Population structure of Msi was driven by patterns of warming since the LGM, and secondarily by geographical barriers. This study will facilitate germplasm conservation, association analyses and identification of potential heterotic groups for the improvement of Miscanthus as a bioenergy crop.

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To breed improved biomass cultivars of Miscanthus ×giganteus, it will be necessary to select the highest‐yielding and best‐adapted genotypes of its parental species, Miscanthus sinensis and Miscanthus sacchariflorus. We phenotyped a diverse clonally propagated panel of 569 M. sinensis and nine natural diploid M. ×giganteus at one subtropical (Zhuji, China) and five temperate locations (Sapporo, Japan; Leamington, Ontario, Canada; Fort Collins, CO; Urbana, IL; and Chuncheon, Korea) for dry biomass yield and 14 yield‐component traits, in trials grown for 3 years. Notably, dry biomass yield of four Miscanthus accessions exceeded 80 Mg/ha in Zhuji, China, approaching the highest observed for any land plant. Additionally, six M. sinensis in Sapporo, Japan and one in Leamington, Canada also yielded more than the triploid M. ×giganteus ‘1993‐1780’ control, with values exceeding 20 Mg/ha. Diploid M. ×giganteus was the best‐yielding group at the northern sites. Genotype‐by‐environment interactions were modest among the five northern trial sites but large between Zhuji, and the northern sites. M. sinensis accessions typically yielded best at trial sites with latitudes similar to collection sites, although broad adaptation was observed for accessions from southern Japan. Genotypic heritabilities for third year yields ranged from 0.71 to 0.88 within locations. Compressed circumference was the best predictor of yield. These results establish a baseline of data for initiating selection to improve biomass yield of M. sinensis and M. ×giganteus in a diverse set of relevant geographies.

Diversions of water from irrigated agriculture are occurring in the western United States to address increasing municipal and industrial demands. Deficit irrigation of alfalfa (Medicago sativa L.) could be a source of water without complete dry‐up of irrigated fields. Water saving potential from alfalfa is high because it is a high water‐use crop produced on 12% of the irrigated land in the United States. The objectives of this paper are to review alfalfa plant–water relations in the Great Plains and Intermountain West, to understand potential water savings through deficit irrigation, and to indentify management practices that maximize water‐use efficiency (WUE). Alfalfa biomass yield exhibits a linear relationship to evapotranspiration (ET) with the slope of a regionally aggregated water production function of 0.16 Mg ha−1 cm−1 Relative ET declines 30% faster than relative biomass yield under deficit irrigation or dryland management. Because early season harvests have greater WUE, combining full irrigation in spring with no irrigation during less efficient water‐use growth periods may be more effective in saving water than season‐long deficit irrigation. Management practices that can influence WUE under deficit irrigation include stand age, growth stage at harvest, and alfalfa variety. A potential complication with controlled deficit irrigation of alfalfa is an uncertain contribution to ET from a water table. As alfalfa roots develop over time, a significant percentage of total ET can come from water tables shallower than 200 cm and the percentage increases as availability of water from precipitation or irrigation declines.

To improve the efficiency of breeding of Miscanthus for biomass yield, there is a need to develop genomics‐assisted selection for this long‐lived perennial crop by relating genotype to phenotype and breeding value across a broad range of environments. We present the first genome‐wide association (GWA) and genomic prediction study of Miscanthus that utilizes multilocation phenotypic data. A panel of 568 Miscanthus sinensis accessions was genotyped with 46,177 single nucleotide polymorphisms (SNPs) and evaluated at one subtropical and five temperate locations over 3 years for biomass yield and 14 yield‐component traits. GWA and genomic prediction were performed separately for different years of data in order to assess reproducibility. The analyses were also performed for individual field trial locations, as well as combined phenotypic data across groups of locations. GWA analyses identified 27 significant SNPs for yield, and a total of 504 associations across 298 unique SNPs across all traits, sites, and years. For yield, the greatest number of significant SNPs was identified by combining phenotypic data across all six locations. For some of the other yield‐component traits, greater numbers of significant SNPs were obtained from single site data, although the number of significant SNPs varied greatly from site to site. Candidate genes were identified. Accounting for population structure, genomic prediction accuracies for biomass yield ranged from 0.31 to 0.35 across five northern sites and from 0.13 to 0.18 for the subtropical location, depending on the estimation method. Genomic prediction accuracies of all traits were similar for single‐location and multilocation data, suggesting that genomic selection will be useful for breeding broadly adapted M. sinensis as well as M. sinensis optimized for specific climates. All of our data, including DNA sequences flanking each SNP, are publicly available. By facilitating genomic selection in M. sinensis and Miscanthus × giganteus, our results will accelerate the breeding of these species for biomass in diverse environments.

