Northern Japonica rice region is susceptible to cold damage, and breeding cold-tolerant rice varieties is the most direct and effective means to address this issue. In this study, 45 accessions of northern Japonica rice were used as experimental materials. Under 14 °C cold stress, seven indicators including germination potential, germination rate, germination index, vigor index of shoot, vigor index of root, average germination days, and germination coefficient were measured. Multivariate statistical methods such as correlation analysis, principal component analysis (PCA), membership function comprehensive analysis, and cluster analysis, were employed to evaluate cold tolerance. The results showed that all germination indicators exhibited varying degrees of decline under cold stress, with the vigor index of root showing the most obvious decrease. By calculating the membership function values of each indicator, the seven indicators were transformed into two comprehensive indicators through PCA. Cluster analysis was then used to categorize the 45 accessions into four groups, successfully screening 13 cold-tolerant materials. Furthermore, a regression equation was established, which identified that germination potential, germination rate, vigor index of root, and germination coefficient are the key indicators for evaluating cold tolerance in northern Japonica rice at the germination stage.

In order to understand the genetic background of flax germplasm resources and breed high-quality flax varieties, genetic diversity analysis, cluster analysis, principal component analysis and population structure were conducted on nine agronomic traits and six quality traits of 387 flax germplasm resources by phenotypic traits and molecular markers (SSR). The genetic diversity index of agronomic traits was between 0.70 and 2.08, and the coefficient of variation was between 5.55% and 129.18%. The genetic diversity index of quality traits ranged from 1.83 to 2.08, and the coefficient of variation ranged between 0.07% and 1.38%. A total of 320 SSR loci were amplified with an average of 11.81 loci per primer pair; the effective allele number was 1.1991-1.8230, PIC of primers varied from 0.2489 to 0.6257; at the genetic similarity coefficient of 0.66, the 387 flax germplasm resources could be divided into five groups, and cluster analysis based on agronomic traits and quality cluster analysis could also be divided the germplasm resources into five groups.

The absorption of selenium by tartary buckwheat to form selenium-enriched characteristics is of great significance for promoting the high-quality development of the tartary buckwheat industry. In this study, 30 representative tartary buckwheat germplasm resources were selected to measure their agronomic traits, dry matter accumulation and translocation characteristics, as well as yield and grain trait indicators. Foliar application of selenium fertilizer was set as a treatment. Principal component analysis (PCA), cluster analysis, and GGE biplot analysis were comprehensively utilized to conduct a thorough evaluation of the growth, development, and selenium response characteristics of different tartary buckwheat germplasms. The results showed that significant variations existed among different tartary buckwheat germplasm resources in terms of agronomic traits, dry matter accumulation and translocation characteristics, yield and its components, and selenium accumulation, distribution, and enrichment traits. Furthermore, foliar selenium application exhibited a promoting effect on all measured growth and development indicators of the germplasm resources. Through cluster analysis, ten selenium-sensitive, 12 selenium-intermediate, and eight selenium-insensitive germplasm resources were screened. GGE biplot analysis identified YYMY002 as a germplasm with high yield, high selenium enrichment, and relative comprehensive superior traits.

The main agronomic traits of 513 faba bean germplasm resources at home and abroad were analyzed. The results showed that the coefficient of variation of 15 agronomic traits ranged from 13.09% to 53.58%, indicating that there was a large genetic variation. The coefficient of variation for the number of pods per plant reached the highest value of 53.58%, with a variation range of 1.00 to 42.00, whereas pod width exhibited the lowest coefficient of variation at 13.09%, varying from 0.80 to 2.23 cm. Correlations among traits highlighted that the number of branches, number of effective branches, number of pods per plant, number of grains per plant, plant height, and height of the last pod are key for developing high-yielding faba bean varieties. The principal component analysis extracted five principal components, with the cumulative contribution rate reaching 72.098%, effectively representing the phenotypic characteristics of these germplasm resources. By calculating the membership function values, a comprehensive score (F-value) was derived, and the top 30 germplasm resources with the best comprehensive traits were identified. The cluster analysis subsequently divided the 513 faba bean germplasm resources into three group: Cluster I included 160 resources (31.19% of the total), characterized by high plant height and yield; Cluster II comprised 221 resources (43.08% of the total), suitable as parental selection and screening of excellent genes; and Cluster III contained 132 resources (25.73% of the total), representing specific germplasm.

