Tea (Camellia sinensis) is grown in at least 66 countries around the world (Pettigrew, 2018) and is currently being explored as a new specialty crop in the southern United States (Orrock et al., 2017). Tea is the most consumed beverage in the world (Food and Agriculture Organization of the United Nations, 2018), and its consumption in the United States is increasing. From 2012 to 2018, U.S. wholesale tea sales increased from $9.79 billion to $12.66 billion (Statista, 2021), but domestically produced tea comprises only a negligible share of the market. Tea plants were introduced to the United States in 1799 (Pratt and Walcott, 2012), and tea has been grown historically in the southeastern part of the country. The first large-scale commercially successful tea venture was the Pinehurst Tea Planation/Charleston Tea Plantation, which was established in 1888 near Charleston, SC; however, interest in tea production waned by the 1900s, primarily as a result of increasing labor costs (Pettigrew, 2018; Shepard, 1899). With the introduction and subsequent improvements in mechanical harvesters for tea, and increasing interest in locally grown produce, opportunities for tea production are once again emerging in the United States. As of 2018, tea was cultivated in 17 states on 181 ha for an annual domestic production total of 5.6 t (Pettigrew, 2018; Pratt and Walcott, 2012). Florida is considered to have suitable areas for tea production, and tea has the opportunity to be a new specialty crop for the southeast region.
Yield maximization is one of the most important components of a successful tea plantation. Although yields can be improved by optimizing management practices, genetic limitations on yield can be problematic for a farmer, especially when costs for replanting with new varieties are high (Carr, 2018). Currently, there are no standard tea varieties available commercially in the United States that have been bred for high yield, and no information is available on yields of tea accessions grown under north-central Florida conditions. We use the term accession here to describe a collection of plants acquired from a single source under a particular name, without implying that the collection is homogeneous or fully characterized, as might be expected of a variety. A successful tea breeding program will need this information to develop and evaluate varieties adapted specifically to produce high yield under the growing conditions in Florida and other U.S. states adjacent to the Gulf of Mexico. However, calculating yield is labor intensive, and tea plants do not reach full yield potential until 5 to 6 years after planting. As the harvestable unit of the tea plant is the immature leaves, tea can be harvested at any stage of plant development. Identifying growth parameters that can predict yield from individual young plants would expedite the data collection needed to inform breeding efforts. Furthermore, if the relationships between plant growth and yield are understood for a particular location (e.g., Florida), we may be able to use specific measurements to optimize cultural practices such as fertilizer application and irrigation.
In a commercial setting, a tea plant receives numerous prunings over the first 5 to 6 years in the field (Goswami, 2011). These initial prunings, called formative prunings, are critical for establishing a central trunk, with three evenly spaced branches that, as the tea plant matures, will grow into the traditional plucking table. In typical high-density commercial plantings, per-plant yield can be expected to increase with plant age until canopy closure, after which mature bushes may compete with neighboring plants, resulting in reduced yields per plant (Carr, 2018). Therefore, yield calculations in a mature planting are a product of both genetic potential and competition created by site-specific factors, and are thus difficult to generalize. To determine differences in genetic yield potential, it is preferable to evaluate tea plants just before canopy closure, reducing the influence of competition on the resulting data. Yields are reported to increase an average of 588% from year 1 to year 5 (Goswami, 2011), during which time competition may be expected to be minimal, and yield data should reflect genetic potential under prevailing environmental conditions.
In our previous work (Orrock et al., 2017), we evaluated the survival and establishment of eight tea accessions available commercially in the southeastern United States, at the Plant Science Research and Education Unit in Citra, FL. We determined that the accessions Big Leaf, Fairhope, Georgian, and Large Leaf had the most rapid early growth, measured as pruned biomass; however, the earlier data only examined survival and growth (Orrock et al., 2017). Building on our previous work, the research presented here examines yields of seven tea accessions in Florida over two growing seasons, describes correlations between plant growth measurements and yield, and confirms tea quality among the accessions using caffeine as an objective quality metric (Zhang et al., 2020a).
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Survival of tea accessions following field planting in Citra, FL. Mean number of living plants per block for years 2017 and 2018 are presented for each accession. Plants of each accession were planted in three different blocks following the randomized block design.