January 24, 2013

 

US researchers expect huge insights on small corn plot

 

 

A small plot of a mutant corn strain to be planted this spring is expected by USDA researchers to provide insights into how corn plants respond to insect and fungal attacks.

 

This spring, researchers in Florida will plant a small plot of corn that could yield significant insights into how plants effectively respond to insect and fungal attacks.

 

In October, researchers found a naturally occurring mutant corn strain that completely lacks a family of recently discovered novel biochemicals.

 

Specifically, diterpenoid phytoalexins termed kauralexins are produced in response to pests and pathogens, says Eric Schmelz, a plant physiologist at USDA's Agricultural Research Service, Centre for Medical, Agricultural, and Veterinary Entomology in Gainesville, Fla.

 

Given this line of corn originated from a natural mutation, he says researchers are able to conduct field investigations on it this spring. Schmelz is part of a group of USDA researchers with a long-standing history of uncovering plant biochemical responses that dynamically occur when crops are under attack.

 

He explains that when plants are attacked by leaf-eating insects, they give off related volatile organic compounds known as monoterpenes and sesquiterpenes.

 

This indirect "cry for help" can be an effective form of plant defence. More recently, this research group has focused on plant responses to stem-boring insects and associated fungal pathogens. This small change in direction resulted in the discovery of numerous novel biochemicals by Schmelz and other team members. They published research on 10 new chemical structures.

 

Moreover, Schmelz says there are dozens more awaiting discovery and characterisation. He says the role of the novel chemicals ranges from directly increasing the plant defences following attack to regulating production of various chemical signals within the plant which orchestrate wide-ranging defence responses.

 

Already in some experiments, relevant levels of the newly discovered kauralexin class of phytoalexins inhibited the growth of anthracnose stalk rot by 90%.

 

Similarly, sesquiterpene-derived zealexins inhibited the growth of the aflatoxin-producing fungus Aspergillus flavus by 80%.

 

Another scientist in the group, Alisa Huffaker, has focused her research on the role of peptide hormones in plants and their regulation of anti-pathogen and anti-insect defence responses. Schmelz says there is the possibility of some overlap between the newly discovered novel biochemicals and the peptide hormones.

 

This research is beginning to uncover the role of novel biochemicals in how corn defends itself. To better leverage these basic and fundamental research approaches, Schmelz and Huffaker work with corn breeders from other USDA locations that also consider genetics, field level resistance and agronomic traits.