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Alcohol and science

Saving the agave

A decade ago, the tequila industry was pummelled by plant diseases. Rex Dalton meets the scientists working to keep the blue agave diverse enough to survive.

Credit: G. ARIAS/AP/EMPICS

For centuries, artisans working in the adobe haciendas of Mexico's rural valleys have followed tradition to make the powerful spirit tequila. Copying age-old indigenous techniques, they distilled the liquor from sweet juice cooked out of the fat stems of a local succulent, the blue agave (Agave tequilana Weber, var. azul).

But in recent years, tequila makers have had to bring the latest science to the agricultural process to save both the industry and the culture it supports. Some of the oldest and biggest producers are employing scientists, building high-tech laboratories and funding academic research on the blue agave so that researchers from biochemists to geneticists can scrutinize this little-understood plant.

The shift began nearly a decade ago, when disease and pests wiped out much of Mexico's crop of blue agave. The plants are grown in expansive ranches, as a single agave takes years to reach maturity for harvest. But those huge monocultural crops, planted to slake the worldwide thirst for tequila, are also an ideal place for disease to spread. Tequila was nearly destroyed by its own popularity.

The agave plant grows a rounded stem covered with thick, spiked leaves. The plants are harvested at the age of seven years, when sugar content is at its peak. The leaves are cut off, leaving a ‘head’ that looks like a huge pineapple. Heads are then cooked for the sweet juice, which is fermented and distilled into liquor.

Until about 25 years ago, tequila was known mostly as a traditional drink in Mexico, rarely savoured outside the country save by college students and the adventurous. But in the early 1980s, enthusiasm for the beverage blossomed as its better-quality varieties became more widely known — with help from songs such as Jimmy Buffett's classic Margaritaville.

Boom time

Harvest time: the leaves are cut from the head of a mature agave. On average the plant takes seven years to reach this stage. Credit: ZUMA PHOTOS/NEWSCOM

To meet demand, ranchers industrialized the planting process to produce millions of genetically similar blue agave plants for maximum yields. Plantings of blue agave leapt from 16,000 hectares to nearly 50,000 in less than a decade. But by following this route, plant scientists say, the ranchers sowed thousands of hectares with plants whose lack of diversity left the crop susceptible to devastation when disease struck. Agave plantations are generally all of the same variety. Farmers usually cut off the flowering stalk to increase the plant's sugar load, which means that the plants aren't cross-pollinated by bats or other animals as they would be normally. Without that mixing, the blue agave crop is nearly genetically uniform, a situation that renders it particularly prone to disease. A single pathogen can rapidly destroy most of an entire crop.

“We told them this was going to happen,” says Gary Paul Nabhan, an ethnobotanist at Northern Arizona University, Flagstaff, who with Mexican ethnobotanist Ana Valenzuela Zapata wrote a seminal book on the problem1. “But they wouldn't listen to us.”

Beginning in the late 1980s, disease began to rot agaves in the fields. And then, in 1996 and 1997, a climate shift enveloped the prime agave-growing states near Mexico's southwestern Pacific coast. The warmer temperatures and increased rainfall proved devastating for the plants2. Diseases and weevils attacked: a bacterium (Erwinia carotovora) and a fungus (Fusarium oxysporum) were particularly malign, ruining the valuable heads. Ranchers, who must tend fields for years before getting the money from a harvest, were left with unusable agaves. Many decided to cut their losses and abandon agave harvest: by some estimates, the area of planted fields plunged more than 25%.

Producers began to scramble for agaves, and tequila prices skyrocketed. For the first time, tequila makers began tapping other plants for the sugar juices needed for fermentation. Tequila was no longer necessarily made from 100% blue agave — a sacrilege for traditional ranchers and tequila artisans. At least one vocal producer, who spoke out against reducing the tequila standards, was assassinated during public demonstrations.

Traditional tipple

By law, tequila production is limited to five states, with most activity in the state of Jalisco. The Mexican Tequila Regulatory Council certifies two types of tequila: the traditional, which is labelled “100% de agave”, and a lesser variety, which can be described as ‘tequila’ only but must still be made with at least 51% blue agave.

