Location: Food Quality Laboratory
2021 Annual Report
Objectives
Objective 1: Identify, characterize and manipulate key regulatory genes for antioxidant biosynthesis in pre- and post- harvest produce to optimize product quality and nutritive value. [NP 306, C1, PS1A]
Sub-objective 1A: Analyze global gene expression profiles in response to treatments and identify candidate genes and signaling pathways that regulate fruit ripening and biosynthesis of sugars, acids and phenylpropanoids.
Sub-objective 1B: Produce transgenic plants/fruits with increased or reduced expression of selected candidate genes, and determine their functional significance in fruit ripening and nutritive quality.
Objective 2: Identify pre-harvest parameters and develop commercially relevant treatments that enhance microgreen productivity, quality and nutritive value for urban and space farming. [NP 306, C1, PS1B]
Sub-objective 2A: Evaluate the effect of preharvest treatments on microgreen productivity, quality and nutritive value in controlled environment settings.
Sub-objective 2B: Conduct global gene expression analysis of microgreens in response to abiotic stresses encountered in space or under microgravity.
Approach
For first objective, strawberry fruit at early and late stage of fruit development will be treated with BZT and AMD, two compounds showing impact in controlling fruit color and firmness, etc. Global gene expression will be studied to identify candidate genes related to fruit ripening and biosynthesis of sugars, acids and phenylpropanoids. Selected genes can be used as functional markers for industry management and breeders. Once these genes are identified, the already commercially available treatments, such as calcium and UVB, will be applied to determine whether and how these treatments affect expression of the selected genes. The optimum treatments will be identified from two approaches and/or combination of two approaches if there is an additive or synergistic effect. Further, stable or transient transformation with silencing or over-expression gene constructs will be used to assess the function of specific genes in various aspects of fruit physiology and metabolism, including ripening, sensory parameters, responses to stresses, and accumulation and/or retention of health-beneficial secondary metabolites.
For second objective, microgreens, young vegetable seedlings with rich nutrition, such as broccoli, red radish, amaranth and pea will be selected for this study. The seeds of microgreens will be subjected by physical treatments, such as cold plasma, UVC to control pathogen infection and promote seed germination. Seedlings will be treated with different lights, UVB, and calcium and carbon dioxide. Microgreen growth and quality at the production level will be evaluated to determine the best practice for microgreen yield and quality. In collaboration with NASA, microgreen growth and quality will be studied under microgravity and high carbon dioxide. Global gene expression analysis of microgreen responses to stress both in controlled environment systems on earth and in microgravity will be investigated to determine how stress relates to yield and quality at the gene and metabolic pathway level. Putative differentially expressed genes will be used to find which genes are the better markers for future use in industry.
Progress Report
This is the first year report for Project Number 8042-43000-016-00D "Integrated Approaches to Improve Fruit and Vegetable Nutritional Quality with Improved Phenolics Contents" under National Program 306 "Product Quality and New Uses", Component 1, Foods. Objective 1 is to identify, characterize and manipulate key regulatory genes for antioxidant biosynthesis in pre- and post- harvest produce to optimize product quality and nutritive value. Objective 2 focuses on identification of pre-harvest parameters and the development of commercially relevant treatments that enhance microgreen productivity, quality, and nutritive value for urban and space farming. Progress was made in both objectives and their subobjectives.
Under Objective 1, strawberry plants (cultivar Albion) growing in greenhouse were treated with carboxamide (CAD) and phenylacetamide (PAD) analogs. CAD and PAD were previously identified as potential novel plant growth regulators in promote and delay fruit ripening, respectively. The modifications of the chemical groups in CAD and PAD showed the different effects on fruit development and ripening, suggesting the importance of the chemical structures for their biological functions. This will help in identifying their natural compound analogs. In addition, cherry tomato fruits at late green stage were harvested and treated with CAD and PAD. They also showed similar effects for controlling fruit ripening in tomato and strawberry. Hence their effects on fruit ripening are a general phenomenon for non-climacteric and climacteric fruits. Moreover, CAD and PAD also exhibited strong effect on delaying and promoting seed germination respectively. Both CAD and PAD have been filed for USA patent application because of their great potential to be used by growers and industry to control fruit quality and shelf life, and reduce food waste.
In terms of Objective 2, two arugula varieties, Diplotaxis tenuifolia var. Sylvetta and Eruca sativa cv. Astro were selected for selenium biofortification in microgreens. Selenium is a trace element with beneficial health effect, especially for people with some chronic diseases and vegetarians. In both cases, adding 1-10 ppm promoted plant growth and increased yield (fresh weight) from 15-50%. In addition, selenium application increased Astro microgreen selenium content up to about 9 ppm from nearly 0. High light intensity showed additive effect for microgreen yield and selenium uptake. Hence, selenium application will be useful for improving microgreen yield and quality for CEA and urban agriculture.
In collaboration with NASA, calcium uptake in microgreens under microgravity was compared with normal gravity. Calcium deficiency causes bone loss, which is a big challenge for astronauts. Broccoli microgreens under microgravity absorbed about 20% more calcium than those under normal gravity. Further, the plants grew faster under microgravity than normal gravity. The yield of broccoli microgreens with calcium under microgravity was increased by about 64% as compared to normal gravity. Thus, calcium has better impact on plant growth in space than on earth. The overall impact of the accomplishments is that astronauts and people in space have new information for achieving high yield and calcium content microgreens.
Accomplishments
1. Preharvest UVB application increases glucosinolate contents and enhances postharvest quality of broccoli microgreens. Broccoli microgreens have shown potential health benefits due to their high glucosinolate (GL) levels. ARS scientists at Beltsville, Maryland, studied the influence of preharvest UVB irradiation on GL levels in broccoli microgreens and showed the treatments significantly increased total aliphatic GL levels above 15 percent when measured on the harvest day. During storage, broccoli microgreens treated before harvest with UVB and calcium spray maintained overall quality and long shelf life. Furthermore, preharvest UVB treatment significantly maintained health-beneficial compound levels such as GLs and prolonged broccoli microgreens' postharvest quality by inhibiting the expression level of myrosinase, a gene responsible for GL breakdown during postharvest storage. This research provides a simple and practical approach to improve broccoli microgreen nutritional quality for CEA.
