Application of planting method for intercropping flue-cured tobacco and sweet potatoes in prevention and treatment of flue-cured tobacco bacterial wilt

Abstract

The invention discloses application of a planting method for intercropping flue-cured tobacco and sweet potatoes in prevention and treatment of flue-cured tobacco bacterial wilt, and relates to the technical field of flue-cured tobacco planting. (2) tobacco plant transplanting; (3) intercropping sweet potatoes; (4) harvesting tobacco plants and sweet potatoes. The morbidity of flue-cured tobacco bacterial wilt is obviously reduced; the bacterial wilt disease is reduced by changing the nutrient composition of tobacco plant rhizosphere soil; the diversity of tobacco plant rhizosphere soil bacterial communities is increased, the structural composition is optimized, and the complexity of a network structure is enhanced, that is, interaction among beneficial bacterial communities is improved to reduce bacterial wilt diseases; the bacterial wilt disease is reduced by collecting antibacterial metabolites of rhizosphere soil of the tobacco plants.

Description

Technical Field

[0001] This invention relates to the field of flue-cured tobacco planting technology, specifically to the application of a method for intercropping flue-cured tobacco with sweet potatoes in the prevention and control of bacterial wilt in flue-cured tobacco. Background Technology

[0002] Producing high-quality tobacco requires robust seedlings and favorable field conditions. Current tobacco cultivation practices, such as long-term continuous cropping and the excessive use of chemical fertilizers and pesticides, have led to problems like soil nutrient imbalance, compaction, pollution, and pathogen accumulation. These issues increase the incidence of soil-borne diseases, ultimately resulting in decreased tobacco yield and quality, severely limiting the sustainable use of tobacco field soil and the improvement of tobacco quality.

[0003] Bacterial wilt of flue-cured tobacco, caused by Ralstonia solanacearum, is widespread in soil and is recognized globally as the second leading cause of disease. Due to its wide host range, strong survival ability, and complex transmission routes, it has become one of the major biological threats restricting the sustainable development of the flue-cured tobacco industry. At the same time, its control methods still have some limitations. Although biological control was once highly anticipated, it is still difficult to achieve control in the short term due to the short survival time of most exogenous biocontrol bacteria and the potential risks of antibiotics. Moreover, with people's increasing concern about food safety and environmental pollution, the use of traditional chemical fungicides has been gradually restricted.

[0004] Therefore, it is imperative to develop a safer and more effective production management approach to reduce soil-borne diseases in tobacco plants. Summary of the Invention

[0005] In view of this, the present invention provides a method for intercropping sweet potatoes with flue-cured tobacco and its application in the prevention and control of bacterial wilt in flue-cured tobacco.

[0006] The application of a planting method of intercropping sweet potatoes with flue-cured tobacco in the prevention and control of bacterial wilt in flue-cured tobacco includes the following steps:

[0007] (1) Preparation of tobacco fields: In late March, after applying base fertilizer to the tobacco fields, the tobacco fields are ridged, and finally a layer of biodegradable mulch is covered on the soil surface. (2) Transplanting of tobacco plants: Transplanting of flue-cured tobacco in mid-to-late April, with a planting density of 1100-1200 plants / mu, a row spacing of 120cm, and a plant spacing of 50-55cm. (3) Intercropping with sweet potatoes: Harvest the lower tobacco leaves in June, and then intercrop sweet potatoes next to the tobacco plants after harvesting the lower tobacco leaves; (4) Harvesting of tobacco plants and sweet potatoes: The middle tobacco leaves are harvested in July, the upper tobacco leaves are harvested in mid-to-late September, and the sweet potatoes are harvested in early to mid-October.

[0008] Furthermore, in step (3), sweet potatoes are intercropped next to the tobacco plants within 0-10 days after the harvest of the lower tobacco leaves.

[0009] Furthermore, in step (3), a row of sweet potatoes is placed on each side of each row of tobacco plants in the tobacco ridge.

[0010] Furthermore, in step (3), the distance between the sweet potato and the tobacco plant is 11-13 cm, and the plant spacing between sweet potatoes is 23-27 cm.

