Common Bermudagrass Research Articles

Ironstone and red mud barriers to reduce subsurface movement of soil phosphorus.

Loss of phosphorus in seepage may contribute to eutrophication of downstream water bodies. This study examined the potential use of pedogenic ironstone and untreated red mud (bauxite refining residue) as P sorbents in a permeable reactive barrier (PRB) to mitigate such loss. Effects of ironstone and red mud on P sorption (batch), transport (columns), saturated hydraulic conductivity (KS), and growth of common bermudagrass (Cynodon dactylon; greenhouse) were examined. Both materials had sorption maxima of ∼30mmol Pkg-1 or about five times that of a P-enriched sandy soil; however, sorption by red mud greatly increased with decreasing pH. Transport of P through columns of ironstone and red mud (diluted with nonreactive sand) was similar and slower compared to soil+sand. However, when red mud was mixed with soil, increased sorption at lower pH resulted in greater P retention compared to ironstone+soil (76%vs. 13%). Although addition of ironstone to soil up to 20% did not reduce KS, red mud at even 5% did. Soil amendment with red mud increased bermudagrass growth and P uptake. Given long-term neutralization of red mud in an acidic soil and increased P sorption, it may be suitable in a PRB if incorporated at a low rate and/or co-incorporated with a coarser material.

Genetic variability and QTL mapping of morphological traits and inflorescence prolificacy in African bermudagrass

AbstractAfrican bermudagrass (Cynodon transvaalensis Burtt‐Davy) (2n = 2x = 18) has unique morphological characteristics such as finer leaf blades and shorter internodes that are important to improving turf qualities (i.e., texture and density) as compared to other Cynodon species. It has been extensively used to cross with common bermudagrass (Cynodon dactylon Pers. var. dactylon) in developing high‐quality interspecific [C. dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy] F1 hybrid cultivars for turf use. However, the molecular basis of its morphological variation is unknown. Accordingly, the objectives of this study were to estimate the heritability and identify quantitative trait loci (QTL) associated with morphological and reproductive traits. A first‐generation self‐pollinated (S1) population of 109 individuals was evaluated for plant height (PH), leaf blade width (LBW) and leaf blade length, stem internode diameter and length, and inflorescence prolificacy (IP) in a replicated field trial over three seasons (2018–2020). The broad‐sense heritability estimates ranged from 0.31 (PH) to 0.80 (IP). Twenty‐four QTL were identified and nine of them were consistent ones. Fifteen candidate genes were found at a major and consistent QTL region associated with LBW. Frequent QTL colocations were found among morphological traits and between morphological traits and IP, partially explaining the significant correlation. The findings provide critical information and resources toward understanding the genetic basis associated with morphological and reproductive traits within C. transvaalensis and could contribute to marker‐assisted selection for breeding new turf‐type bermudagrass cultivars.

Evaluation of chemical control and seasonal application options for smutgrass (Sporobolus indicus)

AbstractSmutgrass is a non-native perennial weed that is problematic because of its poor palatability to cattle and its difficulty to control once established. Limited literature exists to explain the effectiveness of herbicides other than hexazinone for smutgrass control and forage injury. This study aimed to evaluate seasonal applications of labeled herbicides used on forage for maximum smutgrass control. The second objective was to evaluate preemergent herbicides and hexazinone for their ability to control smutgrass germinating from seed. Hexazinone, nicosulfuron + metsulfuron-methyl, and glyphosate + imazapic were the most effective postemergence treatments, while quinclorac exhibited little activity on smutgrass. Common bermudagrass forage fully recovered from all treatments by 3 mo after treatment. Hexazinone, nicosulfuron + metsulfuron methyl, glyphosate, and imazapic were applied postemergence to smutgrass in spring, summer, and fall. Summer applications of hexazinone resulted in the greatest level of control, while spring treatments provided the least control. Applications of hexazinone or glyphosate resulted in the most effective smutgrass control. However, fall applications resulted in the least forage injury. Results of the study of preemergence herbicides indicate that treatments with indaziflam and hexazinone provide adequate control of germinating smutgrass seedlings in the greenhouse at 0.25×, 0.5×, and 0.75× of the lowest recommended labeled rate for seedling grass control. Indaziflam treatments prevented the emergence of any visible smutgrass seedling tissue, compared to hexazinone, which fully controlled the germinating seedlings by 21 d after treatment, whereas pendimethalin significantly reduced seedling numbers at the 0.5× and 0.75× rates.

