Accelerated short-term genetic testing for loblolly pine families

Abstract

The following experiment was done to test the hypothesis that acceleration of seedling growth increases the juvenile.sbd.mature correlation for growth. Growth traits of 18 open-pollinated loblolly pine (Pinus taeda) families were compared across (i) field trials measured 8 years after planting (mature age), (ii) a short-term test environment with a supplemental incandescent light source (20-h photoperiod) and a higher fertilizer level, and (iii) a short-term test environment with no supplemental day length and a lower fertilizer level. The ranking of two seedlots of known, extreme performance and the juvenile-mature correlations were used as the criteria of early testing success. Juvenile-mature (family mean) correlations were low (r = 0.13) for the growth-accelerating environment relative to the natural day length environment (r = 0.59) and two check seedlots ranked correctly only in the natural day length environment. The genetic correlations between the short-term tests are high for total height (r''G = 0.79) but lower for height produced after first budset, the trait that has shown value as a juvenile indicator (r''G = 0.54). The growth-accelerating treatment increases growth per unit time but prompts abnormal shoot development. The nonaccelerating treatment with no supplemental light offered the most promise for genetic testing of 1st-year loblolly pine seedlings.