Improving drought resistance in Zoysiagrass (Zoysia spp.) is a target for both private and public breeding programs. The performance of 26 elite experimental zoysiagrasses was compared under progressive drought stress with Palisades, Diamond, and Zeon. Environmental conditions were warmer and drier in 2020 (66 days) than 2021 (45 days). Irrigation was applied once weekly using potential evapotranspiration (ETo) rates and crop coefficients (Kc) of 0.6 (non-stress), or 0.40, 0.30, and 0.25 deficit treatments. Turfgrass quality, leaf wilt, normalized difference vegetative index, normalized difference red edge, and volumetric water content were recorded weekly. Genotypes with the highest means (statistical "a" group) contributed to a turfgrass performance index (TPI). Elite zoysiagrass with TPI >= Palisades (19) were Zoysia japonica Steud. ecotypes DALZ 1311 (22), 1601 (19), and 1603 (21), and finer textured interspecific hybrids, DALZ 1701 (18), 1713 (26), 1714 (18), and 1801 (24). Relative to an irrigation schedule using a 0.6 Kc, these genotypes survived extreme deficit irrigation, which conserved 40.1% (45,859.6 L) and 66.4% (44, 592.2 L) of water in 2020 and 2021, respectively. Overall, this study demonstrated that significant water consumption could be reduced with proper cultivar selection and deficit-based irrigation management while maintaining an acceptable turfgrass quality under drought conditions. Genetic variation exists in zoysiagrass for quality, leaf wilt, and green cover under soil drying conditions. Some Zoysia japonica ecotypes and hybrids exhibited high quality and low leaf wilt equal to or better than Palisades. Afternoon leaf wilt predicted turfgrass quality in zoysiagrass under water-deficit conditions. Within 3 weeks of resuming irrigation, most zoysiagrasses recovered to acceptable quality.

‘DALZ 1701’ (Reg no. CV‐292, PI 702798) is a third‐generation hybrid resulting from mating interspecific hybrid ‘TAES 5723‐47’ with Zoysia japonica (Steud.) ‘ Meyer’. In the 2019 National Evaluation Turfgrass Program, which ran from 2019 to 2022 in 15 locations, DALZ 1701 was put to the test. In 9 of 13 locations, DALZ 1701 established more quickly than Meyer, similarly to Emerald and Zeon but slower than Empire. DALZ 1701's turfgrass quality was generally better than Meyer's and on par with that of Emerald, Empire, and Zeon. Compared with Meyer, DALZ 1701 displays a dark green genetic color. In Dallas, TX, DALZ 1701 maintained its quality under drought stress more effectively than Meyer and similarly to Emerald, Empire, and Zeon; however, it had more wilt avoidance than Emerald and Zeon. Like Meyer and Innovation, DALZ 1701 showed freezing tolerance but had improved fall color retention. DALZ 1701 appeared to have greater tolerance than Meyer to large patch ( Rhizoctonia solani Kühn), spring yellowing [take‐all patch ( Gaeumannomyces graminis (Sacc.) von Arx & D. Olivier)], hunting billbug ( Sphenophorus venatus vestitus Chittenden), and zoysiagrass mite ( Eriophyes zoysiae Baker, Kono, and O'Neill) damage. Additionally, DALZ 1701 has shown quality comparable to Diamond and Palisades but superior to Meyer under moderate shade in Dallas, TX. In the transition zone and southern portions of the United States, where zoysiagrass is widely grown, DALZ 1701 is adaptable to a variety of conditions.

'DALSA 1618' (Reg. no. CV-291, PI 702594) is a first-generation intraspecific St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] hybrid developed by Texas A & M AgriLife Research in Dallas, TX, from a cross between a drought-resistant polyploid female parent, TAES 5384 (PI 300130, GRIN National Plant Germplasm System), and a semi-dwarf shade-tolerant diploid pollen donor, 'Amerishade'. DALSA 1618 was formerly tested as 'TAES 5896-09' and 'TXSA-156'. Superior performance and quality from 2010 to 2015 in space-plant nurseries across multiple environments led to advancing DALSA 1618 to replicated trials in 10 National Turfgrass Evaluation Program (NTEP) locations across the southcentral and southeastern United States. DALSA 1618 was one of the top performers in the 2016 NTEP (2016-2020). It established faster than 'CitraBlue' and similarly to other tested commercial cultivars. DALSA 1618 exhibited high turfgrass quality in standard and ancillary trials and earlier spring greenup, which was generally better than 'Floratam'. Drought resistance of DALSA 1618 was similar to Floratam (a drought-resistant aneuploid). Tolerance to moderately dense shade was tested in Dallas, TX, from 2017 to 2020, where DALSA 1618 exhibited improved shade tolerance relative to Floratam. This array of environmental testing indicates DALSA 1618 possesses a unique combination of drought and shade tolerance that would allow its use across the southcentral and southeastern United States.