Differential Regulations of Antioxidant Metabolism and Cold-Responsive Genes in Three Bermudagrass Genotypes under Chilling and Freezing Stress.

As a typical warm-season grass, bermudagrass growth and turf quality begin to decrease when the environmental temperature drops below 20 °C. The current study investigated the differential responses of three bermudagrass genotypes to chilling stress (8/4 °C) for 15 days and then freezing stress (2/-2 °C) for 2 days. The three genotypes exhibited significant variation in chilling and freezing tolerance, and Chuannong-3, common bermudagrass 001, and Tifdwarf were ranked as cold-tolerant, -intermediate, and -sensitive genotypes based on evaluations of chlorophyll content, the photochemical efficiency of photosystem II, oxidative damage, and cell membrane stability, respectively. Chuannong-3 achieved better tolerance through enhancing the antioxidant defense system to stabilize cell membrane and reactive oxygen species homeostasis after being subjected to chilling and freezing stresses. Chuannong-3 also downregulated the ethylene signaling pathway by improving CdCTR1 expression and suppressing the transcript levels of CdEIN3-1 and CdEIN3-2; however, it upregulated the hydrogen sulfide signaling pathway via an increase in CdISCS expression under cold stress. In addition, the molecular basis of cold tolerance could be associated with the mediation of key genes in the heat shock pathway (CdHSFA-2b, CdHSBP-1, CdHSP22, and CdHSP40) and the CdOSMOTIN in Chuannong-3 because the accumulation of stress-defensive proteins, including heat shock proteins and osmotin, plays a positive role in osmoprotection, osmotic adjustment, or the repair of denatured proteins as molecular chaperones under cold stress. The current findings give an insight into the physiological and molecular mechanisms of cold tolerance in the new cultivar Chuannong-3, which provides valuable information for turfgrass breeders and practitioners.

CdWRKY2 transcription factor modulates salt oversensitivity in bermudagrass [Cynodon dactylon (L.) Pers.

Common bermudagrass [Cynodon dactylon (L.) Pers.] has higher utilization potential on saline soil due to its high yield potential and excellent stress tolerance. However, key functional genes have not been well studied partly due to its hard transformation. Here, bermudagrass "Wrangler" successfully overexpressing CdWRKY2 exhibited significantly enhanced salt and ABA sensitivity with severe inhibition of shoot and root growth compared to the transgenic negative line. The reduced auxin accumulation and higher ABA sensitivity of the lateral roots (LR) under salt stress were observed in CdWRKY2 overexpression Arabidopsis lines. IAA application could rescue or partially rescue the salt hypersensitivity of root growth inhibition in CdWRKY2-overexpressing Arabidopsis and bermudagrass, respectively. Subsequent experiments in Arabidopsis indicated that CdWRKY2 could directly bind to the promoter region of AtWRKY46 and downregulated its expression to further upregulate the expression of ABA and auxin pathway-related genes. Moreover, CdWRKY2 overexpression in mapk3 background Arabidopsis could partly rescue the salt-inhibited LR growth caused by CdWRKY2 overexpression. These results indicated that CdWRKY2 could negatively regulate LR growth under salt stress via the regulation of ABA signaling and auxin homeostasis, which partly rely on AtMAPK3 function. CdWRKY2 and its homologue genes could also be useful targets for genetic engineering of salinity-tolerance plants.

Genetic diversity and population structure of bermudagrass (Cynodon spp.) revealed by genotyping-by-sequencing.

