Xiu-Mei Yang

Marigold (Tagetes spp.), a widely cultivated popular ornamental plant that is highly susceptible to fungal diseases, particularly leaf spot and stem wilt, which can substantially reduce its ornamental and economic value. This study aimed to identify the causal pathogens responsible for these diseases and evaluate the efficacy of selected antifungal agents against them. The causal agent of leaf spot was identified as Alternaria alternata, whereas stem wilt was caused by the Fusarium solani species complex (FSSC), based on Koch’s postulates, morphological characterization, and molecular identification. The antifungal activities of five commercially available fungicides were subsequently evaluated against both pathogens. The results showed that isomycete fluridine suspension (40%), metalaxyl–oxametrin suspension (32%), eugenol liquid (0.3%), pyrazolesterin methyl thiobacillin suspension (41%), and pyrazolesterin tebuconazole suspension (30%) demonstrated varying degrees of inhibitory activity. The EC50 values for A. alternata ranged from 10.588 to 49.604 mg/L, while those against FSSC ranged from 12.273 to 27.921 mg/L. These findings provide insights into the potency of these fungicides and offer a scientific basis for developing integrated disease management strategies for marigold cultivation, although further research is required to validate and evaluate their long-term efficacy and environmental safety.

The rose industry in China faces significant challenges due to viral pathogens such as Prunus necrotic ringspot virus (PNRSV), apple stem grooving virus (ASGV), rose virus C (RVC), and Citrus tatter leaf virus (CTLV). This study aims to establish a rapid, efficient, and accurate detection method for these viral diseases to aid in their prevention and control. Based on morphological and microscopic observations, coat protein and polyprotein gene sequences of these viruses were retrieved from the NCBI database, and specific primers were designed based on highly conserved regions. Primer concentration, cDNA concentration, and annealing temperature were optimized to develop a multiplex RT-PCR detection system. The optimal reaction system was established with a total volume of 50 μl, with upstream and downstream primer concentrations of 0.3 μmol/liter for ASGV and CTLV, and 0.2 μmol/liter for PNRSV and RVC, with template cDNA at 2.0 ng/μl. Using touchdown PCR, we performed 10 cycles with an annealing temperature gradient of 65 to 55°C, decreasing by 1°C per cycle, followed by 20 cycles with a constant annealing temperature of 55°C. This method was successfully applied to 23 cut rose samples, yielding clear and distinct bands. These results demonstrate that the method can efficiently and accurately detect single or combined infections of the four rose viruses, offering a valuable tool for the rose industry in China.