Effects of different fertilization treatments on quality characters and phenolic content of Cabernet Sauvignon fruit

Abstract: 【Objective】The study examined the effects of different fertilization treatments on characters and phenolic content in wine grapes in order to provide reference for rational fertilization in wine grape orchards.【Methods】With Cabernet Sauvignon as the experimental materials, a fertilization experiment  was carried out in the vineyard of Junding Winery Co, Ltd. in Penglai production area for 4 consecutive years. The fruit quality indicators such as single cluster weight, 100-berry weight, soluble solids, skin re-covery, seed recovery, number of seeds, and contents of phenolic substances in pericarp and seeds were measured at the mature stage, and the principal component analysis method was used to comprehensive- ly evaluate the treatments. SAS analysis method was used to calculate the influence and ratio of ele- ments.【Results】Fertilization treatments had significant effects on cluster weight and phenolic sub-stances in Cabernet Sauvignon, but had no significant effects on other quality indicators. The total solu-ble solid content in different fertilization treatments was in the range of 20.7% (T12)-22.9% (T2); 100-berry weight 120.2 (T10)-133.5 (T2) g; skin recovery 11.7% (T9)-15.8% (T1); seed recovery 5.8% (T4)-7.1% (T6); and per cluster number of berries 52.8 (T4)-60.0 (T6). The total phenol content in T7 was the highest, which was 10.650 mg∙g^{- 1}, 17.876%-83.797% higher than the other treatments. The content of flavanol in different fertilization treatments ranged from 38.859 (T6) to 62.647 (T2) mg·g-1, and the content of flavanol in T2 was significantly (28.2% to 61.2%) higher than that in T4, T6, T8, T10 and T12. Except for T4 and T6, there was no significant difference in anthocyanin content among the other fertilization treatments, and the content in T9 treatment was the highest, which was 2.515 mg∙g^-1. Tannin content in T9 was the highest (2.746 mg∙g^-1), which was significantly higher than that in the oth-er treatments. Except for T5, T6 and T11, there was no significant difference in total phenol content among the other treatments. The total phenol content in T3 was the highest (26.265 mg∙g^-1), which was 25.909%, 24.421% and 29.695% higher than in T5, T6 and T11, respectively. Seed flavanol content in different fertilization treatments was in the range of 356.1 to 597.5 mg∙g^-1. It was highest in T8, which was significantly and 23.330% (T3) to 67.786% (T6) compared with the other treatments beyond T10 and T12. The content of total flavonoids in T8 treatment was significantly higher compared with other treatments except for T2, T3, T4, T6, T7, T10 and T12. Except for T1, T6, T9 and T11, there was no sig-nificant difference in the content of seed tannin among the other treatments, which was in the range of 9.452 (T5) to 11.777 (T3) mg ∙ g^{- 1}. The seed tannin content in T3 was significantly and 35.954% ,37.984%, 52.470% and 33.744% higher than in T1, T6, T9 and T11, respectively. The total amount of fertilizer applied decreased by 6.8% to 11.2%, and cluster weight, total skin phenols, total skin flavo-noids, and skin tannins were significantly increased by 16.8%-33.8%, 17.4%-26.4%, 29.3%-33.1%,18.1%-35.5%, respectively. Under the same amount of fertilizer application, fertilization ratio had an ef-fect on fruit quality. T9 and T10 treatments were more suitable for increasing seed recovery of Cabernet Sauvignon. Mg had the greatest influence on peel recovery and total phenol, anthocyanin, flavonoid and tannin contents; K had the greatest influence on seed recovery and total phenols, total flavonoids, flava- nols and tannins. A total of 5 principal components were extracted by principal component analysis, and their eigenvalues were 4.573, 3.221, 1.960, 1.727, and 1.212, with a cumulative contribution rate of 84.612%. The five principal components could show the effects of different treatments on quality pa-rameters of Cabernet Sauvignon. A strong correlation was found between Y1 and skin recovery, and to-tal phenols, anthocyanins, total flavonoids and tannins in skin. Y2 was strongly correlated with total phe-nols, total flavonoids, flavanols and tannins. Soluble solids and 100 berry weight were strongly correlat-ed with Y3. Y4 and Y5 were strongly correlated with single panicle weight and flavanol, respectively. T9 treatment was more beneficial to increase the ratio of skin to fruit, total phenols in skin, anthocyanins in skin, total flavonoids in skin and tannins in skin. T8 treatment was more beneficial to increase total phe-nols in seed, total flavonoids in seed, flavanols in seed and tannins in seed. T2 treatment is more condu-cive to the improvement of total soluble solid content, the weight of 100 grains and the content of flava-nols in skin. T6 treatment was more beneficial to improve the quality of single panicle.. Except for T6, the comprehensive evaluation scores of the fertilization treatments were higher than T1, and that of T9 was the highest.【Conclusion】The optimal fertilizer application rates for optimal comprehensive quality of Cabernet Sauvignon under the experimental conditions were 124.5 kg∙hm^-2, 0.0 kg∙hm^-2, 112.5 kg∙hm^-2,168.8 kg∙hm^-2, MgO 23.3 kg∙hm^-2 for N, P2O5, K2O, CaO and MgO, respectively.