Location: Genetic Improvement for Fruits & Vegetables Laboratory
2023 Annual Report
Objectives
Objective 1: Generate once-fruiting strawberry selections and varieties for the Mid-Atlantic and surrounding region, for use in traditional matted-row and/or annual plasticulture production systems, with emphasis on high yield; excellent fruit quality; long shelf life; and resistance to Colletotrichum, Botrytis, and foliar and fruit-rot diseases. [NP301, C1, PS1A, PS1B]
Objective 2: Generate repeat-fruiting strawberry breeding selections with an open plant architecture; adequate runner production; high continuous yield; large fruit with excellent quality; and resistance to Colletotrichum, Botrytis, and foliar and fruit-rot diseases for use in developing varieties for extended-season production systems. [NP301, C1, PS1A, PS1B]
Objective 3: Dissect the molecular, genetic, and environmental factors affecting strawberry production-efficiency traits, especially disease resistance and control of plant architecture, through initiation and development of plant organs such as stolons, branch crowns, and inflorescence structures. [NP301, C3, PS3A]
Objective 4: Identify or generate new strawberry mutant genetic stocks for determining the functions or regulation of genes affecting disease resistance. [NP301, C3, PS3A]
Approach
Standard plant breeding methods will be used to generate superior strawberry cultivars for traditional production practices and fruiting for the traditional short spring season. Novel evaluation practices for fruit quality and flavor will be developed and incorporated into the annual breeding cycle. A seedling screen for resistance to anthracnose crown rot, an emerging disease of worldwide importance, will be developed to identify resistant strawberry plants and increase the breeding population’s average resistance to the disease. New cultivars resulting from selection based on increased disease resistance, fruit quality, yield, and shelf life will be released. To help satisfy demand for year-round availability, similar methods will be used to generate improved strawberry plants that fruit for an extended season from April through December. Because the longer-fruiting plants will face weather and pest challenges that are not problems during the traditional fruiting season, new comparison methods will be developed to facilitate identification of plants that produce fruit within the traditional season, and produce equally well outside the traditional strawberry season. Additional research will be done to optimize the season-extending “low-tunnel” production system developed in the previous Project Plan to better evaluate advanced breeding selections. Inheritance of the strawberry’s capacity for continuous fruiting will be studied with both classical and molecular genetics. Characterization of novel mutant diploid lines with microscopy, hormone physiology and analysis, genetics, and genomics will illuminate genetic control and regulation of stolon production, a trait of vital importance to strawberry nurseries and growers.
Progress Report
Objective 1: In the 2022 replicated evaluations, B2875, an early-season selection repeated its superior performance the previous year. B2875 has with high yield of large, showy, sweet fruit with good postharvest shelf life. An early-season cultivar with high yield of large, sweet fruit resistant to anthracnose fruit rot is highly desirable in the industry.
Objective 2: In Spring 2023 the repeat-fruiting yield trials were established for the purpose of testing whether the population for this objective can move forward without the protection of low tunnels. Two replications were established under low tunnels and two were established without. One reference cultivar will be tested with one selection not previously evaluated in yield trials, and six selections that performed very well in previous years but have not yet been evaluated together.
Objective 3: Evaluations of mutant populations continue in order to establish the gene number and action responsible for each mutant.
Objective 4: Segregation ratios of individual families revealed that resistance is controlled by more than just the one gene identified in Florida. In Fall 2022 about 70% of the seedlings were identified as susceptible. Segregation ratios of the families showed the same genetic architecture for resistance to anthracnose crown rot as for repeat fruiting. The genetic architecture was confirmed through conversations about unpublished data at an international meeting March 2023. Informative crosses were used to identify seven likely-resistant parents and many more likely-susceptible parents. The crossing plan in place Fall 2022 was modified to ensure that no cross was made between two known-susceptible parents January/February 2023.
This is the final report for the Project 8042-21220-257-000D which ended March 2023. It was replaced by the new NP301 Project 8042-21220-260-000D entitled “Strawberry Crop Improvement through Breeding, Genetics, Genomics, and Molecular Biology”.
