Among wine professionals, grape varieties have increasingly become a topic of discussion. Grape varieties have long been subjects of debate regarding their relationship to selling prices, compatibility with cultivation regions, and the correlation between cultivation difficulty and costs. However, the nature of these discussions has recently undergone a shift. The term PIWI has begun to appear frequently in many of these conversations.
PIWI is an abbreviation of the German term Pilzwiderstandsfähige Rebsorten, meaning fungal disease-resistant grape varieties. While derived from German, the term PIWI has now gained international currency.
This article examines why PIWI varieties currently attract such attention in the wine industry and explicates the characteristics of PIWI varieties.
Development History of PIWI Varieties
Among wine grape varieties currently under cultivation, some originated through natural crossbreeding while others were created through artificial hybridization. All grape varieties classified as PIWI are artificially developed varieties.
Generally, grape vines are mass-produced through clonal propagation techniques to preserve their genetic varietal characteristics. The specific method employed is vegetative propagation through cuttings. By propagating cuttings from vines with desirable genetic traits for wine production, genetic cross-pollination and the resulting trait alterations can be avoided. That is, the conventional practice of growing grapevines from seed is not employed in standard nursery production.
Conversely, PIWI development fundamentally employs seed propagation. Cultivation from seed constitutes an indispensable prerequisite for developing grape varieties that possess both high disease resistance traits and genetic characteristics suitable for wine production.
The rationale is clear. Varieties considered suitable for wine production belong to the species Vitis vinifera (European grapevine). Meanwhile, varieties exhibiting superior disease resistance belong to American or Asian wild grape species. Since PIWI varieties must possess genetic characteristics from both groups, intentional genetic hybridization is generated by cross-pollinating flowers from separate vines with respective characteristics, producing varieties that inherit the superior traits of both parents.
Creating a single PIWI variety requires an extraordinarily extended timeframe. Following the principles of heredity known as Mendelian inheritance, even when crossing parents with optimal characteristics, offspring generations do not necessarily inherit only the superior traits of both parents. Various offspring generations emerge: individuals with exceptional disease resistance but extremely low yields, individuals expressing undesirable aromatic compounds strongly in wine, individuals with excellent wine quality but lacking disease resistance expression. To produce varieties with the characteristics desired by breeders from among these diverse offspring, rigorous selection must be repeated.
Furthermore, PIWI varieties must be classified as Vitis vinifera species in botanical taxonomy. As a principle stipulated by wine laws, wine is required to be produced from grapes of the Vitis vinifera species in most countries. The technique necessary to satisfy this requirement is called multiple backcrossing.
Multiple backcrossing is a technique whereby offspring generations from crosses between Vitis vinifera and other species are repeatedly crossed with Vitis vinifera to bring the genetic composition progressively closer to that of Vitis vinifera. In multiple backcrossing, pollination-based crossing is conducted as with the parental generation. That is, genetic hybridization occurs in multiple backcrossing as well. Consequently, desirable traits that had been inherited may be lost. Through these repetitions, with selection upon selection, PIWI varieties are produced.
The first variety registration for a PIWI variety was Regent, a red wine variety developed at the Julius-Kühn-Institut (JKI) in Germany, in 1994. However, the Regent variety was hybridized in 1967. Approximately 30 years elapsed from development to varietal registration for Regent. While the development period for PIWI varieties varies somewhat by variety, 20-30 years is typical. The average development period is stated to be approximately 25 years. One reason PIWI varieties have attracted attention in recent years is that variety groups developed 30 years ago have finally been registered and become available for use.
Development Generations and Objectives
A relatively unknown fact is that PIWI varieties possess developmental generations. The current latest generation is the fourth generation, though development itself has entered the fifth generation. Many varieties that have appeared on the market in recent years belong to the third generation, but the largest planted area belongs to second-generation varieties.
PIWI Development Beginning in France
While Germany currently occupies the forefront of PIWI development, first-generation PIWI varieties were produced in France. First-generation varieties were developed around 1900 in Colmar. Varieties belonging to the first generation include Maréchal Foch and Léon Millot. These varieties were developed as part of measures against phylloxera (Phylloxera, Japanese name: grape phylloxera), which posed a serious problem at the time, in addition to improving disease resistance.
The characteristic of the first generation was that they were simple hybrid varieties between European and American varieties without multiple backcrossing. Being simple crosses, they strongly exhibit the foxy flavor characteristic of Vitis labrusca varieties used as the American parent species. First-generation varieties were primarily used in France for Armagnac production until around 1960.
