Laboratory for Fundamental and Applied Research in Chemical Ecology (FARCE), University of Neuchâtel, Rue Emile-Argand 11, 2000, Neuchâtel, Switzerland.
Neuchâtel Platform of Analytical Chemistry (NPAC), University of Neuchâtel, Avenue de Bellevaux 51, 2000, Neuchâtel, Switzerland.
New Phytol. 2018 Jan;217(1):355-366. doi: 10.1111/nph.14757. Epub 2017 Sep 6.
Domesticated plants are assumed to have weakened chemical defenses. We argue, however, that artificial selection will have maintained defense traits against specialized herbivores that have coexisted with the crops throughout their domestication. We assessed the performance of eight species of insect herbivores from three feeding guilds on six European maize lines and six populations of their wild ancestor, teosinte. A metabolomics approach was used in an attempt to identify compounds responsible for observed differences in insect performance. Insects consistently performed better on maize than on teosinte. As hypothesized, this difference was greater for generalist herbivores that are normally not found on teosinte. We also found clear differences in defense metabolites among the different genotypes, but none that consistently correlated with differences in performance. Concentrations of benzoxazinoids, the main chemical defense in maize, tended to be higher in leaves of teosinte, but the reverse was true for the roots. It appears that chemical defenses that target specialized insects are still present at higher concentrations in cultivated maize than compounds that are more effective against generalists. These weakened broad-spectrum defenses in crops may explain the successes of novel pests.
驯化植物被认为其化学防御能力减弱了。然而，我们认为人工选择将维持针对与作物在整个驯化过程中共同生存的专门食草动物的防御特性。我们评估了来自三个取食群的 8 种昆虫食草动物在 6 个欧洲玉米品系和其野生祖先大刍草的 6 个种群上的表现。采用代谢组学方法试图确定导致昆虫表现差异的化合物。昆虫在玉米上的表现始终优于大刍草。正如假设的那样，通常在大刍草上找不到的一般性食草动物的这种差异更大。我们还发现不同基因型之间的防御代谢物存在明显差异，但没有一个与表现差异一致。玉米中主要的化学防御物质苯并恶嗪类化合物的浓度在大刍草的叶片中趋于较高，但在根部则相反。看来，针对专门昆虫的化学防御物质在栽培玉米中的浓度仍然高于对一般食草动物更有效的化合物。这些在作物中减弱的广谱防御可能解释了新型害虫的成功。