In the aftermath of the crop plagues, tequila producers have turned to scientists to revive their crops. But there are only a few specialists, and a very limited literature in agave science. “You don't find many agave publications in journals,” says Eulogio Pimienta Barrios, an ecological physiologist at the University of Guadalajara. Historically, producers held any specialized agave knowledge close for competitive purposes. But that situation is changing, as producers bring in academic researchers for studies. Just two years ago, the chemical structure of the sugar of the blue agave, a fructan, was described for the first time — showing that it holds promise for food products for diabetics3. And last summer, two of the biggest tequila distillers, Herradura and Sauza, signed a cooperative research agreement to share information about agave science.

Villages such as Amatitán, 40 kilometres west of Guadalajara, are the nexus of agave culture, where friends sing songs about tequila at informal gatherings. Here, the family-owned Herradura distillery still produces tequila on its 135-year-old hacienda. The agave heads are cooked in old-style ovens and juices fermented in open-top vats: not very different from the way tequila was made in the nineteenth century. But now providing scientific insight is Aideé Orozco Hernández, a biochemist who has worked for the company for about four years. Orozco has installed a laboratory with sophisticated equipment for research into plant breeding and production techniques.

Another 15 kilometres west, in the town of Tequila itself, sits the distillery of Sauza, owned by a multinational liquor giant. In 1999, the firm hired plant physiologist Ignacio del Real Laborde. The new cooperative scientific approach, says del Real, is a symbol of the need to see beyond local rivalries and think in terms of a global market. “It doesn't help to have your neighbour doing bad things,” he says. “Some people weren't doing proper agriculture before, but we are now.”

Agave heads pack more sugar if the plants aren't allowed to flower. Credit: R. DALTON

More still needs to be done to adopt sustainable practices, says Valenzuela, who is based at the University of Guadalajara. Ranchers, she says, are reluctant to try new approaches because they fear economic losses.

One such issue is whether to allow some plants to flower and so allow cross-pollination. Farmers say they can't afford to lose agaves to pollination and want to maintain their plants' valuable characteristics. “Some are changing,” says Valenzuela. “But industry people are not paying enough attention to the erosion of biodiversity.”

Orozco and other tequila scientists are trying to address this by creating more diverse agave lines for large-scale planting. Last year, Herradura harvested seeds from experimental fields where the agaves were allowed to pollinate naturally. Some 400 agave lines were selected from this experiment for further study, says Orozco, and the best lines will be chosen for breeding and planting. “We are very confident that new knowledge about the plant will give us more efficiency and quality,” she says.

But for del Real, there are limits to applying sustainable agricultural techniques. He doubts whether natural pollination will ever be widespread in agave cultivation, because he fears that the plants could hybridize, creating a version that wouldn't be considered true agave by the tequila regulators. “Valenzuela's view is very respected,” he says, “but we need more basic academic research to understand this plant.”

To that end, Sauza is funding projects at half a dozen Mexican universities. At the Center for Research and Advanced Studies in Irapuato, Guanajuato, molecular biologist June Simpson is probing plant genetics. About ten varieties of A. tequilana have been identified; her institute's research has shown that all are basically genetically identical, although their colours and shapes can vary slightly4.

“When I present these data to agronomists or farmers, they say they can't be true,” Simpson says, “because they see differences in the plants.” In an added twist, she says, a study now in press has found some diversity among these varieties when sampled from a broader area.

She is working to develop a test to identify blue agave through genetic fingerprinting, and her institute is using genetic markers to explore for certain key genes associated with plant sugar production. “All of this is aimed at understanding real genetic improvement,” she says. “Then people can do plant breeding.”

Glut and disease

But all these new studies cannot staunch the rising fear that another agave crisis could occur. Mexican officials now are predicting a glut of agaves for at least the next three years, with production peaking at nearly 1.8 million tonnes in 2008. Production facilities can accommodate only about half of those, says Alvaro García Chávez, a rural development official in Jalisco.

With agave prices plunging as a result, many ranchers have cut back on caring for their plants — which, in turn, creates bastions for disease and pests. Already, some estimate that 10% of the agave fields are afflicted with disease. “I hope for the best,” says del Real. “But yes, I am concerned.”

To create new markets for agaves, government officials have encouraged the development of a diabetic-friendly food syrup based on the agave's fructan. But the project uses only a small fraction of excess agaves, leaving scientists and authorities looking for answers to the plant's boom-and-bust cycles.

In the end, they may have to hope for a renewed thirst for their drink. Perhaps the new US hit country song, Joe Nichols's Tequila Makes Her Clothes Fall Off, will again pump up demand.

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Dalton, R. Saving the agave. Nature 438, 1070–1071 (2005). https://doi.org/10.1038/4381070a

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