Journal of Agronomy and Crop Science最新文献

Global seasonal heat and drought have become the main limiting factors affecting maize growth and grain yield. Huanong138 (HN138) and Zhengdan958 (ZD958) were used as the experimental material. The greenhouse experiment was conducted to uncover tassels and ear morphological development and grain fertility rate of maize under three stressors (heat (H), drought (D), and heat + drought (H + D)) at tasselling for 14 days. On average of the two hybrids, grain yield decreased by 17.3%, 31.2% and 45.4% in H, D and H + D, respectively, compared with CK. The grain fertility rate of stress treatments significantly reduced by 11.6%–28.7% under natural pollination (H♀ × H♂, D♀ × D♂), and reduced by 6.7%–24.7% under the condition of positive pollination (CK♂ × H or/and D♀), while reduced by 24.2%–48.9% under the condition of reverse pollination (CK♀ × H or/and D♂) than control, respectively. Moreover, pollen quantity, total spikelet number and density of tassels, silk viability significantly decreased, while anthesis silking interval was prolonged by 0.5–3.4 days in two genotypes under individual and combined stress than control. Individual and combined stress treatments suppressed grain sucrose metabolism via coordinated downregulation of sucrose synthase (SS) by 16.1%–59.2% and sucrose-phosphate synthase (SPS) activities by 2.6%–44.9% in developing grains, concomitantly triggering sucrose translocation to leaves and stalk, suggesting source-sink redistribution under stress constraints. Notably, the reduction of grain yield mainly resulted from stunted pollen development and limited sugar transport. These provided a strategy for future selected hybrids with the shorter ASI, higher pollen viability and quantity adapting well to climate change.

The cultivation strategy of ‘postponed nitrogen with increased panicle fertilization (PNIPF)’ boosts rice yield but the balance between lodging remains unclear. We evaluated three panicle nitrogen ratios (0%, 20% and 40% of total 165 kg N ha⁻¹) in two late indica rice varieties (Meixiangzhan 2 and Taiyou 871) to assess this trade-off. Results demonstrated that: (1) Compared to R₀, PNIPF to 20% showed no difference on yield, while R₄ raised grain yield by 4.84% and 8.69% but increased lodging index by 30.5% and 35.8% in TY871 and MXZ2. (2) Relative to R₀, R₄ induced taller plants with elevated center of gravity, reduced culm diameter, diminished culm mechanical strength, and decreased structural carbohydrate content (cellulose −29.2%, lignin −23.8%). The effect of R₂ is weaker than R₄ on plant morphology. (3) Compared to R₀, R₄ manifested more profound anatomical deterioration than R₂. (4) Significant variety differences existed; PNIPF exhibited a more profound impact on MXZ2 than TY871 by inferior morphological, physiological and anatomical traits. We recommend limiting panicle nitrogen to below 20% to achieve synergistic improvement of yield and lodging resistance in high-quality late indica rice production.

High temperatures impact sweet maize production; however, their specific effects on grain yield and kernel quality across different growing seasons remain unquantified. This study investigated high-temperature season effects, evaluated the yield and kernel quality responses in two sweet maize hybrids with different heat tolerance, and analysed the response mechanisms of dry matter accumulation (DMC), flowering, and grain filling in South China. Two contrasting sweet maize hybrids were planted annually in spring, summer, and autumn over a 2-year field experiment in Guangdong, South China. An evaluation of extreme degree days at different growth stages revealed that the sweet maize crops experienced high-temperature stress during their reproductive stages in the spring and summer growing seasons. In the high-temperature season, ‘HMT8’ showed heat sensitivity, with the grain yield significantly decreasing because of the lower kernel weight. The reduced grain-filling rates, especially in the early stages, contributed to lower kernel weight, which may be related to the decreased leaf area index (LAI) and post-anthesis DMC. Comparatively, ‘GLT27’ was heat-tolerant, with the grain yield slightly increasing because of the increased kernel number. However, it appeared cold-sensitive during the grain-filling stages in autumn. ‘GLT27’ exhibited stable or slightly increased pollen viability, LAI, post-anthesis DMC, and grain-filling rates. Furthermore, both hybrids showed reduced sucrose and elevated free amino acid content in the high-temperature seasons. Early grain-filling and post-anthesis DMC rather than reproductive organ viability may limit sweet maize during high-temperature seasons. Managing crops by selecting varieties and cultivation practices for different annual growing seasons is crucial.

