Nitrogen (N) is a key factor in the positive response of cereal crops that follow leguminous crops when compared to gramineous crops in rotations, with the nonrecyclable rhizosphere-derived N playing an important role.  However, quantitative assessments of differences in the N derived from rhizodeposition (NdfR) between legumes and gramineous crops are lacking, and comparative studies on their contributions to the subsequent cereals are scarce.  In this study, we conducted a meta-analysis of NdfR from leguminous and gramineous crops based on 34 observations published worldwide.  In addition, pot experiments were conducted to study the differences in the NdfR amounts, distributions and subsequent effects of two major wheat (Triticum aestivum L.)-preceding crops, corn (Zea mays L.) and soybean (Glycine max L.), by the cotton wick-labelling method in the main wheat-producing areas of China.  The meta-analysis results showed that the NdfR of legumes was significantly greater by 138.93% compared to gramineous crops.  In our pot experiment, the NdfR values from corn and soybean were 502.32 and 944.12 mg/pot, respectively, and soybean was also significantly higher than corn, accounting for 76.91 and 84.15% of the total belowground nitrogen of the plants, respectively.  Moreover, in different soil particle sizes, NdfR was mainly enriched in the large macro-aggregates (>2 mm), followed by the small macro-aggregates (2–0.25 mm).  The amount and proportion of NdfR in the macro-aggregates (>0.25 mm) of soybean were 3.48 and 1.66 times higher than those of corn, respectively, indicating the high utilization potential of soybean NdfR.  Regarding the N accumulation of subsequent wheat, the contribution of soybean NdfR to wheat was approximately 3 times that of corn, accounting for 8.37 and 4.04% of the total N uptake of wheat, respectively.  In conclusion, soybean NdfR is superior to corn in terms of the quantity and distribution ratio of soil macro-aggregates.  In future field production, legume NdfR should be included in the nitrogen pool that can be absorbed and utilized by subsequent crops, and the role and potential of leguminous plants as nitrogen source providers in crop rotation systems should be fully utilized.

The practice of intercropping leguminous and gramineous crops is used for promoting sustainable agriculture, optimizing resource utilization, enhancing biodiversity, and reducing reliance on petroleum products.  However, promoting conventional intercropping strategies in modern agriculture can prove challenging.  The innovative technology of soybean maize strip intercropping (SMSI) has been proposed as a solution.  This system has produced remarkable results in improving domestic soybean and maize production for both food security and sustainable agriculture.  In this article, we provide an overview of SMSI and explain how it differs from traditional intercropping.  We also discuss the core principles that foster higher yields and the prospects for its future development.

Monitoring agricultural drought using remote sensing data is crucial for precision irrigation in modern agriculture.  Utilizing unmanned aerial vehicle (UAV) remote sensing, we explored the applicability of an empirical crop water stress index (CWSI) based on canopy temperature and three-dimensional drought indices (TDDI) constructed from surface temperature (T_s), air temperature (T_a) and five vegetation indices (VIs) for monitoring the moisture status of dryland crops.  Three machine learning algorithms (random forest regression (RFR), support vector regression, and partial least squares regression) were used to compare the performance of the drought indices for vegetation moisture content (VMC) estimation in sorghum and maize.  The main results of the study were as follows: (1) Comparative analysis of the drought indices revealed that T_s-T_a-normalized difference vegetation index (TDDIn) and T_s-T_a-enhanced vegetation index (TDDIe) were more strongly correlated with VMC compared with the other indices.  The indices exhibited varying sensitivities to VMC under different irrigation regimes; the strongest correlation observed was for the TDDIe index with maize under the fully irrigated treatment (r=−0.93). (2) Regarding spatial and temporal characteristics, the TDDIn, TDDIe and CWSI indices showed minimal differences.  Over the experimental period, with coefficients of variation were 0.25, 0.18 and 0.24, respectively. All three indices were capable of effectively characterizing the moisture distribution in dryland maize and sorghum crops, but the TDDI indices more accurately monitored the spatial distribution of crop moisture after a rainfall or irrigation event.  (3) For prediction of the moisture content of single crops, RFR models based on TDDIn and TDDIe estimated VMC most accurately (R²>0.7), and the TDDIn-based model predicted VMC with the highest accuracy when considering multiple-crop samples, with R² and RMSE of 0.62 and 14.26%, respectively. Thus, TDDI proved more effective than the CWSI in estimating crop water content.

