Partial substitution of organic nitrogen with synthetic nitrogen enhances rice yield, grain starch metabolism and related genes expression under the dual cropping system

Anas Iqbal; Huimin Xie; Liang He; Shakeel Ahmad; Izhar Hussain; Haneef Raza; Abdullah Khan; Shangqin Wei; Zhao Quan; Ke Wu; Izhar Ali; Ligeng Jiang

doi:10.1016/j.sjbs.2020.11.039

Partial substitution of organic nitrogen with synthetic nitrogen enhances rice yield, grain starch metabolism and related genes expression under the dual cropping system

Saudi J Biol Sci. 2021 Feb;28(2):1283-1296. doi: 10.1016/j.sjbs.2020.11.039. Epub 2020 Nov 17.

Authors

Anas Iqbal¹, Huimin Xie¹, Liang He¹, Shakeel Ahmad², Izhar Hussain^{3

4}, Haneef Raza⁴, Abdullah Khan¹, Shangqin Wei¹, Zhao Quan¹, Ke Wu¹, Izhar Ali¹, Ligeng Jiang¹

Affiliations

¹ Key Laboratory of Crop Cultivation and Farming Systems College of Agriculture, Guangxi University Nanning 530004, China.
² College of Agriculture, Guangxi University Nanning 530004, China.
³ Rice Research Institute Guangdong Academy of Agricultural Sciences, Guangdong, China.
⁴ University of Haripur, Haripur, Khyber Pakhtunkhwa 22620, Pakistan.

Abstract

Improving grain filling in the presernt farming systems is crucial where grain filling is a concern due to the extreme use of chemical fertilizers (CF). A field experiment was conducted at the experimental station of Guangxi University, China in 2019 to test the hypothesis that cattle manure (CM) and poultry manure (PM) combined with CF could improve rice grain filling rate, yield, biochemical and qualitative attributes. A total of six treatments, i.e., no fertilizer (T₁), 100% CF (T₂), 60% CM + 40% CF (T₃), 30% CM + 70% CF (T₄), 60% PM + 40% CF (T₅), and 30% PM + 70% CF (T₆) were used in this study. Results showed that the combined treatment T₆increased starch metabolizing enzymes activity (SMEs), such as ADP-glucose phosphorylase (ADGPase) by 8 and 12%, soluble starch synthase (SSS) by 7 and 10%, granule bound starch synthesis (GBSS) by 7 and 9%, and starch branching enzyme (SBE) by 14 and 21% in the early and late seasons, respectively, compared with T₂. Similarly, higher rice grain yield, grain filling rate, starch, and amylose content were also recorded in combined treatments. In terms of seasons, higher activity of SMEs , grain starch, and amylose content was noted in the late-season compared to the early season. The increment in these traits was mainly attributed to a lower temperature in the late season during the grain filling period. Furthermore, our results suggested that an increment in starch accumulation and grain filling rate were mainly associated with the enhanced sink capacity by regulating key enzyme activities involved in Suc-to-starch conversion. In-addition, RT-qPCR analysis showed higher expression levels of AGPS2b, SSS1, GBSS1, and GBSE11b genes, which resultantly increased the activities of SMEs during the grain filling period under combined treatments. Linear regression analysis revealed that the activity of ADGPase, SSS, GBSS, and SBE were highly positively correlated with starch and amylose accumulation. Thus, we concluded that a combination of 30% N from PM or CM with 70% N from CF is a promising option in terms of improving rice grain yield and quality. Our study provides a sustainable fertilizer management strategy to enhance rice grain yield and quality at the lowest environmental cost.

Keywords: AC, amylose content; AGPase, ADP-glucose pyrophosphorylase; Amylose content; CF, chemical fertilizer; CM, cattle manure; DAA, days after anthesis; DBE, starch debranching enzyme; Enzyme; GBBS, granule bound starch synthase; Grain yield; N, nitrogen; PM, poultry manure; Rice; SBE, starch branching enzyme; SS, sucrose synthase; SSS, soluble starch synthase; Starch synthesis; Temperature.