A 10-yr, four-phase collaborative effort among three universities was conducted to develop new hybrid zoysiagrasses (Zoysia spp. Willd.) with improved turf quality, winter hardiness, and pest resistance in comparison to commercial zoysiagrass cultivars, especially 'Meyer' (Z. japonica Steud.). In Phase 1, breeding efforts produced 2,858 new progeny that were evaluated for 2 yr across three sites. In Phase 2, only 60 (2%) of 2,858 progeny were selected for advancement to 10 replicated multiyear field trials (Phase 3). Phase 3 revealed 10 promising progeny (assigned DALZ numbers) that required further intensive field and laboratory testing in Phase 4. Phase 4 revealed differences in establishment rate, and DALZ 1701, 1702, 1707, and 1810 had moderate-to-good turf performance across seven sites, whereas DALZ 1808 had similar or slightly lower performance. Meyer consistently performed poorly, and 'Innovation', a recently released hybrid cultivar, had poor-to-moderate performance in comparison to the experimental genotypes, which illustrates the improvements achieved in zoysiagrass breeding in the last 10 yr. Freeze tolerance (LT50, lethal temperature killing 50% of the plants) ranged from -9.8 degrees C (Diamond) to -14.1 degrees C (DALZ 1812) with a mean of -12.5 degrees C. Evidence of large patch [Rhizoctonia solani Kuhn, anastomosis Group (AG) 2-2 LP] in the top 10 DALZ genotypes was 15 to 40% lower than Meyer on several dates. Results indicate that there are multiple genotypes for potential release in the future with improved turf color, winter hardiness, freeze tolerance, large patch resistance, and finer leaf texture suitable for USDA plant hardiness zones ranging between 5b and 8a.

Thirty fine-textured inter- and intra-specific zoysiagrass ( Zoysia spp.) hybrids and eight Z. pacifica (Goudsw.) M. Hotta & S. Kuroki genotypes were tested in comparison to Z. matrella (L.) Merr. cultivars, ‘Diamond’ and ‘L1F’, for their performance under low-input golf course putting green management practices from 2014 to 2018 in Dallas, TX. Turfgrass quality, shoot density, genetic color, fall color, spring greenup, and winter survival were visually rated on a 1 to 9 scale (9 = high quality, dark green, very dense, and complete greenup). Seedheads were rated in spring, summer, and fall as a percentage of plot cover. Thirteen elite hybrids from seven different pedigrees were selected, and ball roll distance was measured 8 times between 15 August and 14 September in 2017. Clear statistical differences were not observed among pedigrees for most traits except seedhead production under the low-input management conditions. However, strong genotype differences were evident. The results suggest under-utilized species could be exploited by plant breeders to use as parental lines and develop hybrids with desirable traits such as finer leaf texture, low seedhead production, fall color retention and early spring green up. One Z. minima (Colenso) Zotov × Z. matrella hybrid and one ( Z. minima × Z. matrella ) × Z. japonica Steud. hybrid have been advanced to the 2019 National Warm-Season Putting Green Trial conducted by the National Turfgrass Evaluation Progra (NTEP) for multi-location and multi-year performance testing.

