Optimizing irrigation strategies for sustainable crop productivity and reduced groundwater consumption in a winter wheat-maize rotation system.

Inefficient irrigation practices have hindered crop yields, wasted irrigation water resources, and posed threats to groundwater levels and agricultural sustainability. This study evaluated different irrigation strategies for a winter wheat-summer maize rotation system to identify sustainable practices for maintaining yields while reducing groundwater depletion. A two-year field experiment was conducted, implementing three optimized irrigation strategies during the winter wheat season: I-4 (irrigated until the soil water content (SWC) of the 40 cm soil layer reaches 60% of field capacity (FC), I-6 (irrigated until the SWC of the 60 cm soil layer reaches 80% FC), and a rainfed (R) as control. Irrigation was repeated when the SWC dropped to the specified level. No irrigation level was used during the summer maize season, except for irrigation after sowing that ensuring the normal emergence of maize. WHCNS (Water Heat Carbon Nitrogen Simulator) model was developed to simulate soil water dynamics, field water consumption, and yield of both crops. The result indicated WHCNS model accurately simulated water dynamics, consumption, and grain yield. Compared to R treatment, the I-4 treatment significantly increased annual crop yield by 19.83%-28.65% (p < 0.05), while maintaining similar crop water productivity. Furthermore, the I-4 treatment achieved comparable yields to the I-6 treatment, but with a 33.91% reduction in irrigation water use, resulting in a 33.46% increase in crop water productivity and a 90.53% increase in irrigation water productivity. From a sustainable perspective, the I-4 treatment effectively reduced field water losses and maintained relatively high soil water storage, particularly in the topsoil, which was beneficial for the early growth of subsequent crops. The R treatment greatly contributed to groundwater recharge when precipitation was sufficient, while it led to severe yield losses. Overall, under the condition of annual rotation planting systems, the I-4 treatment sustainably maintained yields with less irrigation, decreasing groundwater consumption. This approach could conserve regional water resources and groundwater table while upholding agricultural productivity and achieving system sustainable water use.

The potential for soil C sequestration and N fixation under different planting patterns depends on the carbon and nitrogen content and stability of soil aggregates.

The winter wheat-summer maize rotation system is common in the Huang-Huai-Hai Plain due to its consistent yield, however, it may cause soil quality degradation and increased risk of greenhouse gas emissions. To evaluate the effects of different planting patterns on soil organic carbon (SOC) and total nitrogen (TN) sequestration, as well as aggregate and C-N distribution, a three-year field experiment that included three annual double-cropping rotation patterns: winter wheat-maize (W-M), winter wheat-soybean (W-S), and winter wheat-sweet potato (W-SP) was conducted from 2020 to 2022, with W-M as the control. Our research revealed significant differences in soil carbon sequestration rates among the various planting systems. Specifically, the SOC stock in the W-S system was 12.21 % to 24.51 % higher than that of the W-M system and 10.28 % to 35.73 % higher than that of the W-SP system. While TN stock demonstrated an increase of 9.85 % to 37.39 % compared to the W-M system and 8.14 % to 67.43 % compared to the W-SP system. Moreover, SOC and TN sequestration were largely related to soil aggregates, with macroaggregates being the primary component in both W-S and W-M planting patterns, while microaggregates were more common in W-SP patterns. The accumulation of SOC and TN occurred mainly in macroaggregates, leading to a significant increase in C and N content in soil macroaggregates under the W-S planting pattern. The structural equation model suggested that the TN stock had both direct and indirect effects on SOC sequestration, with a total impact coefficient of 0.872. Our three-year field results indicate that the W-S model is advantageous in enhancing soil C and N sequestration capacity and had great potential in reducing greenhouse gas emissions in farmland.

Genetic mapping and candidate gene analysis for melon resistance to Phytophthora capsici.

Phytophthora blight is one of the most serious diseases affecting melon (Cucumis melo) production. Due to the lack of highly resistant germplasms, the progress on disease-resistant research is slow. To understand the genetics of melon resistance to Phytophthora capsici, an F2 population containing 498 individuals was developed by crossing susceptible line E31 to highly resistant line ZQK9. Genetic analysis indicated that the resistance in ZQK9 was controlled by a dominant gene, tentatively named MePhyto. Through bulked-segregant analysis (BSA-Seq) and chromosome walking techniques, the MePhyto gene was mapped to a 52.44 kb interval on chromosome 12. In this region, there were eight genes and their expression patterns were validated by qRT-PCR. Among them, one wall-associated receptor kinase (WAK) gene MELO3C002430 was significantly induced in ZQK9 after P. capsici inoculation, but not in E31. Based on the non-synonymous mutation site in MELO3C002430, a cleaved amplified polymorphic sequence (CAPS) marker, CAPS2430, was developed and this maker was co-segregated with MePhyto in both F2 population and a collection of 36 melon accessions. Thus MELO3C002430 was considered as the candidate gene and CAPS2430 was a promising marker for marker-assisted selection (MAS) in breeding. These results lay a foundation for revealing the resistance mechanism of melon to P. capsici.

Transcriptome analysis clarified genes involved in resistance to Phytophthora capsici in melon.

Phytophthora blight caused by Phytophthora capsici is a devastating disease for melon plant. However, the underlying resistance mechanisms are still poorly understood. In this study, the transcriptome differences between the resistant ZQK9 and susceptible E31 at 0, 3, and 5 days post-inoculation (dpi) were identified by RNA-seq. A total of 1,195 and 6,595 differentially expressed genes (DEGs) were identified in ZQK9 and E31, respectively. P. capsici infection triggered massive transcript changes in the inoculated tissues. Genes related to plant defense responses were activated, which was reflected by a lot of up-regulated DEGs involved in pathogenesis-related (PR) genes, hormones biosynthesis and signal transduction, secondary metabolites biosynthesis and cell wall modification in resistant ZQK9. The dataset generated in this study may provide a basis for identifying candidate resistant genes in melon against P. capsici and lay a foundation for further research on the molecular mechanisms.