Cultivar and sowing date selection are major factors in determining the yield potential of any crop and in any region. To explore how climate change affects these choices, this study performed a regional scale analysis using the well-validated APSIM-maize model for the Northeast China Plain (NEC) which is the leading maize (Zea mays L.) producing area in China. Results indicated that high temperature had a significantly negative effect on grain yield, while effective accumulated temperature and solar radiation had significant positive effects on grain yield and kernel number. Cloudy and rainy weather in flowering stage had significant negative effects on kernel number. Delayed sowing led to less cloudy and rainy weather during flowering and reduced the negative effect on kernel number. Higher diurnal thermal range and less precipitation during the grain-filling stage also increased the 1000-kernel weight. Delayed sowing, however, also significantly increased the risk of early senescence and frost (>80%) in middle and high latitude areas. In the middle and high latitude areas of the NEC, the grain yield of a long-season cultivar (LS) under early sowing (I) (6.2–19.9%) was significantly higher than under medium sowing (II) or late sowing (III), and higher than that of an early sown (I) short-season (SS) and medium-season cultivar (MS). In the low latitude area of the NEC, the grain yield of MS under medium sowing date (II) was higher than that under I and III, meanwhile, this was also higher than that of SS and LS. Therefore, under climate warming, LS sown earlier in high and medium latitudes and MS sown medium in low latitude were the appropriate cultivar and sowing date choices, which could mitigate the stress of high temperatures and reduce the risk of early senescence and frost. Cultivar and sowing date selection are effective measures to alleviate negative effects of climate change on maize production in the NEC, and provides valuable advice for breeders on cultivar selection, and the choice of varieties and sowing dates for farmers in actual production.

CRISPR/Cas system has developed a new technology to modify target genes. In this study, CasΦ2 is a newly Cas protein that we used for genome modification in Arabidopsis and tobacco. PDS and BRI1 of marker genes were chosen for targeting. CasΦ2 has the function to cleave pre-crRNA. In the presence of 10 mM Mg²⁺ irons concentration, sgRNA3 type guided CasΦ2 to edit target gene and generate mutation, and a mutant seedling of AtBRI1 gene with an expected male sterile phenotype was obtained. In the process of tobacco transformation, the gene editing activity of CasΦ2 can be activated by 100 nM Mg²⁺ irons concentration, and sgRNA1 type guided CasΦ2 to edit target gene. Mutant seedlings of NtPDS gene with an expected albino were obtained. The results indicate that CasΦ2 can effectively edit target genes under the guidance of different sgRNA type in the presence of Mg²⁺ ions. Together, our results verify that the CRISPR/CasΦ2 system is an effective and precise tool for genome editing in plants.

High yields and low carbon emissions are new challenges for modern crop production. Balancing the crop yield and reducing greenhouse gas (GHG) emissions has become a new field of agronomic technology innovation. Cereal–legume intercropping is a typical diversification planting system, which has been expected to achieve the dual goals of high production and low GHG emissions. However, the synergistic effect of integrating various technologies in an intercropping system on GHG emissions and whether it will achieve the high yield and low emissions goal remains to be determined. Therefore, bibliometric analysis has investigated the worldwide development trend of cereal–legume intercropping designs. The literature on the GHG emissions of the cereal–legume intercropping system was summarized. Additionally, the effects and mechanisms of different agricultural management methods regarding soil nitrous oxide and carbon dioxide emissions in the cereal–legume intercropping system were summarized. The research on GHG emissions of cereal–legume intercropping systems in non-growing seasons must be revised. In situ observations of GHG emissions from intercropping systems in different regions should be strengthened. This work is valuable in supporting and evaluating the potential of GHG reduction in a cereal–legume intercropping system in various farming areas.