A total of 24 progenies from Saccharum robustum L. and Nanjian chewing cane through reciprocal crosses were used. Correlation analysis, principal component analysis, cluster analysis, and comprehensive evaluation associated with seven important agronomic traits were performed. The results showed that there were differences in agronomic traits among different germplasm materials in the same planting period experiment, and there were differences in agronomic traits among different planting period experiment in the same germplasm materials. The variation coefficient of agronomic traits ranged from 11.17% to 43.37%. The variation of sugar yield and sugarcane stalk yield was the largest, which was 43.37% and 42.20%, respectively, the variation of plant height was small. The correlation analysis showed that sugarcane stalk yield and sugar yield were significantly positively correlated with single stalk weight and effective stalk number, respectively, and sugarcane stalk yield was significantly positively correlated with sugar yield. The yield-sugar factor, stalk diameter-sugar factor and stalk diameter-quality factor were extracted via principal component analysis, and the cumulative contribution rate was 81.39%. The results of cluster analysis showed that the 24 germplasm materials were divided into three groups at the Euclidean distance of 6.00, which were basically consistent with the results of principal component scores. Among them, the seven agronomic indexes of group III were excellent, with high yield and high sugar. Yunrui 12-38-27, Yunrui 12-38-18, Yunrui 12-9-45, Yunrui 12-9-9 and Yunrui 12-38-29 ranked top five based on their comprehensive evaluation D values.

In order to clarify the suitable planting pattern and nitrogen application rate for rapeseed relay cropped rapeseed after wheat, a field experiment was conducted in Dalad Banner, Inner Mongolia. Five nitrogen application rate gradients (0, 30, 60, 90 and 120 kg/ha) were set under three planting modes, including straw removal+tillage (T1), straw returning+tillage (T2), and straw removal+no tillage (T3). The optimal nitrogen rate was determined based on rapeseed biomass, nutrient accumulation, and economic benefits. The results showed that the aboveground biomass, carbon accumulation and potassium accumulation of rapeseed under T2 treatment were all higher than those under T1 and T3 treatments. Under T2 treatment, the average of fresh grass weight, dry grass weight, carbon accumulation, and potassium accumulation of all nitrogen application treatments could reach 60.5 t/ha, 8.0 t/ha, 2981 kg/ha, and 253 kg/ha, respectively. Nitrogen application rate significantly affected the biomass and nutrient accumulation of rapeseed under different planting modes. The biomass and nutrient accumulation of rapeseed increased with the increase of nitrogen application rate within the nitrogen application rate range. Compared with no nitrogen application treatment, the fresh grass weight and dry grass weight of rapeseed increased by 39.8% and 35.1% respectively when the nitrogen application rate was 30 kg/ha, 63.0% and 67.9% at 60 kg/ha, 78.1% and 89.0% at 90 kg/ha, 86.5% and 98.1% at 120 kg/ha. The trend of nutrient accumulation of rapeseed green manure was basically consistent with that of biomass. The input costs and outputs of rapeseed for different purposes varied under different planting modes and nitrogen application rates. Considering the factors such as biomass, nutrient accumulation, and economic benefits of rapeseed for different purposes under different modes, rapeseed can be planted with no-tillage method with wheat straw removal following wheat harvest. The optimal nitrogen application rate for rapeseed as silage feed is 120 kg/ha, and for rapeseed as green manure, the optimal nitrogen application rate is 90 kg/ha.

Drought experiments were carried out in different stages of tuberous root differentiation and formation by potting soil cultivation to analyze the changes of reactive oxygen species metabolism and endogenous hormone content in sweetpotato roots. The results showed that drought stress caused the decrease of sweetpotato fresh tuber weight per plant, and the earlier the drought, the greater the effect. Compared with normal irrigation treatment (CK), the O₂^-. content in sweetpotato roots was significantly decreased and H₂O₂ content was significantly increased under drought stress. The increase of H₂O₂ was effectively inhibited after rehydration. Drought stress at different periods resulted in the decrease of activities of peroxidase (POD) and catalase (CAT) in sweetpotato roots, and ascorbate peroxidase (APX) activity increased significantly in early, middle and late stages of sweetpotato root differentiation and formation under drought stress. The results showed that the root system of sweetpotato mainly relied on APX to remove reactive oxygen species under drought stress, and SOD also made great contribution to the removal of reactive oxygen species during the early and middle stages of drought stress. After rehydration, the APX activity in sweetpotato roots decreased, while POD activity increased, indicating that sweetpotato root recovered the damage caused by drought stress by enhancing POD activity to improve antioxidant capacity after rehydration. In addition, the free proline content in sweetpotato roots increased under drought stress, and as an osmotic regulator to resist drought stress, the proline content in sweetpotato roots decreased after rehydration. Compared with CK, the contents of ABA and JA in sweetpotato roots for the treatments of D_8-14 and D_15-21 were significantly increased, while the contents of GA and IAA were significantly decreased, and the decreasing ranges were smaller than the increasing ranges of ABA and JA. When drought treatment (D_22-28) was carried out at late stage of root differentiation and formation, the contents of these four endogenous hormones in sweetpotato roots did not change significantly. These results indicated that when sweetpotato was subjected to drought stress in early and middle stages of tuberous root differentiation and formation, it responded strongly by increasing the contents of JA and ABA in roots. However, when sweetpotato was subjected to drought stress during tuberous root differentiation and formation stage, only JA had a significant increase.

