बीज बायोप्रिमिंग: पौधों की वृद्धि के लिए एक व्यापक दृष्टिकोण
Seeds are the connecting link between two generations and primarily the first form of plant life just like a new born baby. They serve an important asset in agriculture production. About 90% of all food crop grown on this world are propagated by seed. Moreover they are an important part in international trade. Apart from these vital functions, unfortunately, they are involved in transmission of diseases so called as seed born diseases.
Seed borne disease refers to the particular plant diseases that are transmitted by seed. Common seed borne diseases are: Bunts, smuts, spots, rotting, blights, anthracnose etc. Pathogens may be present on seeds either externally or internally and cause infection during or prior to germination.
They are responsible for considerable loss of yield in various crops. History has encountered many popular threatful events related to loss due to seed borne diseases like Irish famine, Bengal famine etc.
Management of plant diseases is important for most crops, and it is particularly crucial for the production of high-quality seed as they are the primary carrier of pathogens inoculums.
Seed born diseases can be managed by physical methods (heat treatment i.e. hot air and hot water treatment), cultural method (Manipulation of planting & harvesting times, nutrient and water management), Chemical methods (Use of various chemicals for seed treatment) and biological methods (Use of various bio control agents).
Treatment of seeds can become an exceptionally important way of eradicating or reducing seed borne pathogens, especially when seeds are grown for seed production, or where there is a need of good quality seed with minimum fungal infection.
Chemical methods are used since long time and it is highly accurate in its performance. But, now days due to arbitrary use of chemicals, they are frequently known for the negative impacts they may have on the environment and even on the consumers.
Thus there is immediate need to bring some safe, eco-friendly and protective approach to manage these diseases.
Seed priming
Seed priming is a process in which the seeds are allowed to be soaked in water or solution having low osmotic potential. The soaking is employed in such a way that germination related activities begin without creating a way for radical emergence.
There are plenty of benefits of having primed seeds such as it reduce the time of germination and accelerate the rate of germination as in rice. Apart from this, seed emerges faster and uniformly. Seed priming withstand the crop to effectively compete with weeds. Moreover, it increases seed performance under stress conditions like salinity for better establishment of the crop
Biopriming
Biopriming is a currently a popular method of seed treatment in which seeds are allow to underwent various positive changes. Biological aspect involves the treatment of seeds beneficial microorganisms while physiological aspect includes the hydration of seeds with the solution like water.
Both these biological and physiological aspect protect the seed from various seed- and soil borne diseases. A layer of biocontrol agents are applied over the seeds. Seed biopriming craves a beautiful path for the successful establishment of the bioagent. Thus, seed biopriming is a combination of application of bioagents with hydration of seeds.
Advantages of Seed Biopriming
- Application of bioprimed seeds reduces the risk to non target organisms.
- Bioprimed seeds decrease the cost of disease control per hectare, increase seed vigor and provide protection to seed forming coat of antagonists
- Furthermore, combination of treatments with chemicals can be applied more precisely
- It helps in breaking of seed dormancy and improve emergence, providing a better platform for plant stand.
- The beauty of using bioprimed seeds is that is safe for human and environmental health.
- It is considered as a safer, cheaper and easily applicable biocontrol method.
Common antagonists use in Seed Biopriming
There are number of available biological formulation against different conditions. The biological candidates can be fungal agents like Trichoderma viridae, Trichoderma harzianum, Trichoderma hamatum, Gliocladium roseum, Chaetomium bostrycoide etc.
Several bacterial agents serves as seed biopriming agents such as Pseudomonas fluroscence, Pseudomonas aureofaciens, Pseudomonas aeruginosa, Serratia polymuthica, Bacillus subtilis, Agrobacterium strain strain etc.
