Context: 

The recent study revealed that cucumber mosaic virus (CMV) is responsible for 25-30% yield losses in banana plantations in India.

More on the News

• According to the U.N. Food and Agriculture Organisation (FAO), plant pests and diseases destroy nearly 40% of the world’s annual crop, costing the world more than $220 billion. Of that, plant viruses alone contribute to over $30 billion in losses each year.
• A team of researchers recently reported developing an RNA-based antiviral agent that confers strong protection against cucumber mosaic virus, a widespread and destructive plant virus. 
• In the new study, the researchers used RNA silencing, a natural defense mechanism found in plants. 

Cucumber Mosaic Virus (CMV)

• CMV is a plant virus that infects over 1,200 species, including many economically important crops. It is transmitted by aphids and can cause significant yield losses. 
• Symptoms include mosaic patterns on leaves, stunted growth and distorted fruits. 
• CMV was first identified in 1916 as the causal agent of a cucumber and muskmelon disease in the United States. 
• In pumpkins, cucumbers and melons, infection rates can soar up to 70%. Affected plants develop mosaic discoloration, stunted growth and commercially unviable fruits.

RNA-Based Antiviral Technology 

• When a virus infects a plant, it introduces double-stranded RNA (dsRNA) which acts like a red flag for the plant’s immune system.
• The plant responds by activating Dicer-like enzymes (DCLs) which slice the dsRNA into small fragments called small interfering RNAs (siRNAs). 
• These siRNAs then guide the plant’s defense system to recognize and destroy the viral RNA, preventing the infection from spreading.
• To make plants more resistant to diseases, scientists are studying RNA-based methods such as host-induced gene silencing (HIGS) and spray-induced gene silencing (SIGS) to boost their natural immunity.

Other RNA-based crop protection techniques: 

• Host-induced gene silencing (HIGS): HIGS works by genetically modifying plants to produce virus-fighting dsRNA in their own cells. This provides continuous protection throughout the plant’s life. 
• But regulations, high production costs and the potential for viral resistance limit its widespread use.
• Spray-induced gene silencing (SIGS): It is a non-transgenic and more flexible approach for crop protection that involves applying double-stranded RNA (dsRNA) or small RNAs (sRNAs) to plant surfaces to trigger RNA interference (RNAi). 
• Leaves absorb the RNA and triggers the plant’s natural immune response without altering its original DNA.

• While SIGS doesn’t require genetic modification and is cost-effective and environmentally friendly, its effectiveness is limited.

• This is because traditional dsRNA formulations produce a random mix of siRNAs, many of which fail to silence the virus efficiently.

A new approach to enhance effectiveness of RNA silencing against CMV.

• Instead of using randomly generated dsRNA, researchers designed “effective dsRNA” which is a genetically engineered dsRNA enriched with highly functional siRNA. 
• These specially selected siRNA bind to the virus’s genetic material to trigger a stronger antiviral response.
• Through rigorous testing, the most effective siRNA sequences against CMV were identified and incorporated into dsRNA constructs, ensuring high siRNA concentration for maximum plant defence efficiency.
• When applied to infected plants, the engineered dsRNA and siRNA reduced CMV levels by up to 80%, with some cases achieving complete viral suppression.
• The dsRNA formulation outperformed traditional dsRNA because the plant processed them into active siRNA more efficiently, creating a stronger immune response.
• The team found this method to be more effective against multiple CMV strains.

Key advantages of the new approach: 

• It’s more precise because the plant’s immune system is directed toward the viral particles’ most vulnerable genetic regions, boosting its ability to fight infection. 
• It provides a stronger defense because the more effective dsRNA targets multiple regions of the viral genome simultaneously.
• The effective dsRNA can be redesigned in about a month to target new viral strains.

Plant Based Disease

Mains Question:

Q. Plant-based diseases pose a significant challenge to global food security by contributing to substantial crop losses. Discuss the measures needed to address this issue, with a special focus on the role of emerging technologies in disease detection, prevention and management.