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Restoration of native plant communities requires adapted germplasm; thus, information is needed to guide native seed collection and production. Analysis of genetic variation has potential to provide insight into diversity and relatedness of natural populations. Our objectives were to examine genetic diversity of native species in Minnesota to discover if variation is related to biomes or distance, and possibly to develop seed collection zones. Our study included prairie cordgrass (Spartina pectinata), purple prairie clover (Dalea purpurea), and spotted joe-pye weed (Eupatorium maculatum). Using amplified fragment length polymorphisms, we analyzed 100 samples from eight populations for prairie cordgrass, 152 samples from nine populations for purple prairie clover, and 127 samples from 10 populations for spotted joe-pye weed. We found moderate to high levels of genetic diversity within each species. Small populations were not necessarily lower in diversity than larger ones. Analysis of molecular variance results indicate clear population differentiation. However, rather than displaying geographic or ecological associations, the variation had discontinuous patterns. Therefore, we were not able to develop unambiguous recommendations for seed collection. We discuss the applicability of molecular markers in detecting adaptive potential.

The effects of alfalfa, red clover, and perennial ryegrass as cover crops on soybean cyst nematode (SCN) and soybean and corn yields were evaluated in Waseca, Lamberton, and Rosemount, MN. The cover crops were interseeded in soybean at 0 or 2 wks after planting soybean in 2002 and killed with herbicide before planting corn in 2003. As expected, SCN-susceptible soybean supported higher SCN population density than SCN-resistant soybean. Reduction of SCN population density by red clover (up to 40%) and alfalfa (up to 55%) was observed in some sampling occasions at Lamberton and Rosemount, probably due to reduced soybean growth, but the effect was inconsistent. No significant reduction of SCN population by the two crops was detected at Waseca. While perennial ryegrass did not affect SCN population density in most cases, up to 46% higher egg population densities were observed in the perennial ryegrass treatment as compared to the control at Waseca. SCN-resistant soybean produced higher yield than susceptible soybean at all sites. While alfalfa reduced soybean yield at Lamberton (up to 50%) and Rosemount (up to 11%), red clover and perennial ryegrass reduced soybean yield only at Lamberton (up to 38%) and Waseca (up to 34%), respectively. No difference in corn yield was observed at Waseca. At Lamberton, alfalfa and red dover planted at the time of planting soybean reduced corn yield in the following year 17 and 13%, respectively, and perennial ryegrass planted 2 wks after planting soybean reduced corn yield 13%. At Rosemount, significant reduction of corn yield was observed with red clover (15-21%) interseeded in SCN-snsceptible soybean and with alfalfa (12%) and red clover (12%) interseeded in SCN-resistant soybean at the time of planting soybean. The results suggest that an even later planting date of cover crops in soybean may reduce yield loss due to competition and make these cover crops more appropriate for use in the soybean-corn rotation in Minnesota.

Symbiotic [N.sup.2] fixation capacity may affect productivity of the perennial legume Illinois bundleflower [Desmanthus illinoensis (Michx.) MacMill. ex B.L. Rob. & Fernald]. Our objective was to estimate [N.sub.2] fixation of three Illinois bundleflower accessions managed for forage. Herbage yield ranged from 1.02 Mg [ha.sup.-1] to 3.69 Mg [ha.sub.-1] in Year 1, and 2.99 Mg [ha.sup.-1] to 8.27 Mg [ha.sup.-1] in Year 2. Accessions differed in herbage yield, aboveground N yield, and [N.sub.2] fixed at certain locations in Year 1, but not in Year 2. Percentage of N derived from the atmosphere (%Ndfa) varied with location but not with accession in either year. The [sup.15]N natural abundance method gave lower estimates of %Ndfa than the [sup.15]N enrichment method. In yr 1, [N.sub.2] fixation ranged from 0 to 30 kg [ha.sup.-1] N ([sup.15]N natural abundance method), 11 to 43 kg [ha.sup.-1] ([sup.15]N enrichment method), and 0 to 50 kg [ha.sup.-1] N (total N difference method), and in Year 2 these estimates at two locations were 60 to 67 kg [ha.sup.-1] N, 79 to 127 kg [ha.sup.-1] N, and 67 to 142 kg [ha.sup.-1] N, respectively. Differences in [N.sub.2] fixation among locations could have been due to rhizobial strains. At the high-yielding location with the greatest [N.sub.2] fixation, over one-half of the nodules were occupied by indigenous rhizobial strains, whereas at other locations, strains from commercial inoculaut accounted for most nodules. Symbiotic [N.sub.2] fixation by Illinois bundleflower could be enhanced by new rhizobial inoculums., ILLINOIS BUNDLEFLOWER, an herbaceous perennial legume (subfamily Mimosoideae) native to the central USA (Luckow, 1993), may fulfill the need for a persistent, high-quality forage legume to complement warm-season grasses. DeHaan [...]

