Document Type : Full Paper
Authors
1 Department of Plant Production and Genetics, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran
2 Department of Plant Protection, Faculty of Agriculture, Lorestan University, Khorramabad, Iran
Abstract
Keywords
Main Subjects
Extended Abstract
Introduction
Worldwide, approximately 4200 species of flowering plant parasites have been identified, belonging to 274 genera. Of these, only about 30 genera are recognized as problematic agricultural weeds. The most damaging among these include genera such as Cuscuta, Arceuthobium, Orobanche, and Striga. Within the Cuscuta genus, Cuscuta campestris Yunck. (commonly known as dodder) stands out as a particularly troublesome parasitic weed due to its extensive global distribution, broad host range, and the limitations of current control methods.
Dodder species parasitize a wide array of agricultural crops, garden plants, and even other weeds. Lacking true roots and leaves, dodder cannot photosynthesize. Instead, it develops specialized structures called haustoria, which penetrate the host plant’s vascular tissues to extract water, nutrients, and vital organic molecules. This parasitic action severely impedes the host plant’s growth and productivity. Field infestations by Cuscuta have been shown to significantly reduce crop yields; for instance, studies report decreases in root sugar content by 2.6% in sugar beet and a substantial 40% decline in fruit yield for eggplant.
Eggplant (Solanum melongena L.), an annual plant originating from India, is globally cultivated in tropical and subtropical regions for its versatile fruit. Nutritionally, it is comparable to tomatoes. In 2022, global eggplant production reached 59.3 million tons from 1.9 million hectares, with Iran contributing 596 thousand tons from 20 thousand hectares.
Silicon is recognized as an essential element in plant nutrition, playing a vital role in enhancing tolerance to both biotic and abiotic stresses. Primarily present as silicates in the soil, silicon becomes available for plant uptake in the form of silicic acid. Recent research has highlighted the capacity of silicate-solubilizing bacteria to convert soil silicates into plant-available silicic acid. This microbial action not only reduces the reliance on synthetic silicate fertilizers but also improves the uptake of silicon and other essential nutrients by crops.
Given this context, the present study was designed to investigate the interactions between eggplant and dodder (representing a significant biotic stress) and to explore the potential of using sodium silicate and silicate-solubilizing bacteria as mitigating agents.
Key changes and why:
Materials and Methods
A three-factor factorial pot experiment was conducted in a completely randomized design (CRD) with six replications at the Bu-Ali Sina University research greenhouse in 2022. The factors investigated were: dodder infestation (infested vs. uninfested eggplant), sodium silicate application (0 vs. 100 mg/kg soil), and inoculation with a commercial silicate-solubilizing bacterial product (0 vs. 10 mL/kg soil). Measurements of eggplant and dodder growth and physiological traits were taken two months after eggplant emergence.
Results and Discussion
The results revealed a significant synergistic effect when sodium silicate and silicate-solubilizing bacteria (SSB) were co-applied. In non-infected eggplant, the combined application of sodium silicate and SSB led to substantial increases in key growth parameters, including shoot dry weight (+73%) and root dry weight (+74%). Furthermore, this treatment significantly enhanced plant defense mechanisms, evidenced by a dramatic increase in silicon content (+229%) and lignin content (+108%). Physiological indicators of defense activation were also notable, with rises in phenylalanine ammonia-lyase (PAL) activity (+85%), catalase (CAT) activity (+83%), peroxidase (POD) activity (+11%), superoxide dismutase (SOD) activity (+84%), and lipoxygenase (LOX) activity (+218%). Conversely, this synergistic treatment effectively reduced oxidative stress markers, as indicated by a decrease in H₂O₂ content (-28%) and malondialdehyde (MDA) content (-39%). However, when eggplant was co-infected with dodder and treated with both sodium silicate and SSB, the parasitic interaction caused detrimental effects on growth and silicon accumulation. Shoot dry weight decreased by 32%, root dry weight by 41%, and silicon content by 28%. Despite these growth reductions, the plant’s defense responses were strongly activated. Lignin content increased by 53%, and the activities of defense enzymes such as PAL (+27%), CAT (+214%), POD (+202%), SOD (+194%), and LOX (+156%) were significantly elevated. Oxidative stress markers also increased under dodder infection, with H₂O₂ content rising by 58% and MDA content by 94%. The concurrent production of lignin, coupled with elevated PAL and POD activities during the dodder-eggplant interaction, suggests a fortified cell wall structure. These biochemical modifications, alongside physical alterations in the host plant’s cuticle, collectively contribute to a modified cell wall that confers resistance against parasite penetration.
Conclusion
The synergistic co-application of sodium silicate and silicate-solubilizing bacteria (SSB) significantly reduced dodder biomass. Crucially, this combined treatment effectively compensated for the biomass losses typically inflicted by dodder infestation on eggplant. This indicates that the synergistic application of sodium silicate and SSB can serve as a protective strategy against the detrimental effects of this parasitic weed on eggplant growth.
Author Contributions
A Aliverdi conceived, planned, and carried out the experiments. He analyzed data. AA Chitband wrote the first manuscript and contributed to the interpretation of the results. All authors provided critical feedback and helped shape the research, analysis and manuscript.
Data Availability Statement
Data sharing is not applicable to this article as no new data were created or analyzed in this study.
Acknowledgements
The study was supported in part by the Bu-Ali Sina University.
Ethical considerations
The authors avoided data fabrication, falsification, plagiarism, and misconduct.
Conflict of interest
The author declares no conflict of interest.
)