Council for Agricultural Research and Economics (CREA), Research Centre for Engineering and Agro-Food Processing (CREA-IT), Pescara.
Department of Diagnostics and Public Health, University of Verona.
Eur J Histochem. 2020 Sep 23;64(3):3149. doi: 10.4081/ejh.2020.3149.
The present study investigated the morphology of fresh and brine-cured table olives (TOs) as well as the changes that occur when drupes are attacked by the fruit fly Bactrocera oleae. Morphological analyses were performed using light microscopy (LM) and environmental scanning electron microscopy coupled with energy dispersive spectroscopy (ESEM-EDS). The LM analysis was carried out with visible light to evaluate sections stained with either PAS or Azan mixtures as well as unstained sections observed at fluorescence microscopy. The results of the analyses showed that: i) Azan and PAS staining played a useful complementary role, increasing the information provided by the histological analysis. Indeed, in both fresh and brine-cured TOs, epidermal layers and mesocarpal cells were clearly revealed, including sclereid cells. The histological analysis allowed also to identifying the presence of secoiridoid-biophenols (seco-BPs) in both cell walls and vacuoles, as well as in the drupe regions that had been attacked by fruit flies, where they were found at higher concentrations; ii) in fresh and brine-cured olives, the excitation at 480 nm revealed the distribution of the fluorophores, among which the seco-BP are enclosed; iii) the ESEM-EDS analysis revealed the natural morphology of fresh olives, including the dimensions of their cell layers and the size and depth of the mechanical barriers of suberized or necrotic cells around the larva holes. In addition, the elemental composition of regions of interest of the drupe was determined in fresh and brine-cured TOs. The results highlighted the effectiveness of combined use of LM and ESEM-EDS in order to obtain a picture, as complete as possible, of the structural morphology of TOs. Such analytical combined approach can be used to support multidisciplinary studies aimed at the selection of new cultivars more resistant to fly attack.
本研究调查了新鲜和盐腌橄榄（TO）的形态以及油桃被果实蝇 Bactrocera oleae 攻击时发生的变化。使用光学显微镜（LM）和环境扫描电子显微镜结合能量色散光谱（ESEM-EDS）进行形态分析。LM 分析是在可见光下进行的，以评估用 PAS 或 Azan 混合物染色的切片以及在荧光显微镜下观察的未染色切片。分析结果表明：i）Azan 和 PAS 染色发挥了有用的互补作用，增加了组织学分析提供的信息。事实上，在新鲜和盐腌 TO 中，表皮层和中果皮细胞都被清晰地揭示出来，包括硬化细胞。组织学分析还允许在细胞壁和液泡中以及被果实蝇攻击的油桃区域中鉴定出次生环烯醚萜 - 生物酚（seco-BP）的存在，在这些区域中发现了更高浓度的 seco-BP；ii）在新鲜和盐腌橄榄中，在 480nm 处激发揭示了荧光团的分布，其中包含 seco-BP；iii）ESEM-EDS 分析揭示了新鲜橄榄的自然形态，包括其细胞层的尺寸以及围绕幼虫孔的木质素化或坏死细胞的机械屏障的大小和深度。此外，还确定了新鲜和盐腌 TO 中油桃感兴趣区域的元素组成。结果突出了 LM 和 ESEM-EDS 联合使用的有效性，以获得尽可能完整的 TO 结构形态图像。这种分析组合方法可用于支持旨在选择对飞蝇攻击更具抗性的新品种的多学科研究。
