In a recent paper published in the journal Frontiers in Microbiology, researchers Chunlan Ming, Yushuai Zhang, Mengze Li, Mohamed G. Moussa, Tengfei Liu, Hang Wang, Yongfei Ma, Wuxing Huang, Zicheng Xu, Jiayang Xu, and Wei Jia investigate a sustainable solution for one of the most destructive soil-borne diseases in agriculture. Tobacco black shank, caused by the pathogen Phytophthora nicotianae, poses a constant threat to global tobacco production, often leading to severe root rot, blackened stems, and total plant death. While chemical fungicides are currently the standard defense, their environmental impact and the rise of resistant pathogen strains have created an urgent need for greener alternatives. The research team explored how transforming tobacco stalks—a common agricultural byproduct—into a specialized form of biochar could provide a low-cost, eco-friendly shield for the plants.

The study focused on a specific type of material known as ball-milled phosphorus-modified biochar, which was created by combining mechanical grinding with a phosphoric acid treatment. This dual-modification process completely reshaped the surface of the biochar, creating a dense and uniform pore structure with an abundance of active chemical groups. When added to the soil at a rate of just 0.5 percent by weight, this modified biochar significantly altered the plant’s internal chemistry. The researchers found that the material acted as a catalyst for the plant’s own immune system, allowing the tobacco seedlings to mount a much stronger defense against the invading pathogen.

The quantitative results of the study highlight the superior performance of the ball-milled phosphorus-modified biochar compared to standard treatments. In infected plants, the application of this biochar reduced the length of disease lesions by 37.01 percent. It also played a critical role in managing oxidative stress, which typically ravages plant cells during an infection. The biochar treatment decreased levels of harmful reactive oxygen species, such as hydrogen peroxide and superoxide anions, by approximately 47 percent and 55 percent, respectively. Simultaneously, it boosted the activity of essential antioxidant enzymes. Most notably, the activity of superoxide dismutase, a key enzyme for neutralizing cellular toxins, increased by 158.71 percent compared to the untreated infected plants.

Beyond direct disease suppression, the modified biochar helped maintain the plant’s vital functions under stress. Chlorophyll levels, which are essential for photosynthesis and energy production, typically plummet during a black shank infection. However, tobacco plants treated with the specialized biochar showed chlorophyll a and b levels that were 59.74 percent and 73.23 percent higher than those in the infected control group. This maintenance of green pigment allows the plants to continue producing the energy needed to survive the infection and sustain growth. The researchers also noted a significant increase in defense-related hormones, such as jasmonic acid and indole-3-acetic acid, which signal the plant to strengthen its cell walls and produce antimicrobial compounds.

The study concludes that the success of this biochar lies in its ability to reshape the metabolic profile of the tobacco plant. Detailed analysis showed that the treatment promoted the biosynthesis of phenylpropanoids and essential amino acids like phenylalanine, tyrosine, and tryptophan. These metabolic pathways are responsible for producing the structural and chemical barriers that prevent the pathogen from spreading through the plant’s tissues. By turning tobacco waste into a high-value soil amendmentA soil amendment is any material added to the soil to enhance its physical or chemical properties, improving its suitability for plant growth. Biochar is considered a soil amendment as it can improve soil structure, water retention, nutrient availability, and microbial activity.   More, this research provides a dual benefit: it offers a powerful new tool for sustainable disease management while providing a productive use for millions of tons of agricultural residue produced each year.

Source: Ming, C., Zhang, Y., Li, M., Moussa, M. G., Liu, T., Wang, H., Ma, Y., Huang, W., Xu, Z., Xu, J., & Jia, W. (2026). Ball milled phosphorus modified biochar improved Nicotiana tabacum L. resistance against Phytophthora nicotianae: reducing oxidative damage, increasing defense hormone content and promoting phenylpropanoid metabolism. Frontiers in Microbiology, 16, 1734991.