GRAD® 1 Riesling

GRAD® Riesling Clone 1 in brief:

  • A revival of the finest Riesling line yet introduced to New Zealand! The GRAD®1 Riesling is a specially selected and regenerated high health clone derived from a single, over 40 year old, vine of D.S.I.R. heat-treated Gm239 (which was in turn derived from the original early-1960s Frank Berrysmith import of Gm239 Riesling).
  • Very intensely aromatic and flavour-rich, with pronounced tropical (mango and papaya) characters backed by lime, Seville orange, and tangerine characters along with good balanced acidity.
  • Relatively early ripening (sometimes surprisingly so in GRAD’s experience, compared to other Riesling clones), with proven capability for making rich late-harvest Rieslings or earlier-picked full-flavoured dry styles.
  • Tested free of detectable virus by PCR test. Foundation vines for multiplication at Stanmore Farm nursery have proven free of GLRaV1,2,3, and GVA by multiple E.L.I.S.A. tests, and the Stanmore Farm vines are consistently free of GLRaV3 by E.L.I.S.A. testing under the N.Z. Grafted Grapevine Standard regime.
  • The D.S.I.R. heat-treated Gm239 genetic line from which the GRAD®1 clone was re-selected, made up more than half of the renown Corbans Amberley Rielsing planting, and is still widely utilised in leading older plantings  extant in Waipara that are producing renown dry and sweet Rieslings. It was also highly prominent in the original Montana Marlborough Riesling plantings (now long-since lost to phylloxera).
  • Numerous trophies, gold medals, and critical accolades have been awarded to Rieslings (particularly in recent times from Waipara) made from the old D.S.I.R. heat-treated Gm239 genetic line, but the GRAD®1 clone is the only high-health, PCR tested, clonal re-selection developed to date to further improve upon this exceptional genetic line.
  • Carefully selected and regenerated in the GRAD® r&d nursery for freedom from contamination by crown gall bacterium which has been found to be persistently present (probably at between 10 – 70% infection rate) in most plantings of the D.S.I.R. heat-treated Gm239 Riesling line.
  • Vines grafted with GRAD® 1 Riesling are exclusively available in New Zealand through Stanmore Farm nursery under license from GRAD®.
  • E-mail for orders or inquires:
    Phone: 0800 Stanmore (0800 782 666)
  • Mobile: 027 544 0140
  • A comprehensive non-propagation contract must be signed off as part of your purchase order.
  • Download 1 page PDF Fact Sheet on GRAD 1 Riesling



In 1963 Frank Berrysmith imported Riesling clone Gm239 from Geisenheim University in Germany. The clone was a success in his vine trials, but as with virtually all of his early imports, by the late 1960s all of its foundation vines at Te Kauwhata had become virus infected. As part of its 1960s – early 1970s national foundation vine stock virus elimination programme, D.S.I.R. thus decided to heat-treat material from Berrysmith’s Gm239 Riesling.  High-health explants from this were released in the early 1970s and were bulked up so that cuttings could be distributed through Massey University. However, by far the largest source of this Riesling line was Wayne Thomas’s vine nursery set up at Avondale in Auckland to supply cuttings to Montana Wines for their huge expansion plantings into Gisborne and Marlborough in the later 1970s. After the Montana project was delivered, this facility went on also to supply cuttings to the relatively short-lived ‘Penfolds New Zealand’ business. In addition, in the 1970s, a ‘mass-selection’ of the D.S.I.R. heat-treated Gm239 Riesling was nominally released to the industry.

It might be thought therefore that as one of New Zealand’s earliest and most widely propagated and distributed Riesling lines from the 1960s onward, the Gm239, and then its complete supercession by the heat-treated D.S.I.R. explants, would have had a long and widespread impact. However, with more or less one exception — in the Waipara wine region — this did not prove to be the case. Phylloxera in Gisborne and Marlborough saw this line become close to extinct in these regions (as grafted vines with later-introduced Gm clones replaced it), and smaller early plantings in Martinborough and Auckland also declined until very few remain, if any. In the meantime however, and notwithstanding that in the 1970s and part of the 1980s Muller Thurgau vine numbers and wines (sometimes blatantly sold as ‘Riesling’) heavily overshadowed it, the h.t. Gm 239 Riesling line produced some exceptionally good wines. It was, in particular, prominent in the original, late 1970s and early 1980s, Montana Marlborough Rieslings which I can personally attest were very fine wines that showed a good deal more concentration and style than the vast majority of the region’s Rieslings produced nowadays from other clones and vastly larger crops.

