Relative fusiform rust resistance of loblolly and slash pine sources and families in Georgia and South Carolina

Abstract

Loblolly and slash pine seedlings from the fusiform rust resistant orchards developed cooperatively by the USDA Forest Service and the Georgia Forestry Commission had significantly less rust 7 to 8 years after planting on four of five sites in the Southeastern United States than seedlings of the same species from orchard sources developed primarily for silvicultural improvement. Loblolly and slash pine family plantings varied in rust susceptibility on eight sites after 5 to 7 years. Although rust incidence was relatively low, many families contributed to a significant interaction effect of family by location in the 7-year-old planting. This significant interaction indicates that relative performanc e of families is affected by the variation in virulence of the rust pathogen at different locations. This finding supports the hypothesis that mixes of resistant families will limit fusiform rust infections more effectively than single family plantings.