Bermudagrass (Cynodon spp.) breeding and cultivar development is hampered by limited information regarding its genetic and phenotypic diversity. To explore diversity in bermudagrass, a total of 206 Cynodon accessions consisting of 193 common bermudagrass (C. dactylon var. dactylon) and 13 African bermudagrass (C. transvaalensis) accessions of worldwide origin were assembled for genetic characterization. Genotyping-by-sequencing (GBS) was employed for genetic marker development. With a minor allele frequency of 0.05 and a minimum call rate of 0.5, a total of 37,496 raw single nucleotide polymorphisms (SNPs) were called de novo and were used in the genetic diversity characterization. Population structure analysis using ADMIXTURE revealed four subpopulations in this germplasm panel, which was consistent with principal component analysis (PCA) and phylogenetic analysis results. The first three principal components explained 15.6%, 10.1%, and 3.8% of the variance in the germplasm panel, respectively. The first subpopulation consisted of C. dactylon accessions from various continents; the second subpopulation was comprised mainly of C. transvaalensis accessions; the third subpopulation contained C. dactylon accessions primarily of African origin; and the fourth subpopulation represented C. dactylon accessions obtained from the Oklahoma State University bermudagrass breeding program. Genetic diversity parameters including Nei's genetic distance, inbreeding coefficient, and Fst statistic revealed substantial genetic variation in the Cynodon accessions, demonstrating the potential of this germplasm panel for further genetic studies and cultivar development in breeding programs.

A bermudagrass variant exhibits strong tolerance to low temperature associated with enhanced sugar metabolism and cold‐responsive pathways

AbstractAs a warm‐season turfgrass, bermudagrass (Cynodon) is sensitive to low ambient temperature. The objectives of this study were to evaluate cold tolerance of a new variant Chuannong‐3 under field condition and to further elucidate metabolic and molecular bases of cold tolerance in the Chuannong‐3 as compared to triploid Tifdwarf (Cynodon transvaalensis × Cynodon dactylon) and tetraploid common bermudagrass 001 (C. dactylon). The Chuannong‐3 was identified as a triploid bermudagrass based on ploidy analysis. Chuannong‐3, Tifdwarf, or common bermudagrass 001 exhibited different tolerance to low temperature in field (Chuannong‐3 > common bermudagrass 001 > Tifdwarf). The Chuannong‐3 maintained significantly lower oxidative damage to cell membrane system, chlorophyll loss, and inhibition of photochemical efficiency as well as higher water‐soluble carbohydrate content than Tifdwarf or common bermudagrass 001 in winter of 2022 and 2021. Further study found that Chunanong‐3 exhibited the highest glucose, fructose, sucrose, raffinose content, raffinose synthase activity, and CdSPS1 expression as compared to Tifdwarf and common bermudagrass 001, which provided potential protection against chilling and freezing damages. Chilling and freezing stresses significantly up‐regulated ABA‐dependent (endogenous ABA level, CdABF1, CdDHN4, and CdLEA3) and ABA‐independent (CdWRKY2, CdCBF1, and CdCOR440) pathways in three bermudagrasses, but the most pronounced effects were detected in the Chuannong‐3. These findings indicated that Chuannong‐3 had better ability to acclimate to low temperature stress in relation to up‐regulation of sugar accumulation and metabolism, ABA signaling, and CBF‐COR pathway. This new variant Chuannong‐3 could be a valuable bermudagrass grown in temperate and transition zones.

131 Evaluating Supplementation Programs for Growing Calves Grazing Bermudagrass Pastures

Abstract Due to factors such as, high delivery costs, supplement availability, and labor; producers are interested in supplement delivery alternatives. Our objective was to determine gain in response to hand-fed (HF) or self-fed (SF) summer supplementation programs at the University of Arkansas Livestock and Forestry Research Station, on 20, 0.81-ha common bermudagrass pastures at a stocking rate of 5 growing calves per pasture (BW ± SD = 247 ± 24.6) over three years. This was a 2 x 2 + factorial arrangement of treatments, which included: Control (CON) – only free choice mineral; HF 1.13 kg/d by-product-based supplement offered only late summer (LS) or all summer (AS); SF tub supplement (PVM Cattle Tub, Positive Feed Ltd., Sealy, TX) either LS or AS. The HF supplement in year was a 50:50 blend of soybean hulls and corn gluten feed, in year 2 an extruded dried distillers grains cube (MasterHand Milling, Lexington NE) was used for HF, while in year 3 corn gluten feed was the HF supplement. Data were analyzed as a generalized randomized complete block design using the mixed procedure of SAS (SAS Inst. Inc., Cary, NC). Fixed effects in the model included supplementation treatment, year, and year by treatment interaction. Even though different HF supplements were used each year there was no year X treatment interactions (P ≥ 0.10); therefore, results are presented pooled across years. Early summer ADG was greater for HFAS (P < 0.01) than CON and SFAS, while supplemental efficiency (SE, kg added gain/kg supplement) in early summer was less (P = 0.05) SFAS than HFAS. Late summer ADG was greater for HF than SF and CON; while SE did not differ (P = 0.52) among treatments. Total supplement costs, in US dollars per steer for SF, were $67.50 when fed AS and $49.36 when fed in late summer only. Supplement costs for HF were much lower, $33.54 and $15.72/steer for AS and LS, respectively. Cost of added gain for SF was $28.33 and $16.14/kg for SFAS and SFLS, respectively. When providing supplement by HF, cost of added gain was $3.32 and $1.68/kg for HFAS and HFLS, respectively. With these results, we determined the most cost-effective way to add gain with supplement to growing calves grazing bermudagrass pasture is to hand-feed. When calves were HFAS, total supplement costs were higher, but considering the greater ADG, ending bodyweight, and supplemental efficiency ratio, HF supplements should provide a positive net return. Calves on this experiment did not respond as expected to the SF supplement, likely because the bermudagrass pastures in this experiment averaged over3% CP and were in excess of 10% even in the LS sampling periods.