Kentucky bluegrass (Poa pratensis L.) floral induction requires a lengthy, uninterrupted period of cold temperature with a short photoperiod. Our objective was to develop an efficient artificial vernalization procedure to facilitate breeding experiments. The stage of plant development and length of vernalization period necessary for floral induction was determined for six cultivars: Abbey, Aspen, Midnight, Park, Rugby, and Trenton. Plants were exposed progressively to three temperature and light-controlled environments: (i) seedlings were grown in a 12-h photo- and thermal period with a 20 [degrees] C day/14 [degrees] C night temperature regime and high irradiance of 30 W [m.sup.-2] from germination until 3, 5, 9, or 13 wk after emergence (approx. 8, 26, 145, and 198 leaf stage, respectively); (ii) plants were then vernalized for an 8-h photoperiod at 5 [degrees] C constant temperature and low irradiance of 7 [W.sup.-2] for 4, 8, or 12 wks; and (iii) plants were transferred to particle development conditions of 18-h photoperiod and 12-h thermal period with a 18 [degrees] C day/15 [degrees] C night temperature regime and high irradiance of 30 [W.sup.-2] for 16 wk. No panicles were observed on plants with the 4-wk vernalization treatment. For all cultivars except Midnight, the 9-wk plant development and 12-wk vernalization treatment resulted in floral induction of all plants. The same four cultivars responded to this treatment with a mean panicle number greater than five panicles per plant and the time from seedling emergence to 75% of the panicles emerged was approximately 28 wk. This study has demonstrated that an artificial vernalization procedure could be developed that would make reproductive material of Kentucky bluegrass available throughout the year independent of season or climate.

The effects of alfalfa, red clover, and perennial ryegrass as cover crops on soybean cyst nematode (SCN) and soybean and corn yields were evaluated in Waseca, Lamberton, and Rosemount, MN. The cover crops were interseeded in soybean at 0 or 2 wks after planting soybean in 2002 and killed with herbicide before planting corn in 2003. As expected, SCN-susceptible soybean supported higher SCN population density than SCN-resistant soybean. Reduction of SCN population density by red clover (up to 40%) and alfalfa (up to 55%) was observed in some sampling occasions at Lamberton and Rosemount, probably due to reduced soybean growth, but the effect was inconsistent. No significant reduction of SCN population by the two crops was detected at Waseca. While perennial ryegrass did not affect SCN population density in most cases, up to 46% higher egg population densities were observed in the perennial ryegrass treatment as compared to the control at Waseca. SCN-resistant soybean produced higher yield than susceptible soybean at all sites. While alfalfa reduced soybean yield at Lamberton (up to 50%) and Rosemount (up to 11%), red clover and perennial ryegrass reduced soybean yield only at Lamberton (up to 38%) and Waseca (up to 34%), respectively. No difference in corn yield was observed at Waseca. At Lamberton, alfalfa and red clover planted at the time of planting soybean reduced corn yield in the following year 17 and 13%, respectively, and perennial ryegrass planted 2 wks after planting soybean reduced corn yield 13%. At Rosemount, significant reduction of corn yield was observed with red clover (15–21%) interseeded in SCN-susceptible soybean and with alfalfa (12%) and red clover (12%) interseeded in SCN-resistant soybean at the time of planting soybean. The results suggest that an even later planting date of cover crops in soybean may reduce yield loss due to competition and make these cover crops more appropriate for use in the soybean-corn rotation in Minnesota. [ABSTRACT FROM AUTHOR]

Symbiotic N2 fixation capacity may affect productivity of the perennial legume Illinois bundleflower [Desmanthus illinoensis (Michx.) MacMill. ex B.L. Rob. & Fernald]. Our objective was to estimate N2 fixation of three Illinois bundleflower accessions managed for forage. Herbage yield ranged from 1.02 Mg ha-1 to 3.69 Mg ha-1 in Year 1, and 2.99 Mg ha-1 to 8.27 Mg ha-1 in Year 2. Accessions differed in herbage yield, aboveground N yield, and N2 fixed at certain locations in Year 1, but not in Year 2. Percentage of N derived from the atmosphere (%Ndfa) varied with location but not with accession in either year. The 15N natural abundance method gave lower estimates of %Ndfa than the 15N enrichment method. In yr 1, N2 fixation ranged from 0 to 30 kg ha-1 N (51N natural abundance method), 11 to 43 kg ha-1 (15N enrichment method), and 0 to 50 kg ha-1 N (total N difference method), and in Year 2 these estimates at two locations were 60 to 67 kg ha-1 N, 79 to 127 kg ha-1 N, and 67 to 142 kg ha-1 N, respectively. Differences in N2 fixation among locations could have been due to rhizobial strains. At the high-yielding location with the greatest N2 fixation, over one-half of the nodules were occupied by indigenous rhizobial strains, whereas at other locations, strains from commercial inoculant accounted for most nodules. Symbiotic N2 fixation by Illinois bundleflower could be enhanced by new rhizobial inoculums. [ABSTRACT FROM AUTHOR]