Recipient Organization
MICHIGAN STATE UNIV
(N/A)
EAST LANSING,MI 48824
Performing Department
FD SC HUM NUTR ANR
Non Technical Summary
Berry production and consumption is increasing rapidly in the U.S., leading to opportunities and strains on the industry. The pillars of berry quality are color, size, firmness, sweetness, and flavor. Of these, flavor and sweetness drive consumer acceptance. Flavor is a challenging phenotype to optimize because of its chemical complexity and many influencing factors, including crop genetics and horticultural practices. Plant growth regulators (PGRs) are a promising tool for optimizing flavor because they are relatively inexpensive and already routinely used by growers. The objectives of this project are to 1) measure the effects of 3 PGR treatments on strawberry and blueberry volatile chemistry and sugar and anthocyanin content, 2) elucidate mechanism by measuring the effect of PGR treatments on flavor volatile gene expression, and 3) validate treatment efficacy by measuring PGR treatment effects on sensory attributes and consumer liking. By testing treatments in new and legacy cultivars in Florida (southern highbush) and Michigan (northern highbush; strawberry), we can provide specific guidance to inform PGR treatment selection for most growers and breeding targets for northern and southern highbush. Through existing extension programs, research results will be communicated to blueberry and strawberry stakeholders. The results of this work may extend to other berry crops, such as raspberry, blackberry, and grape, and positive results will lay the groundwork for future proposals. This project supports Foundational Knowledge of Plant Products program goals of regulating the biosynthesis of plant metabolites that improve the quality of food and micronutrient biosynthesis beneficial to human health.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
0%
Goals / Objectives
The following three objectives were formulated to enable us to achieve our primary goal of optimizing sensory quality of berry crops.Aim 1. Evaluate PGR treatments for their ability to modulate blueberry and strawberry quality parameters and flavor chemistry. H1. We hypothesize that ethylene and abscisic acid will increase ester concentration, methyl jasmonate will increase terpene concentration, and all PGR treatments will increase anthocyanins relative to untreated control samples.Aim 2. Conduct transcriptomic analyses to understand the molecular mechanisms leading to modified chemical composition by PGRs. H2. We hypothesize that finding the metabolic pathways and modulators being affected by PGRs will provide targets for future breeding and genome editing manipulation.Aim 3. Measure and model the relationship between berry chemistry and consumer perception of sweetness, flavor, and overall liking. H3. We hypothesize that strawberries with higher ester concentrations and blueberries with higher terpene and ester concentrations will be sweeter and better liked.
Project Methods
Aim 1. Evaluate PGR treatments for their ability to modulate blueberry and strawberry quality parameters and flavor chemistry. Plant care and PGR treatment. In years 1-2, southern highbush blueberry 'Kestrel' and 'Emerald' located at the Plant Science Research and Education Unit in Citra, FL, and 'Duke' and 'Bluecrop' northern highbush blueberry bushes grown at the MSU campus Horticulture Teaching and Research Center (HTRC) will be used. 'Albion' strawberry plants used for this work will be grown in the MSU Plant Science Research Greenhouse Complex and maintained using standard irrigation and fertigation regimes. In year 2, we will additionally test 'Colossus' SHB blueberry grown at UF, 'Peachy Blue' NHB blueberry grown at MSU, and 'Monterrey' strawberry grown at MSU.In the first year, field-grown highbush blueberry bushes and greenhouse-grown strawberries will be subjected to one of three PGR treatments using a 4-gallon automatic sprayer (maintained at 30 psi). The sameresearch assistant will apply the PGR treatments, harvest samples, and prepare samples for analyses in both sites to standardize practices. Through pilot testing, we have selected three PGRs that influence flavor volatile biosynthesis either through fruit ripening (1-aminocyclopropane-1-carboxylate, ACC; ABA) or stress response processes (MeJA). PGRs will be applied once at the onset of ripening (~7 days prior to harvest) at a single concentration informed by previous pilot testing (ACC - 4 mM; ABA - 2 mM; MeJA - 5 mM).The most efficacious treatments will be applied in year 2to 8 blueberry and strawberry cultivars,and volatile and sensory analysis will be carried out with all cultivars. Treatment replicates will consist of five individual plants, and in all years, treatments will be compared to control plants and replicated four times according to a complete randomized block design.Fruit harvest. Ripe (fully blue) blueberries will be harvested from each treatment when the first 30% of the berries on plants turn blue. Color development will be evaluated by tracking the relative percentage of blue versus green berries on fruit-bearing canes from each plant.Strawberries will be harvested based on complete and uniform color development.Fruit quality and aroma quantification. At commercial harvest, berries will be picked and divided into two separate pools within each treatment replicate for quality analyses