18 Influence of Pregnant Cattle Grazing Endophyte-Infected Tall Fescue on Innate Immune Response of Male Offspring

Abstract The objective was to evaluate the influence of dams grazing endophyte-infected tall, toxic, fescue (E+) during gestation on innate immune response of male offspring to an endotoxin challenge. Crossbred pregnant multiparous cows (n = 36) bred to Red Angus sires were housed in replicated E+ or novel endophyte-infected, non-toxic, fescue (NE+) pastures before breeding and through the length of gestation. After parturition, cows and calves were moved to a common bermudagrass pasture until calves were weaned. From this calf-crop, a subset of post-weaned steers (E+ n = 8; NE+ n = 8) were selected for a lipopolysaccharide (LPS) challenge. Steers (302 ± 36 d of age; 261 ± 62 kg body weight) were fitted with jugular vein catheters >7 h before sampling. Blood was collected every 30 min starting 2 h before (Pre-LPS) and 9 h following (Post-LPS) LPS administration (0.5 µg/kg body weight). Sickness behavior score (SBS), cortisol, and glucose were analyzed every 30 min. Complete blood count (CBC) and rectal temperature (RT) were analyzed hourly. Peak concentration, time at peak concentration, baseline, return to baseline, and area under the curve (AUC) were evaluated for cortisol and glucose. Cortisol and glucose were determined by radioimmunoassay and hexokinase colorimetric assay, respectively. The CBC data were analyzed using a Hemavet hemocytology analyzer. Pre-LPS and Post-LPS cortisol, glucose, SBS, RT, and CBC were analyzed using the MIXED procedure of SAS specific for repeated measures with treatment, time, and the interaction as fixed effects and dam sire breed as a random effect. Peak concentration, time at peak concentration, baseline, return to baseline, and AUC for cortisol and glucose were analyzed using the MIXED procedure of SAS with treatment as a fixed effect and dam sire breed as a random effect. There was a Pre-LPS treatment by time interaction for RT (P < 0.05). Pre-LPS monocyte count was lower in offspring of dams grazing E+ relative to NE+ during gestation (P < 0.05). Pre-LPS hematocrit was increased in offspring of dams grazing E+ relative to NE+ during gestation (P < 0.05). There was a Pre-LPS effect of time on SBS (P < 0.05). As expected, Post-LPS cortisol, glucose, RT, WBC, neutrophil count, lymphocyte count, lymphocyte percentage, eosinophils count, eosinophils percentage, hematocrit percentage, RBC, and platelets changed over time in response to LPS (P < 0.05). Post-LPS lymphocyte count and monocyte percentage were decreased in offspring of dams grazing E+ relative to NE+ during gestation (P < 0.05). Post-LPS eosinophils count, eosinophil percentage, and hematocrit were increased in offspring of dams grazing E+ relative to NE+ during gestation (P < 0.05). There was a Post-LPS treatment by time interaction for monocyte count and neutrophil percentage (P < 0.05). Preliminary results suggest an altered innate immune response of male offspring of dams grazing toxic relative to novel fescue during gestation.

