Sunrouge

Sunrouge is an anthocyanin-rich, red-leaf tea cultivar — 赤い緑茶, “red green tea,” in the phrase its own breeders and vendors use for it. It is the only cultivar in this collection that is not purely Camellia sinensis: two generations back, one grandparent is Camellia taliensis, a wild tea relative still used for tea-making in Yunnan. Sunrouge was bred at NARO’s Makurazaki Tea Research Station in Kagoshima specifically to put that species’ anthocyanin pigment into a plant that could actually be farmed, processed by machine, and sold — something no earlier Japanese red-leaf tea had managed. Registered in 2011, it was developed jointly with Nippon Paper Group, and its own release paper frames it less as a beverage cultivar in the usual sense than as a functional-food and natural-pigment crop that happens to also be drinkable as tea.

Lineage

• Cha Chuukanbohon Nou 6 (茶中間母本農6号, “Tea Intermediate Parental Stock No. 6”) ♀ — the seed parent. Not a commercial cultivar but a purpose-bred breeding line, itself an interspecific cross made in 1993 between:
  • Camellia taliensis ‘Akame’ (タリエンシス（赤芽）) ♀ — the wild tea relative that contributes the anthocyanin trait itself, along with a tree habit (upright, large-leaved, strong apical dominance) that later had to be bred back out.
  • Okumusashi (おくむさし) ♂ — a late-budding, cold-hardy registered green tea cultivar (Cha Norin No. 26, bred in Saitama from Sayamamidori × Yamatomidori and registered in 1962) that contributed cultivated-tea growth habit and cold tolerance.
• Pollen parent of Sunrouge itself — unrecorded. Sunrouge came from open (natural) pollination, not a controlled cross.

This is a two-generation, partly interspecific lineage rather than either a landrace selection or a single controlled cross. Cha Chuukanbohon Nou 6 was bred and registered specifically as a high- anthocyanin breeding stock — not for drinking, since its own tree habit and flavour still resembled its wild parent too closely for that — and then left to set seed naturally in the field at Makurazaki. Sunrouge is the individual selected out of that open-pollinated seedling population, chosen because it combined Cha Chuukanbohon Nou 6’s anthocyanin content with a growth habit closer to an ordinary tea bush. No descendants of Sunrouge are documented in the sources consulted; it is still a young enough cultivar, and commercial planting only picked up after Nippon Paper’s patent lapsed in 2013.

History

Why this had not been bred before

Japanese tea breeding has a long history of doing the opposite of what produced Sunrouge. Any seedling whose new shoots came up reddish — called akame (赤芽), “red bud” — was routinely culled from sencha breeding programmes, because anthocyanin pigment was considered a flaw that dulled the green colour and clean taste buyers expected. A native anthocyanin-bearing tea variety, Benibana-cha, had long existed in Japan, but it was fragile and low-yielding and was never bred into a commercially plantable cultivar. It took the rise of interest in functional foods from the 1990s onward — the same period that produced anthocyanin-rich sweet potato, potato and rice cultivars in Japan — for anyone to treat red pigment in tea as a trait worth breeding for rather than against.

From wild relative to registered cultivar

The programme’s first cross was made in 1993, at what was then the Kurume Branch of the Ministry of Agriculture and Forestry’s Vegetable and Tea Science Experiment Station — now NARO’s Makurazaki Tea Research Station — by breeder Takeda Yoshiyuki. Camellia taliensis ‘Akame’ was used as the seed parent and Okumusashi as the pollen parent. Seed was collected in October 1994, sown that December, and the resulting line — first tracked under the working name F95181 — was field-grown and characterised through 1999, then further evaluated as both individuals and lines from 2000 to 2003. It combined Okumusashi’s cultivated growth habit with anthocyanin levels equal to or exceeding Benibana-cha, so in October 2004 it was registered as a breeding stock — not a tea for sale — under the name Cha Chuukanbohon Nou 6, with a Plant Variety Protection Act application to follow (completed 2008).

Cha Chuukanbohon Nou 6 was, by design, not good tea: its tree still grew like its wild parent — tall, sparsely branched, strongly apically dominant — and its anthocyanin content dropped off sharply outside the first flush. From 2000 the researchers let it cross naturally in the field and collected the resulting seed; those seeds were sown at Makurazaki in 2001, planted out and individually selected from 2002, screened for anthocyanin content in 2006, and tested for suitability to photoautotrophic (tissue-culture) propagation in 2007 — a method needed because the line’s cuttings rooted poorly in ordinary propagation beds. Two candidate clones went into 2008 clonal trials: ‘Makura-Ko 02-712’ (a cross of a Benibana-cha-derived line with a separate taliensis hybrid) and ‘Makura-Ko 03-1384’ (a natural-cross seedling of Cha Chuukanbohon Nou 6). The latter proved the better anthocyanin-rich tea cultivar, and on 3 June 2009 the breeders applied to the Ministry of Agriculture, Forestry and Fisheries for its registration as Sunrouge (application published 18 August 2009, Application No. 23800). Registration under the Plant Variety Protection Act (種苗法) was completed on 20 December 2011, as Registration No. 21262. Nippon Paper Group, Inc. was a development partner from early on and held a patent on the cultivar until 2013, after which commercial planting began to spread beyond the original research plots — today it is grown commercially in Kagoshima, including on Tokunoshima, where a local processor supplies the specialist single-cultivar shops that sell it.

