SeedQuest Vegetables - from - Harris Moran Seed - Corn

NEWSLETTER

A new
Rp1-D virulent
race of rust was widespread in North America
for
the first time in 1999

An update on common rust and Rp-resistant sweet corn
by Jerald Pataky, University of Illinois, Urbana, IL

Common rust, caused by the fungus Puccinia sorghi, can decrease yields of sweet corn. Ear weight and number of marketable ears per acre are reduced about 5% for each 10% of the leaf area infected by rust. When cool, wet weather favors rust development, severity often reaches 20% to 35% on hybrids with moderate reactions and about 40% to 60% or more on susceptible hybrids.

Even under these adverse conditions, rust can be controlled successfully by growing resistant hybrids or by timely applications of fungicides.

Rp-resistance and new races of rust in North America

Over 25 different Rp genes (Rp = resistant to Puccinia) occur in corn. The Rp1-D gene has been used effectively in sweet corn for the past 20 years to control common rust in North America. Based on conservative estimates, Rp-resistance has added nearly $2 million annually for the past decade to the value of sweet corn grown for processing in the Midwestern United States.

For the past 10 years, sweet corn breeders and pathologists have been working with many other Rp-genes in anticipation that virulence against Rp1-D would become frequent in populations of P. sorghi in North America. A new Rp1-D virulent race of rust was widespread in North America for the first time in 1999.