Responses of soybean ancestral lines and cultivars to simulated acid rain

During 1985, 1986, and 1987, field and greenhouse experiments were conducted on four ancestral lines and two cultivars from each of the northern and southern gene pools. The ancestral lines have contributed approximately 80% of the genes to their respective gene pools. Representatives from the northern germplasm collection included Mandarin, Manchu, AK Harrow, Richland, 'Amsoy 71', and 'Williams 82'. The southern germplasm collection was represented by CNS, S 100, PI 54610, Tokyo, 'Lee 74', and 'Essex'. Spray-to-wet applications of simulated acid rain (SAR) were applied at three acidity levels (pH 2.8, 3.2, and 4.3). Field experiments were grown under optimum and sub-optimum soil conditions (pH and fertility) at two diverse locations to determine if soybean response to SAR was affected by edaphic factors. In general, SAR had no effect on seed yield. In cases where yield was affected, there were more positive than negative effects. There was no consistent trend with respect to optimum vs sub-optimum soil conditions. Seed weight was affected by SAR for some lines but was not necessarily related to yield. In general, photosynthesis, transpiration, and stomatal frequency were not affected by SAR. Early stages of plant growth (leaf and stem weight) in the greenhouse was affected by SAR, but measurements taken on the same characteristics during later growth stages were not significant. These results indicate that soybean cultivars in general will not be detrimentally affected by acid rain based on the response of their ancestral lines and evaluations of selected cultivars derived from them.