Objective 1: Over the life of the project, two once-fruiting cultivars, ‘Keepsake’ and ‘Cordial’, were patented and licensed in the U.S. and Canada. Both demonstrate the breeding population’s improvement for postharvest quality. Data collection for at-harvest and postharvest fruit quality evaluation has increased and relies less on subjective ratings and more on instrumentation: a gloss meter; a color meter; a meter that measures sugar content; and two meters that measure acidity in two different ways (pH and titratable acidity). In the 2021 and 2022 replicated evaluations, B2875, an early-season selection with high yield of large, showy, sweet fruit with good postharvest shelf life, was identified for testing by commercial nurseries and probable patent application during the life of the next project.
Objective 2: Over the life of the project, the repeat-fruiting breeding population’s plant architecture and runner production have been improved substantially to match that of commercial repeat-fruiting cultivars. Yield is superior to the leading repeat-fruiting cultivar in the Mid-Atlantic. The genetic control of repeat-fruiting in commercial strawberry was demystified: two genes, one dominant and one recessive, function to mask the activity of a third gene that confers repeat fruiting. The use of low tunnels in evaluations has been fine-tuned to use a single reference cultivar and a single optimal plastic film to cover the low tunnels in typical Maryland conditions. Evaluations have transitioned from selection of future parents from among observation plots to selections of a possible cultivars in replicated evaluations. In 2021 and 2022, three selections performed comparably to the reference cultivar in replicated evaluations and will be tested together in the next project.
Objective 3: Over the life of the project, EMS mutagenesis of the Hawaii 4 inbred line of a diploid strawberry model resulted in over 80 plants with morphological or developmental variation. These were sorted into groups, and selected plants within groups exhibiting abnormal runnering, low or no fruit production, abnormal fruit shape, and abnormal plant architecture were subjected to genetic, physiological, and biochemical, as well as morphological analyses, along with two mutants from a previous EMS mutagenesis of the 5AF7 line.
Objective 4: Over the life of the project, the emerging disease, anthracnose crown rot, became naturally established in the project’s research fields, eliminating the need to develop an artificial inoculation protocol. In Fall 2021, about 50% of the seedlings were identified as susceptible (crown death or foliar symptoms). Segregation ratios of individual families revealed that resistance is controlled by more than just the one gene identified in Florida. In Fall 2022 about 70% of the seedlings were identified as susceptible. Segregation ratios of the families showed the same genetic architecture for resistance to anthracnose crown rot as for repeat fruiting. The genetic architecture was confirmed through conversations about unpublished data at an international meeting March 2023. This genetic architecture, highly unusual for plants but observed for two traits in octoploid strawberry, is information that should be key to planning future research on strawberry. Informative crosses were used to identify seven likely-resistant parents and many more likely-susceptible parents. The crossing plan in place Fall 2022 was modified to ensure that no cross was made between two known-susceptible parents January/February 2023.
Accomplishments
1. ‘USDA Lumina’ strawberry cultivar was released. Strawberries that fruit early in the strawberry season are highly desirable to capture higher prices and to attract customers to U-pick farms early each year. Several early-season cultivars are available, but each is lacking in one or more key traits. ARS researchers at Beltsville, Maryland, released ‘USDA Lumina’, an early-season strawberry that combines all these key traits: winter-hardiness; high yield; resistance to anthracnose fruit rot, low botrytis fruit rot; and large, sweet, beautiful fruits that do not split open in the field or turn dark in refrigerated storage. Plants of ‘USDA Lumina’ were sent to three U.S. and one Canadian nurseries for propagation. A U.S. plant patent application is in process. ‘USDA Lumina’ is expected to have greatest value to growers in the Mid-Atlantic and other hot growing conditions where other cultivars fail to perform.
Review Publications
Islam, N., Krishnan, H.B., Slovin, J.P., Natarajan, S.S. 2023. Metabolic profiling of a fast neutron soybean mutant reveals increased abundance of isoflavones. Journal of Agricultural and Food Chemistry. 71(26):9994-10003. https://doi.org/10.1021/acs.jafc.3c01493.
Upadhyay, R.K., Motyka, V., Pokorna, E., Dobrev, P.I., Lacek, J., Shao, J.Y., Lewers, K.S., Mattoo, A.K. 2023. Comprehensive profiling of endogenous phytohormones and expression analysis of 1-aminocyclopropane-1-carboxylic acid synthase gene family during fruit development and ripening in octoploid strawberry (Fragaria× ananassa). Plant Physiology and Biochemistry. 196:186-196. https://doi.org/10.1016/j.plaphy.2023.01.031.
