Yong-Cheng Wu

Low light is an abiotic stress that has a significant impact on crop growth. However, the impact of low light on rapeseed yield has not been well documented. Our study aims to examine the potential effects of low light on the photosynthesis antioxidant capacity and yield composition of leaves by simulating low light environments. According to the study results, low light reduces key photosynthetic enzymes and sucrose synthase activity in rapeseed leaves, leading to a decrease in leaf carbohydrate accumulation. The reduced number of pods per plant and the number of pods per grain are the direct factors leading to the decrease in rapeseed grain yield, while the increase in grain weight compensates for some of the yield loss. In addition, low light increased the content of malondialdehyde in leaves and altered the activities of catalase (CAT) and superoxide dismutase (SOD). Low light inhibits photosynthesis in leaves, reduces leaf productivity, and leads to a decrease in yield. High-yielding varieties have stronger antioxidant capacity and lower production of malondialdehyde. By revealing the effects of low light on the photosynthesis and antioxidant capacity of rapeseed leaves, this studyprovide new insights into the composition of low light affecting rapeseed grain yield and explain significant guidance for the planting and management of different rapeseed varieties in low light areas.

Background: Mature rapeseed pods typically shatter when harvested, resulting in approximately 8–12% yield loss. Adverse weather conditions and mechanized harvesting can diminish pod yield by up to 50%, primarily owing to delays in harvesting and mechanical collisions. The pod shatter resistance index (PSRI) assesses pod damage. Recent research focused on comparing pod shatter resistance among varieties, evaluating methods, and studying gene knockout mechanisms. However, there remains a pressing need to broaden the scope of research. In particular, it is essential to recognize that pod shatter, a complex trait, influenced by genetics, environment, agronomic practices, and harvest techniques. Future studies should integrate these factors to develop comprehensive strategies to mitigate pod shatter, enhancing rapeseed yields and agricultural mechanization. This review explores factors affecting pod shatter resistance and strategies to improve it. Methodology: Scoping literature review that adhered to the methodological framework for systematic reviews was performed using search engines such as Google Scholar, Web of Science, and the Chinese National Knowledge Infrastructure. This review aimed to identify pertinent articles, which were subsequently subjected to thorough screening and evaluation. The protocol for this literature review involved the following key steps: definition of research questions, development of a search strategy, development of data extraction strategy, synthesis of the extracted data, and organization and analysis of the extracted data. Results: The review presents strategies for enhancing rapeseed yield during mechanized harvesting, focusing on four key areas: (i) selecting and breeding shatter-resistant varieties using DNA markers to establish a robust germplasm resource; (ii) optimizing cultivation technologies and agronomic measures to elicit favorable interactions between compact plant-type genotypes and the environment, thereby facilitating nutrient-related regulatory mechanisms of rapeseed pods to improve pod dry weight and resistance; (iii) innovating combine header design and structure to better suit rapeseed harvesting; and (iv) providing training for operators to enhance their harvesting skills. These comprehensive measures aim to minimize yield loss, increase production efficiency. Conclusion: To effectively reduce yield loss during mechanized harvesting of rapeseed, it is crucial to enhance resistance to pod shattering by addressing both internal physiological factors and external environmental conditions. This requires a holistic approach that includes genetic improvements, optimization of ecological conditions, careful cultivation management, and precise harvesting timing, along with ongoing research into traits related to machine harvesting to boost production efficiency and sustainability.

