Cocoa mirids are the most important insect pests of cocoa in West Africa. This study investigated the effect of environmental parameters that are modulated by overhead shade, i.e. light intensity and temperature, on nutrient and phenolic concentrations in cocoa and their subsequent effect on mirid feeding. Eight-month-old cocoa seedlings were maintained for 50 days in two growth chambers set to day temperatures of 25oC or 30oC. Each chamber had sections with different light intensities (541, 365 and 181 µmolm-2s-1 PAR). For the field studies at Akim-Tafo in Ghana, eight-month-old plants of three cocoa clones were subjected to shaded (PAR= 180 µmol m-² s-1, between 11:00 and 12:00) and unshaded (PAR= 1767 µmol m-² s-1 between 11:00 and 12:00) treatments for 50 days after which nutrient measurements and mirid choice tests were carried out. No significant effect of environment was observed on the phenolic concentration of stems under controlled environment chamber conditions. However, in the field, the phenolic concentration of stems was significantly greater for unshaded compared with shaded plants (P=0.04). Under controlled conditions, the leaf nitrogen concentration increased slightly with light intensity (P=0.003). The same trend was seen in stems but only at 30oC. In the field, the impact of overhead shade on nitrogen varied between cocoa clones. The concentration of carbohydrates in both leaves and stems in the field was higher under unshaded conditions. When subjected to feeding tests, stems from unshaded cocoa had significantly more mirid feeding lesions (P=0.003) after 24 hours exposure to mirids compared to shaded cocoa. Mirid feeding therefore appears not to be deterred by the higher phenolic levels but rather there was a preference for cocoa tissue grown under unshaded conditions. These findings highlight the need to consider the growing environment of cocoa clones when screening for varieties with resistance to mirids.

中文翻译：

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受光和温度介导的可可植物养分浓度变化的影响的 Mirid 摄食偏好

Cocoa mirids是西非可可最重要的害虫。本研究调查了受顶棚遮荫调节的环境参数（即光照强度和温度）对可可中营养物质和酚类物质浓度的影响，以及它们对日光采食的后续影响。将 8 个月大的可可幼苗在设置为 25oC 或 30oC 的日间温度的两个生长室中保持 50 天。每个腔室都有不同光强度的部分（541、365 和 181 µmolm-2s-1 PAR）。在加纳 Akim-Tafo 的田间研究中，对三个可可克隆的八个月大植物进行了遮荫（PAR = 180 µmol m-² s-1，在 11:00 和 12:00 之间）和无阴影（PAR = 1767 µmol m-² s-1 在 11:00 和 12:00 之间）处理 50 天，然后进行营养测量和微量选择测试。在受控环境室条件下，没有观察到环境对茎的酚类浓度的显着影响。然而，在田间，与遮荫植物相比，未遮荫植物茎的酚类浓度显着更高（P = 0.04）。在受控条件下，叶片氮浓度随光照强度略有增加（P=0.003）。在茎中也看到了相同的趋势，但仅在 30oC 时。在田间，顶棚遮荫对氮的影响因可可无性系而异。在无遮荫条件下，田间叶和茎中碳水化合物的浓度较高。在进行饲养测试时，与阴影可可相比，在暴露于 mirid 24 小时后，来自未阴影可可的茎具有明显更多的 mirid 进食损伤（P = 0.003）。因此，高水平的酚类物质似乎不会阻止 Mirid 进食，而是偏爱在无阴影条件下生长的可可组织。这些发现强调了在筛选具有抗蚜虫能力的品种时需要考虑可可无性系的生长环境。