxygenases, were upregulated in the 35S-NtSABP2 overexpressing line and might be candidates for incorporation into our citrus improvement program.