Coffee genes help hackers home in on the perfect brew

 作者:阎骛     |      日期:2019-03-05 11:10:05
By Penny Sarchet Read more: Click here to read the original, longer version of this story. IT GETS you up in the morning and powers you through the day. Now coffee aficionados have been given a new tool in their quest for the ideal cup – the coffee genome. Scientists have sequenced the genome of robusta coffee (Coffea canephora), uncovering many genes involved in making caffeine and aromas (Science, Armed with this knowledge, growers and blenders could make higher quality, tastier varieties of coffee, and help protect the plants from climate change and disease. “It’s like somebody turned on the lights,” says Tim Schilling, executive director of World Coffee Research, a collaboration formed by the coffee industry and based at Texas A&M University, College Station. He says coffee lovers could taste the fruits of these labours in around five years. Traditional methods for breeding new varieties can take 12 years or more to reach farmers. The first item on the agenda is protecting the coffee crop. Climate change is a big problem for the farmers. Coffea arabica, closely related to robusta, makes up most of the world’s crop but only grows within a certain temperature range. As warming kicks in, arabica farming is being pushed up the mountains, and the total area suitable for it is shrinking. “We have seen the average temperature increase,” says Alejandro Martinez, who owns a coffee farm in El Salvador. “Ideally, [the genome] will accelerate the development of varieties that can [cope with] the dramatic impact of climate change on the crop.” Coffee is also threatened by diseases like coffee rust fungus. Coffee breeders should be able to use the genome to quickly breed resistance into the coffee crop. Then there is the caffeine level. For years scientists have been searching for a decaffeinated coffee that tastes as good as high-caffeine varieties, and the genome could help make one. The sequencing team found a set of genes probably involved in making caffeine. The expression of these genes could be tweaked to alter the caffeine content of the coffee, says team leader Philippe Lashermes of the Institute of Research for Development, Montpellier, France. The genome will speed up research, says Paulo Mazzafera at the University of Campinas in São Paulo, Brazil. He studies proteins called transcription factors that regulate caffeine production by switching other genes on or off. “This coffee genome will give us more information on [how] the transcription factor genes we have selected work,” he says. We could also make better-tasting coffee, says Christopher Hendon of the University of Bath, UK, who studies coffee as a hobby. When you buy ordinary coffee on the high street, it is usually a mix of arabica for flavour, and robusta, which doesn’t taste as good but gives the high-caffeine kick customers have come to expect. Hendon suggests boosting the caffeine content of the robusta bean. “You could substitute less robusta into the same blend, and get the same amount of caffeine,” says Hendon. Non-speciality coffee could then include more arabica and taste better, without losing its punch. Hendon says the robusta genome could also help make new flavours of speciality coffee. For instance, around 5 per cent of a coffee bean is chlorogenic acid, which doesn’t taste very nice. So he proposes getting rid of it. “That would be a very powerful tool,” says Hendon. The resulting coffee would be “incredibly sweet and very floral”, because the acid would probably be converted into substances like sugar and citric acid. “That would be cool!” The genome could unlock new flavours in coffee, says speciality coffee roaster James Hoffmann of Square Mile Coffee Roasters in London. He says it also offers the opportunity to improve coffee yields and pest resistance without compromising quality. “The coffee genome could unlock new flavours and improve yields and pest resistance” The coffee genome might help create new flavours, but it’s not just genes that dictate taste. “I have tasted coffees that come from the same varietal but taste different depending on where they are grown,” says coffee farmer Alejandro Martinez in El Salvador. Another key determinant of flavour is how the bean is roasted. Speciality roaster James Hoffmann of Square Mile Coffee Roasters in London collects data on bean moisture content, roast temperature and the colour of ground coffee, and tracks their effects on the flavour. The aim is to “improve quality and also increase consistency”, he says. This is being taken a step further by Morten Münchow of the University of Copenhagen in Denmark. He is trying to determine the effects of roast temperature and time on the flavour of speciality coffees. “I’m trying to map out the parameter space of speciality coffee,” he says. The water you use is also key, says Christopher Hendon of the University of Bath, UK. He spends his weekends studying coffee with the 2014 UK barista champion Maxwell Colonna-Dashwood. This year they found that the relative levels of various ions in the water affects the flavour. Calcium and magnesium ions bring out the flavour of coffee, while bicarbonate kills it (Journal of Agricultural and Food Chemistry,