[0011] Compared with the prior art, the present invention has the following beneficial technical effects: (1) This invention significantly reduces the incidence of bacterial wilt in flue-cured tobacco; (2) This invention reduces bacterial wilt disease by changing the nutrient composition of the rhizosphere soil of tobacco plants; (3) This invention reduces bacterial wilt disease by increasing the diversity of the rhizosphere soil bacterial community of tobacco plants, optimizing its structural composition and enhancing the complexity of its network structure, that is, improving the interaction between beneficial bacterial communities. (4) This invention reduces bacterial wilt disease by collecting antibacterial metabolites from the rhizosphere soil of tobacco plants. Attached Figure Description

[0012] Figure 1 The study investigated the effects of different intercropping methods on the incidence and pathogen count of bacterial wilt in tobacco fields. Figure A shows the effect of different intercropping methods on the incidence of bacterial wilt in tobacco fields; Figure B shows the effect of different intercropping methods on the pathogen count of bacterial wilt in tobacco fields; Figure C shows the correlation coefficient between pathogen count and bacterial wilt incidence; Figure T1 shows the disease incidence in tobacco intercropped with sweet potato in Example 1; Figure T2 shows the disease incidence in tobacco intercropped with corn in Comparative Example 1; and Figure CK shows the disease incidence in tobacco used as a control in Comparative Example 2. Figure 2 This study investigates the effects of different plant intercropping methods on soil nutrients in tobacco fields. Figure A shows the effect of different plant intercropping methods on organic carbon in the soil; Figure B shows the effect of different plant intercropping methods on ammonium nitrogen; Figure C shows the effect of different plant intercropping methods on nitrate nitrogen; Figure D shows the effect of different plant intercropping methods on available phosphorus; and Figure E shows the correlation between organic carbon, available phosphorus, nitrate nitrogen, and available phosphorus content and the incidence and number of bacterial wilt pathogens in tobacco fields. Figure 3 The effects of different plant overlays on the diversity of rhizosphere soil bacterial communities in flue-cured tobacco. Figure A shows the effect of different plant overlays on Shannon; Figure B shows the effect of different plant overlays on Chao; Figure C shows the effect of different plant overlays on Ace; and Figure D shows the correlation between bacterial community diversity index and disease incidence and pathogen abundance. Figure 4 The effects of different plant intercropping methods on the composition of rhizosphere soil bacterial communities in flue-cured tobacco were investigated. Figure A shows the effect of different plant intercropping methods on the abundance of Ascomycota; Figure B shows the effect of different plant intercropping methods on the abundance of Basidiomycota; Figure C shows the effect of different plant intercropping methods on the abundance of Chytridiomycota; Figure D shows the effect of different plant intercropping methods on the abundance of Mortierellomycota; Figure E shows the correlation between the abundance of Chytridiomycota, Ascomycota, Basidiomycota, and Mortierellomycota and the incidence and abundance of bacterial wilt; Figure F shows the differences in bacterial genus-specific communities between the T1 and T2 intercropping treatments and the CK treatment. Figure 5 The effects of different plant intercropping methods on rhizosphere soil metabolites of flue-cured tobacco; Figure 6 This study investigates the effects of intercropping sweet potatoes with flue-cured tobacco at different stages on the incidence and pathogen abundance of bacterial wilt in tobacco fields. Figure A shows the effect of intercropping sweet potatoes with flue-cured tobacco at different stages on the incidence of bacterial wilt in tobacco fields, while Figure B shows the effect of intercropping sweet potatoes with flue-cured tobacco at different stages on the pathogen abundance of bacterial wilt in tobacco fields. Figure 7 This study investigates the effects of intercropping sweet potatoes at different stages of flue-cured tobacco cultivation on soil nutrients in tobacco fields. Figure A shows the effect of intercropping sweet potatoes at different stages on organic carbon in the soil; Figure B shows the effect of intercropping sweet potatoes at different stages on ammonium nitrogen; Figure C shows the effect of intercropping sweet potatoes at different stages on nitrate nitrogen; and Figure D shows the effect of intercropping sweet potatoes at different stages on available phosphorus. Figure 8 The effects of different plant overlays on the composition of rhizosphere soil bacterial community in flue-cured tobacco plants; Figure 9 The effects of different plant intercropping methods on rhizosphere soil metabolites of flue-cured tobacco; Figure 10 The effects of different sweet potato intercropping densities on the incidence and pathogen abundance of bacterial wilt in tobacco fields; the effects of different sweet potato intercropping densities on the incidence of bacterial wilt in tobacco fields; the effects of different sweet potato intercropping densities on the pathogen abundance of bacterial wilt in tobacco fields; Figure 11 The effects of different sweet potato densities intercropping with flue-cured tobacco on soil nutrients in tobacco fields were investigated. Figure A shows the effect of different sweet potato densities on organic carbon in the tobacco field soil; Figure B shows the effect of different sweet potato densities on ammonium nitrogen; Figure C shows the effect of different sweet potato densities on nitrate nitrogen; and Figure D shows the effect of different sweet potato densities on available phosphorus. Figure 12The effect of sweet potato planting at different densities on the composition of rhizosphere soil bacteria community of tobacco plants; Figure 13 The effects of different densities of sweet potatoes intercropped with flue-cured tobacco on the microclimate of the tobacco field; Figure A shows the effect of different densities of sweet potatoes intercropped with flue-cured tobacco on the temperature of the tobacco field; Figure B shows the effect of different densities of sweet potatoes intercropped with flue-cured tobacco on the humidity of the tobacco field; Figure C shows the effect of different densities of sweet potatoes intercropped with flue-cured tobacco on the CO2 concentration of the tobacco field. Figure 14 The impact of different densities of sweet potatoes as overlays for flue-cured tobacco on the economic benefits of tobacco fields; Figure 15 The effects of different sweet potato intercropping locations on the incidence and pathogen quantity of bacterial wilt in tobacco fields were investigated. Figure A shows the effect of sweet potato intercropping location on the incidence of bacterial wilt in tobacco fields, and Figure B shows the effect of sweet potato intercropping location on the pathogen quantity of bacterial wilt in tobacco fields. Figure 16 The impact of different sweet potato placements on the economic benefits of tobacco fields; Figure 17 A diagram showing the different positions of sweet potatoes for the tobacco curing sleeve; In the figure, a, b, c, d, ab, bc, and cd represent the degree of significance of the differences. , Indicates the degree of correlation. Detailed Implementation

