Qué son y cómo funcionan los fosfitos, una defensa natural para los cultivos. (#590 2014-11-22)

Agriculture and Phytos: Enhancing Plant Defense Mechanisms

Importance of Phytos in Agriculture

• The use of phosphites is crucial for enhancing the natural defenses of plants, maximizing yield, and improving grain quality. They complement traditional insecticides and herbicides.

• Dr. Marcelo Carmona discusses the role of phosphites in extensive crop management during training sessions for technicians in Brazil.

Plant Defense Mechanisms

• Plants have both passive and active defense mechanisms. Passive defenses include structural or biochemical traits that exist before pathogen infection, such as thickened cell walls.

• Active defenses are formed in response to stress or pathogen attack, including morphological changes like gum formation within vascular tissues to halt pathogen spread.

Elicitors and Their Role

• An elicitor is a substance that triggers plant defense responses without causing cellular damage, mimicking the action of pathogens but without their harmful effects.

• Elicitors can be chemical or biological; they enhance systemic resistance across the plant against various pathogens, acting similarly to a broad-spectrum vaccine.

Acetylsalicylic Acid Activation

• Acetylsalicylic acid (ASA), activated by many pathogens and chemical elicitors like phosphites, serves as a messenger that mobilizes plant defenses throughout its system.

• ASA induces defensive responses that prepare plants to better resist future infections from fungi, bacteria, viruses, nematodes, and insects.

Historical Context of Phosphite Use

• The origin of phosphite usage dates back to intensive agriculture post World War II when there was a need for simpler phosphorus supplementation methods due to resource scarcity.

• Phosphite (phosphorous acid), distinct from phosphoric acid used in fertilizers, was synthesized in laboratories leading to discoveries about its suppressive effects on certain plant diseases caused by pathogens like Phytophthora.

Research Developments with Phosphites

• Initial findings indicated that phosphites acted as fungicides against specific pathogens such as Phytophthora, leading to their adoption in crops like potatoes and tomatoes.

• Ongoing research at agricultural faculties aims to explore technologies that induce enhanced defense mechanisms in extensive crops facing significant pathogenic threats.

Understanding the Role of Phosphite in Soil Fungi Management

Behavior of Phosphite Molecules

• The discussion begins with exploring the behavior of phosphite molecules against soil fungi, particularly in soybean crops affected by end-of-cycle diseases. It also touches on similar diseases in wheat and corn.

Seed Treatment Innovations

• The speaker highlights a pioneering study on seed treatment using phosphites, led by a collaborative group from agronomy faculties and research institutions, presented at an international soybean congress.

Mechanism of Action

• Phosphites can move through plant roots via xylem and phloem, providing coverage during germination. This mobility enhances their effectiveness against soil pathogens.

Advanced Research Developments

• Ongoing experiments are assessing the compatibility of phosphites with inoculants to ensure they complement rather than displace existing treatments, emphasizing modern agricultural practices.

Dual Activation Pathways for Plant Defenses

• The potential for phosphites to activate plant defenses through both jasmonic acid and salicylic acid pathways is discussed. This dual activation could lead to additive or synergistic effects in disease resistance.

Evaluating Efficacy and Environmental Impact

Duration of Defense Activation

• The duration of defense activation by manganese phosphite is crucial; it must coincide with infection onset for maximum efficacy.

Integration with Traditional Practices

• Biopesticides like phosphites should not compete but rather work alongside traditional fungicides and insecticides, enhancing overall management systems without compromising safety or effectiveness.

Unique Properties of Phosphites

• Unlike conventional fungicides that struggle with certain pathogens, phosphites excel as effective biopesticides due to their unique movement capabilities within plants.

Towards Sustainable Agricultural Practices

Need for Disruptive Agricultural Innovations

• A call for innovative practices that challenge existing paradigms is made, stressing the importance of sustainable production methods that integrate new technologies effectively.

Holistic Approaches in Agriculture

• Emphasizing a holistic view in agriculture is essential; integrating research and technology can lead to more sustainable practices while respecting good agricultural practices.

Integrated Management Concepts

• There’s a need to apply integrated management concepts more rigorously than before. Historical approaches have often fallen short in practical application despite extensive discussions over the years.

The Role of Manganese Phosphite and Glyphosate in Weed Control

Challenges with Glyphosate Usage

• Glyphosate, the most widely used herbicide globally, has shown weaknesses when misused or not integrated into a comprehensive management program.

• There is an increasing prevalence of glyphosate-resistant and tolerant weed species, highlighting the need for modifications in application strategies.

Scientific Perspectives on Glyphosate Effects

• Some scientific discussions suggest that glyphosate may sequester essential metals like manganese, potentially weakening plant defense systems.

• Research indicates that certain enzymatic systems responsible for cellular damage protection are diminished following glyphosate application.

Enhancing Plant Defense with Manganese Phosphite

• Combining glyphosate with manganese phosphite significantly boosts defensive enzymes and reduces root diseases, particularly in cases involving Macrophomina.

• Optimal conditions for using phosphites are crucial to maximize their effectiveness and allow plants to reach their full potential.

Understanding Inducers vs. Fungicides

• Unlike fungicides that target pathogens directly, inducers work by enhancing the plant's natural defenses; however, they require careful consideration of various growth factors.

• The success or failure of an inducer can be erratic due to uncontrolled variables such as soil quality, genotype, nutrition, and environmental conditions.