Growth of loblolly pines measured 14 years after screening for fusiform rust resistance

Assessing rust resistance and growth of loblolly pine indicates that many progeny selected for resistance to fusiform rust exhibit reduced growth after 14 years in the field on a site with low rust incidence. Fifty different crosses of loblolly pines with rust resistance (Pinus taeda L.) were planted in Louisiana to evaluate diameter growth. Selection of crosses for outplanting was done by screening nine-month-old rust-inoculated seedlings for symptoms without galls. Crosses with lowest incidence of fusiform rust after 9 months had the smallest diameters after 14 years. Diameters ranged from 2.1 to 11.9 inches with a mean of 8.2 inches for the 50 crosses. Large diameters occurred in the susceptible open pollinated check. If crosses that are highly resistant to fusiform rust are planted where rust incidence is low, such as on this site, a significant reduction in wood production can result. Crosses from parent 209 in this study are excellent examples of resistant crosses with reduced diameter growth in the test plantation. Discretion in family selection should be used in planning for optimum wood harvest.