[0013] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] Example 1 The application of the tobacco-sweet potato intercropping method in the prevention and control of bacterial wilt in tobacco includes the following steps: (1) Preparation of tobacco fields: On March 20, 2025, after applying base fertilizer in the tobacco fields, the tobacco fields were ridged with a ridge height of about 30 cm. Finally, a layer of biodegradable mulch film with a thickness of 0.008-0.01 mm was covered on the soil surface. (2) Transplanting of tobacco plants: The tobacco plants will be transplanted on April 25, 2025. The planting density is 1100-1200 plants / mu, the row spacing is 120cm, and the plant spacing is 50-55cm. (3) Intercropping sweet potatoes: Harvest the lower tobacco leaves on June 2, 2025. On the third day after the harvest of the lower tobacco leaves, intercrop sweet potatoes next to the tobacco plants. Intercrop a row of sweet potatoes on each side of each row of tobacco plants in the tobacco ridge. The spacing between sweet potatoes is 23-27 cm and the distance between sweet potatoes and tobacco plants is 11-13 cm. (4) Harvesting of tobacco plants and sweet potatoes: The middle tobacco leaves will be harvested on July 23, 2025, the upper tobacco leaves will be harvested on September 15, and the sweet potatoes will be harvested on October 13.

[0015] Experiment Example 1: The Effects of Intercropping Different Plants on Bacterial Wilt Disease in Tobacco Fields Comparative Example 1 (1) Preparation of tobacco fields: (1) Preparation of tobacco fields: On March 20, 2025, after applying base fertilizer in the tobacco fields, the tobacco fields were ridged with a ridge height of about 30 cm. Finally, a layer of biodegradable mulch was covered on the soil surface with a thickness of 0.008-0.01 mm. (2) Transplanting of tobacco plants: The tobacco plants will be transplanted on April 25, 2025. The planting density is 1100-1200 plants / mu, the row spacing is 120cm, and the plant spacing is 50-55cm. (3) Intercropping with corn: Harvest the lower tobacco leaves on June 2, 2025. On the third day after the harvest of the lower tobacco leaves, intercrop corn next to the tobacco plants. Intercrop a row of corn on each side of each row of tobacco plants in the tobacco ridge. The spacing between corn plants is 23-27 cm and the distance between corn and tobacco plants is 11-13 cm. (4) Harvesting of tobacco plants and corn: The middle tobacco leaves were harvested on July 23, 2025, the upper tobacco leaves were harvested on September 15, and the corn was harvested on October 13, 2025, which is recorded as T2.

