Kirari 31

Kirari 31 is an early-budding sencha, kabusecha and gyokuro cultivar bred at the Miyazaki Prefectural Agricultural Experiment Station’s Tea Research Branch, crossed in 1994 from Sakimidori and Saemidori — two cultivars from the same station, both already valued for colour and quality rather than sheer volume. It buds about four days ahead of Yabukita and comes close to doubling Yabukita’s first-flush yield, while its sencha, kabusecha and gyokuro were judged equal to or better than Saemidori’s. It was bred against a run of split-bark and winter-bud frost damage that had been troubling early-budding cultivars, and the combination of early growth with strong, early-acquired cold tolerance is the trait the whole nineteen-year development programme was built around.

Lineage

• Sakimidori (さきみどり) ♀ — the seed parent, contributing vivid, stable leaf and liquor colour and slightly early budding. Itself a controlled cross of NN27 (♀, an unreleased breeding line out of Yabukita x Shizuoka Zairai No. 16) and ME52 (♂, a Miyazaki landrace selection), crossed in 1979 and registered nationally in 1997.
• Saemidori (さえみどり) ♂ — the pollen parent, contributing early budding, high umami and strong processing quality. Itself a cross of Yabukita (♀) and Asatsuyu (♂), per Kirari 31’s own release-paper pedigree chart.

This is a controlled cross, not a landrace selection, made deliberately at the Miyazaki station. It has a close reciprocal counterpart, Haruto 34 (はると34), crossed at the same station in 1997 with the parents reversed — Saemidori as seed parent, Sakimidori as pollen parent — and registered in 2020 (per NARO’s handbook, not independently re-verified here). Kirari 31 also shares its pollen parent with NARO’s own Seimei (Fushun x Saemidori, bred separately at Makurazaki, Kagoshima, around the same period) — one instance of a broader pattern of Saemidori being reused across Japan’s late-twentieth- century tea-breeding programmes for its early budding and quality. No descendant of Kirari 31 itself is documented in the sources consulted here.

History

Crossing and individual selection, 1994-1999

Sakimidori (seed parent) and Saemidori (pollen parent) were crossed in 1994 at the Miyazaki Prefectural Agricultural Experiment Station’s Tea Research Branch. Seed was collected in October 1995, and 1,290 seeds were sown directly into an individual-selection field that November. The resulting seedling population was managed and screened as a group for three years, 1996 to 1998; 28 individuals with superior leaf colour and disease resistance were propagated by cuttings in June 1998, and all 28 clonal lines were field-planted in May 1999. One of those 28 — carried under the trial designation Mi99-23 — was tracked separately in a clonal comparison trial from 1999 to 2003, examining growth and quality; this is the line that became Kirari 31.

Regional trials, 2004-2013

From 2004 the line moved into wider testing under the trial name Miyazaki No. 31 (宮崎31号). A national-programme clonal adaptability trial (系適試験, “11th group”) ran at Mie, Kyoto, Kochi and Kumamoto, and broader regional adaptation trials ran at public tea-research institutes in ten prefectures overall (including Miyazaki) plus NARO’s own Vegetable and Tea Science Research Station. Shizuoka began a dedicated mochi-disease trial and Kagoshima a dedicated split-bark frost-injury trial that same year. A further funded round from 2011 to 2013 tested its adaptability for gyokuro and kabusecha specifically; by then the acknowledgements list fifteen prefectural and institutional collaborators in total — Mie, Kyoto, Kochi, Kumamoto, Shizuoka, Kagoshima, Saitama, Shiga, Nara, Kagawa, Fukuoka, Saga, Nagasaki, Miyazaki and NARO’s own institute — on top of the two dedicated disease trials. (The funding line moved with it: the designated national tea-breeding programme that had run since 1958 ended in 2010, and the station worked under the newer Agri-Food Science and Technology Research Promotion Programme from 2011.)

Combining cultivation, yield, quality, cold-tolerance and disease-resistance data from 2010 to 2012, all eleven trial sites active by then rated the line “promising” or “somewhat promising”; Mie, Shiga, Fukuoka and Kumamoto gave it the top rating. Sencha quality was rated excellent outright, and gyokuro and kabusecha quality equal to or better than Saemidori’s — enough, together with its cold tolerance, ring-spot resistance and yield, for the review committees to judge it ready for wider cultivation as a mountainous-region-capable green tea line.