Rapeseed is an essential source of edible oil, primarily cultivated in temperate regions worldwide. This crop exhibits a marked sensitivity to elevated temperatures, particularly during the stages preceding and following flowering. The ongoing challenges posed by global climate change and increasing temperatures significantly threaten its yield. It is essential to elucidate the dynamics of rapeseed's response to sustained heat stress (HS), especially during the flowering phase, to advance research on enhancing its heat tolerance. In the present study, we analysed transcriptomic modifications in rapeseed plants subjected to HS at 33°C, spanning from the pre-flowering stage to the commencement of blooming. Our findings revealed that rapeseed produced diminutive flowers with nonviable pollen and exhibited a decline in pistil receptivity. Transcriptome analysis revealed that 5588 and 5994 genes were upregulated and downregulated, respectively. KEGG enrichment analysis demonstrated that these DEGs were linked to hormone signal transduction pathways, energy metabolism (including starch and sucrose metabolism and glutathione metabolism), and plant-specific MAPK signalling pathways. Furthermore, genes encoding reactive oxygen species (ROS) scavenging enzymes and heat shock transcription factors were prominently expressed under HS conditions. This study provides foundational insights into the mechanisms underlying heat tolerance in rapeseed and holds significant implications for the genetic enhancement of heat-tolerant rapeseed varieties.

Increasing waterlogging events due to intense rainfall pose a significant threat to global food security, risking the production of the third most important staple crop, maize by 25%–34%. Therefore, futuristic studies focusing on understanding the stage-wise response of maize to varying intensities of waterlogging, along with effective mitigation strategies, are essential. In this context, studies were conducted over 2 years (2022–23 and 2023–24), involving three factors: crop growth stages, different waterlogging durations, and mitigation strategies. Among the growth stages, waterlogging at 15 days after emergence (DAE) was found to be the most sensitive, resulting in poor root morphological features, impaired physiological activities, and the highest grain yield reduction (46.01%). In contrast, maize plants exhibited higher tolerance to waterlogging at 25 DAE. Similarly, increasing waterlogging duration from 3 to 15 days consistently reduced maize growth and grain yield. Regarding mitigation strategies, foliar application of urea (2%) improved stomatal conductance by 41.32%, net photosynthetic rate by 36.03%, and dry matter accumulation compared to water-sprayed plants. Consequently, it increased grain yield by 17.37%, enhancing stress tolerance and yield stability. Notably, urea spray (2%) on plants subjected to 3–5 days of waterlogging at 25 DAE effectively prevented the negative impacts of waterlogging on grain yield by promoting superior growth and yield-determining traits. Thus, this study demonstrates that foliar application of 2% urea is an effective and practical strategy to minimise waterlogging-induced yield losses by enhancing stress recovery and tolerance in maize.

Drought stress prior to anthesis slows down maize silk extension and thus causes the greater anthesis and silking interval, resulting in a significant reduction in grain set. This study aims to characterise the transcriptional and physiological responses of silk elongation to moderate drought stress. A trial of two hybrids with contrasting drought tolerance, AN591 and ZD909, under well-watered (WW) and moderate flowering drought stress (FDS) conditions was performed. Compared to the WW group, the silking under FDS was delayed by 1 day in AN591 and by 3.3 days in ZD909, suggesting that AN591 exhibits greater resilience to FDS than ZD909. The comparative transcriptomic profiling between FDS and WW for both hybrids highlighted the significance of sugar metabolism in promoting silk elongation, while also identifying phenylalanine metabolism and phytohormone signalling as inhibitory factors. Pathways exclusive to AN591 were largely linked to carbon and energy metabolism, while those in ZD909 were primarily associated with stress defence, suggesting AN591 was better adapted to FDS. Physiological assays confirmed that stronger sucrose decomposition in AN591, regulated by cell wall invertase, alleviated FDS-induced suppression on silk elongation. This may also explain its reduced lignin synthesis and other defence responses. Conversely, the unique phytohormone signalling in ZD909, characterised by negative auxin response and positive abscisic acid response, may further exacerbate the inhibitory effect on silk elongation by driving more sugar consumption. Together, combined transcriptomic and physiological analyses revealed that the trade-off between growth and defence was mediated through adjustments in sucrose metabolism, phytohormone signalling and secondary metabolic pathways.

Climate-induced increases in temperature and water scarcity threaten global soybean production. While the individual effects of drought or heat stress on yield are well documented, their combined impact on specific yield components remains poorly defined. To address this gap, we conducted a two-year study in Japan using a temperature gradient chamber and a single soybean cultivar. The study applied four temperature gradients under well-watered and drought stress conditions to examine seed yield and its components. Combined drought and heat stress reduced total yield more than either stress alone. In 2024, average yield under combined stress declined by 19.4% compared to 2023, coinciding with an increase of 1.5 kPa in maximum vapour pressure deficit and 2.5°C in maximum temperature. This yield reduction was primarily attributed to lower seed weight on branches rather than on the main stem. Pearson correlation and multiple regression analyses identified the number of nodes per branch as the key yield determinant under stress conditions. We further found that the transition from vegetative growth to beginning bloom was the most stress-sensitive stage. During this period, maximum temperature and vapour pressure deficit reached 53.3°C and 10.7 kPa, significantly inhibiting node formation on branches and limiting subsequent pod and seed set. These findings advance understanding of how concurrent drought and heat stress constrain soybean yield through specific developmental pathways, and underscore the need to incorporate branch-level traits into stress-resilient breeding strategies.