Breeding turfgrasses using classical plant breeding methods is a long-term process which requires a breeder to sort through large segregating populations by phenotypically evaluating the plants across multiple environments and over several years. The quality and frequency of phenotypic data collection at a field-scale is currently the bottleneck limiting the efficiency and accuracy of classical phenotype-based breeding. The use of unmanned aerial vehicle (UAV) remote sensing has proven to be viable method to collect geospatial data rapidly and at fine spatial and high temporal scales in major agricultural crops. In this study, UAV remote sensing and machine learning algorithms were utlilzed to evaluate drought stress on zoysiagrass (Zoysia spp.) breeding nursery planted in 2017. Selections of the top 2% best-performing hybrids under drought stress were made using visual parameters (turfgrass quality under normal and drydown conditions) as well as UAV-derived NDVI (normalized difference vegetation index). The results suggest an agreement between the conventional selection methods and proposed UAV phenotyping approaches.

Shadetolerance is an important factor for cultivar selection in urban areas. Diploid (2n = 2x = 18) cultivars of St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] with moderate to high shade tolerance have been popular choices for residential and commercial landscapes in the southern United States. This study evaluated 26 elite drought resistant diploid and interploid (polyploid x diploid) hybrids and four commercial cultivars under 75% continuous shade from 20 June 2017 through 30 Oct. 2018. Biweekly data were collected during the growing season for percent green cover, visual turfgrass quality, canopy color, shoot density, and daily leaf elongation rates (DER; mm d(-1)). Spring greenup was rated annually, and to gray leaf spot incidence was rated when naturally occurring. All genotypes lost green cover through 2017, and greenup was delayed transitioning into the summer of 2018 when most diploids struggled to recover from disease, shade, and winter injury whereas, on an average, interploid hybrids reached up to 84.0% green cover. Daily leaf elongation rates were lower for diploids than polyploids in both years. Turfgrass quality, color, and density generally declined under shade as expected. Overall, three interploid hybrids (DALSA 1329, 1404, and 1406) were the top performers demonstrating good retention of turfgrass performance traits and reduced DER under shade.

St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] is a popular shade-tolerant turfgrass but has a higher water use rate compared with other warm-season turfgrasses. In an effort to improve drought resistance in St. Augustinegrass, the Texas A&M turfgrass breeding program has used embryo rescue technology and developed interploid (polyploid x diploid) hybrids to facilitate the combination of desirable traits from across ploidy levels. In this study, we determined the drought response and minimal water requirements of eight diploid and 18 interploid hybrids compared with 'Floratam', 'Palmetto', 'Raleigh', and 'TamStar' during similar to 90 d of dry-down under a rainout shelter in 2015 and 2016. Digital images of percentage green cover were taken weekly and entries with green cover <= 50 +/- 1% were supplied with 2.54 cm of water. Genotypic differences were observed, but overall, interploids demonstrated better drought response than diploids, as indicated by longer days to reach 50% green cover and a turfgrass quality of 5.0. Nine interploid hybrids, including TamStar, did not require any water to maintain above 50% green cover in both years as compared with Floratam, Raleigh, and Palmetto. Our results also show that minimum turfgrass quality of 5.0 was not maintained at the 50% green cover threshold and that 75-80% green cover more accurately represents the minimum quality for future drought evaluations in our geographic conditions.

'DALZ 1308' (Reg. no. CV-285, PI 691612) is a first-generation interspecific hybrid developed in 2004 by crossing a genotype of Zoysia minima (Colenso) Zotov and Z. matrella (L.) Merr. 'Diamond.' After field evaluations in Dallas, TX (2004-2009) and Gainesville, FL (2006-2008), DALZ 1308 was selected for advancement to the 2013 Warm-season Putting Greens National Turfgrass Evaluation Program (NTEP). DALZ 1308 was evaluated at 10 NTEP locations (2013-2018) as well as in Dallas, TX (2014-2017) and Gainesville, FL (2013-2017). DALZ 1308 exhibited a diminutive growth habit with narrower and shorter leaf blades and dwarf canopy height as compared to Diamond and L1F; shorter internode length, smaller node, and smaller internode diameter as compared to L1F; superior ball roll as compared to Diamond and L1F in Arizona, Kentucky, and Texas; resistance to tawny mole crickets; and reduced seedhead incidence and density during the growing season. As compared to Diamond and L1F, DALZ 1308 has shown to have reduced winter injury with fabric cover in Bloomington, IN. Although characteristics varied by location, DALZ 1308 exhibits good turfgrass quality, high shoot density, medium-green genetic color, and extended fall and winter color retention. Initial greenhouse experimentation under moderate shade shows that DALZ 1308 has a greater percent green cover as compared to 'Palisades', Diamond, and 'Zorro'. Overall, DALZ , 1308 is an ultradwarf zoysiagrass suitable for golf course putting greens in a wide range of environments across the United States.

