Damages caused by meteorological disasters in tea plants propagated by plug cutting were investigated in 6 tea gardens. While the above-ground parts of the tea plants grew spindly, growth of the under-ground parts was poor. Phenomena of lodging or blowing off of young tea plants, cutting of fine roots, lignification of roots, and expansion of cone-shaped holes at the base of tea trees were observed. Roots were lignified along the shape of plug, like a wooden pestle. When the spindly grown above-ground part was shaken by the wind, the lignified root rotated with a mortar-shaped hole digging at the base of tea plants. When a plastic mulch film was spread on the ground before transplanting to control weeds, the soil under the film become wet and soft, and growth of the roots was poor due to over-humidity.

We examined a predictive model for the yield of newly plucked shoots and their quality in order to develop a support system that can formulate an optimal plucking plan by distributing the production amount in a time-series order according to the processing capacity of the tea factory.

In this model, we track the growth of new shoots that begin in early spring and change from the beginning of new shoots budding until the growth of the banjhi shoot reaches 100%, and even after the banjhi shoots reaches 100%. Assuming that, the new shoot growth score model was considered as a model showing the quantity of growth change from the time of bud opening.

Furthermore, we created a series of models that can predict the yield of plucked new shoot and their fiber content according to the time-series changes with the new shoot growth score from the correlation between the rate of banjhi shoot and the yield　of plucked new shoot and fiber content obtained so far.

As a result, using this model, it will be possible to develop a system that can obtain an optimal plucking plan of the plucked new shoots according to the processing capacity of the tea factory in time-series order.

In this study, I calculated the number of samples required to achieve the desired accuracy for estimating the density of the tea green leafhopper, Empoasca onukii, in tea fields. I used the beating method in multiple quadrats in the fields. Analysis of the distribution pattern of E. onukii in the field, based on the total number of adult larvae, revealed an index of basic contagion (α) of -0.0787 and a density-contagiousness coefficient (β) of 1.13, indicating a slightly concentrated distribution. These α and β values suggested that at least one individual per quadrat (a B5-sized whiteboard) is required to ensure an accuracy level D = 0.3 in the case of using 10 boards. I also extrapolated them to an A4 size by generating dummy data, and estimated that the number of quadrats required was almost the same as that for the B5 size. Further, I explored methods to estimate the mean density from either the presence ratio of the leafhopper in the quadrats or the maximum count from a single quadrat. I applied the Kohno-Sugino equation as the model equation to establish the relationship between the mean (x) and the frequency rate of presence (y), and derived the nonlinear regression equation y = 1 - exp (-0.846x^0.981). As for the relationship between the mean value (x) and the maximum value (y), a linear regression equation of y = 3.02x was derived. These results contribute to preliminary investigations prior to precise density estimation.

Tea cultivar ‘Saeakari’ has characteristic aroma similar to beans, edamame, green peas, corn, and chestnut. The key odorants the tea cultivar ‘Saeakari’ headspace were isolated and identified them using aroma extract dilution analysis performed via gas chromatography-olfactometry. This research identified that 2-acetyl-1-pyrroline is responsible for the characteristic aroma of ‘Saeakari’. Moreover, it also enhanced the edamame and sweet flavor of ‘Saeakari’. It was also present in large quantities in the cultivars ‘Asatsuyu’ and ‘Saemidori’. These two cultivars belong to the same strain as ‘Saeakari’. Therefore, these three cultivars would have inherited 2-acetyl-1-pyrroline from the tea strain.