|YU, YUAN - University Of Florida|
|YU, QIBIN - University Of Florida|
|Baldwin, Elizabeth - Liz|
|GMITTER, FREDERICK - University Of Florida|
Submitted to: BMC Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2017
Publication Date: 8/22/2017
Citation: Yu, Y., Bai, J., Chen, C., Plotto, A., Yu, Q., Baldwin, E.A., Gmitter, F. 2017. Identification of QTLs controlling aroma volatiles using a 'Fortune' x 'Murcott' (Citrus reticulata) population. BMC Genomics. 18:646. doi:10.1186/s12864-017-4043-5.
Interpretive Summary: Flavor improvement is highly prioritized in mandarin breeding programs. The molecular markers linked to mandarin fruit aroma could facilitate genetic improvement and help release new mandarin cultivars with improved fruit flavor. In the present study, we investigated aroma volatiles in a mandarin, then we identified quantitative trait loci (QTL) regions controlling mandarin aroma volatiles and validated molecular markers in relevant citrus germplasm. The technology could be used to screen mandarin individuals efficiently as seedlings to select for specific volatile compounds to improve flavor, without waiting for fruiting which would otherwise take years.
Technical Abstract: Flavor is an important attribute of mandarin (Citrus reticulata Blanco) and flavor improvement via conventional breeding is very challenging largely due to the complexity of the flavor components and traits. Many aroma associated volatiles of citrus fruit have been identified, which are directly related to flavor, but knowledge of genetic linkages and relevant genes for these volatiles, along with applicable markers potentially for expeditious and economical marker-assisted selection (MAS), is very limited. The objective of this project was to identify single nucleotide polymorphism (SNP) markers associated with these volatile traits. Aroma volatiles were investigated in two mandarin parents (‘Fortune’ and ‘Murcott’) and their 116 F1 progeny using gas chromatography mass spectrometry (GCMS) in 2012 and 2013. A total of 150 volatiles were identified, including one acid, 12 alcohols, 20 aldehydes, 14 esters, one furan, five aromatic hydrocarbons, 16 ketones, one phenol, 27 sesquiterpenes, 15 monoterpenes, and 38 unknown. A total of 208 quantitative trait loci (QTLs) were identified for 95 volatile compounds using genotyping data generated from a 1536-SNP Illumina GoldenGate assay. In detail, 25 of the QTLs were consistent over more than two sampling times. 41 QTLs were identified for 17 aroma active compounds. Other 41 QTLs were for 18 sesquiterpenes and mapped onto four genomic regions. 50 QTLs were for 14 monoterpenes and mapped onto five genomic regions. Candidate genes for some QTLs were also identified. A QTL interval for monoterpenes and sesquiterpenes on linkage group (LG) 2 contained geranyl diphosphate synthase 1 (GPS1), terpene synthase 3 (TPS3), terpene synthase 4 (TPS4), and terpene synthase 14 (TPS14) genes. Some fruit aroma QTLs were identified and the candidate genes in terpenoid biosynthetic pathways were found within the QTL intervals. These QTLs were validated in 13 citrus genotypes and could lead to an efficient and feasible MAS approach to mandarin flavor improvement.