Summer 2005

Taking the Bite Out of the Blight

by Zoë Hoyle

The fungus Scirrhia acicola, better known as brown spot needle blight, attacks 28 species of pines. But it inflicts the most damage on the longleaf pine, killing seedlings in the earliest stage of their development. Researchers at the Southern Institute of Forest Genetics in Saucier, MS, combine the latest in genetic mapping tools with classic genetic breeding to give longleaf seedlings a better shot at surviving the blight.

Longleaf pines start their lives in a unique grass stage, the seedlings almost stemless, resembling clumps of long shining grass. The grass stage can last anywhere from 2 to over 10 years, depending on growing conditions. Longleaf pine is most susceptible to brown spot needle blight during this stage. The fungus attacks the needles, leaving only a bare stem. Seedlings infected with the blight either die or grow very slowly. Heavily infected longleaf pine seedlings may stay in the grass stage for a decade or more. Seedlings with resistance to the blight grow much faster and taller, with height gains persisting for decades.

Following the grass stage, the seedling enters a period of rapid growth, called early height growth, sometimes known as the rocket stage. Seedlings can resist the blight much more easily during this stage. That's why, says Saucier unit project leader Dana Nelson, the group has focused on prompting longleaf seedlings to enter the early height growth stage sooner.(...continued...)

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