Regulation of subsoiling tillage on the grain filling characteristics of maize varieties from different eras

Grain filling is the key stage for achieving high grain yield. Subsoiling tillage, as an effective conservation tillage, has been widely used in the maize planting region of China. This study was conducted to explore the effects of subsoiling on the grain filling characteristics of maize varieties of different eras. Five typical maize varieties from different eras (1970s, 1980s, 1990s, 2000s and 2010s) were used as experimental materials with two tillage modalities (rotation tillage and subsoiling tillage). The characteristic parameters (Tmax: the time when the maximum grouting rate was reached, Wmax: the grain weight at the maximum filling rate, Rmax: the maximum grouting rate, P: the active grouting stage, Gmean: the average grouting rate; A: the ultimate growth mass) and rate parameters (T1: the grain filling duration of the gradually increasing stage, V1: the average grain filling rate of the gradually increasing stage, T2: he grain filling duration of the rapidly increasing stage, V2: the average grain filling rate of the rapidly increasing stage, T3: the grain filling duration of the slowly increasing stage, V3: the average grain filling rate of the slowly increasing stage) of grain filling of two tillage modalities were analyzed and compared. The results showed that the filling parameters closely correlated with the 100-kernel weight were significantly different among varieties from different eras, and the grain filling parameters of the 2010s variety were better than those of the other varieties, the P and Tmax prolonged by 4.06–19.25%, 5.88–27.53% respectively, the Rmax and Gmean improved by 5.68–14.81%, 4.76–12.82% and the Wmax increased by 10.14–32.58%. Moreover, the 2010s variety helped the V2 and V3 increase by 6.49–13.89%, 4.55–15.00%. In compared with rotation tillage, the grain yield of maize varieties from different eras increased by 4.28–7.15% under the subsoiling condition, while the 100-kernel weight increased by 3.53–5.06%. Under the same contrast conditions, subsoiling improved the Rmax, Wmax and Gmean by 1.23–4.86%, 4.01–5.96%, 0.25–2.50% respectively, delayed the Tmax by 4.04–5.80% and extended the P by 1.19–4.03%. These differences were major reasons for the significant increases in 100-kernel dry weight under the subsoiling condition. Moreover, subsoiling enhanced the V2 and V3 by 0.70–4.29%, 0.00–2.44%. The duration of each filling stage and filling rate of maize varieties from different eras showed different responses to subsoiling. Under the subsoiling condition, the average filling rate of the 1970–2010s varieties were improved by 1.18%, 0.34%, 0.57%, 1.57% and 2.69%. In the rapidly increasing period, the grain filling rate parameters of the 2010s variety were more sensitive to subsoiling than those of the other varieties. The rapidly increasing and slowly increasing period are the key period of grain filling. Since the 2010s variety and subsoiling all improve the grain filling rate parameters of two periods, we suggest that should select the variety with higher grain filling rate in the rapidly increasing and slowly increasing period, and combine subsoiling measures to improve the grain filling characteristic parameters of maize in production, so as to achieve the purpose of increasing 100 grain weight and yield.

GC-MS-based metabolite profiling of key differential metabolites between superior and inferior spikelets of rice during the grain filling stage