The objective of this study was to test the freezing tolerance of a medium‐fine textured ecotype (DALZ 1301) of zoysiagrass (Zoysia spp.) and six fine‐textured interspecific hybrids (DALZ 1304–1309) derived from crosses between Z. minima (Colenso) Zoltov. or Z. pauciflora (Mez.) and Z. matrella (L.) Merr. after cold acclimation under field (FE‐1 and FE‐2) and controlled‐environment conditions (GC‐1 and GC‐2) in 2014 and 2015. Following acclimation, samples were subjected to six freezing treatments (–3, –5, –7, –9, –11, and –13°C) for 1 h, thawed, and placed under optimum greenhouse conditions for recovery. Greenup was visually rated on a 1 to 9 scale (1 = brown; 9 = completely green; 5 = acceptable) at 5 wk. Lethal temperatures (LT50) for each genotype were determined by nonlinear regression. Mean LT50 for field‐acclimated samples ranged from –5.5°C (DALZ 1307) to –9.3°C (Meyer). Mean LT50 for controlled‐acclimation samples ranged from –1.6°C (DALZ 1304) to –9.9°C (Meyer) in GC‐1 and from –4.8°C (DALZ 1304) to –9.4°C (Meyer) for GC‐2. The LT50 of DALZ 1301 and Meyer were statistically similar, but interspecific hybrids were less freeze tolerant than Meyer. Results suggest a limited potential of Z. minima, Z. pauciflora, and Z. matrella lines to impart freezing tolerance. Additionally, high correlations (R2 = 0.718–0.767) of lethal temperatures with field and controlled acclimation experiments, suggest controlled‐environment acclimation is suitable for testing freezing tolerance in zoysia.

St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] is a popular warm‐season turfgrass in Gulf Coast regions of the United States. Diploid St. Augustinegrass produces fertile seed, but triploids and higher polyploids are mostly sterile. Polyploid St. Augustinegrass cultivars have been selected for their resistance to southern chinch bugs, St. Augustine Decline, and drought tolerance but lack the cold hardiness and shade tolerance of diploids. However, because of sterility barriers, the polyploid germplasm had not been fully used as breeding material until 2009 when we reported the development of interploid hybrids using embryo rescue technology. The objective of the present study was to backcross these first‐generation interploid hybrids with diploid males to produce second‐generation hybrids. Sterility barriers were found to be much greater with second‐generation crosses yielding only 0.00 to 2.69% progeny per interploid hybrid. Using this technique, the embryos are generally rescued 3 wk postpollination, thereby causing a heavy demand on one's time to process spikelets before embryos abort. Our preliminary findings show the use of cold storage at 7°C to potentially extend the processing period up to 2 mo with a slight drop off in efficiency (4.37–6.03% crossability). Our results also show the potential of first‐generation hybrids to exhibit superior performance under drought when compared with diploid cultivars Palmetto and Raleigh. Tested second‐generation interploids did not exhibit superior performance in drought. Nonetheless, our results emphasize the utility of embryo rescue technology in facilitating gene exchange between ploidy levels to generate hybrids with superior performance.

KSUZ 0802 (Reg. No. CV‐282, PI 678793) is a fine‐textured, cold‐tolerant zoysiagrass (Zoysia spp.) hybrid co‐developed and jointly released by Texas A&M AgriLife Research, Dallas, TX, and the Kansas Agricultural Experiment Station, Manhattan, KS. KSUZ 0802 is an F1 interspecific hybrid developed in 2001 from a cross between Zoysia matrella (L). Merr. ‘Cavalier’ and an ecotype of Z. japonica Steud. named Anderson 1, a derivative of ‘Chinese Common’. After years of testing (2004 –2008) for turf quality and winter survival at Manhattan, KS, KSUZ 0802 was advanced to a nine location test (2009 –2012) in the transition zone (Wichita and Manhattan, KS, Columbia, MO, Fletcher and Jackson Springs, NC, Stillwater, OK, Knoxville, TN, Virginia Beach and Blacksburg, VA, and Dallas, TX. The freezing tolerance, spring green‐up, and fall color retention of KSUZ 0802 is equivalent to ‘Meyer’, but KSUZ 0802 has a finer leaf texture. KSUZ 0802 is also superior to Meyer for turf quality and resistance to bluegrass billbug damage. KSUZ 0802 is well suited for use on golf course fairways and tees, home lawns, and other recreational areas in the transition zone.

