Tomato yellow leaf curl virus (TYLCV) is a prominent viral pathogen that adversely affects tomato plants. Effective strategies for mitigating the impact of TYLCV include isolating tomato plants from the whitefly, which is the vector of the virus, and utilizing transgenic lines that are resistant to the virus. In our preliminary investigations, we observed that the use of growth retardants increased the rate of TYLCV infection and intensified the damage to the tomato plants, suggesting a potential involvement of gibberellic acid (GA) in the conferring of resistance to TYLCV. In this study, we employed an infectious clone of TYLCV to inoculate tomato plants, which resulted in leaf curling and growth inhibition. Remarkably, this inoculation also led to the accumulation of GA₃ and several other phytohormones. Subsequent treatment with GA₃ effectively alleviated the TYLCV-induced leaf curling and growth inhibition, reduced TYLCV abundance in the leaves, enhanced the activity of antioxidant enzymes, and lowered the reactive oxygen species (ROS) levels in the leaves. Conversely, the treatment with PP333 exacerbated TYLCV-induced leaf curling and growth suppression, increased TYLCV abundance, decreased antioxidant enzyme activity, and elevated ROS levels in the leaves. The analysis of the gene expression profiles revealed that GA₃ up-regulated the genes associated with disease resistance, such as WRKYs, NACs, MYBs, Cyt P450s, and ERFs, while it down-regulated the DELLA protein, a key agent in GA signaling. In contrast, PP333 induced gene expression changes that were the opposite of those caused by the GA₃ treatment. These findings suggest that GA plays an essential role in the tomato’s defense response against TYLCV and acts as a positive regulator of ROS scavenging and the expression of resistance-related genes.

To scientifically evaluate the effects of three environmentally friendly fumigants, dazomet, metham sodium, and calcium cyanamide, on soil microbial community changes, soil from a greenhouse with 7 years of continuous cropping was studied. Soil samples were collected from unfumigated soil (CK), dazomet-fumigated soil (DZ1), metham sodium-fumigated soil (MS1), calcium cyanamide-fumigated soil (CC1) at seedling recovery stage, dazomet-fumigated soil (DZ2), metham sodium-fumigated soil (MS2), and calcium cyanamide-fumigated soil (CC2) at fruiting stage. The effects of different fumigant treatments and treatment periods on soil microbial community changes, tomato yield, and soil-borne diseases were analyzed. The results showed that the application of soil fumigants significantly reduced the richness and diversity of soil bacterial and fungal communities at the seedling recovery stage. Three months after transplanting (at the fruiting stage), the soil microbial diversity gradually recovered. After fumigation, the relative abundance of soil bacteria and fungi at the phylum level changed. Under different fumigation treatments, the trends in the relative abundance changes of species during the seedling recovery and fruiting stages after fumigation exhibited certain differences. Analysis of the dominant soil microbial communities at the genus level revealed that fumigation effectively eliminated pathogenic genera such as Fusarium, but the inhibition rate of pathogens increased during the seedling recovery stage after fumigation. By comprehensively considering microbial community changes during the seedling recovery and fruiting stages after fumigation, as well as indicators such as yield, incidence of soil-borne diseases, and disease index, among the three fumigation treatments, the DZ treatment demonstrated the best overall performance. It increased beneficial genera while reducing the majority of pathogenic genera in the soil. Even after three months, when the plants transitioned from the seedling recovery stage to the fruiting stage, the relative abundance of harmful genera remained suppressed, and the abundance of some beneficial genera increased. However, given the broad-spectrum microbial eradication by fumigants and the time-limited suppression of pathogenic communities, it is essential to supplement beneficial microorganisms promptly after soil fumigation, such as by applying microbial fertilizers in combination.

To study the effects of dazomet, which is a soil fumigant and microbial inoculant (Trichoderma harzianum) on the bacterial and fungal diversity of continuously cropped strawberry soil, this work aimed to provide a theoretical basis for the treatment of continuously cropped strawberry. The soil of a strawberry greenhouse with continuous cropping for 10 years was used as the research object, and rhizosphere soil samples from strawberry continuous cropping were collected before dazomet fumigation (M0), after dazomet fumigation (M1), after dazomet fumigation in the fruit early phase without the addition of T. harzianum (H0), and after the addition of T. harzianum (H1). The diversity of soil bacteria and fungi was detected via the Illumina HiSeq high-throughput sequencing platform. The results revealed that the richness and diversity of the soil bacterial and fungal communities decreased after dazomet fumigation and that the addition of T. harzianum after dazomet fumigation increased both the richness of the soil bacterial communities and the diversity of the fungal communities. At the genus level, the composition ratios of the soil bacterial and fungal communities in the different treatments also substantially differed. The bacterial community compositions of H0 and H1 were the most similar, while the fungal community compositions of M0 and H0 were the most similar. The analysis of beneficial and harmful dominant genera in the soil revealed that dazomet fumigation could kill pathogenic fungi such as Ilyonectria and Fusarium in the soil and reduce beneficial bacteria and fungi such as Streptomyces, Flavobacterium, Mortierella, and Talaromyces. The addition of T. harzianum to dazomet fumigation can increase the abundance of beneficial bacteria and fungi such as Bacillus, Flavobacterium, and Cladorrhinum in the soil as well as reduce the abundance of pathogenic fungi such as Monilinia, Ilyonectria, and Fusarium. In summary, the use of dazomet fumigation combined with microbial inoculation changed the microbial structure of continuously cropped soil, increased the abundance of beneficial bacteria and fungi, and reduced the abundance of the vast majority of pathogenic fungi in the soil. Therefore, dazomet fumigation combined with microbial inoculation is an effective method for overcoming obstacles to continuous cropping of the strawberry.