First-generation varieties also experienced uprooting as “non-Aryan” with the rise of National Socialist ideology, based on their origins. Planted area continued to decline after World War II, though they are still cultivated in Switzerland, Austria, and southern Germany.
Second Generation Representing PIWI Varieties
Many varieties widely known today as PIWI varieties, such as Regent and Solaris, belong to the second generation. The second generation comprises varieties developed from the 1960s through the 1980s, characterized as the first generation to employ multiple backcrossing. Second-generation varieties underwent repeated selective breeding and purpose-oriented selection, resulting in classification as Vitis vinifera species in botanical taxonomy.
The primary development objectives of the second generation were further enhancement of disease resistance, improvement of wine quality through reduction of foxy flavor, and early ripening. These development objectives were achieved, triggering increases in PIWI variety planted area. Regent remains the most widely planted PIWI variety. Due to its early-ripening characteristic, Solaris is frequently used in Germany for Federweißer (young wine undergoing fermentation).
While varieties such as Solaris are also cultivated in Italy, they have attracted attention from high-latitude production regions because they can be harvested with high juice sugar content even in cold regions where conventional varieties prove unsuitable for cultivation.
Third Generation Elevating Wine Quality
The variety group called the third generation underwent development from 1990 onward. The third generation includes many varieties whose names have been heard with increasing frequency in recent years, such as Cabernet Blanc, Cavertin, and Souvignier Gris.
For the third generation, development focus was placed on creating alternative varieties possessing taste and aromatic characteristics similar to conventional varieties through further multiple backcrossing, and on further enhancing resistance to downy mildew and powdery mildew. Also from this period, the early-ripening development policy emphasized in the second generation underwent a 180-degree reversal, with late ripening becoming prioritized.
Foxy flavor, which was still occasionally noted through the second generation, has been improved to a level where it is barely perceptible or completely imperceptible in the third generation. It has been stated that distinguishing between conventional varieties and PIWI varieties in blind tastings has become virtually impossible. In panel tastings by experts, third-generation varieties have been evaluated as equivalent to conventional varieties for red wine grapes, and partially superior for white and rosé wine grapes.
One major reason vintners and winemakers were negative toward introducing PIWI varieties was the presence of foxy flavor. However, with advances in grape breeding and substantial improvements in wine quality, reasons to reject PIWI varieties are diminishing.
Fourth Generation Expanding Disease Resistance and Current Development Directions
In the fourth generation of PIWI varieties, represented by varieties such as Saubitage and Calardis Blanc, further enhancement of disease resistance has become the development focus. Against the background of expanding downy mildew damage in Southern European regions due to climate change impacts, improvement of resistance to downy mildew in particular has been pursued. Additionally, the methodology for improving disease resistance has advanced from conventional approaches, with the objective of incorporating multiple resistance markers into a single variety.
Furthermore, from the fourth generation onward, more active efforts have been made to improve grape cluster morphology. Improvement of cluster morphology has enhanced resistance to Botrytis (gray mold), resulting in varieties more comprehensively resistant to diseases.
The directions introduced in fourth-generation development continue in current fifth-generation and subsequent development. Fifth-generation objectives include developing varieties with greater numbers of resistance markers, expanding the scope of improvement beyond cluster morphology to include aspects such as shoot growth direction to create more easily cultivated varieties, conferring resistance to frost and diseases other than the conventionally targeted downy mildew and powdery mildew, and improving suitability to cultivation regions. Expanding varietal diversity also remains an important continuing priority.
Reasons for Being Called the Future of Wine
PIWI varieties are currently also called “Super Bio.” This designation derives from the substantial reduction in required protective agents, particularly copper compounds, compared to conventional varieties.
With highly disease-resistant PIWI varieties, protective treatments can reportedly be reduced by up to 80% compared to conventional varieties. Even with PIWI varieties, protective treatments cannot be eliminated entirely. However, in practical terms, the number of protective treatments required—typically 8-12 times annually—can be reduced to 2-4 times. Reduction in treatment frequency directly translates to reduction in protective agents used.
