Mapping the distinctive aroma of "wild strawberry" using a Fragariavesca NIL collection María Urrutia JL Rambla, Antonio Granell
Introduction: Aroma Strawberry fruit quality Organoleptic quality: aroma Complex mix of hundreds of compounds. Only 20 contribute to strawberry scent Composition and proportion varies between species and varieties. Nutritional quality: Antioxidant capacity High polyphenol accumulation (Data from Schieberle & Hoffmann 1997, Ulrich et al. 1997, 2007)
Introduction: F.vesca Woodland strawberry: Fragaria vesca Model species for Fragaria genus Characteristics Wild (barely cultivated) Small fruits Very short shelf life Nice aroma High antioxidant capacity Main advantages Genetics: Diploid (2n = 2x = 14) Genetic tools Saturated genetic maps (Sargent et al. 2004, 2011) Sequenced reference genome (Schulaev et al. 2011) Co-linearity betweenf. vesca and F. x ananassa genomes (Rousseau-Guetin et al 2008, Tennessen et al 2014).
Introduction: NIL collection development NIL collection in F. vesca Near Isogenic lines (NIL): Mapping populations based on introgression lines All lines share the same genetic background Recurrent parental (F. vesca) Each line harbors an exotic homozygous introgression Exotic parental (F. bucharica) R LFStem SFStem SDFlow EFlow Urrutia M Theoretical Applied Genetics 128, 1261-1275 2015
Introduction: NIL collection Nutritional quality analysis Nutritional quality Sugar and polyphenol acumulation 25 major QTL and 24 one-year QTL for polyphenols 5 major QTL for sugars Urrutia M., W. Schwab, T. Hoffmann and A. Monfort.. Plant Science 2016
Methodology: Organoleptic traits Volatile detection Detection and relative quantification of volatile compounds GC-MS GC: Physical separation of volatiles by temperature gradient (35-250ªC) MS: Sample ionization and separation by m/z Colaboration with Dr. Antoni Granell at IBMCP (Valencia, Spain)
Results: Organoleptic traits composition harvest 2012 2013 Volatile accumulation Identified volatile compounds (VOC) Unambigously: 88 Tentatively: 12 Including 19 key compounds for strawberry aroma
Results: Organoleptic traits composition harvest 2012 2013 Volatile accumulation Long acyl-moieties esters (E)-2-iso. Fatty acid derived Aldehydes, terpenoids & butyl acetates Benzoids & furans Butanoates, acetates, long chain alcohols & ketones
Results: Organoleptic traits genetic variability Volatile variability Nerolidol Methyl 2-aminobenzoate (E)-2-hexenal (Z)-2-hexenal Furaneol Mesifurane
Results: Organoleptic QTLs detection Volatile QTL 50 major volatile QTL
Results: Organoleptic QTLs Volatile QTL: Key compounds FaNES1 FaOMT
Results: Differential Expression Analysis NILs selection Whole transcriptome sequencing (RNAseq) of fruits of 3 NILs and the recurrent parental F. vesca RV. NILs were selected according to phenotypic criteria: Fb5:0-35 Fb5:50-76 Fb7:0-10 RNAseq: Samples collected per triplicate in 2013. Paired Ends sequencing in a HiSeq-2000 sequencer (Ilumina, CA, USA) at CNAG (Barcelona, Spain) Volatile QTL Polyphenolic QTL
Results: Differential Expression Analysis Differential expression analysis Number of DEG in each line and related to F. vesca DEG genes: Analysis of 3 replicas. DEG genes related to RV or between lines 500 most variable genes (a1)
Results: Genes Location Manhattan plot. DEG location Phisical position of DEG in each line shows a cis position Fb5:0-35 Fb7:0-10 Genome assembly version 2.0
Discussion Candidate genes: Esters LOX Fb7:0-10 8 major ester QTL Putative LOX (g.23606, g.26949 ): DE and cis- located Putative AAT (g.19411, g.23453, g.34009, g.34011): DE and in cis Fb5:0-35 12 major ester QTL Putative AAT (g.09934): down-regulated and cis- located AAT
Discussion Candidate genes: Terpenoids TPS Fb5:0-35 1 major QTL for a-pinene Putative terpene synthases (g.09971, g.09977 & g.09972): DE and located in cis Fb5:50-76 1 major QTL for nerol and 1-year QTL for myrtenol Putative terpene synthase (g.12094): Downregulated and cis- located Fb7:0-10 2 major QTL for limonene and myrtenol Putative terpene synthase (g.23886): Up-regulated and trans- located
Discussion Application NILs Genotyping Traits QTL & mqtl RNAseq Candidate Genes Linked markers Candidate gene validation F. x ananassa breeding programs