‘Kanaemaru’ is a new cultivar of green tea (Camellia sinensis (L.) O.Kuntze) released by Institute of Fruits Tree and Tea Science, NARO (NIFTS), Japan. ‘Kanaemaru’ was selected from seedlings obtained from a cross between KNA F183 and Kanaya 13 in 1994. It was announced for application for variety registration as No.34332 under the Plant Variety Protection and Seed Act Japan on Feb.13, 2020.

‘Kanaemaru’ is medium cultivar, which opens budding one day later than ‘Yabukita’ and plucks the first crop one day earlier than in local adaptability test. Rooted cutting of ‘Kanaemaru’ was weaker than its ‘Yabukita’, but after planting the former was stronger than later. Plant growth habit is little spreading. The yield and green tea quality of ‘Kanaemaru’ were superior than those of ‘Yabukita’ at first and second crop. A similar tendency is shading cultivation.

‘Kanaemaru’ has higher disease resistance to grey blight (Pestalotiopsis longiseta (Spegazzini) K. Dai & Tak. Kobayashi) and medium resistance to anthracnose (Discula theae-sinensis (I. Miyake) Moriwaki & Toy. Sato) and blister blight (Exobasidium vexans Massee), though it is susceptible to bacterial shoot blight (Pseudomonas syringae pv. theae (Hori 1915) Young, Dye & Wilkie 1978). It has higher insect resistance to white peach scale (Pseudaulacaspis pentagona (Targioni-Tozetti)).

The cold resistance of ‘Kanaemaru’ such as cold drought damage and freezing damage, was equal to or slightly stronger than that of the strength-resistant ‘Sayamakaori’.

It can be cultivated in major tea-producing areas where ‘Yabukita’ can be cultivated.

To identify climate change impacts on tea cultivation within Shizuoka Prefecture, Japan, correlation analyses between meteorological data and first crop situation data were conducted, and a regression equation for estimating tea harvest dates of first crops was derived. Using the regression equation and climate model datasets of 1-km spatial resolution, future tea harvest dates of first crops were estimated, and were overlaid with a tea plantation map of Shizuoka Prefecture, which was created separately. It was estimated that tea harvest dates of first crops in Shizuoka Prefecture would advance by three to seven days under the RCP2.6 scenario and by more than ten days under the RCP8.5 scenario by the end of the 21st century.

The bark split frost injury in tea plants is considered to occur as follows. A trunk freezes under the night sub-freezing conditions, and ice is formed in the cambium. Water absorbed from roots is supplied there, and as a result, the ice is enlarged, and a bark split occurs. In this study, we clarified a new water supply path other than the water absorption from roots.

First, we examined the origin of the liquid that leaked from the branch that we placed under the sub-freezing conditions. We assumed that it was the sap that leaked from the inside of the branch because the leaked liquid included theanine and sucrose based on the results of ingredient analysis of the leakage liquids. Furthermore, when we observed the liquid leakage point of the bark of the branch with a stereoscopic microscope, we observed an extremely small crack on the bark. We then examined the water supply path to the ice in the cambium under the night low temperature conditions. We could confirm only minimal water absorption and transpiration of the nursery stock under the 5 ℃ - dark condition, and the water absorption from roots was insufficient for a bark split. On the other hand, when we put a branch in rock wool containing the acid fuchsin solution under the sub-freezing conditions, the acid fuchsin solution penetrated only the part where the bark split of the branch had occurred. These results show that the water supply to the ice in the cambium, which causes bark split, occurs through extremely small cracks on the bark under sub-freezing conditions.

The mulberry scale, Pseudaulacaspis pentagona (Targioni-Tozetti), is one of the most important pests of tea. The scales inhabit the leafy parts of the branches; therefore, pesticide applied from above may not reach the scales efficiently. To determine the most effective method of pesticide application using riding-type sprayers, water-sensitive paper was placed in tea bushes, and different volumes of water were sprayed over the bushes. Two sprayer models, each with two types of nozzle, were tested using the elevated boom nozzles alone, the specialized ground-level anti-scale nozzles alone, or the elevated boom nozzles together with the anti-scale nozzles. After spraying, the proportion of the paper covered with water was measured. For both the KJS4-BR model (Kawasaki Kiko Co., Ltd., Shimada, Japan) and the OMS-7F model (Ochiai Cutlery Manufacturing Co., Ltd., Kikugawa, Japan), the proportion of the paper covered by the elevated boom nozzles and anti-scale nozzles together was equal to or greater than that covered by either nozzle type alone, regardless of spray volume. This suggests that combined use of the elevated boom nozzles and anti-scale nozzles may effectively promote adherence of pesticide droplets to tea branches. In most cases where both nozzle types were used, the deeper and more inward the placement of the paper in the tea bush, the larger the proportion of the paper covered. Based on these results, it appears that combined use of the elevated boom nozzles and anti-scale nozzles is optimal for scale control.

