Horyoku

Horyoku (ほうりょく) is a green tea cultivar of unusual ancestry: like Benihomare, it descends from Assam-type tea seed introduced to Japan in the 1870s in the wake of Tada Motokichi’s mission to Assam, Darjeeling and Ceylon, which makes it — despite being processed into green tea — genetically closer to Indian Assam tea than to the Chinese-type (var. sinensis) stock behind almost every other cultivar in this collection. It was never submitted for Japan’s national Cha Norin cultivar registration and holds no Plant Variety Protection registration either, so in the strict sense it is not a “released” cultivar at all — a working selection that never went to market on its own. Its documented legacy is narrow but real: it is the seed parent of Ryofu (りょうふう, Cha Norin No. 45), a cultivar registered in 1997 specifically to carry Horyoku’s disease resistance into a plantable, quality sencha cultivar.

Lineage

• Assam-type (アッサム系) open-pollinated seedling — NARO’s own published pedigree chart for Ryofu gives Horyoku’s own parentage as “アッサム系♀” (Assam-type, female) crossed naturally with an unrecorded pollen parent (“？♂”). It is not a single traceable mother tree so much as an individual picked out of an open-pollinated planting of Assam-type stock.
• Pollen parent — unrecorded, per the same chart.

Ryofu’s own 1999 release paper is more specific about what “Assam-type” means here, describing Horyoku as 多田系印度雑種実生 — a seedling of Tada-line Indian-hybrid stock, i.e. germplasm descended from the tea seed the former shogunate retainer Tada Motokichi brought back from Assam and Darjeeling in 1877. That is the same seed stock behind Benihomare (茶農林1号, 1953), Japan’s first registered tea cultivar — but no source found ties Horyoku’s individual mother tree to Benihomare’s own lineage at Nishigahara, Tokyo. NARO’s pedigree chart credits Horyoku’s own breeding to Shizuoka Prefecture (静岡県育成) rather than to the Meiji-era national trial planting that produced Benihomare, so the honest reading is that the two are parallel products of the same imported seed stock — both naturalised Assam germplasm, both selected in Japan by open pollination rather than controlled crossing — rather than siblings from one identifiable seedling population.

Horyoku is therefore an open-pollinated selection from introduced, non-Japanese germplasm: the same broad category of origin as Benihomare, and unlike either a Zairai landrace selection (Yabukita) or a controlled cross (Ryofu, Kirari 31). Its one well-corroborated descendant is Ryofu, crossed in 1972 at the (national) Tea Research Station, Kanaya, with Horyoku as the seed parent — chosen specifically for its disease resistance — and Yabukita as the pollen parent, chosen for tea quality. Ryofu was registered in 1997 as Cha Norin No. 45 and separately Plant-Variety-Protection-registered in 2001 (registration No. 9204). One further descendant is documented, though not as a cultivar: the breeding line 金系213, a seedling of a 1976 Yabukita × Horyoku cross at Kanaya — the reciprocal orientation, with Horyoku on the pollen side — retained and reported in 2002 for its unusual cluster-type stamens.

History

The broader background — Tada Motokichi’s 1876 mission and the naturalisation of Assam-type seed in Japan by cold selection — is the same story told at greater length in the Benihomare record; Horyoku belongs to that wider Tada-line germplasm without being traceably descended from the specific Nishigahara seedling population that produced Benihomare. Beyond that shared origin, what is documented about Horyoku itself is narrow. NARO’s tea cultivar handbook credits its breeding to Shizuoka Prefecture rather than to a national research station, but names no more specific institution, no breeder, and no selection date. No source consulted — including NARO’s handbook, the Ryofu release paper, the complete Cha Norin registry, or the general reference sites checked — supplies a year in which Horyoku was selected or named.

