Emerging Disease Threatens Cassava Crop

Cassava Roots (Credit: Wikimedia)
Cassava Roots (Credit: Wikimedia)

The New York Times reported today on the emergence of Cassava Brown Streak Virus in regions of Africa where the tuber is a key food crop.  Emphasizing the food’s importance, the Times notes:

“After rice and wheat, cassava is the world’s third-largest source of calories. Under many names, including manioc, tapioca and yuca, it is eaten by 800 million people in Africa, South America and Asia.”

The new virus, a recently characterized emerging variant in East Africa, renders the crop inedible.  The estimated $50 million in research funding aimed at deterring the disease is a small fraction of the amounts spent on diseases that infect humans in the developing world.  Though there are some resistant Cassava plants, researchers have begun work on developing transgenic cassava plants that improve resistance to the virus while remaining desirable as crops.  Unfortunately, this work could take years.  In the interim, famine and disorder could result.

A Broader Trend

Infectious diseases of crops are constantly emerging, and cause a significant burden on agriculture.   The papaya, a significant nutritional crop in Southeast Asia, is threatened by a virus known as Papaya Ringspot virus, which prompted the development of a transgenic papaya in Hawaii during the late 1990’s.  Wheat crops are threatened by a new virulent strain of Wheat Stem Rust – known as Uganda 1999 because that is the location and date where it was identified – which evades resistance genes that have been used in agriculture since the Green Revolution of the mid-20th century.  Perhaps the most famous example is the late blight of the potato, caused by an oomycete called Phytophthora infestans, which caused the great Irish Famine in the mid-1800’s.

Due to this potential to disrupt society, both the US and Soviet bioweapons programs investigated agricultural pathogens including the potato blight, rice blast, and wheat stem rust.  Though authorities are increasingly aware of the danger – whether from naturally occurring outbreaks or intentional acts of terrorism and aggression – the rapid transport of food across agricultural regions and on to markets poses a major challenge for the detection and quarantine of crop pathogens.  As global populations and food requirements continue to increase, addressing the threat to the food supply will only become even more important.

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