A new cultivar ‘Nagomiyutaka’ for green tea was bred at the Tea Branch Facility, Miyazaki Agricultural Research Institute and released on 2010. ‘Nagomiyutaka’ was selected out of seedlings crossed between ‘Saitama No.16’ and ‘Fuku 8’ in 1988.
The characteristics of ‘Nagomiyutaka’ are as follows ;
‘Nagomiyutaka’ is medium budding, the plucking time of the 1st crop is about 1 day later than in ‘Yabukita’. The shape of the plant is slightly erect type and the growth is slightly vigorous.
‘Nagomiyutaka’ is fairly resistant to tea gray blight (Pestalotiopsis longiseta (Spegazzini) Dai et Kobayashi). But it is slightly susceptible to tea anthracnose (Colletotrichum theae-sinensis (Miyake) Yamamoto) and tea blister blight (Exobasidium vexans Massee).
It is middle resistant to cold damage in midwinter and fairly resistant to bark split frost injury in early winter. The yield of ‘Nagomiyutaka’ is higher than that of ‘Yabukita’. The quality is very high for ‘Sencha’ and ‘Kamairicha’, a kind of green tea. The aroma and taste of ‘Nagomiyutaka’ is very good because aroma is sweet smell and taste is very mild.

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Four techniques, ‘direct observation’, ‘sampling’, ‘shaking’ and ‘trapping’, were applied to detect phytoseiid mites in the tea plantation at a low density of Tetranychus kanzawai population. Among the four, ‘sampling’ and ‘trapping’ were reasonable techniques to detect phytoseiid mites in the tea plantation. In the case of which T. kanzawai was observed in the tea plantation, phytoseiid mites should be investigated by the sampling when T. kanzawai was observed on leaves, and be investigated by the trapping when the number of phytoseiid mites on the leaf samples decreased. In the case of which T. kanzawai was not observed in the tea plantation, it is desirable that phytoseiid mites are initially investigated by the trapping on spring and autumn.

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Characteristic off-flavor derived from the so-called “Natsucha-shu” is one of the major problems in summer crop of green tea. The scope of this research is to identify the key odorants in summer crop of green tea. An aroma extract dilution analysis (AEDA) has been applied to the volatile fractions isolated from three different forms of tea leaves, headspace above infused tea leaves and its infusion. Although an aroma extracts isolated from tea leaves had freshly green note, those from the headspace and infusion had its characteristic “Natsucha-shu” note. AEDA revealed 46 odor-active peaks with the flavor dilution factors between 10 and 1000. Among these odorants, 2-isopropyl-3-methoxypyrazine and 2-sec-butyl-3-methoxypyrazine were identified for the first time among the tea volatiles. An aroma extract dilution analysis has deduced that (Z)-1,5-octadien-3-one (metallic-like), 2-isobutyl-3-methoxypyrazine (earthy) and 3-methynonane-2,4-dione (green) were the most prevalent odorants in the headspace above infused sencha; while a odorant, namely, (E,Z)-2,6-nonadienal (green) was also potent odorant present in the infusion.

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The periodic changes in the radioactive cesium concentration of new shoots of tea plants was studied from June 13th, 2011 to July 24th, 2013 and analysis showed a correlation between radioactive cesium concentration of new shoots in the first crop in 2013 and its growth cultivated in Kanagawa Prefecture. It was considered that the transition of ¹³⁷Cs concentration of new shoots could be represented as an exponential function within days after June 13th, 2011. It was suggested that the decrease of the radioactive cesium concentration of new shoots in the first crop was derived from the dilution due to their growth.

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