Bermudagrass is the most important warm-season pasture in the Southern USA with exceptional forage production potential and abiotic stress tolerance. However, it requires high nitrogen (N) supply to reach its full biomass and quality potential. Our objectives were to: (1) develop a nitrogen use efficiency (NUE) screening protocol for bermudagrass in controlled or semi-controlled conditions, (2) identify contrasting genotypes for NUE from natural variants and, (3) develop a knowledge base of NUE in bermudagrass. A collection consisting 290 Cynodon sp. genotypes was first pre-screened in the greenhouse. Thirty-nine genotypes with high NUE, five with low NUE were selected for further evaluations along with 5 checks in greenhouse and hoophouse under four N rates. Biomass, crude protein and N content were evaluated. N uptake efficiency (NUpE), N utilization efficiency (NUtE) and NUE were calculated based on biomass production. Genotypes showed significant influences (P \ 0.0001) in all of the response variables. The genotype 9 N rate interaction was not significant for NUE in both environments. NUE had strong correlation with biomass production and NUpE, which got stronger as N rates increased. In N limiting conditions, bermudagrass showed a trade-off between biomass maintenance and crude protein content. Lower N applications increased biomass production over crude protein. However, when N is abundant the crop has the ability to improve crude protein. Several genotypes presented high NUE due their high NUtE and NUpE. Genotypes with contrasting NUE were selected and subjected to further field evaluation. Superior genotypes for NUE will be used in the breeding program to enhance NUE in bermudagrass.

Wheat is a major cool-season forage crop in the southern United States. The objective of this study is to understand the effect of nitrogen (N) fertilization on wheat biomass yield, quality, nitrogen use efficiency (NUE), and nitrogen nutrition index (NNI). The experiments were conducted in a greenhouse and a hoop house in a split-plot design, with three replications. Twenty wheat cultivars/lines were evaluated at four N rates (0, 75, 150, and 300 mg N.kg−1 soil) in the greenhouse and (0, 50, 100, and 200 mg N.kg−1 soil) in the hoop house. In general, high-NUE lines had lower crude protein content than the low-NUE lines. None of the cultivars/lines reached a plateau for biomass production or crude protein at the highest N rate. The line × N rate interaction for NUE was not significant in the greenhouse (p = 0.854) but was highly significant in the hoop house (p < 0.001). NNI had a negative correlation with NUE and biomass. NUE had strong positive correlations with shoot biomass and total biomass but low to moderate correlations with root biomass. NUE also had a strong positive correlation with N uptake efficiency. Lines with high NUE can be used in breeding programs to enhance NUE in wheat for forage use.

Paspalum notatum is an important forage grass contributing significantly to the coverage of the natural fields of Southern Brazil. Simple sequence repeat (SSR) markers were used to evaluate the genetic similarity of strains within a P. notatum collection. Genomic DNA was extracted in bulk from young leaves of five plants from each accession obtained from the USDA. In the molecular analysis, the eight SSR markers evaluated formed seven distinct groups, and two isolated genotypes, with an average similarity index of 0.29, ranging from zero to 0.83. All the loci were polymorphic and the polymorphism information content ranging from 0.41 to 0.69. The results evidenced a low genetic similarity, which can be explored via parental selection in a breeding program.

Selection of improved genotypes is important for pasture-based feeding systems in subtropical regions. Our goal was to identify hybrids of Paspalum with enhanced forage yield and cold tolerance across 2 sites [Bagé and Eldorado do Sul (ES)], in Rio Grande do Sul, Brazil. We evaluated 19 P. plicatulum × P. guenoarum hybrids, P. plicatulum genotype 4PT, P. guenoarum cultivars Azulão and Baio and, as Control, Megathyrsus maximus cv. Aruana. At both sites, the experimental design was a completely randomized block with 4 replications. Total dry mass (total-DM), leaf-DM and cold tolerance (ColdT) were recorded. At Bagé, hybrid 102069 produced higher total-DM and leaf-DM than the progenitors and cv. Aruana, while at ES, hybrids 102069 and 10308 produced higher total-DM than 4PT, Azulão and Aruana; hybrid 102069 had higher leaf-DM. At Bagé, 16 hybrids displayed ColdT similar to their progenitors and higher than Aruana, while at ES, 12 hybrids showed ColdT similar to Azulão and Baio and higher than 4PT and Aruana. This study demonstrated that hybrids of Paspalum with superior forage yield to their progenitors and Aruana, and hybrids with higher ColdT than 4PT and Aruana are in existence. The hybridization technique shows potential for producing alternative genotypes with higher forage yield and ColdT for sowing in subtropical regions.