Kim S. Lewers’s research while affiliated with Agricultural Research Service and other places

The objectives of this study were to characterize strawberry cultivars grown under two production systems for gloss at harvest as a proxy for freshness and assess cultivar differences regarding the loss of gloss and changes in desiccation scores during refrigerated postharvest storage. Nine strawberry cultivars were grown in an annual plasticulture system for 3 years, harvested twice weekly, and packaged for refrigerated storage. Four of these cultivars also were grown in a low tunnel production system and harvested, packaged, and evaluated similarly. In both cases, berry gloss was measured at harvest and again after 1 and 2 weeks of refrigerated storage. Subjective desiccation scores were assigned to the berries during refrigerated storage. For both traits, effects were primarily determined by the interaction between the cultivar and time of measurement relative to harvest. For either gloss or desiccation, there was no evidence of differences in cultivar rankings based on the production system or packaging event. Cordial and Sweet Charlie were among cultivars that did not show loss of gloss or changes in desiccation scores during storage; therefore, they would not be good choices for studies that test alternative postharvest storage protocols. Keepsake and USDA Lumina were among the glossiest cultivars and those with the highest gloss levels and desiccation scores after both 1 week and 2 weeks of refrigerated storage. The variability of these traits among cultivars indicate that improvement can be made when developing new cultivars.

The non-climacteric octoploid strawberry (Fragaria × ananassa Duchesne ex Rozier) was used as a model to study its regulation during fruit ripening. High performance liquid chromatography electrospray tandem-mass spectrometry (HPLC-ESI-MS/MS) was employed to profile 28 different endogenous phytohormones in strawberry. These include auxins, cytokinins (CKs), abscisic acid (ABA), ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), jasmonates, and phenolic compounds salicylic acid (SA), benzoic acid (BzA) and phenylacetic acid (PAA) together with their various metabolic forms that have remained largely unexplored thus far. ABA, ACC and CK N6-(Δ2-isopentenyl)adenine (iP) were found to be associated with ripening while ABA catabolites 9-hydroxy-ABA and phaseic acid mimicked the pattern of climacteric decline at the turning phase of strawberry ripening. The content of other CK forms except iP decreased as fruit ripened, as also that of auxins indole-3-acetic acid (IAA) and oxo-IAA, and of jasmonates. Data presented here also suggest that both the transition and progression of strawberry fruit ripening are associated with N6-(Δ2-isopentenyl)adenosine-5'-monophosphate (iPRMP) → N6-(Δ2-isopentenyl)adenosine (iPR) → iP as the preferred CK metabolic pathway. In contrast, the ethylene precursor ACC was present at higher levels, with its abundance increasing from the onset of ripening to the red ripe stage. Further investigation of ripening-specific ACC accumulation revealed the presence of a large ACC synthase (ACS) encoding gene family in octoploid strawberry that was previously unknown. Seventeen ACS genes were found differentially expressed in fruit tissues, while six of them showed induced expression during strawberry fruit ripening. These data suggest a possible role(s) of ACC, ABA, and iP in strawberry fruit ripening. These data add new dimension to the existing knowledge of the interplay of different endogenous phytohormones in octoploid strawberry, paving the way for further investigation of their individual role(s) in fruit ripening.

Phytopathogenic fungi in the order Diaporthales ( Sordariomycetes ) cause diseases on numerous economically important crops worldwide. In this study, we reassessed the diaporthalean species associated with prominent diseases of strawberry, namely leaf blight, leaf blotch, root rot and petiole blight, based on molecular data and morphological characters using fresh and herbarium collections. Combined analyses of four nuclear loci, 28S ribosomal DNA/large subunit rDNA ( LSU ), ribosomal internal transcribed spacers 1 and 2 with 5.8S ribosomal DNA ( ITS ), partial sequences of second largest subunit of RNA polymerase II ( RPB2 ) and translation elongation factor 1-α ( TEF1 ), were used to reconstruct a phylogeny for these pathogens. Results confirmed that the leaf blight pathogen formerly known as Phomopsis obscurans belongs in the family Melanconiellaceae and not with Diaporthe (syn. Phomopsis ) or any other known genus in the order. A new genus Paraphomopsis is introduced herein with a new combination, Paraphomopsis obscurans , to accommodate the leaf blight fungus. Gnomoniopsis fragariae comb. nov. ( Gnomoniaceae ), is introduced to accommodate Gnomoniopsis fructicola , the cause of leaf blotch of strawberry. Both of the fungi causing leaf blight and leaf blotch were epitypified. Fresh collections and new molecular data were incorporated for Paragnomonia fragariae ( Sydowiellaceae ), which causes petiole blight and root rot of strawberry and is distinct from the above taxa. An updated multilocus phylogeny for the Diaporthales is provided with representatives of currently known families.

