Effect of foliar spraying of rare earth micronutrient fertilizer on fruit quality of Nanhong pear

Abstract:【Objective】The study aimed to determine the optimal foliar application concentration of rare earth micronutrient fertilizer by comparing the treatment of foliar spraying with rare earth micronutrient fertilizer and the foliar spraying with distilled water (control). Pyrus ussuriensis ‘Nanhong’pear is a characteristic variety in Liaoning region. In recent years, the fruit quality of Nanhong pear has shown a downward trend in fruit taste, flavor, and coloring. The rare earth micronutrient fertilizer is a new type of plant growth regulator with the characteristics of low dosage, low price, and obvious effects. It is widely used in various aspects of agricultural production, however, it has not been popularly used in the production of Nanhong pear. This experiment involved the investigation of the effects of the spray of the rare earth micronutrient fertilizers on the fruit quality of Nanhong pear.【Methods】The Nanhong pear trees with consistent growth potential and growth areas were selected as experimental materials. 2-3 liters of the rare earth micronutrient fertilizer were sprayed, and the fruit quality was tested. Six concentration gradients of the rare earth micronutrient fertilizer were set up, that is, 1200, 1000 and 800 times of the ultrapure rare earth micronutrient fertilizer, 300, 200, 100 times of the chelating rare earth micronutrient fertilizer. The distilled water was used as the control. The foliar sprays were done on 70, 100, and 130 days after flowering, and harvest was done on 145 days after flowering. The indicators of fruit quality were measured every 5 days after harvest, and the expression levels of anthocyanin synthesis related genes and ethylene synthesis related genes in the fruits were analyzed through fluorescence quantitative PCR detection.【Results】The fruit quality of Nanhong pear was significantly improved by the sprays of the rare earth micronutrient fertilizer, the effect of 800 times of the ultrapure rare earth micronutrient fertilizer was the most obvious, especially, and the quality indexs in each stage of postharvest were better than the control group. Among them, the ascorbate content in fruits was significantly increased by 47% compared with the control group at 0 days of storage, the color difference, anthocyanin and soluble solid contents were significantly higher than that of the control group (3.9, 4.4 and 1.3 times, respectively), and the content of stone cells, titrable acid and malondialdehyde were significantly decreased by 34%, 11% and 19%, respectively. The relative expression of anthocyanin synthesis-related genes PuPAL, PuCHS, PuCHI, PuF3H, PuDFR, PuANS and PuUFGT were increased in pericarp. The fruit hardness was significantly increased by 7.5% compared with the control, and the relative expression of ethylene synthesis-related genes PuACS1, PuACO2 and PuERF2 were decreased.【Conclusion】Leaf application of 800 times rare earth fertilizer significantly increased the fruit hardness, soluble solids and ascorbic acid content while Nanhong pear were harvest, the relative expression of genes related to anthocyanin synthesis were up- regulated, such as PuPAL, PuCHS, PuCHI, PuF3H, PuDFR, PuANS and PuUFGT, and increased the anthocyanin content in fruit peel. The production of titrable acid, stone cells, malondialdehyde and ethylene decreased significantly, and the relative expression of ethylene synthesis-related genes PuACS1, PuACO2 and PuEFR2 were down-regulated.