Tuesday, July 7, 2009

Growth Spurts: New Leaf Lettuce Shows Corky Root Resistance

Three new leaf lettuce breeding lines with resistance to corky root, a serious disease of lettuce, have been released by the Agricultural Research Service of the U.S. Department of Agriculture.

Corky root is caused by a bacterium called Sphingomonas suberifaciens which lives in the soil and attacks the plant's roots, causing them to enlarge and develop yellow to brown lesions and longitudinal cracks, taking on a cork-like appearance. Once infected, the roots are unable to effectively absorb water and nutrients, resulting in smaller lettuce heads and yield loss.

Cultural practices and fumigation techniques used to treat corky root are costly and labor-intensive. Developing lines with genetic resistance is still the most common and preferred method to combat the disease.

The new leaf lettuce breeding lines -- one red leaf lettuce and two green leaf lettuces -- have plant weight comparable to or higher than commercial cultivars. The breeding lines have also showed little to no tipburn in test trials. They can be used commercially for production of fresh lettuce or to develop new cultivars.

Source: Agricultural Research Service

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