Theses and Dissertations

ORCID

https://orcid.org/0000-0002-1058-3348

Issuing Body

Mississippi State University

Advisor

Bi, Guihong

Committee Member

Harkess, Richard L.

Committee Member

Zhou, Qian

Committee Member

Schilling, M. Wes

Committee Member

Broderick, Shaun R.

Other Advisors or Committee Members

Blythe, Eugene K.

Date of Degree

5-13-2022

Document Type

Dissertation - Open Access

Major

Horticulture

Degree Name

Doctor of Philosophy (Ph.D)

College

College of Agriculture and Life Sciences

Department

Department of Plant and Soil Sciences

Abstract

Tea is the most popular beverage worldwide, second only to water. The United States is the third largest importer of tea in the world, importing a total of about 260 million pounds tea annually. With increased demand for locally sourced food products, questions are raised regarding whether domestic production of tea is feasible. Compared to major tea producing countries with centuries of growing history, tea production in the U.S. is limited and requires research support in many aspects of tea production. The objectives of this study were to investigate plant growth, leaf morphology, and seasonal chemical compositions in tea leaves of nine tea cultivars grown in Mississippi, United States; evaluate the effects of black, blue and red shade nets on plant growth and seasonal leaf quality of tea plants; and investigate the content of mineral nutrients in tea leaves of different cultivars and one cultivar under different colors of shade nets. The nine tested tea cultivars varied in plant growth, leaf morphology, cold tolerance, biochemical composition [including soluble solids, carbohydrates, total polyphenols (TP), free amino acids (AA), L-theanine, and caffeine], and mineral content in tea leaves. Among all cultivars transplanted to the field from one-gallon containers in spring 2017, ‘BL2’ had the greatest plant growth index (PGI) when measured in Feb. 2018 and Feb. 2019, which may be helpful toward suppressing weeds and early establishment of a tea plantation. ‘Christine’s Choice’ had the highest content of nitrogen, phosphorus, sulfur, zinc, iron, and boron, and the second highest content of potassium, calcium, and magnesium. The cultivars evaluated in this study generally adapted well to the local environment. All tea samples collected from the nine cultivars and three seasons were considered suitable for green tea processing with low total polyphenol to free amino acids ratios (TP/AA) ranging from 1.72 to 3.71. When compared to unshaded control, black, blue, and red shade nets increased PGI, net photosynthetic rate, and stomatal conductance, decreased N content in tea leaves, decreased air and leaf surface temperatures in summer and reduced cold damage in winter. Red shade nets were considered helpful for improving green tea quality by increasing the content of L-theanine and free amino acids in tea leaves collected in spring and fall compared to unshaded control.

Sponsorship

Mississippi State University Agricultural and Forestry Experiment Station Strategic Research Initiative Program (MIS-212050), United States Department of Agriculture (USDA)-Mississippi Department of Agriculture and Commerce Specialty Crop Block Grant Program (G00000343), USDA National Institute of Food and Agriculture Hatch Project (MIS-249180), USDA-Mississippi Department of Agriculture and Commerce Specialty Crop Block Grant Program (G00002402)

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