Location: Crop Genetics and Breeding Research2018 Annual Report
1a. Objectives (from AD-416):
1. Improve the productivity, quality, and persistence of warm-season grasses grown for forages, bioenergy, and turf by enhancing germplasm to increase stress tolerance under a variety of environmental conditions and improving tools that will efficiently assess forage quality. 2. Develop improved production strategies that include warm-season grasses, legumes, and winter cover crops to meet life-cycle objectives for feedstock production and quality, carbon sequestration, and greenhouse gas emission reductions for the Southeast regional conditions.
1b. Approach (from AD-416):
Objective 1: Three bermudagrass populations with desirable traits for forage, good seed production, and synchronous pollination will be used in a system of recombinant recurrent selection to develop a uniform, highly productive seeded bermudagrass for forage and/or turf. Multiple cycles of selection and crossing will be done to create populations that will be tested in multiple replicates at different locations. In napiergrass, a similar approach will be developed to develop vegetatively propagated high yield, disease resistant genotypes for multiple location testing and eventual release. Also for napiergrass, sequence data generated from genomic DNA from the cultivar Merkeron will be used to mine single sequence repeat (SSRs) markers and match them with genotypic traits of interest as marker assisted selection. Similarly, SSR markers will be developed for salt tolerance in segregating populations of seashore paspalum. Near infrared spectroscopy (NIRS) will be developed as a tool to screen for forage and biomass quality from available genotypes with diverse cell wall characteristics. Non-grain sorghum germplasm from multiple sources will be evaluated in replicated trials in the field and greenhouse for susceptibility to anthracnose, root-knot nematodes, and fall armyworm. Selected lines will be used as parents to test hybrids for biotic stress and yield characteristics for eventual public release. Linkage maps will be developed for markers of biotic traits. Objective 2: Replicated tests will be performed to determine appropriate nitrogen-fixing winter legume cover crops (clovers and alfalfa) for use in forage bermudagrass (Tifton 85, Russell) to reduce fertilizer applications and improve forage quality. Similar tests will be conducted for efficient production of biomass from energy cane, napiergrass and biomass sorghum (rotated with traditional row crops). Winter cover crops (lupine, clover, others) will be tested against inorganic and unfertilized controls to determine efficient ways of reducing inorganic fertilizer use. These replicated tests will be conducted at multiple sites. Production systems will be tested to determine water and nutrient requirements for maximum biomass yields of napiergrass using a replicated split block design with three irrigation rates and six fertilizer treatments. In collaboration with other research units, greenhouse gas emission comparisons will be determined for the cropping systems of biomass crops as well as for forage bermudagrass cultivars compared to traditional row crops.
3. Progress Report:
This is a bridging project, which replaced 6048-21000-024-00D pending completion of research review. Progress toward developing the recurrent selection of seeded forage bermudagrass seed basically has stopped due to a combination of weather and the presence of a new invasion species bermudagrass stem maggot (BSM). Breeding will continue but now with greater emphasis on developing material with resistance or tolerance to the pest. For napiergrass marker work, we have proceeded with new collaborators (University of Florida). Major progress has been made in collaboration with the University of Georgia for markers associated with salt tolerance using a variation of pool-based genome-wide association mapping. Near-infrared spectroscopy (NIR) calibrations made from a diverse array of napiergrass genotypes have been completed and we will submit a manuscript this summer involving this work (ARS Lincoln, Nebraska and ARS Peoria, Illinois). Sources of resistance for anthracnose, root-knot nematodes, and fall armyworm resistance have been identified in sorghum and the material is now being used for further improvements. Our research on overseeding legumes into bermudagrass continues this year to combine with previous year’s results. We are continuing collaboration with the University of Georgia personnel for off-site field testing of alfalfa into bermudagrass cultivars. Napiergrass yield data under varying levels of fertilization and irrigation has been used to develop one manuscript (an economic assessment and comparison with other field practices to guide potential growers) and a second is being completed. Lupin and crimson clovers as winter covers to supply nitrogen to established napiergrass and energy cane plots at two locations work was completed. Results are being analyzed for publication and show that some nitrogen is being incorporated into the soil and used to supplement inorganic nitrogen. A manuscript is in preparation for our study on sorghum and cotton grown after a winter cover and blue lupin has out-yielded all other treatments in two separate field locations over four years. This information is being used for continuation of research with blue lupin as a cover. Greenhouse gas analysis of row crops versus forage has stopped due to lack of essential personnel dedicated to running the lab analysis. The results of two years of data will be analyzed to determine appropriateness for publication.
1. New techniques in evaluating bermudagrass susceptibility to the new bermudagrass stem maggot. Bermudagrass is an important perennial grass forage for livestock in southern United States. The bermudagrass stem maggot (BSM) is a new insect pest that has caused extensive damage in grazing and hay fields throughout the South. ARS researchers at Tifton, Georgia, showed that cultivars with coarse leaves and stems are less susceptible to damage by the BSM and should be employed in integrated pest management (IPM) strategies wherever these cultivars are adapted. Results of this study will be used to determine new bermudagrass genotypes to replace current cultivars and will help breeders determine parents for further cultivar improvements.
2. Determined that the sugarcane aphid that is spreading in the U.S. on sorghum is primarily one clone. ARS researchers at Tifton, Georgia, used high throughput sequencing on DNA from the sugarcane aphid and 1.44 Gb of nucleotides were generated. Simple sequence repeat markers were identified, and samples were genotyped from 17 locations across 7 states and one U.S. territory. Genotyping revealed that all samples were one biotype with the exception of a single sample collected from Sinton, Texas which has the predominant biotype as well as another biotype. Thus the invasive sugarcane aphid is spreading in the U.S. as primarily one asexual clone. This information is important as plant resistance as well as insecticide efficacy can be biotype specific.
Knoll, J.E., Anderson, W.F., Harris-Shultz, K.R., Ni, X. 2018. The environment strongly affects estimates of heterosis in hybrid sweet sorghum. Sugar Tech. 20(3):261-274.
Harris-Shultz, K.R., Ni, X., Wadl, P.A., Wang, X., Wang, H., Huang, F., Flanders, K., Seiter, N., Kerns, D., Meagher Jr, R.L., Xue, Q., Reisig, D., Buntin, D., Cuevas, H.E., Brewer, M., Yang, X. 2017. Microsatellite markers reveal a predominant sugarcane aphid (Homoptera: Aphididae) clone is found on sorghum in seven states and one territory of the USA. Crop Science. 57:2064-2072.
Li, Y., Harris-Shultz, K.R., Wang, H., Wadl, P.A., Ji, P. 2017. Population structure and genetic diversity of Phytophthora nicotianae from tobacco in Georgia. Plant Disease. 101:1113-1118.
Uchimiya, M., Knoll, J.E., Anderson, W.F., Harris-Shultz, K.R. 2017. Chemical analysis of fermentable sugars and secondary products in 23 sweet sorghum cultivars. Journal of Agricultural and Food Chemistry. 65:7629-7637.
Uchimiya, S., Knoll, J.E., Harris-Shultz, K.R. 2017. Electrochemical evaluation of sweet sorghum fermentable sugar bioenergy feedstock. ACS Sustainable Chemistry & Engineering. (5):7352-7364.