Rapeseed siliques easily shatter after ripening, resulting in a significant amount of grain loss, which delimits the development of rapeseed machine harvest. However, the effect of nitrogen (N) and density interaction on the characteristics of rape siliques and shattering resistance index is still vague. During the 2021–2022 and 2022–2023 growing seasons, we selected the Jiayou No. 5 rapeseed variety and set three N application levels (N1: 90 kg ha⁻¹, N2: 180 kg ha⁻¹, N3: 270 kg ha⁻¹) and two density treatments (M1: 150,000 plants ha⁻¹, M2: 300,000 plants ha⁻¹) to research the effects of N and density interaction on morphological indexes, physiological indexes, shatter resistance index and yield of direct-seeding rapeseed siliques. The silique shatter resistance index, silique’s length, weight, moisture content, silique shell’s weight, thickness, lignin content, cellulose content and phenylalaninase (PAL) activity all increased first and then decreased with the increase in the N application rate; the N2 treatment increased by 18.38% and 26.92%, respectively, compared to the N1 and N3 treatments; 3.65%, 2.48%; 6.70%, 3.58%; 20.46%, 18.33%; 5.97%, 5.96%; 8.82%, 9.60%; 9.12%, 19.90%; 43.85%, 69%; 2.10%, 11.04%. Compared with the M1 treatment, the silique shatter resistance index, silique’s length, weight, moisture content, silique shell’s weight, thickness, lignin content, cellulose content and PAL activity were lower under M2 treatment. Correlation analysis demonstrated that the silique’s length, water content, silique shell’s weight, thickness, lignin content, cellulose content and PAL activity were significantly positively correlated with the silique shatter resistance index. Therefore, this study shows that N2M1 treatment can carry off synergy between silique shatter resistance and yield.

Field experiments were conducted to study the effects of different proportions of controlled-release nitrogen fertilizer mixed with quick-acting nitrogen fertilizer on the yield and nitrogen utilization efficiency of direct-seeding rapeseed. Using a conventional nitrogen application rate of 180 kg ha⁻¹ as a control, a total of 5 types of available nitrogen fertilizers and different proportions of controlled-release nitrogen fertilizers were mixed for fertilizer treatment. The proportion of available nitrogen fertilizer used was 135 kg ha⁻¹, and the addition ratios of the five types of controlled-release nitrogen fertilizers were 0%, 30%, 50%, 70%, and 100%, respectively (i.e., the proportion of controlled-release nitrogen to the total nitrogen application amount). These ratios were represented as N135R0, N135R1, N135R2, N135R3, and N135R4, respectively. The results showed that there was no significant difference in the number of pods per plant, the number of seeds per pod, or the grain yield under the treatment of controlled-release nitrogen fertilizer mixed with quick-acting nitrogen fertilizer for proportions of 30–50% (N135R1~R3) when compared with the control, and a stable yield was achieved. Mixing controlled-release nitrogen fertilizer under reduced nitrogen application can significantly improve the apparent utilization rate of rapeseed nitrogen fertilizer, but it first increases and then decreases with the increase of the controlled-release nitrogen mixing ratio, reaching its highest under the N135R2 treatment. The agronomic utilization efficiency and partial productivity of nitrogen fertilizer first increased and then decreased with the increased proportion of controlled-release nitrogen, and both reached their highest utilization with the N135R2 treatment. The mixed treatment of controlled-release nitrogen did not affect soil urease activity, but significantly increased soil sucrase activity. The mixed treatment of controlled-release nitrogen also increased soil microbial biomass nitrogen and carbon content. Especially in the flowering stage, the soil microbial biomass nitrogen and carbon content was significantly higher under a controlled-release nitrogen mixing ratio of 30–50%. At the same time, it had a similar effect on soil inorganic nitrogen content. Therefore, a controlled-release nitrogen mixing treatment provided sufficient nitrogen for the key growth period of rapeseed. Under the condition of reducing the amount of nitrogen fertilizer by 25% based on the amount of nitrogen fertilizer applied to conventional rapeseed, the application of controlled-release urea mixed with common nitrogen fertilizer mixed at a ratio of 30–50% can be an effective way to maintain grain yield levels and improve nitrogen utilization efficiency.