The tea green leafhopper, Empoasca onukii Matsuda (Hemiptera: Cicadellidae), is one of the most serious insect pests of tea (Camellia sinensis (L.) O. Kuntze) in the major tea-producing regions of East Asia, including Japan, China, and Taiwan. The damage caused by leafhoppers lead to a great decrease in tea production. The leafhoppers are controlled mainly by insecticides. Broad-scale use of pesticides on tea has resulted in the development of resistance, and the presence of pesticide residues in the product. Acetylated glyceride, which is a food additive, have a highly repellent effects on adults of whiteflies on treated tomato leaves. In this study, we performed field experiments to evaluate the control effect of acetylated glyceride to tea green leafhopper. As a result, the treatment of acetylated glyceride reduced the densities of E. onukii eggs, nymphs and adults on tea shoots and the degree of feeding damage to the same level as chemical pesticides used in conventional control.

As matcha production in foreign countries has increased owing to the global demand for matcha, it is necessary to clarify the characteristics of Japanese matcha to develop Japan’s matcha export strategy. In this study, I focused on the matcha aroma. Odorants that distinguish Japanese matcha from that produced in foreign countries has been identified using aroma extract dilution analysis followed by principal component analysis. The characteristic odorants identified in this study were quantitatively analyzed, including low-boiling point odorants (dimethyl sulfide, methyl aldehydes including 2-methyl propanal, 3-methyl butanal, and 2-methyl butanal) important for the matcha aroma. Results indicated that 2-acetyl-1-pyrroline and furaneol, which were identified as the characteristic odorant representing the Japanese matcha aroma, and low boiling point odorants were abundant in Japanese matcha. These odorants were important volatile compounds responsible for the aroma of Japanese matcha. Although these odorants were generated by heating, they are also affected by shading and fertilizer management, which affect their precursors such as amino acids. Thus, it is indispensable to manage these odorants in Japanese matcha as an index to produce high-quality matcha.

Green tea that is processed from new shoots and leaves of Camellia sinensis L. contains many functional and nutritional ingredients and it has been suggested that green tea would be an important source of folate. However, there has been little information about what kind of tea is rich in folate. In this study, we investigated the contents of folate in teas among different conditions of harvestings and processing and also compared them among cultivars. As the ingredients in tea are usually taken from the infusions, the concentrations of folate in tea infusions prepared with various conditions were compared. The first crop of tea had a higher content of folate than the second crop, followed by the third crop. Younger, new shoots contained more folate than mature shoots. Long-term covering cultivation tended to reduce the folate content of new shoots by approximately 20%. Tea folate content was diminished by the oxidization process used to make semi-fermented tea or black tea; green tea was therefore the richest in folate. Tea folate was eluted not only in hot water but also in cold water-even at 0.5 ℃. Roasting of tea leaves had little effect on the folate content of refined tea; on the contrary, it made folate elution easier. Tea folate had relatively high thermal stability as its content was only slightly affected by roasting, whereas those of catechins were significantly reduced. We found differences in folate content among 66 tea cultivars. In addition, the amount of tea folate in new shoots was positively correlated with the amounts of some amino acids and negatively correlated with those of ester-type catechins. In conclusion, the ideal conditions for maximizing tea folate content would be to make green tea from the younger shoots of the first crop of a folate-rich cultivar. Folate is a nutrient that can be retained in cold-water extraction of green tea.

The growth of cutting plants in the tea cultivar ‘Sunrouge’ was investigated in a nursery bed at the Kanaya research station of our institute. ‘Sunrouge’ originated in an interspecific hybrid between Camellia sinensis and C. taliensis. Survival rates were over 95 % for 4 years, and there were no significant differences between ‘Sunrouge’ and the Japanese leading cultivar ‘Yabukita’. Rooting ability of cutting plants was very good. Excessive callus formation at the base of cuttings was not seen. Plant height, above-ground dry weight and under-ground dry weight in ‘Sanrouge’ plants were smaller than those of ‘Yabukita’ plants. The number of blanches arise from upper axis of cutting of Sunrouge’ were 2.6 and were much than those of ‘Yabukita’. Ordinary cutting propagation of ‘Sunrouge’ in a nursery bed was possible without rooting promoter, special equipment nor techniques.