What is documented is its role in 1972, when the (then) national Tea Research Station at Kanaya used it, already established in its germplasm collection, as the seed parent in a cross with Yabukita. The 1999 release paper for the resulting cultivar, Ryofu, states plainly why Horyoku was chosen: it was 耐病性が強い — strongly disease-resistant — a trait the breeders wanted to combine with Yabukita’s tea-processing quality. That cross went through field selection under the strain names 47-436, then F1-139, then Kanaya No. 17, before being named Ryofu and registered in 1997 as Cha Norin No. 45.

An unregistered cultivar

Horyoku itself never went through that process. It does not appear among the 52 entries of Japan’s complete Cha Norin national tea cultivar registry (1953–2003) — a list that includes both of the other Tada-line Assam selections discussed in this collection, Benihomare (No. 1) and Ryofu (No. 45) — and no Plant Variety Protection Act registration was found under its own name either. No source consulted states why. The available evidence is consistent with Horyoku having functioned as breeding and germplasm material rather than as a cultivar developed for commercial planting in its own right: the only documented uses of it, in any source found, are as a breeding parent at Kanaya — as Ryofu’s disease-resistance donor, and on the pollen side of the retained line 金系213 — and as one entry among many in research trials run on the station’s cultivar collection. That is a reasonable inference from what is documented, not a sourced fact, and it is offered here as such.

One specialist single-cultivar retailer, Shinkoju (品種茶専門店 心向樹, Saitama), lists Horyoku by name across four processing categories — regular-steamed sencha, deep-steamed sencha, pan-fired tea (釜炒り茶), and black tea — evidence that at least a small planting of it exists or existed for retail sale outside institutional collections. At the time of this research the listing was marked sold out (完売), and the page carries no 品種 or 来歴 text describing its origin or characteristics; this was checked against the live page and against Wayback Machine snapshots from 2021 through 2025, all showing the same sold-out listing with no descriptive content, so its absence is a genuine gap in that source rather than a fetch failure.

Characteristics

No source consulted gives Horyoku’s budding time relative to Yabukita, and it has no multi-prefecture adaptability-trial figures of the kind a released cultivar like Ryofu carries. What does exist comes from research papers that used it as one entry among many. A 2011 育種学研究 study of leaf-blade angle measured Horyoku at 22.3 degrees — the smallest angle of the 49 cultivars and lines surveyed, i.e. the flattest, most horizontal leaf posture — and notes separately that Horyoku 葉が巻くことで知られている, is known for its leaves rolling. The same paper’s yield comparison plucked it on 19 April at 50 per cent 出開度 for 864 kg/10a of first-flush fresh leaf, the highest of the five flat-leaved cultivars tested, which the author reads as a counter-example to the general association of upright leaves with yield.

Disease resistance is the trait it was actually valued for. The 1999 Ryofu release paper describes it simply as strongly disease-resistant, and that is what earned it a place as a breeding parent. One pathogen-specific figure exists: in a 1986 wound-inoculation trial of 55 cultivars and lines against gray blight (輪斑病, Pestalotia longiseta), reported in 茶業研究報告 No. 65 (1987), Horyoku formed no lesions at all — one of only two entries in the trial to do so — where Yabukita and Sayamamidori exceeded 45 per cent. No anthracnose or red blight rating was found for it.

On the cup side, the only evidence found is indirect. Shinkoju’s product listing shows Horyoku processed across regular- and deep-steamed sencha, pan-fired kamairicha, and black tea — a wider processing range than most single-region Japanese cultivars are marketed across, which is at least consistent with Assam-type leaf’s traditional suitability for black tea and pan-fired styles. The one sensory record located is a 1964 茶業研究報告 catechin study, which included Horyoku among 28 cultivars sampled at Kanaya in 1960: its laboratory-ground black tea was rated among the poorest of the third-flush samples for liquor colour and astringency, and its proportion of (−)-epicatechin gallate in the second and third flush was among the highest measured. That is a black-tea processing evaluation on a research sample, not a description of Horyoku as sencha; no aroma description, and no green-tea comparison against Yabukita, was found in any source, so none is given here.