科学家报告说，野生辣椒产生辣椒素来保护它们不受真菌的攻击。辣椒素是造成辣椒辛辣味道的化学物质。Joshua Tewksbury及其同事对玻利维亚超过200英里长区域中的辣椒（Capsicum chacoense）的辣椒素浓度和真菌病害率如何变化进行了调查，得出了上述结论。辣椒容易受到在其表面打洞取食的小虫传播的真菌的感染。一旦真菌进入果实中，即便是微量的真菌也足以毁掉辣椒种子。
这组科学家发现更辛辣的辣椒比不那么辣的辣椒在遭到相同数量的虫咬之后出现的真菌病害更少。他们然后在实验室中证实了辣椒素很可能造成了真菌生长的抑制。这组作者说，这些发现表明在所研究的地理范围内，辣椒的辛辣程度随真菌病害的风险而平行增加，这提示这种植物进化出了辣椒素作为对抗真菌的化学防御武器。相关论文发表在美国《国家科学院院刊》（PNAS）上。（生物谷Bioon.com）
生物谷推荐原始出处：
PNAS，doi: 10.1073/pnas.0802691105，Joshua J. Tewksbury，Douglas J. Levey
Evolutionary ecology of pungency in wild chilies
Joshua J. Tewksbury*,†, Karen M. Reagan*, Noelle J. Machnicki*, Tomás A. Carlo*, David C. Haak*, Alejandra Lorena Calderón Peñaloza‡, and Douglas J. Levey§
+Author Affiliations
*Department of Biology, University of Washington, Box 351800, 24 Kincaid Hall, Seattle, WA 98195-1800;
‡Carrera de Biología, Facultad Ciencias Agrícolas, Universidad Autónoma Gabriel René Moreno, Vallecito Km 9 Norte, Santa Cruz de la Sierra, Bolivia; and
§Department of Zoology, PO 118525, University of Florida, Gainesville, FL 32611-8525
Edited by May R. Berenbaum, University of Illinois at Urbana–Champaign, Urbana, IL, and approved May 16, 2008 (received for review March 18, 2008)
Abstract
The primary function of fruit is to attract animals that disperse viable seeds, but the nutritional rewards that attract beneficial consumers also attract consumers that kill seeds instead of dispersing them. Many of these unwanted consumers are microbes, and microbial defense is commonly invoked to explain the bitter, distasteful, occasionally toxic chemicals found in many ripe fruits. This explanation has been criticized, however, due to a lack of evidence that microbial consumers influence fruit chemistry in wild populations. In the present study, we use wild chilies to show that chemical defense of ripe fruit reflects variation in the risk of microbial attack. Capsaicinoids are the chemicals responsible for the well known pungency of chili fruits. Capsicum chacoense is naturally polymorphic for the production of capsaicinoids and displays geographic variation in the proportion of individual plants in a population that produce capsaicinoids. We show that this variation is directly linked to variation in the damage caused by a fungal pathogen of chili seeds. We find that Fusarium fungus is the primary cause of predispersal chili seed mortality, and we experimentally demonstrate that capsaicinoids protect chili seeds from Fusarium. Further, foraging by hemipteran insects facilitates the entry of Fusarium into fruits, and we show that variation in hemipteran foraging pressure among chili populations predicts the proportion of plants in a population producing capsaicinoids. These results suggest that the pungency in chilies may be an adaptive response to selection by a microbial pathogen, supporting the influence of microbial consumers on fruit chemistry.