[0016] Comparative Example 2 (1) Preparation of tobacco fields: On March 20, 2025, after applying base fertilizer in the tobacco fields, the tobacco fields were ridged with a ridge height of about 30 cm. Finally, a layer of biodegradable mulch film with a thickness of 0.008-0.01 mm was covered on the soil surface. (2) Transplanting of tobacco plants: The tobacco plants will be transplanted on April 25, 2025. The planting density is 1100-1200 plants / mu, the row spacing is 120cm, and the plant spacing is 50-55cm. (3) Harvesting of tobacco plants: The lower tobacco leaves were harvested on June 2, 2025, the middle tobacco leaves were harvested on July 23, and the upper tobacco leaves were harvested on September 15, which is recorded as CK.

[0017] Using the tobacco intercropping with sweet potato in Example 1 and the tobacco intercropping with corn in Comparative Example 1 as treatments, and the tobacco monoculture in Comparative Example 2 as a control (CK), the effects of the three on the occurrence of bacterial wilt in tobacco fields were compared.

[0018] I. Impact on the incidence and pathogen quantity of bacterial wilt in tobacco fields Compared with the control (CK) treatment, the incidence of bacterial wilt was reduced by 17.28% and 6.99% in the T1 and T2 treatments, respectively. Figure 1 (Figure A), while the number of pathogens decreased by 24.24% and 12.13%, respectively (Figure A). Figure 1 (See Figure B). Correlation analysis showed that the correlation coefficient between the number of pathogens and the incidence of bacterial wilt reached 0.70, indicating that the incidence of bacterial wilt increases with the increase of the number of pathogens. Figure 1 (Figure C).

[0019] The results above indicate that the T1 treatment (tobacco intercropped with sweet potatoes) was the most effective in reducing bacterial wilt disease in tobacco plants.

[0020] II. Impact on the rhizosphere soil of tobacco plants 1. Impact on soil nutrients in the rhizosphere of tobacco plants Compared with the control (CK) treatment, the organic carbon in the T1 and T2 treatments increased by 34.41% and 17.26%, respectively; ammonium nitrogen decreased by 28.87% and 11.96%, respectively; nitrate nitrogen increased by 84.62% and 23.09%, respectively; and available phosphorus increased by 20.29% and 12.371%, respectively. Figure 2 (Figures A-D).

[0021] Furthermore, the contents of organic matter, available phosphorus, and nitrate nitrogen were all negatively correlated with the incidence of bacterial wilt and the number of pathogens, while ammonium nitrogen showed a significant positive correlation. Figure 2 Figure E shows that nitrogen form transformation under the flue-cured tobacco intercropping planting model may inhibit pathogens through nitrogen source competition (i.e., reduce the ammonium nitrogen content in the soil), thereby inhibiting the reproduction of bacterial wilt pathogens to a certain extent and ultimately reducing the occurrence of the disease.

[0022] 2. Impact on the rhizosphere soil bacterial community of tobacco plants Impact on bacterial community diversity: Intercropping with flue-cured tobacco significantly increased the diversity of soil bacteria in tobacco plants, and the bacterial diversity increased with the number of years of intercropping. Compared with the control (CK) treatment, the Shannon, Chao, and Ace diversity indices of the T1 and T2 treatments increased by 6.66% and 2.23%, 7.74% and 4.43%, and 18.41% and 7.98%, respectively. Figure 3 (Figures A-C). Furthermore, the bacterial community diversity index showed significant and highly significant positive correlations with both disease incidence and pathogen abundance. Figure 3 The diagram (D) illustrates that bacterial community diversity is closely related to disease resistance; the higher the community diversity, the stronger the tobacco plant's ability to resist disease invasion.

[0023] Impact on bacterial community composition: Metagenomic testing results showed that the dominant bacterial communities in all three treatments were Proteobacteria, Firmicutes, Acidobacteriota, Bacteroidota, Actinobacteria, Gemmatimonadetes, Verrucomicrobiota, Chloroflexi, and Myxococcot. Further Pearson correlation analysis revealed that at the phylum level, Acidobacteriota and Actinobacteria, Chloroflexi, and Myxococcota were significantly negatively and significantly positively correlated with the incidence and abundance of each pathogen, respectively, in bacterial wilt disease. Figure 4 (Figure A). Compared with the CK treatment, the abundance of Acidobacteriota decreased by 62.5% and 33.23% in the T1 and T2 treatments, respectively, while the abundance of Actinobacteria, Chloroflexi, and Myxococcota increased by 90.91% and 45.46%, 74.84% and 37.43%, and 149.41% and 83.34%, respectively. Figure 4 Figures B-E). Furthermore, the T1 and T2 intercropping treatments showed significant differences in bacterial genus-specific communities compared to the CK treatment (Figure B-E). Figure 4 (See Figure F). Under the T1 intercropping treatment, the genus-level marker microorganisms, ranked from most significant to least significant in species difference, mainly included Chujaibacter, Mesorhizobium, Tumebacillus, Pseudonocardia, Sphingobacterium, Gaiella, and Streptomyces. Under the T2 intercropping treatment, the genus-level marker microorganisms, ranked from most significant to least significant in species difference, mainly included Niastella, Blastococcus, Rubrobacter, Vicinamibacter, and Ferrovibrio. Under the CK intercropping treatment, the genus-level marker microorganisms, ranked from most significant to least significant in species difference, mainly included Rhodanobacter, Castellaniella, and Dyella.