Background The asynchronous filling between superior spikelets (SS) and inferior spikelets (IS) in rice has become a research hotspot. The stagnant development and poor grain filling of IS limit yields and the formation of good quality rice. A large number of studies on this phenomenon have been carried out from the genome, transcriptome and proteome level, indicating that asynchronous filling of SS and IS filling is a complex, but orderly physiological and biochemical process involving changes of a large number of genes, protein expression and modification. However, the analysis of metabolomics differences between SS and IS is rarely reported currently. Results This study utilized untargeted metabolomics and identified 162 metabolites in rice spikelets. Among them, 17 differential metabolites associated with unsynchronized grain filling between SS and IS, 27 metabolites were related to the stagnant development of IS and 35 metabolites related to the lower maximum grain-filling rate of IS compared with the SS. We found that soluble sugars were an important metabolite during grain filling for SS and IS. Absolute quantification was used to further analyze the dynamic changes of 4 types of soluble sugars (sucrose, fructose, glucose, and trehalose) between SS and IS. The results showed that sucrose and trehalose were closely associated with the dynamic characteristics of grain filling between SS and IS. The application of exogenous sugar showed that trehalose functioned as a key sugar signal during grain filling of IS. Trehalose regulated the expression of genes related to sucrose conversion and starch synthesis, thereby promoting the conversion of sucrose to starch. The difference in the spatiotemporal expression of TPS-2 and TPP-1 between SS and IS was an important reason that led to the asynchronous change in the trehalose content between SS and IS. Conclusions The results from this study are helpful for understanding the difference in grain filling between SS and IS at the metabolite level. In addition, the present results can also provide a theoretical basis for the next step of using metabolites to regulate the filling of IS.

Synthetic nitrogen coupled with seaweed extract and microbial inoculants improves rice (Oryza sativa L.) production under a dual cropping system

The over-reliance on synthetic nitrogen (N) in current farming is a major concern because of its adverse effects on soil quality, the environment, and crop production. Organic fertilizers such as seaweed extract (SE) and microbial inoculants (MI) provide alternatives to chemical fertilizers that could decrease the amount of synthetic N needing to be applied and improve crop growth productivity. This study evaluated the combined effect of SE and MI with reduced N rates on the growth, biomass accumulation, yield, and yield components of an N-efficient rice cultivar (Baixiang 139-A) and N-inefficient rice cultivar (Guiyu 9-B). Field experiments were conducted in the early and late growing seasons at different sites in Guangxi province, China, in 2019. A total of five treatments, such as T1: N 180 + SE 0 + MI 0 (kg ha-1) (control); T2: N 180 + SE 3 + MI 3 (kg ha -1); T3: N 144 + SE 3 + MI 3 (kg ha-1); T4: N 126 + SE 3 + MI 3 (kg ha-1); and T5: N 108 + SE 3 + MI 3 (kg ha-1) were used. The leaf area index (LAI), effective panicle number, grain per spike, grain filling rate, and 1000-grain weight were significantly increased in T2 and T3 compared with the control. T2and T3 enhanced the biomass accumulation and grain yield of rice compared with the control. Furthermore, differences in the growth, yield, and yield components among the different cultivars were significant; however, there were no significant differences among the different locations. T3 increased the LAI, grain filling rate, biomass accumulation, and grain yield of rice by 4.5%, 5.9%, 6.6%, and 5.2%, respectively, compared with the control. Improvements in grain yield were mainly attributed to the enhanced growth and yield components. The correlation analysis also confirmed that LAI, productive tillers, grain filling rate, and biomass accumulation were positively correlated with grain yield. In sum, T3 (N144 + SE 3 + MI 3 (kg ha-1)) could achieve higher grain yield despite a reduction in the usage of chemical N. Generally, this study provides a sustainable nutrient management plan that increases crop production while minimizing costs of chemical N fertilizer application.

Regulation of Subsoiling Tillage on the Grain Filling Characteristics of Maize Varieties From Different Eras

Grain filling is the key stage for achieving high grain yield. Subsoiling tillage has been widely used as a conservation tillage method in the maize planting region of China. This study was conducted to explore the effects of subsoiling on the grain filling characteristics of maize varieties of different eras. Five typical maize varieties from different eras (1970s, 1980s, 1990s, 2000s and 2010s) were used as trial materials with two tillage modalities: rotation tillage and subsoiling tillage. The characteristic parameters and rate parameters of grain filling were compared and analyzed using the selected tillage modalities. The results showed that the grain filling parameters of the 2010s variety were better than those of the other varieties, and these differences mainly manifested in the filling rate parameters of the rapidly increasing and slowly increasing periods. In comparison with rotation tillage, subsoiling improved the maximum grain filling rate and the grain growth during the period of the maximum grain filling rate to different degrees. In addition, subsoiling delayed the appearance time of the maximum grain filling rate, extended the grain filling duration, and improved the mean filling rate. These differences are major reasons for the significant increase in 100-kernel dry weight at harvest for subsoiling in comparison with rotation tillage. Moreover, subsoiling enhanced the filling rate parameters during the rapidly increasing and slowly increasing periods. The filling stage filling duration and filling rate of maize varieties of different eras showed different responses to subsoiling. For example, the grain filling rate parameters of the 2010s variety during the rapidly increasing period were more sensitive to subsoiling in comparison with those of the other varieties.

