1 . Plenty of harvests of corn and other major crops rely on a mysterious phenomenon known as hybrid vigor (杂交活力). When highly naturally-born varieties are crossed, their next generations are taller, hardier, and bear more grain, Researchers report that this vigor is somehow influenced by microbes (微生物) in the soil, perhaps through a plant's immune system .
Charles Darwin was one of the first researchers to describe hybrid vigor. In the early 20th century, biologists began to apply this effect to agriculture by creating naturally-born parent plants that produced hybrid seeds. By the 1940s, almost every farmer in the United States was planting hybrid corn, and the harvests multiplied.
Biologists have proposed several theories about the cause of hybrid vigor, but no definitive explanation has emerged.
Maggie Wagner, plant biologist at the University of Kansas, and her colleagues wondered whether microbes might be it involved. Last year, Wagner and her colleagues found an interesting clue in a field study. They discovered that the leaves and roots of hybrid corn had microbial communities that are different from those living on naturally-born varieties of corn. “Something about being a hybrid makes a plant interact differently with microbes,” Wagner says. It could be that the naturally-born corn's immune systems react more actively to beneficial microbes, compromising their growth. Alternatively, hybrid plants may be better able to defend against weak pathogens (病原体) in the soil.
Wagner says the finding highlights the need for plant growers to match the hybrid crops to the microbial communities with which they live. The findings help scientists realize the importance of understanding the role of soil microbes in making agriculture more productive and sustainable, “This holds great promise.”
1. How did people use the effect of hybrid vigor in agriculture?| A．By producing naturally-born parent plants that bore hybrid seeds. |
| B．By creating naturally-born parent lines that produced hybrid vigor. |
| C．By providing more microbes communities that could produce more seeds. |
| D．By looking for hybrid parent plants in the field that produced hybrid seeds. |
| A．Hybrid plants react worse to weak pathogens in the soil. |
| B．Wagner connected hybrid vigor with microbial communities. |
| C．Being naturally-born makes a plant interact differently with microbes. |
| D．Hybrid corn and naturally-born corn have similar microbial communities. |
| A．Making farmers know what to grow to resist certain diseases |
| B．Helping scientist realize the importance of spreading soil microbes. |
| C．Showing the significance of associating soil microbes with specific crops. |
| D．Highlighting the need for plant growers to find more microbial communities. |
| A．Hybrid corn: a double-edged sword |
| B．How can farmers grow hybrid crops? |
| C．Hybrid vigor: a mysterious phenomenon |
| D．What role do soil microbes play in the harvests of corn? |