Interspecific hybridization between Poa arachnifera Torr. (Texas bluegrass) and Poa pratensis L. (Kentucky bluegrass) has shown to be a proven method for the development of turf-type hybrid bluegrass cultivars for the southern United States. Unlike in P.pratensis, the use of DNA markers for molecular characterization and flow cytometry to determine nuclear DNA contents has not been extensively utilized in P.arachnifera. In this study, 2C nuclear DNA content of 19 different genotypes of P.arachnifera (both males and females) was determined to range from 8.02 to 13.24pg/2C using flow cytometry. The DNA content of the hybrids between P.arachnifera and P.pratensis from two different pedigrees was found to be intermediate between their parents. Furthermore, the utility of the trx (thioredoxin-like) nuclear gene in the identification of interspecific hybrids between P.arachnifera and P.pratensis was demonstrated using sequence and phylogenetic analyses. A newly discovered 851-bp trx allele may serve as a useful marker to differentiate P.arachnifera from P.pratensis and provide insights into the evolutionary origin of P.arachnifera.

Interspecific hybrids between texas bluegrass ( Poa arachnifera Torr.) and kentucky bluegrass ( Poa pratensis L.) are known to exhibit good heat tolerance, which has aided in their adaptation to the warmer climates of the southern United States, but their tolerance to shade has not been investigated. The objectives of this study were to 1) evaluate the growth responses of interspecific bluegrass hybrids ( P. arachnifera × P. pratensis ) in comparison with kentucky bluegrasses and a shade-tolerant cultivar of tall fescue ( Festuca arundinacea Schreb.) under full sunlight and shaded environments, 2) identify optimum times to evaluate shade tolerance using the selected growth measurements, 3) calculate the minimum daily light requirements to retain acceptable turfgrass quality, and 4) determine if trinexapac-ethyl (TE) applications enhance hybrid bluegrass quality under shade. Two 10-week greenhouse experiments (late spring and early fall) were conducted in Dallas, TX. Within each of three light environments a randomized complete block design was used to accommodate three replications of eight genotypes treated with and without TE (0 or 0.228 kg·ha −1 a.i.). Turfgrass quality, leaf elongation rates, clipping dry weights, and percent green cover were measured. Meaningful comparisons were best during the late spring when daily light integrals (DLI) were optimum for healthy plant growth. Shade-tolerant hybrid bluegrasses (DALBG 1201 and TAES 5654) were identified using turfgrass quality and leaf elongation rates. These genotypes exhibited above-acceptable turfgrass quality in all environments, and a reduced leaf elongation rate similar to the tested dwarf-type tall fescue. DLI requirements of DALBG 1201 and TAES 5654 were ≤4 to achieve acceptable quality. TE applications generally did not improve turfgrass quality of genotypes, although leaf elongation rates were significantly reduced in all environments.

DALBG 1201 (Reg. No. CV-101, PI 671854) is a turf-type interspecific F-1 hybrid derived from a cross between Texas bluegrass (Poa arachnifera Torr.) 20-11 (3-88) (PI 655088) as the female parent and a Kentucky bluegrass (P. pratensis L.) ecotype, CS#4, as the pollen parent. DALBG 1201 was evaluated under the designation 01-59-5 and TAES 5653. A total of 47 experimental hybrid bluegrass lines and three commercial checks, 'Rebel Exeda' tall fescue (Festuca arundinacea Schreb.) and 'Reveille' and 'Thermal Blue Blaze' hybrid bluegrass (P. arachnifera x P. pratensis) were evaluated at five locations (Auburn, AL, Starkville, MS, Raleigh, NC, Knoxville, TN, and Dallas, TX) from 2009 to 2012. DALBG 1201 was characterized by its superior turfgrass quality, darker green color, and higher shoot density than Reveille and Thermal Blue Blaze. Its leaf texture was finer than Rebel Exeda and similar to the hybrid bluegrass checks. Linear regression analysis for turfgrass quality indicated that DALBG 1201 was more stress tolerant compared with the three commercial checks and was highly stable across varying environmental conditions. Its superior performance over a wide range of southern test locations suggests that DALBG 1201 cool-season turf-type hybrid bluegrass is well-suited for use on lawns, landscapes, and other recreational sites across the southern United States.

