Suitable stocking density of fish in paddy field contributes positively to 2-acetyl-1-pyrroline synthesis in grain and improves rice quality.

Abstract

Fragrant rice is increasingly popular with the public owing to its fresh aroma, and 2-acetyl-1-pyrroline (2-AP) is the main characteristic component of the aroma in fragrant rice. Rice-fish co-culture is an environmentally friendly practice in sustainable agriculture. However, the effect of rice-fish co-culture on 2-AP in grains has received little study. A conventional fragrant rice (Meixiangzhan 2) was used, and a related field experiment during three rice growing seasons was conducted to investigate the effects of rice-fish co-culture on 2-AP, as well as the rice quality, yield, plant nutrients, and precursors and enzyme activities of 2-AP biosynthesis in leaves. This study involved three stocking density treatments (i.e. 9,000 (D1), 15,000 (D2), and 21,000 (D3) fish fry per hectare) and rice mono-cropping. Rice-fish co-culture increased the 2-AP content in grains by 2.5%~49.4% over that of the mono-cropping, with significant increases in the early and late rice seasons of 2020. Rice-fish co-culture treatments significantly promoted seed-setting rates by 3.39%~7.65%, improved leaf nutrients and rice quality. Notably, the D2 treatment significantly increased leaf total nitrogen (TN), total phosphorus (TP), and total potassium (TK) contents and the head rice rate at maturity stage, while significantly decreased chalkiness degree. There were no significant difference in rice yield. Rice-fish co-culture had positive effects on 2-AP synthesis, rice quality, seed-setting rates, and plant nutrient contents. The better stocking density of field fish for rice-fish co-culture in this study was 15,000 fish/ha. This article is protected by copyright. All rights reserved.