requiring either fresh or frozen fruit. Berries to be used for fresh quality will be placed in a cooler and transported to the lab for storage at room temperature until processing. The average fruit weight will be estimated as well as fruit firmness. Following this, the fruit will be crushed into a fine pulp using a blender, and immediately subjected to analysis of total soluble solids, pH, and titratable acidity. Fruits intended for frozen analyses will be flash-frozen on dry ice in the field, returned to the lab, and stored in a -80 °C freezer until analysis. Fruit (forty blueberries or ten strawberries) will be ground using an analytical mill, and the frozen powder used for extracting and quantifying anthocyanins and volatiles. Anthocyanins will be extracted from fruit powder using 80% MeOH/1% formic acid. The filtered supernatant will be injected into a Waters Xevo G2-XS UPLC/MS/MS at the MSU Mass Spectrometry Core Facility. For volatile analysis, fruit powder will be combined with ascorbic acid, citric acid, linalool-d3 (internal standard), and water. The vortexed mixture will be incubated at 50 °C for 10 minutes and exposed to a DVB/CAR/PDMS SPME fiber for 3 minutes prior to injection in an Agilent 5975 GC/single quadrupole MS at the MSU Mass Spectrometry Core Facility.Aim 2. Conduct transcriptomic analyses to understand the molecular mechanisms leading to modified volatile emission by PGRsPlant material and treatment. In the second year, berries from one cultivar of each crop will be collected for transcriptomic analysis. We will select the best PGR treatment from Year 1/Aim 1 to be applied. Ripe berries from PGR treated and untreated plants will be collected prior to the PGR treatment application, as well as 1, and 7 days after the PGR treatment application for metabolomics and transcriptomics analyses. Berries from three clonal plants will be used as biological replicates.RNA isolation. Once detached from the plant, berries will be immediately frozen in liquid nitrogen or RNA preserving solution, then stored at -80 ?C. RNA extraction will be performed following the recommendations from Spectrum™ Plant Total RNA Kit (Sigma-Aldrich). Strand-specific mRNA libraries will be constructed and sequenced at the University of Florida ICBR facility using NEBNext® Ultra™ Directional RNA Library Prep Kit (NEB, USA) followed by Illumina NovaSeq platform at 2 × 150 cycles run (Illumina Inc., CA, USA).Differential expression analyses. Raw sequencing reads will be filtered and trimmed using Trimmomatic (Bolger et al. 2014). Clean reads will be aligned against the respective reference genomes using STAR (Dobin et al. 2013). For northern and southern highbush blueberry, we will use the most complete genome 'W85' as reference (Mengist et al. 2023). For strawberry, the genome from 'Yanli' will be used as a reference (Mao et al. 2023). Reads mapped to each genomic feature will be counted using HTSeq-count (Anders et al. 2015). Normalization and differential gene expression will be conducted with the R-package DESeq2 (Love et al. 2014). Pairwise comparisons will be performed between treated and untreated plants throughout the time points for each species. Differentially expressed genes (corrected p-value < 0.05, log2 fold change expression ≥ 2) will be further analyzed for gene ontology and KEGG enrichment using the plugin BiNGO in cytoscape (Maere et al. 2005) and AnnotationHub (Morgan et al., 2019), respectively.Aim 3. Measure and model the relationship between berry volatile chemistry and consumer perception of sweetness, flavor, and overall liking. Consumer perception of sensory quality.We will conduct a series of consumer tests (n=100) to characterize the effects of PGR treatments described in Aim 1 on the sensory profiles and consumer liking of strawberries and blueberries.Data will be gathered via consumer tests held in the sensory laboratories on the campus of UF and MSU where evaluations will take place in sensory booths to isolate the participants and minimize biases. In each session, participants will be asked to evaluate a set 4-8 samples, blinded with 3-digit randomized codes for overall liking and liking of appearance, flavor, and texture using the hedonic general labeled magnitude scale (hLMS), to rate the intensity of sweetness, sourness, and flavor using the gLMS, and to rate the firmness of the fruit using a visual analog scale. Subjects will be instructed to rinse their palettes with a bite of cracker and sip of water between samples. Subjects in the pool will be trained in the use of these scales and asked to provide basic demographic information about themselves and their fruit consumption habits. Surveys will be administered using the sensory software RedJade (RedJade Sensory Solutions, LLC; redjade.net).Analysis and modeling.We will conduct Analysis of Variance (ANOVA) and post-hoc means separations on all sensory attributes and hierarchical clustering to identify whether subgroups of consumers with distinct preference patterns exist. To determine which properties of berries most strongly dictate consumer liking, we will model the relationship between physicochemical properties (firmness, °Brix, TA, volatile composition), sensory properties (sweetness, sourness, flavor intensity, firmness) and consumer liking via multiple regression analysis. All analyses will be conducted using the statistical programming language R and R Studio software.