Nitrogen Supply Regulates Vascular Bundle Structure and Matter Transport Characteristics of Spring Maize Under High Plant Density

Nitrogen (N) fertilizer application greatly enhances grain yield by improving dry matter accumulation and grain filling in spring maize. However, how N application rates regulate the vascular bundle structure, matter transport and grain filling of spring maize under a high planting density has been poorly understood thus far. In this study, we analyzed the relationship between grain filling, vascular bundle structure and matter transport efficiency (MTE) of spring maize in the field. Zhongdan909 (ZD909) was used as the experimental material in a 2-year field experiment from 2015 to 2016, and it was grown under different N levels (0, 150, and 300 kg N ha–1) applied to the grain-filling stage of plots with planting densities of 67,500 plants ha–1 (ND) and 90,000 plants ha–1 (HD). Nitrogen application significantly optimized the structure of the big and small vascular bundles. In particular, there was an increase in the total number of small vascular bundles in the peduncle and cob of the ear system, i.e., increases of 51.8% and 25.7%, respectively, and the proportions of small vascular bundles to the total number of vascular bundles in the peduncle and cob were significantly increased. The root bleeding sap and MTE of maize were significantly increased by N application under both ND and HD, as indicated by the significant increase in the rate of 13C-photosynthate allocation to grain and amount of postsilking dry matter at maturity. Moreover, N application greatly improved the mean grain-filling rate (Gmean) under ND and HD by 30.0% and 36.1%, respectively, and the grain-filling rate increased, leading to a distinct improvement in the grain sink at the grain-filling stage. We concluded that nitrogen application significantly optimized the vascular bundle structure of the ear system, increased the MTE and improved photosynthate distribution to the grain, ultimately enhancing the filling rate and grain yield.

Comparative Quantitative Proteomic Analysis Reveals Differentially Expressed Proteins Involved in Grain-Filling Rate of Rice at the Early Ripening Stage

BackgroundGrain-filling ability is a determinant factor of rice potential yield. Grain filling is a biological process of starch accumulation involved a large number of major enzymes implicated in carbohydrates metabolism in developing rice endosperm and is governed by a complex balance between the sink (grains) and the source (assimilates). This study was carried out to analyze the proteomic profile of rice grains and to identify proteins associated with high grain-filling rate during the early ripening period in rice.ResultsTMT and LC-MS/MS were employed in analyzing proteomic profile of grains from two rice cultivars possess contrasting phenotypes in grain filling rate to identify proteins associated with high grain-filling rate during the early ripening stage. The two cultivars differed significantly in grain-filling rate during the period of 0–3 days after full heading, indicating the appropriacy of cultivars selection for quantitative proteomic analysis. A total of 219 differentially expressed proteins in grains between the two cultivars were identified, providing a database for quantified proteomics in rice grains during grain filling stage. Elevated expression of many enzymes involved in starch and sucrose metabolism during rice grain filling was observed. GO and KEGG analyses revealed that the largest portion of differentially expressed proteins during grain filling associated with carbohydrate metabolism and transportation, suggesting a more specific function of those protein in rice grain development. Starch, sucrose, fatty acids and amino acids biosynthesis and metabolism were significantly enriched pathways.ConclusionsAnalysis of protein-protein interactions indicated the implication of the same proteins in several biological processes such as carbohydrate transport and metabolism, fatty acid metabolism, energy production and conversion and secondary metabolites biosynthesis. The data provide valuable information about the roles of biosynthesis, transport and metabolism of carbohydrate and amino acids in rice grain filling and development. The results represent a valuable foundation for further studies of the roles of differentially expressed proteins in underlying grain filling stage in rice and their potential impacts on rice productivity.