General Procedure of Seed biopriming
Soaked the seeds in water for overnight or approximately for 12 hours
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Apply the formulated product of biogent (Trichoderma harzianum, Pseudomonas fluorescens etc) on to the pre soaked seed at the rate of 10-15 gm per kg of seed with the help of gloves or stick and mixed it thoroughly
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Keep the treated seed as heap in shade
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Cover the heap with moist jute sack to maintain high humidity
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Incubate the whole system for 48 hours at room temperature
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The fruitful bioagent grows and get adheres on the surface forming a protective covering around the seed coat
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The divine seeds impregnating the noble creatures are ready to sown in the nursery bed.
Mode of action by seed biopriming agents
Seed biopriming agents exhibit various mechanisms to inhibit the growth of pathogens. The seed biopriming agents may exert directly through antagonism of soil borne pathogens or indirectly by eliciting a plant mediated-resistance response. Direct response results from physical contact or high specificity whereas indirect mechanism does not involve sensing or targeting a pathogen. The different mechanism used by seed biopriming agents are as follows:
- Mycoparasitism
- Competition for nutrients, oxygen and space
- Antibiosis
- By producing volatile compounds
- By production of enzymes which degrades the cell wall of pathogen
Role of seed biopriming in different plant growth promoting activities
Seed biopriming increases overall growth of the plants. It leads to enhance the physiological activity of the plants.
Azotobacter chroococcum, Azotobacter lipoferum and Azotobacter spp. when applied to Maize and Barley results in increase in 100 grain weight, dry matter accumulation, grain yield, biological yield, harvest index, crop growth rate, plant height, number of kernels per ear row and number of grains per ear row.
Pseudomonas spp. increased number of branches, heads per plant, diameter of head, grain number per plant, oil content and grain yield in Safflower crop. In similar, increase in shoot height, root length and seedling weight was observe in Sunflower crop when it is treated with Pseudomonas fluroescens.
Role of biopriming in abiotic stress tolerance
Plants experience various abiotic stresses due to salinity, drought and heavy metal in their life which impaired their growth. Seed biopriming enables the plant to withstand these stresses.
Bacillus pumilus or Bacillus firmus when applied to Potato under salinity, drought or heavy metal condition responds in increase in plant height, number of leaves per plant, number of tubers per plant and tuber yield per plant through. They do so by ACC- deaminase activity, IAA production, phosphate solubilization and siderophore production.
Similarly, Bacillus cereus when incorporated with rice, mungbean or chickpea under saline condition results in increase in seedling height, root and shoot biomass through the mechanism of phosphate solubilization, production of IAA, catalase, protease, chitinase, siderophore and nitrate reduction. Agrobacterum rubi, Burkholderia gladii, Pseudomonas putida or Bacillus subtillis improved seed germination of Radish under saline conditions.
Role of biopriming in biotic stress tolerance
Plants encounter various biotic stresses in the form of pathogens like bacteria, fungi, viruses etc which devastate their normal growth and yield. Biopriming help plant to overcome the diseases causes by these biotic agents.
Trichoderma harzianum protect Maize crop from Fusarium spp. Pseudomonas fluorescens and Clonoastachys rosea act against Alternaria spp. in Sunflower and Carrot respectively.
Pseudomonas fluorescens minimize the loss occur due to downy mildew of Pearl millet. Seed biopriming with Pseudomonas fluorescens and Pseudomonas aureofaciens protect sweet corn from damping off disease.
Conclusion
Bio-priming can provide a high level of protection against seed and soil borne diseases which can be almost equal or even superior to the chemical treatment. They are ecologically safe, economically viable, long term effective and nourish overall growth of plant. However, they posses high specificity, slow action and influence by environmental conditions.
Nevertheless, application with seed biopriming provides all the source of beneficial microorganism to the soil which plants need for better performance. Environmental conditions, pH of soil and crop species must be consider while selecting the type of seed biopriming agents against particular constraints in growth of plant.
So, farmers should be encouraged for adopting it which helps in safe production and increase in yield with no environmental and health hazards. Seeds are source of life, so let’s start protecting it biologically rather than with chemicals.
Author
Anshu Kumar
Ph.D. Research Scholar, Department of Plant Pathology,
Bidhan Chandra Krishi Viswavidyalaya, Mohanpur,
West Bengal - 741252, India
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