Naming and registration

Review committees cleared it for a Plant Variety Protection Act application through late 2012 and early 2013, and on 20 December 2013 the application was filed under the name Kirari 31 (application No. 28772). It was publicly announced on 15 May 2014, and the registration itself was granted on 25 March 2016, as registration No. 25105 — three distinct milestones four years apart, not three sources disagreeing with each other; secondary references giving only “December 2013” or “May 2014” as the registration date are describing the filing and the announcement, not the grant. The full development period, crossing to registration application, ran nineteen years, and six researchers are credited across it: Hiroshi Yoshidome, Minoru Miyamae and Tsuruyoshi Furuno at the Tea Branch Facility, and Hirofumi Nagatomo, Takashi Mizuta and Kenichiro Sato at associated agricultural community development and administration offices.

The name plays on the number 31 itself: the release paper glosses “3” as SUN (太陽, taiyō, “sun”) and “1” as ippai (一杯, “a cupful,” i.e. “to the full”), read together as a shoot growing to the full while bathed in sunlight and yielding tea in abundance — “kirari,” a flash or glitter of light, for the cultivar that results.

Characteristics

Averaged over ten years at the breeding station, Kirari 31’s first-flush budding date runs about four days ahead of Yabukita’s and its plucking date about three days ahead; across the wider trial network the margin was much the same, four days early to bud and two early to pluck. It runs slightly behind Saemidori — one to four days later to bud, depending on the trial. Tree form is intermediate, vigour and branching both stronger than Yabukita’s, with a somewhat acute leaf angle. New leaf is long-elliptical, close to Yabukita’s in size, thickness and colour, and graded somewhat glossy, somewhat soft and somewhat hairy — the same three grades Yabukita takes; mature leaf is larger than Yabukita’s but thinner.

Nursery survival runs a little behind Yabukita’s — 86% against Yabukita’s 88%, though ahead of Saemidori’s 73% — but the gap closes within a year: first-year field survival averages 97% across all three. Second-year canopy spread and growth both outpace Yabukita and Saemidori, and the new leaf holds a visibly deeper green than Saemidori’s from as early as 21 days after budding through to 27 days, measured by chlorophyll meter (SPAD-502).

Yield is the standout trait: averaged over bushes aged five to eight years at the breeding station, first-flush fresh leaf runs 511 kg/10a and, over bushes aged five to seven, second-flush 520 kg/10a — index values of 184 and 162 against Yabukita’s 277 and 322 kg at 100, a scale on which Saemidori’s own 353 and 482 kg index 127 and 150. Cold tolerance is strong and, unusually for an early-budding line, acquired early in the season: split-bark frost-injury resistance already exceeds Sayamakaori’s from early November, and by late November and December matches or exceeds both Sayamakaori’s and Kanayamidori’s — two of the more cold-hardy cultivars in cultivation. Winter-bud frost damage runs lower than both Yabukita and Saemidori, and in a dedicated trial at Saitama, the harshest-winter site in the network, both red-scorch and blue-scorch injury (赤枯れ, 青枯れ — cold-damage symptoms distinct from any pathogen) came in milder than Yabukita’s.

True disease and pest resistance is more mixed. Ring spot disease (輪斑病) is “somewhat strong,” on a level with Sayamakaori and Kanayamidori. Anthracnose (炭疽病) and mochi disease/blister blight (もち病) are both “weak,” and bacterial shoot blight (赤焼病) — a genuine bacterial disease, distinct from the cold-scorch symptoms above despite the similar English name — is “somewhat weak.” Resistance to the mulberry scale insect (クワシロカイガラムシ) is worse still, “extremely weak.” The release paper is explicit that ring spot is the only one of these Kirari 31 can be grown without routinely spraying for; the rest need active management in districts where they occur.

The cup is where the breeding programme’s aims show most clearly. Made as sencha, kabusecha or gyokuro, quality was judged equal to or better than Yabukita’s and Saemidori’s across the trial network, particularly in colour, aroma and liquor colour; a high free amino acid content and correspondingly low tannin content give it a pronounced umami against comparatively little astringency. It suits shaded cultivation for gyokuro and kabusecha as well as open-field sencha — an intentional design goal rather than an incidental strength. At least one specialist retailer (Shinkoju) also sells it deep-steamed and roasted, though sencha, kabusecha and gyokuro remain its only officially registered uses. As a cultivar registered only in 2016, it is still moving from trial plots into commercial planting and remains less widely available than either parent.