Impact of Growing Environment on Anthracnose Severity of Switchgrass Cultivars and Clones

Anthracnose (caused by Colletotrichum navitas) has the potential to significantly reduce biomass yield of switchgrass (Panicum virgatum L.); however, limited information is available on the impact of growing environment on tolerance of switchgrass to anthracnose. Therefore, the major objectives of this study were to (i) examine genotype–environment (G × E) effects on anthracnose severity in populations of switchgrass cultivars and individual genotypes and (ii) determine clonal repeatability estimates and stability analysis of anthracnose tolerance on individual switchgrass genotypes. Two experiments were conducted at one prime and two marginal soil locations in New Jersey. In all, 14 switchgrass cultivars were established from seed in 2008 for experiment 1 and 50 replicated switchgrass clones were planted in 2009 for experiment 2 at all three locations. Anthracnose was rated visually in 2010 for experiment 1 and in 2010 and 2011 for experiment 2. Significant G × E interactions were detected for both experiments (P ≤ 0.05) and anthracnose severity varied by location and cultivar. Clonal repeatability estimates for disease tolerance among clones was 0.78 on a clonal basis and 0.32 on a single-plant basis. Lowland ecotypes exhibited less disease overall than upland ecotypes. Results from this study indicate that selection for improved tolerance to anthracnose should be conducted after evaluation across several environments over multiple years.

Evidence for genetic control of response to sulfur dioxide and ozone in Populustremuloides

This study was designed to estimate the degree of genetic control of the response to sulfur dioxide (SO2) and ozone (O3), alone and in combination, in trembling aspen (Populustremuloides Michx.). Rooted cuttings from 11 randomly selected trees in central Wisconsin were used in the study. Significant interclonal variation was found in the response of the 11 clones to 3-h exposures to 0.50 ppm SO2, 0.20 ppm O3, and 0.35 ppm SO, plus 0.05 ppm O3. Clonal repeatability estimates of 0.464 for SO2 plus O3, 0.620 for O3, and 0.642 for SO2 suggest that much of this variation between clones can be attributed to genetic differences in response to SO2 and O3.