Location: Water Management and Conservation Research
2024 Annual Report
Objectives
Turfgrass is an important element of many urban and rural landscapes with positive impacts on the physical environment, economy, and quality of life for millions. However, the prevalence of drought, heat, and soil salinity in the desert U.S. Southwest are limiting factors for wide-spread utilization of turfgrasses. Therefore, the objectives of this project are:
Obj. 1: Develop drought and heat tolerant turfgrass germplasm for use in hot and arid climates.
1A: Assemble and characterize different turfgrass species germplasm.
1B: Generate additional genetic variability through intra- and inter-specific hybridization of turfgrass species and characterize for resilience to environmental stresses.
1C: Employ high throughput phenotyping using proximal sensing as a quantifiable measure of turfgrass quality and stress tolerance.
1D: Determine genetic mechanisms and metabolites underlying environmental stress tolerance and enhanced turf quality.
Obj. 2: Expand opportunities for environmentally sustainable utilization of turfgrass in arid environments.
2A: Evaluate the impact of management practices on greenhouse gas fluxes, carbon dynamics, and transpiration cooling for warm-season grasses in the desert.
2B: Define the effect of different management practices, water chemistry, and environmental conditions on water use on warm season turfgrasses.
2C: Investigate factors contributing to reduced turfgrass quality and restoration solutions within complex turfgrass systems.
Approach
1. Develop drought and heat tolerant turfgrass germplasm for use in hot and arid climates.
1A: Diverse germplasm of warm season turfgrass species will be assembled and evaluated in small plot in Maricopa, AZ to enhance for environmental stress tolerance and aesthetic value. Three levels of irrigation (80, 60 and 40% of estimated evapotranspiration (ET) replacement) will be examined. The field experiments will be complemented with studies in the controlled environments such as greenhouses or growth chambers.
1B: To generate additional variability and potential hybrids, hybridization will be conducted among different genotypes of bermudagrass and zoysiagrass. In bermudagrass, the tetraploids and hexaploids will be pollinated with the diploid to generate interspecific hybrids. Different species of zoysiagrass will be intercrossed.
1C: To enhances the identification of stress tolerant high quality turfgrass, a high throughput phenotyping (HTP) will be collected using ground-based and unmanned aerial vehicle equipped with proximal sensors. Plant performance for color, quality, and environmental stress tolerance will be assessed via a bi-weekly HTP and visual turfgrass assessment scale.
1D: Genomic analyses will focus on understanding and characterizing genetic mechanisms association with abiotic stress tolerance in turfgrasses using genome-wide association studies, transcriptomics, and metabolomics to identify genomic regions, candidate genes, gene expression networks, and metabolites underlying stress tolerance in turfgrasses.
2. Expand opportunities for environmentally sustainable utilization of turfgrass in arid environments.
2A: Turfgrass ecosystem services including carbon sequestration, effects on microclimate, and urban habitat will be assessed at different management scenarios in Maricopa and in urban Phoenix. Data on turf quality using a visual ranking and imaging, greenhouse gas flux (CO2, N2O, and CH4), soil volumetric water content, and electrical conductivity (EC) will be collected and analyzed. Carbon sequestration for different management scenarios will be quantified from seasonal soil samples.
2B: To educate the stakeholders on turfgrass water requirements, use of impaired water sources, management considerations under reduced irrigation, and management under shade will be conducted in greenhouse utilizing lysimeters. Separately, growth, quality, and water use will be characterized under different water quality irrigation, mowing heights, fertility regimes, and shade. ET will be determined gravimetrically by calculating the mean mass change of the 100% ETa lysimeters every 2-3 days.
2C: Study on heterogeneity and identify factors contributing to reduced turfgrass quality of complex turfgrass systems including irrigation coverage, photosynthetically active radiation variability, and soil characteristics will be conducted utilizing different water sources. Data on normalized difference vegetation index, irrigation audit, and multiple root and soil parameters impacting turfgrass performance and quality will be assessed.
Progress Report
This report is for this new project which began February 2024, and continues research from 2020-13210-001-000D, "Increasing the Utility of Turf in Urban Environments of the Southwest U.S." Please see the report for 2020-13210-001-000D for more information.
In support of Sub-objective 1A, more than 100 saltgrass (Distichlis spicata) accessions were assembled in collaboration with United States Golf Association (USGA) and the USDA-Germplasm Resource Information Network (USDA-GRIN), 78 accessions were established in the field for characterization and deficit irrigation turf characteristics. In addition, 24 seashore paspalum (Paspalum vaginatum) were obtained from GRIN for a salinity and drought stress tolerance study.
