科學(xué)家報(bào)告說(shuō),，野生辣椒產(chǎn)生辣椒素來(lái)保護(hù)它們不受真菌的攻擊。辣椒素是造成辣椒辛辣味道的化學(xué)物質(zhì),。Joshua Tewksbury及其同事對(duì)玻利維亞超過(guò)200英里長(zhǎng)區(qū)域中的辣椒（Capsicum chacoense）的辣椒素濃度和真菌病害率如何變化進(jìn)行了調(diào)查,，得出了上述結(jié)論。辣椒容易受到在其表面打洞取食的小蟲(chóng)傳播的真菌的感染。一旦真菌進(jìn)入果實(shí)中,，即便是微量的真菌也足以毀掉辣椒種子,。
這組科學(xué)家發(fā)現(xiàn)更辛辣的辣椒比不那么辣的辣椒在遭到相同數(shù)量的蟲(chóng)咬之后出現(xiàn)的真菌病害更少。他們?nèi)缓笤趯?shí)驗(yàn)室中證實(shí)了辣椒素很可能造成了真菌生長(zhǎng)的抑制,。這組作者說(shuō),，這些發(fā)現(xiàn)表明在所研究的地理范圍內(nèi)，辣椒的辛辣程度隨真菌病害的風(fēng)險(xiǎn)而平行增加,，這提示這種植物進(jìn)化出了辣椒素作為對(duì)抗真菌的化學(xué)防御武器,。相關(guān)論文發(fā)表在美國(guó)《國(guó)家科學(xué)院院刊》（PNAS）上。（生物谷Bioon.com）
生物谷推薦原始出處：
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.