Urban populations may struggle to access health-promoting fresh fruits and vegetables, and urban agriculture approaches are of increasing interest. In this study, we used five cropping systems for urban environments to produce strawberry fruit, a popular and high-value fruit. Two green roof systems, a hydroponic system, an aquaponic system, and a raised bed system were used to grow six strawberry cultivars: ‘Albion,’ ‘Eversweet,’ ‘Monterey,’ ‘Portola,’ ‘San Andreas’ and ‘Seascape.’ We measured total mass of fruit, marketable mass, size, percentage rotted fruit and mineral content. We found productivity and aspects of fruit quality to vary among cultivars within a cropping system and the best performers in one cropping system may not be the best in another. The most consistent result was that ‘Portola’ was among the best yielding cultivars in all systems, although ‘Monterey’ had reasonably good production in most systems, good berry size in the green roof pots and raised beds, and good mineral content in the aquaponic system. ‘Monterey’ and ‘Portola’ had higher amounts of calcium, silicon and sodium in the aquaponic system than other cultivars. ‘San Andreas’ had higher amounts of copper, potassium, phosphorus and silicon in the hydroponic system. ‘Portola,’ ‘Seascape’ and ‘Eversweet’ had higher amounts of copper and zinc in the green roof planters and ‘Eversweet’ also had higher amounts of zinc and calcium in the raised beds. Given the spatial and financial constraints in urban systems and the variability of performance among cultivars, the cropping system should be selected before the cultivar.

Growing repeat-fruiting strawberries (Fragaria ×ananassa Duchesne ex Rozier) under low tunnels can extend a strawberry harvest season from a few weeks to several months. Yields from multiple dayneutral cultivars have been compared under a single film, and yields from single cultivars have been compared under multiple films, but a study of possible cultivar and film interaction effects in low tunnels has not been reported. From 2014–2018, six cultivars were compared under low tunnels covered with a standard polyethylene film and three other films purported to improve growing conditions. Traits analyzed included total yield, percent rotted yield, berry weight, percent marketable yield, and average market score. ‘Monterey’ performed above average for all traits and better under TIII TES/IR 0.102 mm thick film (TES film) or Kool Lite Plus 0.152 mm thick polyethylene film (KL film). ‘Albion’ performed above average for all traits except yield and better under TES film or Clear TIII 0.102 mm thick polyethylene film (“standard clear” or SC film). ‘Portola’ performed above average for all traits except percent rotted yield, better under SC, KL, and TES films, and had lower percent rotted yield under TES film. Because TES film was helpful to the three better-performing cultivars evaluated, it was considered a good choice for growers to try in on-farm evaluations of available repeat-fruiting cultivars. Generally, yield, berry weight, market score, and percent marketable yield were correlated positively with each other.

Strawberries are an economically important crop partly because they are very popular with consumers. Strawberry growers and breeders would benefit from knowing which cultivars and fruit traits consumers would prefer. The objectives of this study were to (1) determine consumer preference for the fruit of once-fruiting and repeat-fruiting strawberry cultivars available to grow in the Mid-Atlantic to help growers select the most suitable strawberry cultivars based on their marketability, critical sensory quality attributes, and physicochemical measurements; and (2) identify interrelationships between sensory attributes and physicochemical measurements to determine which approaches might result in breeding strawberries consumers will find most appealing. Strawberries from 10 cultivars were harvested and evaluated by a trained sensory panel and instrumentally. ‘Flavorfest’ fruits were rated highest of all 10 cultivars, and ‘Albion’ fruits were rated highest of the repeat-fruiting cultivars. Overall quality was correlated with sweetness and strawberry flavor and aroma, but not sourness. Separation of cultivar means for sweetness was better using an instrument to measure, rather than the panel evaluation. Overall appearance was correlated with visual freshness and glossiness. Light orange-red strawberries (higher L* and b*) appeared fresher and more appealing to the panels than darker more purple-red strawberries. Evaluations of strawberry fruits for berry size, juiciness, and texture were less straightforward.

Background: Consumers purchase fresh strawberries all year long. Extending the fruiting season for new strawberry cultivars is a common breeding goal. Understanding the inheritance of repeat fruiting is key to improving breeding efficiency. Several independent research groups using multiple genotypes and analytic approaches have all identified a single genomic region in strawberry associated with repeat fruiting. Markers mapped to this region were used to evaluate breeding parents from the United States Department of Agriculture - Agricultural Research Service (USDA-ARS) strawberry breeding program at Beltsville, Maryland. Results: Markers mapped to repeat fruiting identified once-fruiting genotypes but not repeat-fruiting genotypes. Eleven of twenty-three breeding parents with repeat-fruiting marker profiles were actually once fruiting, indicating at least one additional locus acting epistatically to suppress repeat fruiting. Family segregation ratios could not be predicted reliably by the combined use of parental phenotypes and marker profiles, when using a single-gene model. Expected segregation ratios were calculated for all phenotypic and marker-profile combinations possible from the mapped locus combined with a hypothetical dominant or recessive suppressor locus. Segregation ratios specific to an epistatic suppressor acting on the mapped locus were observed in four families. The segregation ratios for two families were best explained by a dominant suppressor acting on the mapped locus, and, for the other two, by a recessive suppressor. Not all of the observed ratios could be explained by one model or the other, and when multiple families with a common parent were compared, there was no predicted genotype for the common parent that would lead to all of the observed segregation ratios. Conclusions: Considering all lines of evidence in this study and others, repeat-fruiting in commercial strawberry is controlled primarily by a dominant allele at a single locus, previously mapped by multiple groups. At least two additional genes, one dominant and one recessive, exist that act epistatically to suppress repeat fruiting. Environmental effects and/or incomplete penetrance likely affect phenotype through the suppressor loci, rather than the primary mapped locus. One of the dominant suppressors acts only in the first year, the year the plant is germinated from seed, and not after the plant has experienced a winter.