Genetic transformation has been an effective technology for improving the agronomic traits of maize.  However, it is highly reliant on the use of embryonic callus (EC) and shows a serious genotype dependence.  In this study, we performed genomic sequencing for 80 core maize germplasms and constructed a high-density genomic variation map using our newly developed pipeline (MQ2Gpipe).  Based on the induction rate of EC (REC), these inbred lines were categorized into three subpopulations.  The low-REC germplasms displayed more abundant genetic diversity than the high-REC germplasms.  By integrating a genome-wide selective signature screen and region-based association analysis, we revealed 95.23 Mb of selective regions and 43 REC-associated variants.  These variants had phenotypic variance explained values ranging between 21.46 and 49.46%.  In total, 103 candidate genes were identified within the linkage disequilibrium regions of these REC-associated loci.  These genes mainly participate in regulation of the cell cycle, regulation of cytokinesis, and other functions, among which MYB15 and EMB2745 were located within the previously reported QTL for EC induction.  Numerous leaf area-associated variants with large effects were closely linked to several REC-related loci, implying a potential synergistic selection of REC and leaf size during modern maize breeding.

Ear differentiation, grain development and their interaction with factors in the growing environment, such as temperature, solar radiation and precipitation, greatly influence grain number and grain weight, and ultimately affect summer maize production.  In this study, field experiments involving different sowing dates were conducted over three years to evaluate the effects of temperature factors, average solar radiation and total precipitation on the growth process, ear differentiation, fertilization characteristics, grain filling and yield of summer maize varieties with different growth durations.  Four hybrids were evaluated in Huang-Huai-Hai Plain (HHHP), China from 2018 to 2020 with five different sowing dates.  The results showed that the grain yield formation of summer maize was strongly impacted by the environment from the silking (R1) to milking (R3) stage.  Average minimum temperature (AT_min) was the key environmental factor that determined yield.  Reductions in the length of the growing season (r=–0.556, P<0.01) and the total floret number on ear (R²=0.200, P<0.001) were found when AT_min was elevated from the emerging (VE) to R1 stage.  Both grain-filling rate (R²=0.520, P<0.001) and the floret abortion rate on ear (R²=0.437, P<0.001) showed quadratic relationships with AT_min from the R1 to physiological maturity (R6) stage, while the number of days after the R1 stage (r=–0.756, P<0.01) was negatively correlated with AT_min.  An increase in AT_min was beneficial for the promotion of yield when it did not exceeded a certain level (above 23°C during the R1–R3 stage and 20–21°C during the R1-R6 stage).  Enhanced solar radiation and precipitation during R1–R6 increased the grain-filling rate (R²=0.562, P<0.001 and R²=0.229, P<0.05, respectively).  Compared with short-season hybrids, full-season hybrids showed much greater suitability for a critical environment.  The coordinated regulation of AT_min, ear differentiation and grain development at the pre- and post-silking stages improved maize yield by increasing total floret number and grain-filling rate, and by reducing the floret abortion rate on ear. 

