Afifi Maha, Rezk Alaaeldin, Obenland David, El-Kereamy Ashraf
California Table Grape Commission, Fresno, CA, United States.
Department of Botany and Plant Sciences, University of California Riverside, Riverside, CA, United States.
Front Plant Sci. 2023 Jan 27;14:1060377. doi: 10.3389/fpls.2023.1060377. eCollection 2023.
Red color resulted from anthocyanin pigment, is an essential trait for premium table grape production. Anthocyanin biosynthesis occurs through the flavonoid pathway which includes several enzymatic reactions coded by different genes. The expression of these genes is regulated by different cultural practices, cultivars, environmental conditions, and plant hormones. Recently, we reported that the anthocyanin pathway is regulated by several factors such as light and antioxidant activity. Despite the advances in cultural practices, it is still challenging to produce table grapes with high coloration, especially under the current and expected global climate change in warmer areas such as California. In the current study, we deployed two approaches to improve the accumulation of red pigment in table grapes. The first approach involves improving the expression of critical genes involved in the anthocyanin pathway through hormonal treatments and light manipulation using a reflective ground cover (RGC). The second approach was to reduce the negative effect of heat stress through stimulation of the antioxidant pathway to help remove free radicals. Treatments included ethephon (ET) at 600 mg/L, silicon (Si) at 175 mg/L, and a commercial light-reflective white ground cover (RGC) alone and in various combinations. Treatments were conducted either with or without a combination of cluster-zone leaf removal at veraison (LR) on Flame seedless ( L.). Data collected in 2019 and 2020 showed that the best treatment to improve berry coloration was using ET in combination with Si and RGC, applied at veraison. Adding the LR to this combination did not improve berry color any further, but rather caused a reduction in color development. RGC without conducting LR at veraison significantly increased the quantity of reflected blue and red lights as well as the red (R) to far-red (FR) ratio (R: FR) around clusters. Results were in accordance with the increase in gene expression of (), a key gene in the anthocyanin biosynthesis pathway, as well as (). Manipulating the light spectrum and application of silicon in combination with the ethephon treatment could be used in table grape vineyards to improve the ethylene-induced anthocyanin accumulation and coloration.
红色源于花青素色素，是优质鲜食葡萄生产的一项重要特征。花青素的生物合成通过类黄酮途径进行，该途径包括由不同基因编码的几个酶促反应。这些基因的表达受不同栽培措施、品种、环境条件和植物激素的调控。最近，我们报道花青素途径受光照和抗氧化活性等多种因素调控。尽管栽培措施有所进步，但生产高色泽的鲜食葡萄仍然具有挑战性，尤其是在加利福尼亚等温暖地区当前及预期的全球气候变化情况下。在本研究中，我们采用了两种方法来提高鲜食葡萄中红色素的积累。第一种方法是通过激素处理和使用反光地被物（RGC）进行光照调控，来提高花青素途径中关键基因的表达。第二种方法是通过刺激抗氧化途径来减少热应激的负面影响，以帮助清除自由基。处理包括600毫克/升的乙烯利（ET）、175毫克/升的硅（Si），以及单独和各种组合使用的商业反光白色地被物（RGC）。处理在无核白鸡心（L.）的转色期进行，有或没有结合果穗区叶片摘除（LR）。2019年和2020年收集的数据表明，改善浆果色泽的最佳处理方法是在转色期将乙烯利与硅和反光地被物联合使用。在此组合中加入果穗区叶片摘除并没有进一步改善浆果颜色，反而导致颜色发育减少。在转色期不进行果穗区叶片摘除的反光地被物显著增加了果穗周围反射的蓝光和红光量以及红（R）与远红（FR）的比率（R:FR）。结果与花青素生物合成途径中的关键基因（）以及（）的基因表达增加一致。在鲜食葡萄园操纵光谱并结合乙烯利处理施用硅，可用于提高乙烯诱导的花青素积累和色泽。