[0024] Impact on the complexity of bacterial community network structure: Network topology properties show that the nodes, edges, density, modularity, and clustering coefficient of treatments T1 and T2 are significantly higher than those of CK (Table 1). Furthermore, the proportion of positive correlations in the co-occurrence network of intercropping treatments is greater than that of negative correlations, indicating that bacteria mainly cooperate. Intercropping of flue-cured tobacco increases the complexity of the network structure and enhances the interaction between bacterial communities.

[0025] Table 1. Co-occurrence Network Topology Attributes

[0026] The results indicate that intercropping with flue-cured tobacco improved the diversity of bacterial communities, optimized the composition of bacterial communities, and reshaped the coexistence relationships among bacterial communities (making the synergistic interaction between bacterial communities more stable and effective), with the T1 treatment (flue-cured tobacco intercropping with sweet potato) showing the best optimization and promotion effects.

[0027] 3. Effects on rhizosphere soil metabolites of tobacco plants Compared with the control (CK), the levels of Lipopeptide, Isoquinoline alkaloids, Naringenin, and Phenolic acids increased by 2.71% and 1.13%, 6.48% and 1.27%, 12.82% and 9.56%, and 10.57% and 9.10% in the T1 and T2 treatments, respectively, while the levels of Aminopenicillanic acid, Ylbenzenesulfonic acid, and Garcinia acid decreased by 22.58% and 14.03%, 29.28% and 22.33%, and 32.07% and 12.74%, respectively. Figure 5 ).

[0028] The study further revealed that the first four metabolites all originated from the phenylpropane metabolic pathway, and the compounds produced by this pathway possess antioxidant, defense, and signal transduction activities in plants. These metabolic pathways are interconnected and work together to maintain metabolic homeostasis and physiological processes within organisms, thereby significantly affecting the growth and metabolism of pathogens. The increase in the first four metabolites was greater in the T1 treatment than in the T2 treatment.

[0029] In conclusion, this invention suggests that intercropping sweet potatoes with flue-cured tobacco is the most effective way to reduce bacterial wilt disease.

[0030] Experiment Example 2: The Effects of Intercropping Sweet Potatoes at Different Stages on Bacterial Wilt Disease in Tobacco Fields Comparative Example 3 The application of the tobacco-sweet potato intercropping method in the prevention and control of bacterial wilt in tobacco includes the following steps: (1) Preparation of tobacco fields: On March 20, 2025, after applying base fertilizer in the tobacco fields, the tobacco fields were ridged with a ridge height of about 30 cm. Finally, a layer of biodegradable mulch film with a thickness of 0.008-0.01 mm was covered on the soil surface. (2) Transplanting of tobacco plants: The tobacco plants will be transplanted on April 25, 2025. The planting density is 1100-1200 plants / mu, the row spacing is 120cm, and the plant spacing is 50-55cm. (3) Intercropping sweet potatoes: Harvest the lower tobacco leaves on June 2, 2025. On the 15th day after the harvest of the lower tobacco leaves, intercrop sweet potatoes next to the tobacco plants. Intercrop a row of sweet potatoes on each side of each row of tobacco plants in the tobacco ridge. The spacing between sweet potato plants is 23-27 cm and the distance between sweet potatoes and tobacco plants is 11-13 cm. (4) Harvesting of tobacco plants and sweet potatoes: The middle tobacco leaves were harvested on July 23, 2025, the upper tobacco leaves were harvested on September 15, and the sweet potatoes were harvested on October 13, denoted as T2.

[0031] Sweet potatoes were intercropped on the 3rd day (T1) and 15th day (T2) after the lower leaves of tobacco plants were harvested in the tobacco field, respectively, to compare their effects on reducing bacterial wilt and to explore the mechanism of the difference in effects.

