Aroma volatile characterisation and gene expression analysis during fruit development and ripening of five pear (<i>Pyrus L.</i>) species
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Bartlett, Hongnanguo, Korla Xiangli, Dangshansuli and Housui are representative cultivars from the five cultivated pear species that were chosen to identify aromatic compounds in fruit during developmental, mature and storage periods. We explored the expression levels of aroma formation-related genes during developmental and storage periods. The concentrations of the aromatic compounds first decreased, then increased in all five cultivars. For the climacteric pears, Bartlett and Hongnanguo, the increase continued to optimal sensory quality (OSQ), whereas those for the non-climacteric pears, Korla Xiangli, Dangshansuli and Housui decreased. Aldehydes contributing the 'green' odour and 1,4-benzoquinone were the primary components during early and middle developmental periods. Esters contributing the 'fruity' and 'sweet' odour, were the primary components in Bartlett, Hongnanguo and Korla Xiangli fruits during storage and at OSQ. Methyl- and ethyl-(<i>E, Z</i>)-2,4-decadienoate (pear-like odour), ethyl caproate (liquor odour), and hexyl acetate (fruity odour) were the key characteristic odorants in mature pear fruits of Bartlett, Hongnanguo and Korla Xiangli, respectively. <i>Alcohol dehydrogenase</i> (<i>PbrADH-1</i> and <i>PbrADH-2</i>) and <i>lipoxygenase</i> (<i>PbrLOX3</i>) might participate in the formation of C<sub>6</sub> and C<sub>9</sub> volatile aldehydes and alcohols. The aroma content and volatiles of pear fruits during development and storage probably revealed a common pattern.
本研究选取5个栽培梨品种的代表品种——巴特利特梨（Bartlett）、红果梨（Hongnanguo）、库尔勒香梨（Korla Xiangli）、砀山酥梨（Dangshansuli）与丰水梨（Housui），用于解析果实发育、成熟及贮藏阶段的芳香类化合物组成，并分析了果实发育与贮藏阶段中香气形成相关基因的表达水平。所有5个供试梨品种的芳香化合物浓度均呈现先下降后上升的变化趋势：其中呼吸跃变型梨品种巴特利特梨与红果梨的浓度持续上升直至达到最佳感官品质（optimal sensory quality, OSQ）；而非呼吸跃变型梨品种库尔勒香梨、砀山酥梨与丰水梨的浓度则在达到峰值后下降。带有“青草”气味的醛类物质与1,4-苯醌是果实发育早中期的主要芳香成分。带有“果香”与“甜香”气味的酯类物质，是巴特利特梨、红果梨与库尔勒香梨在贮藏阶段及达到最佳感官品质时的主要芳香成分。(E,Z)-2,4-癸二烯酸甲酯和乙酯（梨香气味）、己酸乙酯（酒香气味）与乙酸己酯（果香气味），分别是巴特利特梨、红果梨与库尔勒香梨成熟果实中的关键特征风味物质。乙醇脱氢酶（Alcohol dehydrogenase，PbrADH-1与PbrADH-2）及脂氧合酶（lipoxygenase，PbrLOX3）可能参与C₆与C₉挥发性醛类及醇类物质的生物合成。梨果实发育与贮藏阶段的香气含量及挥发性物质变化模式可能具有共性。