The commercially longest-lasting stand-out wine from the 1970s and 80s plantings that was heavily influenced by the D.S.I.R. h.t. Gm329 line was however Corbans Amberley Riesling. As best I can determine, like the original Montana Marlborough Riesling plantings, the source of this vineyard’s material was either directly or (perhaps more likely) by second-generation re-selection, from Wayne Thomas’s Avondale glasshouse nursery stock. But in any case, whatever its vines’ precise origins, Corbans Amberley Riesling was actually not made with fruit from a vineyard planted in Amberley (which has no worthwhile vineyard sites) but in Waipara. This 1980s-planted own-roots block was, alas, pulled out in the mid-2000s, but it was predominantly made up, on one side of its planting, with D.S.I.R. heat-treated Gm239 Riesling. On the other side, the clone planted was almost certainly what was imported from U.C. Davis as ‘White Riesling’ by Alister McKissock ca. 1965. The exact U.C.D clonal identity of this vine is presently unclear (and it may not have been a Geisenheim clone introduced to U.C.D. but possibly a Californian-originated one instead), but it produced wines quite readily distinguishable from the h.t Gm239 clone’s much more opulent version, so that in Corbans Amberley Riesling it was always the D.S.I.R. h.t Gm239 that dominated the flavour, aroma, and (thanks to its earlier-ripening) acid balance of the wine. To this it must also be added that the Corbans Amberley Riesling block was populated by more than a few rogues, with Sylvaner quite prominent as a minority variety (and, if what I have seen is correct, once and perhaps still well represented in a planting at Muddy Water vineyard in Waipara). Other rogues in the Amberley Riesling block were (reportedly) Pinot gris and / or ‘Grey Riesling’ / Trousseau Gris, and perhaps also Gewurztraminer.

There was however a serious disease legacy which appears to have followed from the original  Auckland source of this vine stock. It was (and in some re-selected plantings still is) an intermittent crown gall infection which certainly appears in some Waipara re-selections from the h.t. Gm 239 in the Corbans Amberley Riesling block (and likely in other clones and varieties from it). Thus although a number of prominent plantings of the D.S.I.R. h.t. Gm239 Riesling from this source have been made in Waipara, I deliberately chose to eschew vines with this provenance.

This set me on an intensive research path that led me to conclude that by the opening of the 21st century, the original D.S.I.R. heat-treated Riesling line distributed through Massey University was all but extinct, with Waipara remaining of course as the last stronghold of the alternative line sourced first- or second-hand from Wayne Thomas’s Montana / Penfolds nursery. But as already noted, these latter vines’ oldest exemplars took a hammering when the old Amberley Riesling block was all pulled out in the mid-2000s, and now only third and fourth generation ex-Wayne Thomas material, complete with the aforementioned underlying problem of intermittent crown gall, remain.

After a lot of investigation however, in vineyards from Central Otago to Nelson and Martinborough, I was very fortunate in being able to find just a very old (1970s-planted) ex-Massey University D.S.I.R. h.t Gm 239 Riesling vine which P.C.R. testing confirmed was high-health (and in fact free of detectable virus). From that single vine I took sufficient cuttings to establish a selection pool in the GRAD® r&d nursery in Christchurch. Over time, and by using a range of re-propagation techniques including multi-generational high-temperature shoot tip re-propagation, I produced one next-generation clonal line that stood out as the finest vine of all. This has become the foundation mothervine for GRAD® 1 Riesling.


Health status

GRAD® 1 Riesling is free of detectable virus by P.C.R. test, and has subsequently tested negative for GLRaV1, 2, 3, and GVA by E.L.I.S.A., while all G1 mothervines at Stanmore Farm have also tested negative for GLRaV3 by E.L.I.S.A. as part of the testing regime required by the N.Z. Grafted Grapevine Standard.

GRAD® 1 Riesling also comes from a 100% crown-gall-free source. In 17 years of observation and following numerous grafting productions, this GRAD® clonal line (like all GRAD® clones in fact) remains 100% clear of any evidence or symptoms of crown gall.

Its status as a P.C.R. free of detectable virus, and crown-gall free, clone clearly sets the GRAD® 1 Riesling apart from other, vineyard selected, vines of the D.S.I.R. h.t Gm239 lineage. In addition, this clone also of course offers the considerable further advantage of re-selection involving years of observation in the GRAD® r&d nursery for superior vine robustness, earliness of ripening, and intensity of fruit flavour.



