Tomato Plant Defense Boosted by Fungus through Improved Antioxidants

Jim Crocker
30th March, 2024

Tomato Plant Defense Boosted by Fungus through Improved Antioxidants

Image Source: Natural Science News, 2024

Key Findings

  • A less harmful fungus can protect tomato plants from a more aggressive disease-causing fungus
  • The protective fungus 'primes' the plant's defenses, even with a time gap between exposures
  • This method boosts plant antioxidants, strengthening cell walls against the disease
In the ongoing battle against plant diseases, scientists are constantly seeking effective ways to protect crops and ensure food security. One such disease that poses a significant threat to tomato production is caused by a fungus known as Rhizoctonia solani. This pathogen can wreak havoc on tomato plants, leading to substantial crop losses. However, recent research from Ferdowsi University of Mashhad[1] has shed light on a promising method of biological control that could offer a new line of defense for tomatoes. The study focused on different isolates of Rhizoctonia solani, with varying levels of virulence, or ability to cause disease, in tomato plants. Interestingly, the researchers discovered that an isolate of binucleate Rhizoctonia (BNR), which exhibited low virulence, could be used to combat the more aggressive R. solani strains. When tomato plants were inoculated with this less harmful BNR isolate, the plants developed resistance not only to the BNR itself but also to the more virulent R. solani. This resistance induction was not limited to cases where the plants were exposed to both pathogens simultaneously. The protective effect was also observed when there was a time interval between inoculations with BNR and R. solani. This suggests that the BNR isolate has the potential to 'prime' the tomato plants' defense systems, allowing them to respond more effectively to subsequent pathogen attacks. The researchers investigated the biochemical changes in the tomato plants following inoculation with the pathogens. They found increased activity and expression of antioxidant enzymes, such as peroxidase (POX), superoxide dismutase (SOD), and catalase (CAT), which are known to play roles in plant defense mechanisms. The highest levels of these activities, along with the buildup of defensive compounds like lignin and callose, were observed in plants that were simultaneously inoculated with BNR and R. solani. Lignin and callose are substances that strengthen plant cell walls, making it harder for pathogens to penetrate and spread. The study showed that BNR inoculation led to a reduction in hydrogen peroxide (H2O2) accumulation, a reactive oxygen species that can damage plant cells but also signal for defense responses. Remarkably, the most significant priming effect was seen for POX among the antioxidants tested. This suggests that the BNR-induced resistance (BNR-IR) in tomato plants relies heavily on the action of POX. To further confirm the role of POX in this resistance, the researchers used potassium cyanide, an inhibitor of POX activity. Treatment with this inhibitor reduced the tomato plants' basal resistance and the BNR-IR, leading to decreased lignification and callose deposition. This reduction in the plants' physical defenses allowed the pathogen to progress more easily within the plant tissues. The findings of this study are particularly relevant in the context of sustainable agriculture. Chemical control methods, while effective, can have negative environmental impacts and contribute to the development of pathogen resistance. Biological control options, such as using a hypovirulent BNR isolate as demonstrated in this research, offer a more eco-friendly alternative. The results align with previous studies that have explored the use of other biocontrol agents, like Metarhizium anisopliae against Rhizoctonia solani in okra[2], and hypovirulent binucleate Rhizoctonia isolates against Fusarium crown and root rot of tomato[3]. Moreover, the study builds upon earlier research that emphasizes the importance of plant defense mechanisms, such as the octadecanoid pathway and lignification, in combating sheath blight in rice caused by Rhizoctonia solani[4][5]. The current research expands our understanding of these defense responses and how they can be harnessed to protect crops against various pathogens. In conclusion, the study from Ferdowsi University of Mashhad provides valuable insights into how a less virulent pathogen can be used to trigger an immune response in tomato plants, offering a sustainable strategy to control the highly damaging R. solani. By enhancing the plants' own defense systems through biological means, this approach could play a crucial role in safeguarding crops and securing food production in an environmentally responsible way.

AgricultureBiotechPlant Science

References

Main Study

1) Binucleate Rhizoctonia induced tomato resistance against Rhizoctonia solani via affecting antioxidants and cell wall reinforcement.

Published 30th March, 2024

https://doi.org/10.1016/j.heliyon.2024.e27881

Related Studies

2) Effect of Metarhizium anisopliae (MetA1) on growth enhancement and antioxidative defense mechanism against Rhizoctonia root rot in okra.

https://doi.org/10.1016/j.heliyon.2023.e18978

3) Control of Fusarium Crown and Root Rot of Tomato with Hypovirulent Binucleate Rhizoctonia in Soil and Rock Wool Systems.

https://doi.org/10.1094/PDIS.2003.87.6.739

4) Rhizoctonia solani Kühn Pathophysiology: Status and Prospects of Sheath Blight Disease Management in Rice.

https://doi.org/10.3389/fpls.2022.881116

5) Riboflavin induces resistance in rice against Rhizoctonia solani via jasmonate-mediated priming of phenylpropanoid pathway.

https://doi.org/10.1016/j.jplph.2009.08.003


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