To identify and develop drought tolerant maize (Zea mays L.), high-throughput and cost-effective screening methods are needed. In dicot crops, measuring survival and recovery of seedlings has been successful in predicting drought tolerance but has not been reported in C4 grasses such as maize. Seedlings of sixty-two diverse maize inbred lines and their hybrid testcross progeny were evaluated for germination, survival and recovery after a series of drought cycles. Genotypic differences among inbred lines and hybrid testcrosses were best explained approximately 13 and 18 days after planting, respectively. Genotypic effects were significant and explained over 6% of experimental variance. Specifically three inbred lines had significant survival, and 14 hybrids had significant recovery. However, no significant correlation was observed between hybrids and inbreds (R-2 = 0.03), indicating seedling stress response is more useful as a secondary screening parameter in hybrids than in inbred lines per se. Field yield data under full and limited irrigation indicated that seedling drought mechanisms were independent of drought responses at flowering in this study.

Drought stress is thought to promote epicuticular wax accumulation on maize leaves, which reduces plant water loss. We evaluated 62 maize inbred lines and their hybrid testcross progeny for epicuticular wax accumulation on flag leaves at flowering under full and limited irrigation regimes. Extracted wax was measured as a percentage of wax weight to leaf weight (WLW) and leaf area (WLA). Eleven genotypes had above average WLW as both inbred lines and hybrid testcrosses. Thirteen genotypes had above average WLA as either inbred lines or hybrid testcrosses. The drought treatment did not significantly alter WLW or WLA. Heritability of WLW was 0.17 (inbred lines) and 0.58 (hybrid testcrosses). Heritability of WLA was 0.41 (inbred lines) and 0.59 (hybrid testcrosses), suggesting it is a better trait than WLW for epicuticular wax screening. Correlations (r) between inbred lines and their testcross progeny were 0.44 and 0.18, for WLW and WLA, respectively. Heritability of grain weight per ear and plot yield was highest in hybrid testcrosses, with no correlation between inbred and hybrid germplasm. It is not warranted to evaluate epicuticular wax accumulation as the sole drought tolerance mechanism. However, it may be a good secondary trait to observe in relation to grain yield production in hybrids tested under water-limiting conditions.

Kentucky bluegrass (Poa pratensis L.) and tall fescue (Festuca arundinacea Schreb.) are commonly grown cool-season grasses in the United States for home lawns and various sports turf applications. However, environmental conditions such as prolonged periods of drought and heat as well as heavy shade often result in a loss of visual appeal, early dormancy, or death of the turf stand. Hybrid bluegrass (Poa spp.) cultivars derived from Texas bluegrass (P. arachnifera Torr.) x Kentucky bluegrass interspecific crosses may serve as viable alternatives for perennial turfgrass in the southern United States. Methods to aid in the breeding and selection of Texas x Kentucky bluegrasses for these environmental conditions would be useful. The goals of this research were to 1) develop new interspecific hybrid bluegrasses and optimize a seed germination technique, 2) use flow cytometry and molecular markers for the characterization of hybrid progeny, and 3) evaluate the growth response and performance of hybrid bluegrasses maintained in shade. In 2012 and 2013, controlled pollinations were made between different Poa species. Seed from these crosses were germinated through two different techniques that resulted in 61 new interspecific hybrids. A higher percentage of individuals (89%) were recovered through germination on nutrient agar medium than soil. In addition to these hybrids, 52 Texas x Kentucky hybrids created in 2001 were tested for three years in multiple locations across the southern states and the transition zone. Experimental hybrid TAES 5653, registered as DALBG 1201, was the superior genotype.