[0032] I. Impact on the incidence and pathogen quantity of bacterial wilt in tobacco fields Compared with the T1 treatment in Example 1, the T2 treatment in Comparative Example 3 increased the incidence of bacterial wilt and the number of pathogens by 16.41% and 22.27%, respectively. Figure 6 This indicates that the T1 treatment (intercropping sweet potatoes on the 3rd day after harvesting the lower leaves of the tobacco plant) is the most effective in reducing bacterial wilt disease in tobacco plants.

[0033] II. Impact on the rhizosphere soil of tobacco plants The results of Experiment 1 showed that the soil nutrients, bacterial community composition and metabolites in the rhizosphere of tobacco plants under the intercropping model were highly correlated with the incidence of bacterial wilt in tobacco plants. Therefore, this invention further studied the effects of intercropping sweet potatoes at different stages of tobacco planting on these three factors in order to reveal the mechanism by which sweet potatoes reduce the differences in bacterial wilt in tobacco plants.

[0034] Effects on nutrients: Compared with treatment T1, treatment T2 reduced organic carbon, nitrate nitrogen, and available phosphorus by 10.43%, 28.29%, and 6.01%, respectively, while increasing ammonium nitrogen by 18.68%. Figure 7 ).

[0035] Effects on bacterial community composition: Although the dominant bacteria in T1 and T2 treatments were consistent in phylum and genus, their abundance differed significantly, especially in the stress-resistant communities. For example, the relative abundance of Streptomyces, Sphingobacteri, Pseudonocardia, Tumebacillus, Chujaibacte, Candidatus_Udaeobacter, and Hassallia was higher in T1 treatment than in T2 treatment. Figure 8 ).

[0036] Effects on tobacco rhizosphere soil metabolites: Compared with treatment T1, treatment T2 showed a 22.18% decrease in Lipopeptide, 17.60% in Isoquinoline alkaloids, 29.28% in Naringenin, and 13.32% in Phenolic acids, while a 19.79% increase in Aminopenicillanic acid, 10.46% in Ylbenzenesulfonic acid, and 22.19% in Garciniaacid, respectively. Figure 9 This indicates that the T1 treatment had a higher content of metabolites in the phenylpropanoid metabolic pathway, which has an anti-stress function, than the T2 treatment.

[0037] In summary, this invention suggests that planting sweet potatoes on the third day (T1) after harvesting the lower leaves of the tobacco plant under the tobacco-sweet potato intercropping planting model is the most effective way to reduce bacterial wilt disease.

[0038] Experiment Example 3: The effect of intercropping sweet potatoes at different densities (plant spacing) on ​​bacterial wilt disease in tobacco fields. Comparative Example 4 The application of the tobacco-sweet potato intercropping method in the prevention and control of bacterial wilt in tobacco includes the following steps: (1) Preparation of tobacco fields: On March 20, 2025, after applying base fertilizer in the tobacco fields, the tobacco fields were ridged with a ridge height of about 30 cm. Finally, a layer of biodegradable mulch film with a thickness of 0.008-0.01 mm was covered on the soil surface. (2) Transplanting of tobacco plants: The tobacco plants will be transplanted on April 25, 2025. The planting density is 1100-1200 plants / mu, the row spacing is 120cm, and the plant spacing is 50-55cm. (3) Intercropping sweet potatoes: Harvest the lower tobacco leaves on June 2, 2025. On the third day after the harvest of the lower tobacco leaves, intercrop sweet potatoes next to the tobacco plants. Intercrop a row of sweet potatoes on each side of each row of tobacco plants in the tobacco ridge. The spacing between sweet potatoes is <23cm and the distance between sweet potatoes and tobacco plants is 11-13cm. (4) Harvesting of tobacco plants and sweet potatoes: The middle tobacco leaves were harvested on July 23, 2025, the upper tobacco leaves were harvested on September 15, and the sweet potatoes were harvested on October 13, denoted as T1.

