Foliar application of fish protein peptide improved the quality of deep-netted melon

Abstract

To improve the fruit quality of deep-netted melon, fish protein peptide (FPP) with a total protein content greater than 90% at a concentration of 1 g·L⁻¹ was sprayed on leaves after pollination, distilled water was sprayed on the control plants (CK). Field indices such as single melon fresh mass, commercial fruit rate, yield and fruit nutrient contents were evaluated. Soluble sugar, starch, organic acid and the activities of enzymes related to sugar metabolism in the inner, middle and outer layers of melon flesh were also determined. The results showed that the commercial fruit rate and yield per hectare increased by 8.96% and 5.98%, respectively. Nutrient contents increased, including the total amounts of 16 amino acids were 0.34 g/100 g higher than those of CK, and the mineral element contents increased by 15.79%, among which the contents of potassium, phosphorus, zinc, calcium, magnesium and molybdenum were significantly different from those of CK (p < 0.05). FPP treatment significantly increased the soluble sugar content in the outer layer of the mesocarp of deep-netted melon and the ascorbic acid contents in the inner and middle layers of the mesocarp of deep-netted melon. FPP increased sucrose accumulations in fruit by decreasing the activity of neutral invertase (NI), increasing the activity of sucrose phosphate synthase (SPS) and the synthesis direction of sucrose synthase (SS), and by increasing the glucose and fructose contents by enhancing the activity of acid invertase (AI). These findings suggest that exogenous FPP improves the commercial fruit rate, yield, and quality of deep-netted melon.

Keywords:

• Deep-netted melon
• foliar fertilization
• protein hydrolysate
• quality
• sugar metabolism

Disclosure statement

The authors report there are no competing interests to declare.

Additional information

Funding

The work was supported by the National Key Research and Development Program of China (2019YFD1001904) and Beijing Innovation Consortium of Special crops Research System (BAIC4-2023).