A 5 year study was conducted during 1988-1992 to quantify the effects of grazing date and frequency on total organic reserves of prairie sandreed [Calamovilfa ZongifoZia (Hook.) Scribn.] and sand bluestem (Andropogon haZZii Hack.). Treatments consisted of mid-month grazing periods in

Simulated &pasture short duration grazing systems were studied in 1985-86 to determine the effect of grazing schedule and stocking rate on defoliation patterns of individual grass tillers of big bluestem (Andropogon gerardii Vitmm) and little biuestem (ScI&rchyrium scopdwn (Michx.) Nash). Treatments consisted of 3 grazing schedules (2,3, or 4 rotation cycles per 152-day grazing season) and 2 stocking rates (1.3 and 1.8 times the recommended normal). Grazing schedule and stocking rate did not affect the percent tiller height reduction per grazing period except for the combination of 2-cycle grazing and heavy stockbrg which increased percent height reduction. Percent tiller height reduction per grazing period decreased over the grazing season for the 3 and 4-cycle grazing schedules. Grazing schedule and stocking rate had little effect on the height at which tillers were defoliated. Increasing the number of grazing periods reduced the percentage of tillers defoliated per grazing period but increased the cumulative defoliation frequency over the grazing season. Grazing schedule did not affect the percentage of tillers ungrazed over the entire grazing season. Big bluestem was consistently defoltated more intensely and frequently than little bluestem.

parents are needed to avoid excessive inbreeding (Busbice, 1970). It is important to know if forage yields of alfalfa (Medicago sativa Difficulties associated with distinguishing genetically L.) cultivars could be improved by using a subset of genetically diverse diverse individuals have forced most breeders to include parents selected from a larger population of parents for a synthetic larger numbers of parents in their synthetic cultivars to cultivar. We used restriction fragment length polymorphisms to assess minimize inbreeding and conserve genetic variability the level of genetic diversity among 93 alfalfa genotypes previously selected as parents for a potential commercial synthetic cultivar. On for other traits. Over half of the cultivars released bethe basis of average pairwise genetic distances between genotypes, tween 1973 and 1982 were synthesized from more than four synthetic populations (samples) were developed with 2, 4, 8, 12, 40 parental genotypes (Hill et al., 1988). The large 16, or 24 parents selected for genetic dissimilarity (DIS) or similarity amount of genetic variability for forage yield observed (SIM). Resulting synthetic populations were evaluated for forage yield within most alfalfa cultivars suggests that a subset of in replicated field trials at three locations for 2 yr. Forage yields of the original parents could be intermated to produce a populations with low numbers of parents were highly variable among higher yielding synthetic cultivar (Hill and Elgin, 1981). samples, and as number of parents increased, genetic diversity levels In previous studies, we used molecular markers to and yield variation decreased. No significant difference (P Ͼ 0.05) estimate the genetic distance of pairs of alfalfa genowas detected between forage yields of DIS and SIM groups averaged types and the heterozygosity of their single-cross progeover parent number and samples; however, yield variation among nies (Kidwell et al., 1994a,b). These studies included samples within parent number of DIS and SIM groups was highly significant (P Ͻ 0.0001). The SIM group had more sample variation four diploid genotypes with a range of genetic diversity than did the DIS group, and more SIM than DIS populations were and their isogenic tetraploids derived by chromosome among the lower yielding populations. The lack of significant differdoubling. We found that for the tetraploid genotypes ences between the forage yields of DIS and SIM populations may be the genetic distance and heterozygosity estimates had due to linkage equilibrium in the population used for selecting parents significant, positive correlations with each other and and the inability to target heterozygosity to specific genome regions with forage yields of the single-cross progenies. The affecting yield. results suggest that molecular markers may be useful for identifying pairs of genetically diverse parents for producing highly heterozygous and high yielding, single