[0039] Comparative Example 5 The application of the tobacco-sweet potato intercropping method in the prevention and control of bacterial wilt in tobacco includes the following steps: (1) Preparation of tobacco fields: On March 20, 2025, after applying base fertilizer in the tobacco fields, the tobacco fields were ridged with a ridge height of about 30 cm. Finally, a layer of biodegradable mulch film with a thickness of 0.008-0.01 mm was covered on the soil surface. (2) Transplanting of tobacco plants: The tobacco plants will be transplanted on April 25, 2025. The planting density is 1100-1200 plants / mu, the row spacing is 120cm, and the plant spacing is 50-55cm. (3) Intercropping sweet potatoes: Harvest the lower tobacco leaves on June 2, 2025. On the third day after the harvest of the lower tobacco leaves, intercrop sweet potatoes next to the tobacco plants. Intercrop a row of sweet potatoes on each side of each row of tobacco plants in the tobacco ridge. The spacing between sweet potatoes is >27 cm and the distance between sweet potatoes and tobacco plants is 11-13 cm. (4) Harvesting of tobacco plants and sweet potatoes: The middle tobacco leaves were harvested on July 23, 2025, the upper tobacco leaves were harvested on September 15, and the sweet potatoes were harvested on October 13, denoted as T3.

[0040] I. Impact on the incidence and pathogen quantity of bacterial wilt in tobacco fields The three treatments showed a trend of T1 (Comparative Example 4) > T2 (Example 1) > T3 (Comparative Example 5) in terms of bacterial wilt incidence, with significant differences between treatment T1 and treatments T2 and T3, while the differences between the latter two were not significant. In terms of bacterial wilt pathogen count, the trend was T1 > T3 > T2, with significant differences between treatment T1 and treatments T2 and T3, while the differences between the latter two were not significant. Figure 10 ).

[0041] The results above indicate that the T2 and T3 treatments were effective in reducing bacterial wilt disease in tobacco plants.

[0042] II. Impact on the rhizosphere soil of tobacco plants Effects on nutrients: All three treatments showed a trend of T2>T3>T1 for organic carbon, nitrate nitrogen, and available phosphorus, while showing a trend of T1>T2>T3 for ammonium nitrogen. The differences between T1 and T2 and T3 were significant, while the differences between the latter two were not significant. Figure 11 The reason for these trends is speculated to be that sweet potatoes also need to absorb nutrients for growth. When the plant spacing in intercropping is too small (high planting density), they absorb more nutrients from the soil, and the competition with tobacco plants becomes more intense, resulting in a decrease in organic carbon, nitrate nitrogen, and available phosphorus in the rhizosphere soil of the tobacco plants. Similarly, because sweet potatoes with higher planting density release more harmful substances (ammonium nitrogen), the bacterial wilt disease becomes more severe. This result is consistent with the conclusion in Example 1 that "the content of organic matter, available phosphorus, and nitrate nitrogen is negatively correlated with the incidence of bacterial wilt and the number of pathogens, while ammonium nitrogen is the opposite."

[0043] Effects on bacterial community composition: The dominant bacteria in the three treatments were consistent in terms of phylum and genus, but their abundance differed significantly, especially in the stress-resistant communities. For example, the relative abundance of Streptomyces, Sphingobacteri, Pseudonocardia, Tumebacillus, Candidatus_Udaeobacter, Chujaibacte, and Hassallia showed a trend of T2>T3>T1. Similarly, the difference between treatment T1 and treatments T2 and T3 was significant, while the difference between the latter two was not significant. Figure 12 ).

[0044] The results above indicate that the T2 and T3 treatments effectively reduced bacterial wilt in tobacco plants, which is closely related to the relative abundance of nutrients and bacterial community composition in the rhizosphere soil.

[0045] III. Impact on the microclimate of tobacco fields All three treatments showed a trend of T1>T2>T3 in terms of temperature, humidity, and CO2 concentration in the tobacco field, with significant differences between T1 and both T2 and T3, while the differences between the latter two were not significant. Figure 13 This indicates that the smaller the plant spacing when sweet potatoes are intercropped, the higher the temperature and CO2 concentration in the tobacco field due to the denser sweet potato planting. This hinders the flow of O2 between tobacco plants, resulting in slower water evaporation and excessive humidity in the tobacco field, ultimately increasing the incidence of bacterial wilt.

[0046] IV. Impact on the economic benefits of tobacco fields Compared to monoculture tobacco, the costs of processing T1, T2, and T3 increased by RMB 133, RMB 107, and RMB 92 respectively; the profits (tobacco + sweet potato) increased by RMB 209, RMB 344, and RMB 267 respectively; and the net profits increased by RMB 76, RMB 237, and RMB 175 respectively. Figure 14 Although the T2 and T3 treatments showed little difference in reducing bacterial wilt disease in tobacco plants, the T2 treatment was superior to the T3 treatment in improving the economic benefits of tobacco fields.

[0047] In conclusion, this invention suggests that the T2 treatment (with a plant spacing of 23-27 cm for intercropping sweet potatoes) is the most effective in reducing bacterial wilt disease and improving the economic benefits of tobacco fields.

