Western corn root beetle (Diabrotica virgifera virgifera) - insect family of leaf beetles (Chrysomelidae) - is among the most common pests of corn in the United States and the country's agriculture is causing enormous damage: loss of crop losses and the cost of protective measures translate into an annual amount in excess of a billion dollars .
However, about 20 years ago, this pest is able to penetrate into Europe. Today foci of infection have already been registered in Serbia and Bulgaria, Romania and Poland, the Czech Republic and Slovakia, Italy and Austria, Switzerland, Germany, Slovenia and Ukraine, the Netherlands and France, Belgium and the UK. "Adult females lay eggs in the soil, and they hatched larvae feed on the roots of corn - says Manfredo Syufferheld (Manfredo Seufferheld), professor of the University of Illinois in Urbana. - These larvae are very small, but a lot of them at one plant often there are hundreds, therefore yield losses are very noticeable. "
Crop rotation as a panacea diabrotiki
Chemical methods of dealing with leaf beetles have not yielded much success, but in the mid 80's farmers have found, as it seemed, a very effective way to suppress the pest Agrotechnical: strict crop rotation. Since the Western corn root beetle gives only one generation per year, and its larvae were fed exclusively on the roots of corn, farmers began to cultivate their fields two cultures, alternating each year - corn and soybeans. As a result, the year when the corn is replaced by soy, almost all beetle larvae died of starvation, and in the soil were very few animals able to next year again cause damage to crops of corn.
Today, however, this method does not work, complains Professor Syufferheld: "The fact is that diabrotika adapted, adapted to the new conditions. It has become immune to the crop rotation, because the larvae have gained the ability to feed and soy. Accordingly, crop rotation has no effect, not prevents the reproduction and distribution of the pest. We were pretty surprised by it. "
Super-fast evolutionary adaptation
Scientists are faced with a mystery: how corn beetle succeeded in a few years, that is, throughout the generations, to adapt to crop rotation and include in your diet before it inedible for soybeans? After all, according to the generally accepted ideas about the evolution of such a process would proceed much more slowly and take much longer. The first studies have find the solution of the puzzle.
The fact that soybean is protected from pests synthesizing proteins that inhibit digestion insects. However, in the digestive tract corn root beetles resistant crop rotation, the content of digestive enzymes have proved to be so high that they are neutralized soy protein inhibitor. That is what made soy quite edible beetles for such a plant.
It was logical to assume that insects capable digesting soybean, the genes encoding these same digestive enzymes should have increased activity. However, studies have shown that this is not the case.
Intestinal bacteria synthesize digestive enzymes
As a result, the scientists set about searching for another, an additional source of digestive enzymes, and soon came upon a promising track. Their attention was drawn to the intestinal microflora of the insect. "Obviously, it is the bacteria in the intestines that cause the beetle is a significant difference, which is observed when comparing the digestive activity of the animals that are resistant to crop rotation, and non-resistant to it, that is able and unable to eat soy, - explains Professor Syufferheld. - Because the bacteria mutate much faster in their genome in a very short time, there may be hundreds and hundreds of new changes. This is a very dynamic process. "
Indeed, the analysis showed that the species composition of the intestinal flora of beetles capable of digesting soy, is significantly different from that of individuals, not eating soy. Scientists have also made sure that it is this difference and gives these beetles resistant crop rotation had only to suppress their intestinal flora by antibiotics, like insects that their resistance once lost.
Compulsory registration of all the factors in their relationship
According to Professor Syufferhelda, it gives scientists a reason to look at the broader processes of evolution: "We need to approach these complex processes. Everything in life is interconnected. Bacteria colonized the whole of nature, they are ubiquitous. But we should not forget that all the colonies in the world - and people, and insects, and plants, and bacteria - have developed and evolved together. And they continue to do it - again together. "
Who wishes to understand the ecology of insect pests, must take this into account. And do not forget that the nature of land use also has a strong selection pressure. The fact that in the state of Illinois for 85 per cent of the total cultivated area occupied by only two crops - corn and soybeans - has contributed to many changes in the microflora diabrotiki and, ultimately, its spread.
Pest Control now require new approaches, said Professor Syufferheld: "We're not going to spray antibiotics on the fields! So finally destroy the western corn root worm us unlikely. Limit its spread, of course, possible, but to do that we must act with Taking all factors into their relationship. "
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