Effects of Scion/Rootstock Combination on Flavor Quality of Orange Juice from Huanglongbing (HLB)-Affected Trees: A Two-Year Study of the Targeted Metabolomics

Abstract

The bacterial disease Huanglongbing (HLB) has been causing large economic losses in the citrus industry worldwide. Aimed at unraveling the mechanisms of scion/rootstock combination on improving HLB-affected orange juice quality, a specific scion/rootstock combination field trial was designed using three sibling rootstocks and two late-maturing sweet orange scion cultivars. Scion/rootstock combination significantly improved the overall consumer liking of orange juice from the HLB-affected trees. Rootstocks showed significant effects on the consumer liking and overall flavor, while scions had significant effects on the freshness and overall orange flavor intensity of the juice. A PLS-DA model combined with KEGG pathway enrichment analysis and some biomarker metabolites further indicated that scions mainly affected metabolism of alanine, aspartate, and glutamate in orange fruits. Meanwhile, rootstocks had an impact on the biosynthetic pathways of secondary metabolites. Sugars and organic acids were not closely correlated with the overall liking and sensory perception of orange juice. Rather, flavonoids, terpenoids, and volatile aromas played important roles in improving consumer overall liking. These results indicated that an optimum tolerant scion/rootstock combination can make a positive contribution toward improved fruit or juice quality from HLB-affected citrus trees.

Natural Sweeteners and Sweetness-Enhancing Compounds Identified in Citrus Using an Efficient Metabolomics-Based Screening Strategy

“…20,21 Targeted metabolomics conducts precise quantitative detection for defined groups of chemically characterized and biochemically annotated metabolites. 17 As part of our unremitting efforts to explore flavor compounds from fruit crops, in the current study, an efficient strategy based on the combination of untargeted and targeted metabolomics analyses was proposed to hunt for sweeteners from citrus. We first applied a highly sensitive UHPLC/MS method based on untargeted metabolomics with in-house database search and structure annotation to screen the potential natural sweet compounds from citrus.…”

“…Expanding the use of citrus to improve food quality and benefit human health is an effective way to promote the sustainability of citriculture. It was indicated by the preliminary studies that nonvolatile compounds presented in citrus fruits of some cultivars (or selections) are responsible for the increased sweetness. , It can be deduced that those compounds may be novel natural sweeteners and/or sweetness-enhancing compounds, which could be isolated for use in food. Identifying naturally occurring noncaloric sweet compounds also provides an important molecular trait to target in the development of new citrus cultivars that would be more palatable to and broadly accepted by consumers.…”

“…The metabolomics-based methods can handle the high-throughput analysis of multicomponent and multisample simultaneously . Untargeted metabolomics is an intended comprehensive analysis of all measurable analytes in a sample, which enables the identification of unknown metabolites. , Targeted metabolomics conducts precise quantitative detection for defined groups of chemically characterized and biochemically annotated metabolites . As part of our unremitting efforts to explore flavor compounds from fruit crops, in the current study, an efficient strategy based on the combination of untargeted and targeted metabolomics analyses was proposed to hunt for sweeteners from citrus.…”

Integrated Transcriptomics and Metabolomics Analyses Provide Insights Into the Response of Chongyi Wild Mandarin to Candidatus Liberibacter Asiaticus Infection

“…Therefore, analysis on transcriptional level alone might be difficult to screen the critical molecular signals in response to C Las infection. Metabolomics could identify low-molecular-weight metabolites (<1 kDa) that alter their accumulation in response to physiological challenges (Padhi et al, 2019 ; Huang et al, 2020 ). Integrated transcriptomics and metabolomics analysis may identify key HLB-related pathways, in which DEGs and differentially accumulated metabolites (DAMs) are both enriched.…”

Metabolomic analysis elucidates how shade conditions ameliorate the deleterious effects of greening (Huanglongbing) disease in citrus

“…As metabolites are the end‐products of cellular regulatory processes, which are directly related to phenotype, metabolomics provides useful information on the mechanistic link between alterations in cellular responses and physiological functions of plants (Fiehn et al., 2000). Due to this advantage, there has been an increase in metabolomics‐based studies on citrus HLB pathosystem, such as mapping altered primary and secondary metabolisms (Hung and Wang, 2018a,b; Killiny and Nehela, 2017; Nehela et al., 2018; Slisz et al., 2012; Suh et al., 2018), diagnosis of HLB disease (Liu et al., 2020; de Moraes Pontes et al., 2020), metabolites associated with HLB symptoms (Freitas et al., 2015; Nehela and Killiny, 2020), metabolic mechanisms coupled with HLB tolerance or resistance (Killiny et al., 2017, 2018), and effects of scions and rootstocks on juice quality from HLB‐affected citrus (Huang et al., 2020). However, we had lacked the metabolomic insights into how shade or low light conditions affect the cellular metabolism of HLB‐affected citrus trees, how shade‐induced modulations in cellular regulation process relate to leaf and whole‐plant level physiological functioning, and whether leaf metabolome profile under shade relates to overall improvement in the growth and fruit yield of HLB‐affected plants.…”