To explore the effects of silicon (Si) on the physiological characteristics of oat leaves infected by Puccinia graminis f. sp. avenae and clarify the physiological mechanism of silicon-induced resistance to stem rust, a pot experiment was conducted using ʻBayou 1ʼ, an oat cultivar highly susceptible to stem rust, as the experimental material. Four treatments were established: CK (no silicon, no stem rust pathogen inoculation), +Si-P (silicon application, no stem rust pathogen inoculation), -Si+P (no silicon, stem rust pathogen inoculation), and +Si+P (silicon application, stem rust pathogen inoculation). This study investigated the effects of 1.5 mmol/L silicon application on the disease progression, reactive oxygen species content, and antioxidant enzyme activities of oat leaves after stem rust pathogen infection. The results showed that silicon application effectively delayed the disease development process of oat stem rust, and significantly alleviated disease symptoms. Stem rust pathogen infection led to a rapid increase in O₂^-. and hydrogen peroxide content in leaves. Simultaneously, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), malondialdehyde (MDA) content, and relative electrical conductivity of leaves increased rapidly, while ascorbate peroxidase (APX) activity decreased rapidly. Within seven days after stem rust pathogen inoculation, silicon application reduced the reactive oxygen species content in leaves, while increasing the activities of SOD, POD, and CAT, and decreasing APX activity and MDA content. Furthermore, silicon application reduced the relative electrical conductivity of leaves within 11 days after inoculation. Silicon application enhanced the antioxidant defense ability of oat leaves, reduced the degree of membrane lipid peroxidation, and enhanced oat resistance to stem rust.

The effects of nitrogen (N) application on maize yield, root distribution, and N metabolism were analyzed under high-density planting by using the maize cultivar Xianyu 335 as material, setting up a conventional density treatment of 6.75×10⁴ plants/ha (D1) and a high-density treatment of 8.25×10⁴ plants/ha (D2), and applying N at five rates (0, 160, 220, 280, and 340 kg N/ha) per density treatment. The results indicated that with the increasing of N application rate, the maize yield showed a trend of increasing and then decreasing. The yield of D2 treatment was significantly higher than that of D1 treatment and the combination of high-density planting and optimized N application (160-220 kg N/ha) increased the yield by 39.1%-51.8% compared to conventional management. The optimized combination of N rates and planting densities increased root length, root length density, root surface area, root volume, specific root length, as well as the activities of glutamate synthase and glutamine synthetase in roots. The two enzyme activities were positively correlated with root growth distribution. In conclusion, an application of 160-220 kg/ha of N at a planting density of 8.25×10⁴ plants/ha is recommended. This combination enhances nitrogen metabolism enzyme activities, promotes root growth, and increases soil nutrient uptake, thereby improving maize yield. This can serve as a high-yield maize planting model for the Guanzhong region of Shaanxi.

To clarify the production status and limiting factors of intercropping systems in the Hetao Irrigation District, Hanggin Rear Banner, a representative area for crop cultivation in the Hetao Irrigation District, was selected as the research site for the survey. Based on 503 valid questionnaires from 24 administrative villages across eight townships of Hanggin Rear Banner, the results showed that the intercropping systems were widely applied in Hanggin Rear Banner. There were wheat/maize, wheat/sunflower, watermelon/sunflower and maize||soybean (mainly food and cash crops). The wheat/maize and wheat/sunflower relay were cropping the most prevalent, accounting for 42.5% and 23.5%, respectively. Both systems significantly improved land use efficiency, with land equivalent ratios of wheat/maize and wheat/sunflower were 1.48 and 1.29, respectively. There were two main limitations of applying intercropping in this region. On the one hand, field managements were more complex in intercropping than monocultures, with the average number of irrigations and weeding times were higher, with an average of 1.0 and 0.9 times higher than in monocropping, respectively; on the other hand, the average amount of nitrogen application in intercropping systems was 70.7% higher than in monocropping. Overall, it is necessary to further explore field management practices and fertilization strategies suitable for intercropping in the area to reduce water and fertilizer inputs. Meanwhile, the research and development of intercropping machinery, herbicides and other related production materials should be strengthened, and technical training should be carried out to enhance farmersʼ understanding of intercropping.