GRAD® 1 Riesling has been D.N.A. confirmed as  Riesling by testing at the Waite Institute in Adelaide. It is a very robust, semi-upright-growing, vine that sets moderate crops of very high quality, richly flavoured, relatively early-ripening fruit. This latter characteristic is inherited from the D.S.I.R. h.t. Gm 239 line, and this no doubt explains why in Waipara a number of exceptionally rich and fine trophy winning late harvest Rieslings have been produced over the last few decades using the D.S.I.R. h.t. lines’ fruit.

In terms of flavour and aroma, wines made from GRAD® 1 Riesling should be expected very much to follow the established norm for this genetic line, but arguably with enhanced intensity and slightly higher relative ripeness. I have at times described Gm239 and its derivatives as giving Riesling that smells and tastes almost semi-botrytised and very much tropical-fruited even when botrytis is 100% absent. Aromas and flavours of ripe mango, pawpaw, papaya, Seville orange, tangerine and mandarin, jackfruit and perhaps even dried pineapple and hints of Chinese syrup-preserved ginger, are quite characteristic (especially in leaf-plucked / well-exposed fruit). Moderate ‘noble’ botrytis infection principally adds passionfruit characters in the clone.  Its wines are frequently quite voluptuous in the mouth because higher than average dry extract seems to be characteristic (provided over-irrigation and over-production are avoided —use GRAD® 106-8 or GRAD® 44-53 as the rootstocks for the GRAD® 1 Riesling, and grow as dry as possible to achieve maximal dry extract and fruit concentration). Interestingly, apple aromas and flavours, which are so typical of many Riesling clones in New Zealand, are correspondingly not a forté of this genetic line, and neither is ‘green wine-gum’ or Tahitian lime (as with Gm94 for example). In my experience, and as the success of Waipara Riesling from the Corbans Amberley onward has shown, the public palate has something of a definite preference for the D.S.I.R. h.t. Gm 239 genetic line’s richness and flavour spectrum compared to the often leaner and more green apple and green wine gum,and often underlyingly very citric (if not malic) characters of many commercial Marlborough Rieslings.

Qualitative potential

If you look at this genetic line’s track record in New Zealand since its introduction in 1963, no other Riesling clone or clones have produced so many highly successful wines, be it in terms of widespread consumer acceptance and preference (even under small / minor-producer labels), show awards won, or critical accolades gained. The GRAD® 1 clone is the pinnacle of this genetic line in New Zealand, and its qualitative potential — for either dry wines or late-harvest botrytised or non-botrytised styles — is correspondingly second-to=none in the country.


Ripening period

Frequently earlier than virtually any other Riesling available in this country. A good accumulator of sugar and flavour without the drawback of hard acidity or green apple characters, this Riesling is highly reliable in good growing conditions and typically achieves physiological maturity at lower degree day numbers than its peers. Because of these early-ripening characteristics, GRAD® 1 Riesling is definitely the ‘go to’ clone for more marginal Riesling sites, Central Otago sites, and is also your best choice where high sugar accumulation fir late-harvest styles is desired.



Stanmore Farm has several mothervines of GRAD® 1 clone Riesling that are now well established. For information on currently available grafting bud numbers and for forward orders, contact their nursery.

Vines grafted with GRAD® 1 Riesling are available through Stanmore Farm nursery under exclusive license from GRAD®

E-mail for orders or inquires:
Phone: 0800 Stanmore (0800 782 666)  
Mobile: 027 544 0140

Please note that a strict and comprehensive non-propagation contract must be signed off as part of your purchase order.

GRAD® is a New Zealand registered trademark uniquely and exclusively used to identify the vines in the GRAD® vine collection. Use by unauthorised parties to identify any vine material, or other use for commercial gain, is an infringement of this trademark.

Genetic ‘fingerprinting’ and clonal traceability

Vine pirates BEWARE! It is now possible to genetically fingerprint, uniquely identify, and individually detect grapevine clones using the latest-developed molecular genetic sequencing techniques. See the breakthrough research paper by Michael J. Roach et al, “Population Sequencing Reveals Clonal Diversity and Ancestral Inbreeding in the Grapevine Cultivar Chardonnay”, published November 20, 2018 at


Questions about this wine grape? Contact us.

Author: Dr. Gerald Atkinson

Company director, viticulturist, grapevine researcher and historian, and sometime wine-writer.