[0048] Experiment Example 4: The effect of sweet potato intercropping with flue-cured tobacco on bacterial wilt disease in tobacco fields Comparative Example 6 The application of the tobacco-sweet potato intercropping method in the prevention and control of bacterial wilt in tobacco includes the following steps: (1) Preparation of tobacco fields: On March 20, 2025, after applying base fertilizer in the tobacco fields, the tobacco fields were ridged with a ridge height of about 30 cm. Finally, a layer of biodegradable mulch film with a thickness of 0.008-0.01 mm was covered on the soil surface. (2) Transplanting of tobacco plants: The tobacco plants will be transplanted on April 25, 2025. The planting density is 1100-1200 plants / mu, the row spacing is 120cm, and the plant spacing is 50-55cm. (3) Intercropping with sweet potatoes: Sweet potatoes are intercropped on the 3rd day after the tobacco plants are transplanted, see Figure 17 The sweet potato plants are spaced 23-27 cm apart, and the distance between the sweet potatoes and the tobacco plants is 11-13 cm. The lower tobacco leaves will be harvested on June 2, 2025. (4) Harvesting of tobacco plants and sweet potatoes: The middle tobacco leaves were harvested on July 23, 2025, the upper tobacco leaves were harvested on September 15, and the sweet potatoes were harvested on October 13. This is recorded as T2. Example 1 is recorded as T1.

[0049] I. Impact on the incidence and pathogen quantity of bacterial wilt in tobacco fields The two treatments showed a clear trend in morbidity and pathogen count: T2 (16.36%) > T1 (14.56%) and T2 (1.68 × 10⁻⁶) > T1 (14.56%). 6 cfu / g)>T1(0.74×10 6 The trend of CFU / G ( Figure 15 This indicates that the T1 (Example 1) treatment was more effective than the T2 (Comparative Example 6) treatment in reducing bacterial wilt disease in tobacco plants.

[0050] II. Impact on the economic benefits of tobacco fields Compared to monoculture tobacco, the costs of T1 and T2 processing increased by RMB 120 and RMB 95 respectively, while the profits (tobacco + sweet potato) increased by RMB 288 and RMB 241 respectively, and the net profits increased by RMB 168 and RMB 146 respectively. Figure 16 Although the two treatments did not differ significantly in improving the economic benefits of flue-cured tobacco, treatment T1 was superior to treatment T2 in improving the economic benefits of tobacco fields.

[0051] In conclusion, this invention suggests that treatment T1 is superior to treatment T2 in reducing bacterial wilt disease and improving the economic benefits of tobacco fields.

[0052] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The application of a method for intercropping sweet potatoes with flue-cured tobacco in the prevention and control of bacterial wilt in flue-cured tobacco, characterized in that, Includes the following steps: (1) Preparation of tobacco fields: In late March, after applying base fertilizer to the tobacco fields, the tobacco fields are ridged, and finally a layer of biodegradable mulch is covered on the soil surface. (2) Transplanting of tobacco plants: Transplanting of flue-cured tobacco in mid-to-late April, with a planting density of 1100-1200 plants / mu, a row spacing of 120cm, and a plant spacing of 50-55cm. (3) Intercropping with sweet potatoes: Harvest the lower tobacco leaves in June, and then intercrop sweet potatoes next to the tobacco plants after harvesting the lower tobacco leaves; (4) Harvesting of tobacco plants and sweet potatoes: The middle tobacco leaves are harvested in July, the upper tobacco leaves are harvested in mid-to-late September, and the sweet potatoes are harvested in early to mid-October.

2. The application of the planting method of intercropping sweet potato with flue-cured tobacco according to claim 1 in the prevention and control of bacterial wilt in flue-cured tobacco, characterized in that, In step (3), sweet potatoes are intercropped next to the tobacco plants within 0-10 days after the lower tobacco leaves are harvested.

3. The application of the planting method of intercropping sweet potato with flue-cured tobacco according to claim 1 in the prevention and control of bacterial wilt in flue-cured tobacco, characterized in that, In step (3), a row of sweet potatoes is placed on each side of each row of tobacco plants in the tobacco ridge.

4. The application of the planting method of intercropping sweet potato with flue-cured tobacco according to claim 1 in the prevention and control of bacterial wilt in flue-cured tobacco, characterized in that, In step (3), the distance between sweet potatoes and tobacco plants is 11-13 cm, and the plant spacing between sweet potatoes is 23-27 cm.

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