Modern era of agriculture is concerned with the environmental influence on crop growth and development. Shading is one of the crucial factors affecting crop growth considerably, which has been neglected over the years. Therefore, a two-year field experiment was aimed to investigate the effects of shading at flowering (S1) and pod development (S2) stages on nitrogen (N) dynamics, carbohydrates and yield of rapeseed. Two rapeseed genotypes (Chuannong and Zhongyouza) were selected to evaluate the effects of shading on ¹⁵N trace isotopes, enzymatic activities, dry matter, nitrogen and carbohydrate distribution and their relationship with yield. The results demonstrated that both shading treatments disturbed the nitrogen accumulation and transportation at the maturity stage. It was found that shading induced the downregulation of the N mobilizing enzymes (NR, NiR, GS, and GOGAT) in leaves and pods at both developmental stages. Shading at both growth stages resulted in reduced dry matter of both varieties but only S2 exhibited the decline in pod shell and seeds dry weight in both years. Besides this, carbohydrates distribution toward economic organs was declined by S2 treatment and its substantial impact was also experienced in seed weight and seeds number per pod which ultimately decreased the yield in both genotypes. We also revealed that yield is positively correlated with dry matter, nitrogen content and carbohydrates transportation. In contrast to Chuannong, the Zhongyouza genotype performed relatively better under shade stress. Overall, it was noticed that shading at pod developmental stage considerable affected the transportation of N and carbohydrates which led to reduced rapeseed yield as compared to shading at flowering stage. Our study provides basic theoretical support for the management techniques of rapeseed grown under low light regions and revealed the critical growth stage which can be negatively impacted by low light.

This study was aimed to investigate the effects of organic carbon and silicon fertilizers on the lodging resistance, yield, and economic performance of rapeseed. Two cultivars, namely Jayou (lodging-resistant) and Chuannongyou (lodging-susceptible), were selected to evaluate the effects of various fertilizer treatments on rapeseed culm morphology, lignin accumulation, and their relationships with their lodging resistance indices. The results showed that both organic carbon and silicon fertilizer applications increased the plant height, basal stem diameter, internode plumpness, and bending strength of rapeseed in both the studied years. The bending strength was significantly and positively correlated with the lodging resistance index and lignin content. It was found that both organic carbon and silicon fertilizers had improved the activities of lignin biosynthesis enzymes (phenylalanine ammonia-lyase, 4-coumarate:CoA ligase, cinnamyl alcohol dehydrogenase, and peroxiredoxins) and their related genes to increase lignin accumulation in the culm, which ultimately improved the lodging resistance. At the same time, the thickness of the stem cortex, vascular bundle area, and xylem area was increased, and the stem strength was improved. The effect of silicon fertilizer was better than that of organic carbon fertilizer, but there was no significant difference with the mixed application of silicon fertilizer and organic carbon fertilizer. Similarly, silicon fertilizer increased the number of pods, significantly increased the yield, and improved the economic benefit, while organic carbon fertilizer had no significant effect on the yield. Therefore, we believe that organic carbon and silicon fertilizer can improve the lodging resistance of rape stems by improving the lignin accumulation and the mechanical tissue structure. Still, the effect of silicon fertilizer is the best. Considering the economic benefits, adding silicon fertilizer can obtain more net income than the mixed application of silicon fertilizer and organic carbon fertilizer.

A field experiment was conducted in 2018–2020 to investigate the effect of two nitrogen application rates (N₀ = 0 kg ha⁻¹(control), N₉₀ = 90 kg ha⁻¹, and N₁₈₀ = 180 kg ha⁻¹) on morphological and physiological behaviours of two new rapeseed varieties; V₁ = JYJS01 (semi-dwarf variety) and V₂ = CY36 (tall variety). Our results indicated that N application enhanced the plant growth and seed protein content in comparison to control. Contrastingly, compared with control, sugar contents, i.e. sucrose and reducing sugars, decreased significantly in response to an increase in N. Seed oil content also decreased by 8.5% and 5.5%, 6.7% and 3.9% against N₁₈₀ in V₁ and V₂ during 2019 and 2020, respectively. Furthermore, higher nitrogen application rates decreased seed fatty acid proportions by decreasing the sugar availability for fatty acid biosynthesis. Our results demonstrated the highest seed yield (9.4 g plant⁻¹ in 2018/19 and 9.5 g plant⁻¹ in 2019/20) in V₂ against N₁₈₀, and the lowest seed yield (3.2 g plant⁻¹ in 2018/19 and 3.4 g plant⁻¹ in 2019/20) in V₁ at control. These findings imply that a high nitrogen application rate had increased the yield. At the same time, the carbohydrates translocation from stems to seed for fatty acid biosynthesis decreased, which played their significant role in seed physiology for fatty acid metabolisms, ultimately affected the seed quality. However, there is still a dire need to evaluate how nitrogen application affect the carbohydrate availability for fatty acid metabolism in the seed of new winter rapeseed varieties. Graphical abstract