Waterlogging stress severely limits crop photosynthesis and energy supplies, resulting in significant yield reductions. However, the critical duration of waterlogging stress during the maize jointing stage remains unclear, and the physiological and molecular mechanisms underlying its effects on photosynthetic efficiency and energy synthesis in maize require further investigation. In this study, we systematically analyzed the responses of physiological traits, transcriptomic profiles, and the yield formation in maize (Zea mays L.) to varying waterlogging durations imposed during the jointing stage, including 0 days (CK), 2 days (F2), 4 days (F4), 6 days (F6), 8 days (F8), and 10 days (F10). Our results indicate that the (1) grain weight (GW) showed no significant difference between F2 and CK. However, the GW in F4, F6, F8, and F10 decreased significantly by 17.49%, 26.45%, 60.24%, and 100.00%, respectively, compared to the CK. (2) Compared with the CK, the malondialdehyde content progressively increased from F4 to F10, while antioxidant enzyme activity gradually decreased. The chlorophyll content declined by 29.93% to 57.38%, and net photosynthetic efficiency decreased by 13.82% to 38.93%. Although the leaf sucrose content in from F4 to F10 gradually decreased, the leaf starch content remained stable in F4 and F6. In contrast, the starch content in F8 and F10 leaves was significantly reduced by 37.55% and 47.60%, respectively, compared with CK. (3) A transcriptomic analysis revealed that during from F2 to F4, genes encoding photosystem I subunit protein, such as PSAD, and the cytochrome b6f complex proteingene PETC were downregulated. At F6, these key genes encoding photosynthetic proteins were upregulated. However, at F8 and F10, their expression was significantly downregulated. Concurrently, genes related to ATP synthesis (e.g., ATPD) as well as starch and sucrose metabolism (e.g., SPP2, SS1) were also downregulated. In summary, when waterlogging stress persists for no longer than 6 days, plants can maintain their starch content to supply energy for growth, thereby ensuring basic developmental needs. When waterlogging persists for more than 6 days, energy synthesis is impaired, and the nutrient transport to the grains is significantly inhibited, ultimately resulting in a substantial reduction in yield. Therefore, 6 days of waterlogging can be considered the critical threshold for significant yield loss in maize during the jointing stage.

It is of great practical significance to clarify the response trend of yield, leaf nitrogen content, and photosynthetic characteristics of maize varieties released in different years in Jilin province to different nitrogen levels for the breeding of high-yield maize varieties in Northeast China. In this study, six representative varieties popularized and applied in Jilin province since 1970s were used as the materials (1970s: JD101, ZD2; 1990s: SD19, JD159; 2010s: XY335, NH101). Field experiments with four nitrogen levels (0, 125, 250, and 375 kg hm-2) were set up to analyze the effects of nitrogen application on the yield, leaf nitrogen content, and photosynthetic characteristic parameters of maize varieties released in different decades. The results showed that maize grain yield under all nitrogen levels increased with the replacement of varieties, and the yield advantage of modern varieties was more obvious under high nitrogen levels. The increase of grain yield under different treatments was mainly due to the simultaneous increase of kernel numbers per ear and kernel weight. The net photosynthetic rate (Pn) of ear leaf increased with the increase of nitrogen application rate at no more than 250 kg hm-2, and the Pn of modern varieties was significantly higher than that of old varieties. When the nitrogen application rate was 375 kg hm-2, Pn decreased significantly, and the degree of reduction showed that the old varieties were higher than the modern varieties. From silking to dough stage, the decrease of Pn decreased with the increase of nitrogen application and varieties evolution. The light compensation point and dark respiration rate of maize were the highest in 2010s, the second in 1990s and the lowest in 1970s at different stages. Compared with 1990s and 1970s, the light compensation point of maize in 2010s increased by 9.72% and 27.84% on average, and the dark respiration rate increased by 7.82% and 32.98% on average. The specific leaf weight (SLW) of varieties increased with the increase of nitrogen application rate, but SLW decreased with the evolution of varieties under the same nitrogen application rate. The leaf nitrogen content per unit area (Narea) of different varieties increased with the increase of nitrogen application rate, but it was significantly decreased in the old cultivars without nitrogen application, and there was no significant difference among the cultivars treated with nitrogen application rate. The correlation analysis showed that there was a significant positive linear correlation between Pn and SLW, and the relationship between Pn and Narea can be fitted by the quadratic equation, the Narea value of Pn turning with the increase of Narea was 1.57 g m-2. The photosynthetic nitrogen use efficiency (PNUE) of all varieties decreased with the increase of nitrogen application rate, while the PNUE of cultivars at higher nitrogen levels (≥ 250 kg hm-2) increased significantly with the evolution of varieties. Thus, compared with the old varieties, the modern varieties were more beneficial to yield improvement in the higher nitrogen levels (≥ 250 kg hm-2), which was mainly attributed to the higher Pn and PNUE of the modern varieties, while the increase of Pn and PNUE was closely related to the specific leaf weight (SLM), leaf N content (Nmass, Narea), and other characters, which was recommended for reference in the breeding process of maize varieties.