Effects of Gibberellin (GA4+7) in Grain Filling, Hormonal Behavior, and Antioxidants in High-Density Maize (Zea mays L.)

Dense plant cultivation is an efficient approach to improve maize production by maximizing the utilization of energy and nutrients. However, dense plant populations may aggravate the abortion rate of young grains, resulting in fewer kernels per ear. The rate and duration of grain-filling play decisive roles in maize grain yield. Therefore, to increase plant density, enhancing the grain-filling rate, extending the growth period of individual maize plants and regulating crop senescence would be the first priority. In this study, we examined the regulatory effects of GA4+7 under two application methods: shanks and silks were moistened by cotton full with GA4+7 solution at concentrations of 0, 10, 60, and 120 mg L−1. The results showed that GA4+7 improved the grain-filling rate by increasing the content of auxin, gibberellin, zeatin, and abscisic acid in grains compared to control plants. In addition, the auxin, gibberellin, and zeatin contents in the grains were positively and significantly correlated with the maximum grain weight and the maximum and mean grain-filling rates. Moreover, GA4+7 increased the activities of superoxide dismutases, catalases, and peroxidases and reduced the malondialdehyde content in leaves compared with untreated plants. At the concentration of 60 mg L−1, GA4+7 showed the greatest effect on shank and silk applications (Sh-60 and Si-60) followed by 10 mg L−1 (Sh-10) for shank treatment and 120 mg L−1 (Si-120) for silk treatment. Our results suggest that a concentration of 60 mg L−1 GA4+7 for shank and silk application may be efficiently used for changing the level of hormones in grains and antioxidant enzymes in ear leaves, which may be useful for enhancing grain-filling rate and delaying leaf senescence, resulting in an increase in maize grain yield.

Comparative Quantitative Proteomic Analysis Reveals Differentially Expressed Proteins Involved in Grain-Filling Rate of Rice at the Early Ripening Stage

Background Grain-filling ability is a determinant factor of rice potential yield. Grain filling is a biological process of starch accumulation involved a large number of major enzymes implicated in carbohydrates metabolism in developing rice endosperm and is governed by a complex balance between the sink (grains) and the source (assimilates). This study was carried out to analyze the proteomic profile of rice grains and to identify proteins associated with high grain-filling rate during the early ripening period in rice. Results TMT and LC-MS/MS were employed in analyzing proteomic profile of grains from two rice cultivars possess contrasting phenotypes in grain filling rate to identify proteins associated with high grain-filling rate during the early ripening stage. The two cultivars differed significantly in grain-filling rate during the period of 0–3 days after full heading, indicating the appropriacy of cultivars selection for quantitative proteomic analysis. A total of 219 differentially expressed proteins in grains between the two cultivars were identified, providing a database for quantified proteomics in rice grains during grain filling stage. Elevated expression of many enzymes involved in starch and sucrose metabolism during rice grain filling was observed. GO and KEGG analyses revealed that the largest portion of differentially expressed proteins during grain filling associated with carbohydrate metabolism and transportation, suggesting a more specific function of those protein in rice grain development. Starch, sucrose, fatty acids and amino acids biosynthesis and metabolism were significantly enriched pathways. Conclusions Analysis of protein-protein interactions indicated the implication of the same proteins in several biological processes such as carbohydrate transport and metabolism, fatty acid metabolism, energy production and conversion and secondary metabolites biosynthesis. The data provide valuable information about the roles of biosynthesis, transport and metabolism of carbohydrate and amino acids in rice grain filling and development. The results represent a valuable foundation for further studies of the roles of differentially expressed proteins in underlying grain filling stage in rice and their potential impacts on rice productivity.