Multivariate analysis of fruit quality and mineral nutritions in different tissues and soils of Merlot grape

Abstract:【Objective】The characteristics of 100-seed weight, soluble solids, total phenols, anthocyanins, total flavonoids, flavanols and tannins of Merlot grape grape berries under different fertilization conditions in Penglai area were analyzed. The relationships between mineral elements, root layer soil fertility factors and fruit quality indicators in different tissues of Merlot grape in different growth peri- ods were explored in order to screen the main mineral elements of plants and soils that affect the forma- tion of fruit quality and the corresponding key growth periods as theoretical basis for the formulation of  plant and soil nutrition diagnosis. A theoretical fertilization plan based on the best comprehensive fruit quality was initially drawn up to lay a foundation for guiding the rational fertilization and quality improvement of Merlot grape in the Penglai production area. 【Methods】Based on the target yield of 7500 kg·hm-2, the basic dosage of N, P2O5, K2O, CaO, and MgO as each fertilizer raw material per hectare set in the non-complete orthogonal experiment (5416) were N 124.5 kg, P2O5 46.5 kg, K2O 112.5 kg, CaO 112.5 kg, MgO 46.5 kg, respectively. The soil samples were collected in the position of distance of 30 cm from the main stem, at the depth of 0-20 cm and 20-40 cm below the main stem at germination stage (GS), initial flowering stage (IFS), end bloom stage (EBS), veraison stage (VS) and maturity stage (MS) to determine the 0-40 cm alkali-hydrolyzable nitrogen (N), quick-acting phosphorus (P), quickacting potassium (K), exchangeable calcium (Ca) and magnesium (Mg). The leaves, petioles and inflorescences/fruits were collected at full bloom stage (FBS), veraison stage, and mature stage to determine their N, P, K, Ca and Mg contents. The correlation analysis method was used to study the correlation between leaves, petioles, fruit mineral elements, soil fertility factors and fruit quality. Non-orthogonal analysis of variance was applied to initially form the best quality fertilization program.【Results】The 100-seed weight, soluble solids and polyphenol content of Merlot grapes in the Penglai production area of Shandong Province were significantly different under different fertilization conditions. The quality index of Merlot grapes treated with T8 was 0.557, with the highest comprehensive quality. Among the significant and extremely significant relationships between the mineral nutritions of different tissues and the fruit quality of Merlot grape, mineral elements of fruits were mainly related to phenolics, and miner- al elements of leaves were significantly and positively correlated with quality. The correlation between mineral elements of petioles and fruit quality was complex, and extremely significant positive correla- tions appeared in the FBS and MS of K in petioles and 100-seed weight, seed total phenols and seed to- tal flavonoids, respectively, and extremely significant negative correlations occurred in VS. There was also a significant correlation between Ca in petioles at MS and 100-seed weight and skin tannin, respec- tively. The effect of mineral elements in leaves and petioles on the overall fruit quality was relatively weaker than that of mineral elements in fruits, especially the influence of N and P elements in the fruits at VS and the K of fruits in MS on the overall quality of the Merlot grapes. The soil N element at IFS and the soil K element at MS had a greater impact on the overall quality of Merlot grapes. There was a big difference in the theoretical ratio of soil fertility factors when the highest skin and seed phenols were obtained. N had the greatest impact on 100-seed weight and total soluble solids, followed by K. And Ca had the least impact on 100-seed weight and total soluble solids. Similarly, N had the greatest influence on anthocyanins, followed by Mg. Ca had the greatest influence on the total phenols, total fla- vonoids, and tannins of the skin, followed by Mg. Among them, the influence of the soil fertility factors on the total phenols and total flavonoids of the skin was the same, the order was Ca>Mg>K>N>P. P, K, and Mg have greater influence on total seed phenols and seed flavanols, and the order of influence was P>Mg>K. Mg had a greater impact on dermato flavanols, followed by Ca. The order of soil fertility fac- tors affecting both seed tannin and quality index were P>N>Mg>Ca>K.【Conclusion】The effect of soil fertility factors in the root layer of Merlot grape on the quality of fruits had obvious tissue specificity, and each fruit quality index was coordinated by different mineral elements. The assumed order of influ- ence on the best comprehensive quality of soil fertility factors would be P>N>Mg>Ca>K, and the theo- retical ratio would be N2P3K3Ca4Mg3, that is, the optimal fertilization rate per acre would be N 62.5 kg, P2O5 46.9 kg, K₂O 112.5 kg, CaO 168.8 kg, MgO 46.9 kg.