In 2019, the European Commission, the executive body of the EU, adopted the European Green Deal as a climate change measure. The core strategy in the agricultural sector of this highly ambitious policy is the Farm to Fork (F2F) strategy. The F2F strategy sets objectives of reducing pesticide use by 50% by 2030 and converting 25% of all agricultural land to organic farming. In Germany specifically, the objective is to increase organic cultivation area to 50% of total agricultural land. The promotion of this policy strongly bolsters the presence of PIWI varieties in wine grape cultivation and constitutes the reason PIWI varieties are called “the future of wine.”
Grapevines are regarded as a cultivation crop requiring protective treatments to an extent unparalleled compared to other crop cultivation. In wine grape cultivation, while vineyards accommodating organic cultivation have increased, centered in Europe, the quantity of protective agents required annually, particularly copper compounds, remains at elevated levels.
While chemically synthesized agents are prohibited in organic cultivation settings, downy mildew risk has become extremely elevated in recent years across European regions in grape cultivation, against the background of climate change. For downy mildew countermeasures, excluding chemically synthesized agents, copper compounds constitute the only effective treatment method. Each winery has years when copper compounds must be sprayed up to the upper limit permitted for organic cultivation. While conversion to organic cultivation is advancing, the quantity of agents used has not substantially decreased accordingly. This is why achieving F2F strategy objectives in grape cultivation settings is considered impossible under current circumstances. PIWI varieties address this challenge.
In PIWI variety cultivation, the number of protective treatments required becomes less than half that of conventional cultivation. Accompanying this, the quantity of protective agents used also substantially decreases. Furthermore, fuel required to operate machinery such as tractors used during protective treatments decreases, and exhaust emissions also decrease. Reduction in tractor operation frequency also mitigates soil compaction. These effects align precisely with the F2F strategy and furthermore with European Green Deal policy. Moreover, as a practical matter, it has even been stated that achieving these policy objectives is impossible unless replanting from conventional varieties to PIWI varieties is promoted.
The virtually sole method for the wine sector to realize policies for the planet’s future is introducing PIWI varieties. This is why PIWI varieties are called “the future of wine.”
Another Dimension of Wine’s Future
PIWI varieties are additionally expected to fulfill a role bearing wine’s future from another aspect: improvement of winery labor and economic environments.
In recent years, costs for wine production have continued to rise. All costs have continued to increase: prices of all materials including protective agents and vineyard equipment, various energy costs such as electricity, gas, and gasoline, and labor costs. This situation has directly impacted already-struggling winery management. In recent years, some wineries have ceased operations due to inability to secure working capital.
Fundamentally, wineries constitute a business with low profitability relative to the heavy labor involved. Successor shortage has long existed as a major problem. Recent deterioration of the business environment has exacerbated this situation. However, PIWI varieties possess the potential to substantially improve these circumstances.
When cultivation varieties are changed from conventional varieties to PIWI varieties, protective treatment frequency substantially decreases. Accompanying this, quantities of agents used also decrease. That is, costs expended on agents are reduced. Furthermore, water and fuel for tractors and other machinery required for protective treatments can have their usage quantities substantially reduced. Since work frequency becomes less than half, worker burden also becomes less than half.
Additionally, PIWI varieties have undergone development of varieties possessing characteristics that can facilitate work in aspects other than protective treatments and development of varieties possessing characteristics to avoid yield reduction. While specific verification reports have not yet been reached, PIWI variety cultivation is expected to enable obtaining harvests exceeding conventional quantities at labor costs below conventional levels, moreover with grapes of better health status and higher quality. PIWI varieties are regarded as varieties possessing the potential to improve winery profitability in all aspects.
Grape varieties possessing the potential to rescue wineries that might have become economically unviable, wineries that while still sustainable now might have become unsustainable in the future. In this sense as well, PIWI varieties can be called “the future of wine.”
Continuing Expansion of Planted Area
Over recent years, PIWI varieties have continued to increase planted area. In 2022, PIWI variety planted area within Germany was approximately 3,000 hectares, about 3% of total grape cultivation area in Germany. While still a minimal area as planted area, white wine PIWI varieties show substantial growth with annual increase rates of approximately 20%.
Currently, viewing Germany alone, substantial growth is occurring in white wine varieties. In 2021, white wine PIWI planted area was only about half that of red wine PIWI planted area, whereas in 2022, planted area steadily increased, narrowing the gap with red wine varieties. Conversely, red wine varieties showed slightly decreased planted area during the same period. The cause is Regent, which possesses an overwhelmingly large planted area of over approximately 1,600 hectares as a PIWI variety, the largest single planted area in Germany. This red wine variety increasingly faces replanting because disease resistance is not as high as expected and furthermore, as an early-ripening variety, it is unsuitable for recent cultivation conditions, and has been reducing planted area in recent years. While nearly all other red wine PIWI varieties are increasing planted area, because Regent’s decrease is large, the result is decreased planted area for red wine varieties in total.