An unusual name for a Japanese cultivar

サンルージュ is written only in katakana, with no kanji form — itself a small tell, since most Japanese tea cultivars carry a kanji or hiragana name rooted in a place, a virtue, or a piece of classical imagery. Sunrouge’s name is built from two foreign loanwords instead: “sun” from English and “rouge,” French for red. The intended picture, per the breeders’ own explanation, is a red bud reaching toward the sun, likened to a stick of rouge or lipstick — an appropriately modern, faintly cosmetic name for a cultivar bred as much for its pigment as for its cup.

Three firsts, loosely bundled

Shinkoju’s own listing markets Sunrouge simply as 日本初の赤い緑茶品種 — “Japan’s first red-coloured green tea cultivar.” That single claim is really shorthand for three distinct firsts documented across the breeding record: it is the first Japanese tea cultivar registered from a deliberate interspecific cross bringing in a wild Camellia relative rather than staying within C. sinensis; it is the first anthocyanin-rich tea to be bred into a plant that could actually be commercially cultivated, where the older Benibana-cha never was; and it reverses decades of green-tea breeding practice that had treated red-shooted (akame) seedlings as defects to cull, making anthocyanin content a breeding target for the first time rather than a fault.

Characteristics

Sunrouge buds moderately early: in the 2011 trial at Makurazaki its buds opened around 18 March, about four days before Yabukita’s 22 March, though first-flush plucking landed on the same date as Yabukita’s and later flushes ran progressively later. The tree is of intermediate, many-branched habit — spreading wider than Yabukita rather than upright — with young shoots and mature leaves smaller than those of its Cha Chuukanbohon Nou 6 parent. New shoots turn a red-purple colour at their peak, but the colour fades if the flush is left unharvested past that day. Cutting propagation is difficult: survival in ordinary propagation beds is lower than Yabukita’s, which is why the original release relied on photoautotrophic (tissue-culture) propagation; a 2021 trial using a refined propagation-bed method at NARO’s Kanaya station reported over 95% survival, though growth was still slower than Yabukita’s. Disease resistance is mixed — slightly resistant to anthracnose, highly resistant to gray blight (Pestalotiopsis longiseta), but only weakly resistant to brown blight — while cold hardiness is good: NARO’s cultivar handbook rates its resistance to red wither (赤枯れ) and to split-type freeze injury (裂傷型凍害) as strong, and to blue wither (青枯れ) as moderately strong. Fresh-leaf yield across three 2011 pluckings on four-year-old bushes totalled 5,038 kg/ha, a shade ahead of Yabukita’s ~4,965 kg/ha in the same trial but well behind the parental line’s ~7,193 kg/ha.

The defining trait is, of course, the anthocyanin content: 0.09–0.22%DB depending on flush and year, against roughly 0.01%DB in Yabukita — near-negligible by comparison. Catechin content is lower than Yabukita’s but higher than the parental line’s, and caffeine runs slightly above Yabukita’s. Processed by the standard green-tea machine line, the resulting liquor is described in the release paper as blackish and the taste as bitter — Sunrouge was never bred to make a better-tasting green tea, only a functional and pigment-bearing one, and that trade-off shows. The anthocyanin content proved practically robust, though: it did not change measurably when fresh leaf was held at room temperature for 14 hours, nor during standard mechanical drying.

The colour change that makes Sunrouge recognisable — a neutral-pH liquor that shifts to pink or red when an acid such as lemon juice is added — comes directly from anthocyanin chemistry rather than any separate additive. Anthocyanins are flavylium-based pigments whose molecular structure changes with pH: in neutral or mildly alkaline liquid, the flavylium cation loses a proton and shifts toward colourless hemiketal and pale blue-violet quinonoidal forms, which is what gives Sunrouge’s plain liquor its muted, blackish cast. Adding acid reverses that equilibrium, protonating the pigment back toward the red flavylium cation and restoring a vivid pink-to-red colour — the same mechanism behind a red-cabbage pH indicator. Vendors sell this as a feature: shinkoju markets it for lemon, soda water and herbal pairings specifically so buyers can watch the colour shift.

Sunrouge’s anthocyanins have drawn dedicated health research distinct from ordinary green tea catechin studies. Nesumi et al. (2012) note the anthocyanins had already been isolated and characterised by that point, with functional activity under investigation; the Nippon Paper-linked seedling-technology paper (Shimizu, 2012) frames the cultivar’s anthocyanins as having a claimed anti-fatigue effect. A more substantial functional study (Wasai, Kawaoka & Tachibana, 2016) found that Sunrouge showed the strongest amylase-inhibiting and α-glucosidase-inhibiting activity of 50 existing green tea cultivars tested, that a single dose suppressed post-meal blood glucose rise in both mouse and human glucose-tolerance tests, that the effective human dose was identified as 1.0 g of Sunrouge powdered tea, and that long-term feeding trials in obesity-model mice suggested habitual intake could help prevent hyperglycaemia — positioning Sunrouge as a candidate anti-metabolic-syndrome functional food rather than simply a novelty-coloured drink.