To scientifically assess the effects of environmentally friendly fumigants on soil microbial communities, soils from a 7-year continuous cropping tomato greenhouse were studied, with unfumigated soil used as the control (CK). Rhizosphere soil samples treated with dazomet (DZ), metam sodium (MS) and calcium cyanamide (CC) were collected at the seedling recovery and fruiting stages. The influences of different fumigants and growth stages on soil microbial communities, tomato yield and soil-borne diseases were investigated. The results indicated that soil fumigation significantly decreased microbial community richness and diversity at the seedling recovery stage, which gradually recovered at the fruiting stage. The variation trends of microbial relative abundance at the phylum and genus levels differed among the treatments at both stages. At the phylum level, Actinobacteria and Proteobacteria were the dominant bacterial phyla, and Ascomycota was the dominant fungal phylum. Genus-level clustering revealed that the bacterial communities under MS and CC were similar to those under CK at the fruiting stage, whereas the fungal communities under all the fumigation treatments were significantly distinct from those under CK. Fumigation effectively inhibited pathogenic genera, including Amesia, Fusarium, Rhizopus and Ascobolus, at the seedling recovery stage, but some pathogens recovered at the fruiting stage. The relative abundance of Fusarium in the MS treatment increased to 8.25%. DZ treatment performed optimally: it increased beneficial genera such as Bacillus and Streptomyces at the seedling recovery stage, suppressed harmful genera, including Amesia and Fusarium, and further enriched Remersonia at the fruiting stage. Fumigation significantly improved tomato yield and reduced the incidence of soil-borne diseases. The yield of CC was the highest, at 35.41% greater than that of CK, but it was not significantly different from that of DZ in terms of cost. In conclusion, the DZ treatment had the best overall effect.

Blossom-end rot (BER) in tomatoes is a physiological disorder primarily caused by the disruption of calcium absorption and transport. This study cultivated tomatoes using a trough-based vermiculite system. Two treatments were established: a calcium-deficient nutrient solution and a calcium-deficient nutrient solution supplemented with 0.1 mg/L BR (n = 40 plants per treatment). The activities of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD), as well as the contents of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂), were measured in the leaves. Calcium ion content was also determined in various plant parts. Statistical analysis of differences was performed using Duncan’s multiple range test at a significance level of p < 0.01. Concurrently, transcriptome sequencing of root, stem, and leaf tissues was conducted via high-throughput sequencing technology. The results showed that foliar application of BR under calcium deficiency significantly reduced the incidence of BER (from 26.67% to 6.67%) and effectively increased calcium ion content in leaves, stems, and roots. At the physiological level, BR treatment markedly enhanced the activities of CAT, POD, and SOD in leaves (by 105.70%, 117.12%, and 82.77%, respectively), while reducing H₂O₂ and MDA contents (by 36.90% and 16.38%, respectively). This indicates that BR alleviates membrane lipid peroxidation damage by enhancing the antioxidant defense system. Gene Ontology (GO) enrichment analysis revealed that the differentially expressed genes (DEGs) were primarily involved in biological processes, such as secondary metabolic processes, response to oxygen-containing compounds, and cell wall organization. KEGG pathway analysis further indicated significant enrichment in pathways, including phenylpropanoid biosynthesis, plant hormone signal transduction, and plant–pathogen interaction. Additionally, key genes, such as the cytochrome c oxidase (COX) gene (Solyc03g013460.1), exhibited a gradient up-regulation pattern (root > stem > leaf) in the oxidative phosphorylation pathway. In conclusion, BR likely enhances tomato tolerance to calcium deficiency stress and effectively reduces BER incidence through multiple pathways: regulating calcium absorption and distribution, activating the antioxidant system, modulating hormone signaling pathways, and enhancing energy metabolism. These findings provide a theoretical basis for the application of BR in agricultural production.

To study the effects of different microbial agents on the microbial community structure of continuously cropped strawberry soil after soil fumigation, seven treatments were applied: T1 (Trichoderma harzianum + Bacillus subtilis + actinomycetes), T2 (Trichoderma harzianum + Bacillus subtilis), T3 (Trichoderma harzianum + actinomycetes), T4 (CK) (water control), T5 (Bacillus subtilis), T6 (actinomycetes) and T7 (Trichoderma harzianum). A high-throughput sequencing platform (Illumina HiSeq 2500) was used to analyze the soil bacterial and fungal communities and their compositions. Compared with the T4 (CK) treatment, the application of microbial agents increased the richness and diversity of soil bacteria and fungi, and the effects of single microbial agents and compound microbial agents differed. The richness, diversity indices and population sizes of bacteria and fungi in the T6 treatment were the highest. The Chao1, observed species and Shannon indices of bacteria were 22.51%, 23.56% and 5.61% greater, respectively, than those of T4 (CK). The Chao1, observed species, Shannon and Simpson indices of fungi were 41.28%, 41.83%, 128.02% and 88.65% higher, respectively, than those of T4 (CK). At the genus level, the bacterial community compositions of T2 and T6 were the most similar, and the fungal community compositions of T1 and T5 were the most similar. Analysis of the genera in the dominant communities revealed that the application of microbial agents after dazomet fumigation increased the numbers and recovery rates of soil bacteria and fungi, especially the beneficial fungal genera, Lecanicillium, Cladosporium, Saccharomyces and Aspergillus. An investigation of strawberry growth and yield-related indicators revealed that the T6 treatment resulted in the lowest seedling mortality and the highest yield. In summary, adding microbial agents to soil with continuous cropping of strawberry after fumigation with dazomet is a scientifically sound and effective method for reconstructing the balance of the soil microbial flora and overcoming the obstacles associated with continuous cropping. In this study, the T6 (actinomycetes) treatment presented the best performance.