PIWI variety planted area is also increasing outside Germany. PIWI variety seedlings produced in Germany are being exported not only to conventional wine grape production countries such as France, Spain, and Italy, but also supplied to Denmark, the Netherlands, Sweden, and other countries where wine grape cultivation had not previously been conducted.
In Italy, where downy mildew damage expansion is progressing, PIWI variety planted area has reportedly already increased to approximately 2,000 hectares, and domestic PIWI variety development and varietal registration are being actively advanced. Currently, PIWI variety development is most advanced in Germany, followed by Austria, Switzerland, Italy, Hungary, Japan, Sweden, and others.
Growth Period as a Selection Option
While disease resistance constitutes the primary reason PIWI varieties are selected as cultivation varieties, that is not the sole reason in all cases. Adjusted growth periods also constitute a reason for selecting PIWI varieties.
PIWI varieties have been intentionally adjusted during development to ripen early or ripen late. This characteristic works very advantageously depending on cultivation region. For example, in conventional cultivation regions centered in Southern European countries, selecting late-ripening varieties holds important significance for responding to recent climate change. Conversely, in northern cold regions where wine grape cultivation had not previously been conducted, selecting early-ripening varieties enables securing high maturity levels even with short summers. Such factors sometimes influence variety selection with greater importance than disease resistance.
Additionally, the fact that PIWI varieties have characteristics adjusted to enable replacement of conventional varieties also holds significance. The existence of PIWI varieties with similar characteristics to early-ripening conventional varieties yet adjusted for late ripening enables replanting while minimizing impacts on product lineups that occur when making wine.
In production regions where used varieties are specified on labels, even with similar taste profiles, different grape varieties may pose sales challenges. Conversely, in production regions where variety names are not traditionally stated on labels, or where stated but not prominently, changes in cultivation varieties are considered to proceed relatively easily. Indeed, currently, regions increasing PIWI variety planted area are primarily such regions where sales challenges are less likely.
How Far Will PIWI Varieties Expand?
While changing varieties cultivated from conventional varieties to PIWI varieties certainly brings substantial benefits to wineries, it simultaneously brings disadvantages. However similar the characteristics, as long as they are different varieties, wine taste and style inevitably change. Moreover, with newly developed PIWI varieties, knowledge regarding optimal vinification methods and styles has not yet accumulated, necessitating proceeding entirely through trial and error. While clear deficiencies possessed by early development generations have been overcome, the reality is that the current situation cannot yet be characterized as one where conventional varieties are being switched to PIWI varieties with unreserved enthusiasm.
Conversely, political elements are also becoming strongly involved in replacement with PIWI varieties. The European Green Deal and accompanying F2F strategy promote PIWI variety planted area expansion from aspects different from discussions regarding wine quality. Factors such as the extent to which subsidies will be provided for policy realization should substantially influence winery decisions going forward.
Currently, regions already exist where 40% of regional wine grape cultivation area consists of PIWI varieties. Wineries in such regions market PIWI varieties as distinctive varieties, yet in many regions, producers remain undecided whether to treat PIWI varieties as alternative varieties to conventional varieties or as distinctive varieties.
Being newly developed varieties constitutes both an advantage and disadvantage for sales promotion of PIWI varieties. Approaches vary: whether to perceive the lack of widespread variety name recognition as advantageous and actively promote novelty, or to treat them as alternative varieties for use in blends and such until names become known while pursuing improved profitability within wineries.
While phrases such as SDGs and environmentally friendly suggest that corresponding products are demanded, reports have also been made in some cases that emphasizing environmental considerations with wines made from PIWI varieties conversely resulted in worsened sales, indicating that PIWI variety sales policies also remain exploratory. Revenue improvement pursued through replanting would be meaningless if it leads to decreased sales.
In recent years, PIWI varieties have certainly attracted attention and shown high planted area growth rates. However, in actuality, while they will eventually demonstrate greater presence, excluding emerging production regions, unless external factors such as massive subsidy investment occur, a long-term perspective including observation appears necessary.
