Instituto de Investigaciones Agropecuarias, INIA-La Platina, Santiago, Chile.
Instituto de Investigaciones Agropecuarias, INIA-La Platina, Santiago, Chile; Doctorado en Ciencias Silvoagropecuarias y Veterinarias, Campus Sur, Universidad de Chile, Santiago, Chile.
Plant Physiol Biochem. 2018 May;126:32-38. doi: 10.1016/j.plaphy.2018.02.009. Epub 2018 Feb 21.
Most table grape (Vitis vinifera L.) varieties require gibberellic acid (GA) applications to obtain an adequate berry size in order to satisfy market requirements. However, GA treatments also produce severe berry drop in some cultivars, which occurs mainly after a cold storage period during post-harvest. Berry drop in bunches treated with GA has been related to the hardening and thickening of the pedicel produced by the over-accumulation of cellulose and its lignification. The main goal of this study was to compare the morphology and gene expression in pedicel samples of genotypes contrasting for berry drop susceptibility. These genotypes are Thompson Seedless, which exhibits a low incidence of berry drop, and a genetic line (Line #23) of INIA's breeding program that is very susceptible to berry drop at harvest and after storage in bunches sprayed with GA. The parameters measured to study this phenomenon during fruit growth and post-harvest storage included fruit detachment force (FDF), hardness and thickness of the pedicel and berry drop frequency. Histological analyses of pedicel structures at harvest showed an increase in cell size and deposition of lignin in the cortex zone in both contrasting genotypes treated with GA. The expression profile in both genotypes of the key lignin biosynthesis genes Vv4CL4, VvCCR1L and VvCAD1 analyzed by quantitative real time PCR (qPCR) revealed evident changes in response to GA treatments. In particular, gene VvCAD1 is overexpressed (100X) in pedicels of line #23 treated with GA after 30 and 45 days in cold storage compared to control. Moreover, the frequency of berry drop was higher for Line #23 treated with GA than for the control (23% vs. 1%). Our results suggest that gibberellic acid regulates the expression of the biosynthesis of lignin genes, generating changes in cell wall composition and pedicel structure that result in an increase in berry drop.
大多数鲜食葡萄（Vitis vinifera L.）品种需要施用赤霉素（GA）才能获得足够大的浆果大小，以满足市场需求。然而，GA 处理也会导致一些品种严重落粒，主要发生在采后冷藏期之后。GA 处理的果穗落粒与花梗的硬化和加粗有关，这种加粗是由纤维素的过度积累及其木质化引起的。本研究的主要目的是比较对浆果脱落敏感的基因型的花梗样本的形态和基因表达。这些基因型是汤普森无核葡萄（Thompson Seedless），其落粒率较低，以及 INIA 育种计划的一个遗传系（Line #23），在 GA 处理后收获和冷藏时极易落粒。在果实生长和采后贮藏过程中，为研究这种现象而测量的参数包括果实脱落力（FDF）、花梗硬度和厚度以及落粒频率。在收获时对花梗结构进行的组织学分析表明，GA 处理的两种对比基因型的细胞大小增加，皮层区木质素沉积增加。通过定量实时 PCR（qPCR）分析，两种基因型的关键木质素生物合成基因 Vv4CL4、VvCCR1L 和 VvCAD1 的表达谱显示，GA 处理后有明显变化。特别是，GA 处理后，Line #23 的 VvCAD1 基因在冷贮 30 和 45 天后表达上调（100 倍）。此外，GA 处理的 Line #23 的落粒频率高于对照（23%对 1%）。我们的结果表明，赤霉素调节木质素生物合成基因的表达，导致细胞壁组成和花梗结构发生变化，从而增加落粒。
