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New Vegetable Varieties Resist Diseases

Multiple disease resistance benefits growers and consumer

photo of whitaker squash
Whitaker squash.
Photo by J. Ogrodnick

Resistant Squash. A summer squash called Whitaker got a lot of media attention a year ago, along with the man responsible for its successful breeding: Cornell horticulturist Richard Robinson. This work of ten years’ duration, accomplished with the assistance of plant pathologists R. Provvidenti and H. M. Munger and research support specialist Joe Shail, has been supported in part by an IPM grant.

Why is Whitaker such big news? Multiple resistance is the answer. Whitaker is resistant to four significant diseases, three viral and one fungal. No other squash can resist this many diseases. Multiple resistance means reduced pesticide use, control of diseases that have never before been adequately controlled, improved quality, higher yield, and longer storage life. Resistance to a single disease isn’t nearly as significant. A squash that resists one disease can be lost to another.

Robinson continued refining Whitaker this year, attempting to add resistance to one more disease and to the cucumber beetle. He was assisted in this effort by Mike Hoffmann, of Cornell University’s Department of Entomology. Robinson also worked on transferring Whitaker’s resistance to other squashes.

Resistant Broccoli and Cabbage. A similar effort to Robinson’s is underway in the laboratory of Cornell’s Elizabeth Earle. She used a cell culture procedure called protoplast fusion to transfer disease resistance into crucifer vegetables from other species. Following the initial fusion experiments she began working with Cornell horticulturist Mike Dickson to produce resistant broccoli and cabbage of marketable quality. They now have broccoli lines that are resistant to either blackrot or Alternaria leaf spot and some broccoli/cabbage crosses that are resistant to both. Six of the 18 broccoli lines tested in 1998 showed good resistance to blackrot. According to Earle, "This was an increase in percentage of resistance over earlier generations. It could mean that resistance is becoming uniform in these strains."

Blackrot is a bacterial disease that causes leaves to become discolored and brittle. When weather conditions favor its development, blackrot causes stunting, wilting, and even plant death. Alternaria leaf spot is a fungal disease that appears as dark spots sometimes covered with a black mold. It can render whole heads of cabbage worthless.

Seed for Sale. Seed for Whitaker summer squash and for the resistant broccoli plants is readily available to growers for the first time this spring.