Insects make spicy chili

If you are a fan of habañero salsa or excellent Thai food, you owe a lot to bugs, whether they are flightless or species that can only be observed through a microscope. A new study shows that they are the cause of hot peppers.

The spicy chillis is its defense mechanism for microbial fungi to penetrate through the injection holes on the outer shell caused by insects. The fungus of a large family called Fusarium destroys chilli seeds before they are eaten by birds and spread widely.

Joshua Tewsbury, assistant professor of biology at the University of Washington, said: 'For the wild peppers, the large number of seeds damaged by fungi before being dispersed is the biggest danger. Both mushrooms and birds eat chili, but mushrooms cannot spread seeds, only harm chili seeds. '

The fruit of the tree uses sugar and fat to attract 'customers' like birds and birds that will carry seeds everywhere. But insects and mushrooms also want to enjoy sugar and fat in the fruit, but then they cause death for the chicks of the chilli.

However, the researchers found that the pungent taste of chili actually served as a unique defense mechanism. The pungent taste is derived from capsaicinoid - the chili-protecting chemicals are not attacked by fungi by significantly slowing the growth rate of microorganisms.

Tewksbury, the lead author of the research paper, said: 'Capsaicin does not affect the dispersal of seeds by birds that do not feel the pungency, so they continue to eat chili, but the fungus destroys Chili seed is quite sensitive to this chemical. '

'The defense mechanism does not affect the breeding or dispersing of such seeds, making the field of chemistry very valuable to plants. This is also a good example of the power of natural selection '.

The study was published August 11 online in the Proceedings of the National Academy of Sciences. Co-authors of the study include Karen Reagan, Noelle Machnicki, Tomás Carlo, and David Haak (of the University of Washington); Alejandra Lorena Calderón Peñaloza (Autonoma University Gabriel Rene Moreno) in Bolivia; and Doughlas Levey (of the University of Florida). The research was funded by the National Science Foundation and the National Geographic Society.

Scientists collected chilli samples from seven different populations of the same species in an area of ​​1,000 square miles in Bolivia. In each population, they randomly selected and counted the number of scars on the outer skin of the peppers caused by insects. These traces are the result of half-winged insects - such as stink bugs, aphids or aphids. They have a suction mouth arranged into a structure like a mine that can penetrate the fruit's crust.

The scientists found that not all peppers produce capsaicinoids, so in the same population there are more spicy plants than jalapeño while other fruits have a spicy taste like bell peppers. But the frequency of spicy fruit plants is higher in areas with large populations of half-winged insects. They attack the chilli, making chili easily invasive.

Scientists also found that spicy fruit trees became even more spicy, having higher rates of capsaicinoids in areas where fungal attack became common. But in areas where there are fewer insects, and less likely to be attacked by fungi, most plants lack spicy flavor. Here the peppers on the plant produce corticosteroids, but only about half the amount of capsaicones that plants in the area are strongly attacked by fungi.

The two beetles belonging to the half-winged faction attack the ripe pepper, their previous attacks still remain.As a result, chilli are invaded by fungi that damage the seed of the plant.(Photo: Washington University)

The use of chemicals as a defense measure is not unique to peppers. Tomatoes, for example, also have a lot of substances that make the unripe tomato a very unpleasant taste, thereby giving the tomato seeds the chance to mature and spread. But unlike chili, tomatoes as well as most other fruits lose their chemical defense mechanisms when ripe fruit. Scientists believe that this is a necessary step because birds and other animals can then eat the fruit and spread the seeds. According to Tewsbury, the problem with the strategy of the fruit makes the fruit susceptible to fungal attack in the mature stage.

Tewsbury said: 'Peppers increase the chemical defense intensity or the pungent taste when the fruit ripens. This is a very different form. Peppers can spread because birds do not feel the pain when they eat capsaicin. I think that many plants want to have a way to prevent fungal attacks without affecting the 'partner' that disperses the seeds. However, it is difficult to do this. "

In fact, chili contains capsaicin is the reason people eat chili first. Peppers and corn are the earliest domesticated plants in the world.

'Before humans can keep cold to preserve food, they have probably adapted to eating chili especially in the tropics. At that time, if you live in a warm and humid climate, eating becomes very dangerous because everything is full of bacteria, many of which are harmful. Perhaps humans have added chili to the stews because the spicy stew can partially kill bacteria '.

All chili species originated in South America. The current wild pepper plant lives from Central South America to the southeastern United States. The explorers brought chilli to Europe but chili was not popularly used there. From Europe, chillies find their way into Asia and Africa, where they become popular ingredients in most tropical dishes.

Tewsbury said: 'In the northern hemisphere, any adaptive benefits to chili consumption are not as large as equatorial regions because bacteria are contaminated on less common foods and are also easier to keep food cold. . Perhaps that's why the northern hemisphere's food is a bit boring. '

'In equatorial areas, it is not easy to keep food cold, we can die very quickly unless we find a way to protect ourselves from the bacteria we eat on our stomachs daily.'