A Scientific Battle for the "Queen of Oilseeds"
In the diverse agroclimatic zones of Odisha, a silent war is being waged on sesame fields, threatening a crop that is both a cultural staple and an economic lifeline.
Often called the "Queen of Oilseeds" for its exceptionally high-quality oil, sesame is a crucial crop for Odisha's agricultural economy4 . However, its reign is threatened by a host of destructive diseases.
To understand the disease challenges, an intensive survey was conducted during the flowering to capsule ripening stages across ten different agroclimatic zones of Odisha7 .
The survey revealed that almost all sesame fields were infected by more than one disease, painting a picture of widespread vulnerability7 .
| Disease | Causal Agent | Type of Pathogen | Prevalence / Severity |
|---|---|---|---|
| Charcoal Rot / Macrophomina Stem and Root Rot | Macrophomina phaseolina | Fungus | Found in all surveyed fields7 |
| Cercospora Leaf Spot | Cercospora sesami | Fungus | Prevalence grade of 1-2 (on a 0-5 scale)7 |
| Alternaria Blight | Alternaria sesami | Fungus | Prevalence grade of 2-47 |
| Powdery Mildew | Erysiphe cichoracearum | Fungus | Prevalence grade of 0-37 |
| Phyllody | Phytoplasma | Bacterium-like organism | Incidence of 0-2.3%7 |
| Phytophthora Blight | Phytophthora sp. | Oomycete | Observed in some patches7 |
| Fusarium Wilt | Fusarium oxysporum | Fungus | Incidence of 0.5-9.78%7 |
Charcoal Rot stands out as the most pervasive and destructive threat with incidence ranging from 8.0% to 23.8%7 .
The highest incidence of charcoal rot was recorded at Balianta with 23.8% infection rate7 .
Almost all sesame fields were infected by more than one disease, showing widespread vulnerability7 .
Charcoal rot is a global problem, identified as a major threat to emerging sesame industries in countries like Australia and a significant cause of yield loss in Eastern India5 3 . The fungus is resilient, surviving in the soil as microsclerotia (resting structures) and infecting plants under conditions of high temperature and low soil moisture3 .
The economic impact is staggering. Yield losses due to charcoal rot in India are estimated to range from 6% to a devastating 71.5%, with some reports suggesting losses can reach 100% at certain growth stages3 . This makes it one of the most serious constraints to sesame production.
Faced with these challenges, researchers are moving away from chemical fungicides and focusing on sustainable, eco-friendly solutions. One such study conducted at Odisha University of Agriculture and Technology tested the effectiveness of various biocontrol agents and plant extracts against charcoal rot3 .
The research aimed to screen the efficacy of microbial biocontrol agents and plant extracts in inhibiting the growth of Macrophomina phaseolina in a controlled laboratory setting3 .
| Treatment Agent | Type | Mycelial Growth of M. phaseolina (mm) | Key Finding |
|---|---|---|---|
| Control | - | 90.0 (full plate) | Pathogen grew unchecked |
| Pseudomonas flourescens | Bacterial Biocontrol Agent | 48.5 | Showed antagonistic activity |
| Bacillus subtilis | Bacterial Biocontrol Agent | 42.0 | Showed antagonistic activity |
| Trichoderma fasciculatum | Fungal Biocontrol Agent | 34.0 | Significantly checked growth |
| Trichoderma virens | Fungal Biocontrol Agent | 28.7 | Significantly checked growth |
| Trichoderma asperellum | Fungal Biocontrol Agent | 20.0 | Significantly checked growth |
| Allium sativum (Garlic) extract | Botanical | 18.0 | Most effective phyto-extract |
| Trichoderma viride | Fungal Biocontrol Agent | 14.7 | Most effective biocontrol agent |
The scientific importance of these results is profound. They demonstrate that potent, natural alternatives to chemicals exist. Trichoderma viride and garlic extract were particularly effective, with garlic extract proving to be a readily available and affordable option for farmers3 . These agents work by competing for space and nutrients, producing antibiotics, or directly parasitizing the disease-causing fungus.
Beneficial fungi that act as natural antagonists against pathogens3 .
Botanical solutions containing natural antimicrobial compounds3 .
Improve soil health and promote beneficial microorganisms3 .
Used in breeding programs to develop disease-resistant varieties8 .
The comprehensive survey of Odisha's agroclimatic zones provided the essential first step: a clear map of the enemy and its strongholds. The follow-up research offers a hopeful path forward, demonstrating that eco-friendly management can be highly effective.
Integrating these findings—using resistant varieties developed through breeding programs, applying biocontrol agents like Trichoderma viride, and leveraging natural botanicals like garlic extract—presents a viable strategy for Odisha's farmers3 8 . Protecting the "Queen of Oilseeds" is not just about preserving a crop; it's about safeguarding economic stability, promoting sustainable agriculture, and ensuring this ancient plant continues to thrive for generations to come.