【Objective】 Mining the key drought-resistant genes of maize, revealing its drought-resistant molecular mechanism, and providing genetic resources and theoretical guidance for the cultivation of new drought-resistant maize varieties.【Method】Transcriptome data combined with weighted gene co-expression network (WGCNA) and screening methods for physiological and biochemical indicators of drought resistance were used to identify ZmPAL genes associated with drought resistance and rewatering. Genome-wide analysis of the genes encoding PAL was performed using bioinformatics methods. Quantitative real-time fluorescence PCR (qRT-PCR) was used to detect the expression of ZmPAL genes under drought treatment conditions, as well as the expression characteristics of ZmPAL5 among different inbred lines and the expression patterns in different tissues. Finally, genetic transformation was used to analyze the drought resistance function of ZmPAL5 in maize, and the deletion-type Arabidopsis mutant was analyzed for drought resistance with the help of CRISPR/Cas9 technology for the PAL5 homologous gene.【Result】Nineteen maize ZmPAL genes were identified, six of which were clustered on chromosome 5 and encoded proteins that were mostly hydrophilic acidic proteins and relatively evolutionarily conserved in the PAL family of genes. The promoter region of ZmPAL genes contained a large number of cis-acting elements associated with hormonal and abiotic stress responses. Six core genes were identified, four of which were significantly up-regulated for expression after drought treatment. In particular, ZmPAL5 showed an 8.57-fold increase in expression after drought stress. The expression level of ZmPAL5 was found to be significantly higher in the drought-resistant inbred line Zheng 8713 than in the drought-sensitive inbred line B73 under both drought stress and rewatering treatments. Meanwhile, ZmPAL5, a constitutively expressed gene, showed a high level of expression in young stems. Overexpressed ZmPAL5 maize grew well under drought stress, and its relative water content, lignin, chlorophyll, soluble protein, proline content, and activities of superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase were 1.52, 1.49, 1.47, 1.43, 1.44, 1.41, 1.53, 1.41, and 1.35 times, but the malondialdehyde content was 0.65 times that of the wild type. The PAL5-deficient Arabidopsis mutant was sensitive to drought. Under drought stress, its physiological and biochemical indexes showed the opposite trend to those of overexpression of ZmPAL5 maize. 【Conclusion】 Six core genes (ZmPAL3, ZmPAL5, ZmPAL6, ZmPAL8, ZmPAL11, and ZmPAL13) were screened in response to drought stress, in which the expression of ZmPAL5 was positively correlated with drought resistance. ZmPAL5 positively regulated the drought resistance and resilience of the plant by influencing the content of osmotically regulated substances and antioxidant enzyme activities.

In order to study the effects of nitrogen-fixing bacteria on maize growth and antistress enzyme in different saline-alkali soils, five nitrogen-fixing bacteria were selected, including Bacillus stratosphericus, Bacillus subtilis, Bacillus cereus, Bacillus aerophilus and Serratia liquefaciens, and the effects of nitrogen-fixing bacteria on the growth, root morphology and antistress enzyme activities of maize were studied by pot experiments using the liquid medium without inoculation of nitrogen-fixing bacteria as the control. The results showed that the five nitrogen-fixing bacteria could increase the growth and root morphology indexes of maize, and promote the dry matter accumulation of maize in saline-alkali soil. Compared with the control, the aboveground dry matter of the five nitrogen-fixing bacteria was increased by 22.22%, 62.96%, 44.44%, 40.74% and 37.04% in mild saline-alkali soil, respectively. The aboveground dry matter in severe saline-alkali soil was increased by 29.41%, 29.41%, 41.18%, 23.53% and 11.76%, respectively. The five nitrogen-fixing bacteria increased the activities of antioxidant enzymes such as CAT, SOD and POD in maize in mild and severe saline-alkali soil, and significantly decreased the content of malondialdehyde (MDA). A comprehensive analysis of the membership function method showed that Bacillus subtilis had the best effect on the growth promotion and stress resistance of maize in mild saline-alkali soil, while Bacillus cereus had the best effect on growth promotion and stress resistance of maize in severe saline-alkali soil. The study indicates that the application of nitrogen-fixing bacteria can effectively enhance the adaptability and productivity of maize in saline-alkali soils, holding significant practical value.

The aims were to explore the main functions and characteristics of GGE double plot, and to select new maize varieties with high and stable yield. In this study, the yield data of 5 new maize combinations in 7 experimental sites were analyzed by GGE-biplot, the high yield, stable yield and adaptability of maize varieties tested at high altitudes in northwest Guizhou were evaluated, and the discrimination and representativeness of the test sites were analyzed. The results showed that the experimental sites could be divided into two ecological zones, with Panzhou as an ecological zone and Liupanshui, Hezhang, Dafang, Nayong, Shuicheng and Weining as an ecological zone. ‘Huinongdan No.5’ performed well in high and stable yield. The results showed that Panzhou and Dafang were the best experimental sites with high discrimination and good representativeness. This study provided a theoretical basis for comprehensive evaluation of new maize varieties and selection of experimental sites.