In support of Sub-objective 1B, 18 half-sib zoysiagrass were generated through intra- and inter-specific hybridization of four zoysiagrass species that will be evaluated in controlled and field environments. To hybridize bermudagrass, 36 tetraploids genotypes, as seed parent, and 12 diploid bermudagrass, as pollen parents, were planted in a half-diallel crossing block in the field. Because of the heat stress, pollen viability is limited and seed set was not observed the first season.
In support of Sub-objective 1C, to employ high throughput phenotyping using proximal sensing and RGB-imaging as a quantifiable measure of turfgrass quality and stress tolerance, active spectral reflectance and RGB-image data are being collected and are being analyzed.
For Sub-objective 1D, RNA-Seq was conducted for chilling tolerance in bermudagrass. Transcriptome data analysis has been delayed waiting for the release of hybrid bermudagrass genome sequence.
To address Sub-objective 2A, turfgrass field plots were established in Maricopa, Arizona, for which four bermudagrass varieties were planted in three replications and two separate irrigation treatments. Data capture methods included RBG-image collection and canopy temperatures, which have been thoroughly tested along with methods established.
For Sub-objective 2B, a study with two separate experimental runs were conducted to evaluate the impact of canopy heights on a hybrid bermudagrass, evapotranspiration, and response to deficit irrigation. An experiment is currently being established to evaluate the impact of fertilizer rate on a hybrid bermudagrass’ response to deficit irrigation.
Supporting Sub-objective 2C, boundary layer maps and sampling locations have been established for the first site along with soil samples collected and initial quality data. An initial irrigation audit has been performed along with new seed establishment.
Accomplishments
1. Turf bermudagrass hybrids show differential response to drought stress. Harnessing natural genetic variation is commonly used to enhance resilience to drought stress. A total of 48 bermudagrass hybrids, including two commercial cultivars (Tifway and TifTuf), were evaluated for drought tolerance, water use efficiency, and recovery after prolonged drought using dry down experiment in the greenhouse. Plants were subjected to acute water stress for four weeks and then rewatered. Turf area cover, color, quality, and normalized difference vegetation index (NDVI) calculated from active spectral reflectance were used to assess the health and vigor of the hybrids during progression of the drought stress and through recovery. Analysis of the data identified highly drought tolerant with full recovery after re-watering, moderately tolerant, and susceptible hybrids to prolonged drought stress without recovery. These results show a prevalence of genetic diversity for drought tolerance that could prove instrumental in the identification of bermudagrass cultivars resilient to drought stress and improved water use efficiency.
2. Quantification of ecosystem services provided by turfgrass in arid environments. The recording of relevant ecosystem services of turfgrasses in arid environments is an important step in maintaining sustainable turfgrass systems. Turfgrass field plots consisting of four different turf-type bermudagrasses were planted in Maricopa, Arizona and will be maintained under high management or low management scenarios. Preliminary results show differences in turfgrass quality, reflectance, uniformity, and winter color retention.
Review Publications
Ramalingam, A.P., Rathinagiri, A., Serba, D.D., Madasamy, P., Muthurajan, R., Prasad, P.V., Perumal, R. 2024. Drought tolerance and grain yield performance of genetically diverse pearl millet [Pennisetum glaucum (L.) R. Br.] seed and restorer parental lines. Crop Science. https://doi.org/10.1002/csc2.21271.
Serba, D.D., Fang, T., Wu, Y. 2024. Directional breeding generates distinct genetic diversity in hybrid turf bermudagrass as probed with simple sequence repeat SSR markers. HortScience. 59(4):453-461. https://doi.org/10.21273/HORTSCI17525-23.
Hejl, R.W., Conley, M.M., Serba, D.D., Williams, C.F. 2024. Mowing height effects on 'TifTuf' bermudagrass during deficit irrigation. Agronomy. 14(3). Article 628. https://doi.org/10.3390/agronomy14030628.
Hejl, R.W., Williams, C.F., Monaco, T.A., Serba, D.D., Conley, M.M. 2023. Hybrid bermudagrass responses to impaired water sources. HortScience. 58(8):907-914. https://doi.org/10.21273/HORTSCI17206-23.
Serba, D.D., Wu, Y., Hejl, R.W., Williams, C.F., Bronson, K. 2023. Spectral reflectance estimated genetic variation in hybrid turf bermudagrass. Grass Research. 3. Article 22. https://doi.org/10.48130/GR-2023-0022.
Hejl, R.W., Stiles, J.F., Baltrusaitis, J., Williams, C.F., Eisa, M., Ragauskaite, D., Serba, D.D. 2024. Urea cocrystals as a potential fertilizer for turfgrass: Responses of 'Tifway’ hybrid bermudagrass and nitrogen release behavior. HortTechnology. 34(4):474-480. https://doi.org/10.21273/HORTTECH05423-24.