The extended day length promotes earlier flowering of bermudagrass.

Day length is a very critical environmental factor affecting plant growth and development. The extension of light application time has been shown to promote flowering in the long-day plant and to shorten breeding time in some crops. However, previous research on the regulation of bermudagrass flowering by light application time is scarce. Therefore, this study investigated the effect of day length on the growth and flowering of bermudagrass by prolonging the light application time in a controlled greenhouse. Three different light application times were set up in the experiment: 22/2 h (22 hours light/2 hours dark), 18/6 h (18 hours light/6 hours dark), 14/10 h (14 hours light/10 hours dark). Results showed that extending the light application time not only promoted the growth of bermudagrass (plant height, fresh weight, dry weight) but also its nutrient uptake (nitrogen (N) and phosphorous (P) content). In addition, daily light integrals were different when flowering under different light application times. Most importantly, under the 22/2 h condition, flowering time was successfully reduced to 44 days for common bermudagrass (Cynodon dactylon [L.] pers) genotype A12359 and 36 days for African bermudagrass (Cynodon transvaalensis Burtt-Davy) genotype ABD11. This study demonstrated a successful method of bermudagrass flowering earlier than usual time by manipulating light application time which may provide useful insights for bermudagrass breeding.

Genetic variability and QTL mapping of winter survivability and leaf firing in African bermudagrass

AbstractTurf‐type bermudagrass is susceptible to winterkill when grown in transition zone climates. Minimizing water use in turfgrass management is of societal significance. African bermudagrass (Cynodon transvaalensis Burtt‐Davy) has been extensively used to cross with common bermudagrass (C. dactylon Pers. var. dactylon) in the creation of F1 hybrid cultivars. Little information regarding the molecular basis of winter survivability and drought resistance in African bermudagrass is available. Accordingly, the objectives of this study were to quantify genetic variability and identify quantitative trait loci (QTL) associated with winter survivability traits (spring greenup, SG; spring greenup percent green cover, SGPGC; winterkill, WK), and leaf firing (LF) in African bermudagrass. A total of 109 first‐generation self‐pollinated (S1) progeny of ‘OKC1163’ were evaluated in a field trial in a randomized complete block design with three replications for four seasons. Significant genetic variation existed for all the traits examined, and the broad‐sense heritability estimates ranged from .36 to .54 for the winter survivability traits and .80 for LF. Ten QTL were identified for winter survivability traits and two for LF based on a preexisting high‐density linkage map, which was aligned, reoriented, and renamed as to a recently published reference genome. Seven of 12 QTL were consistently identified at least in 2 yr. The colocation of two QTL, one for winter survivability and another for LF, suggests the possibility of improving both traits together. Findings provide new insights to genetic control of winter survivability traits and LF and contribute genetic resources for marker‐assisted selection in turf‐type bermudagrass improvement.

Bermudagrass Establishment, Aesthetics, and Function in Response to the Microbial Inoculant Klebsiella variicola and Fertilizer Timing

The incorporation of biostimulants, including microbial inoculants, into turfgrass management programs has increased during the past decade as a result of the potential benefits of their use, including increased nutrient uptake, enhanced growth, and improved stress tolerance. However, minimal research has been conducted on warm-season grasses, and questions still exist regarding microbial inoculant application timing, frequency of inoculation, and need for supplemental nitrogen. Therefore, the objective of our research was to investigate the influence of nitrogen fertilizer and microbial inoculant application timings on the establishment of common bermudagrass [Cynodon dactylon (L.) Pers.] in the field and in a controlled environment. Treatments containing fertilizer had a consistently greater normalized difference vegetation index, turfgrass color, and turfgrass quality than treatments that contained only the Klebsiella variicola microbial inoculant (KV). Establishment of bermudagrass plots in response to treatments containing fertilizer had more than 90% cover at the conclusion of the study (8 weeks after seeding), whereas KV treatments and the untreated check never exceeded 70% cover. However, the greatest change in carbon efflux was often observed in the field in response to treatments that supplied KV 3 weeks after seeding. In the greenhouse, the greatest root and shoot weights were typically observed in response to treatments containing fertilizer, whereas KV-alone treatments resulted in root and shoot weights either similar to or less than the untreated check.

Comparative analysis reveals chromosome number reductions in the evolution of African bermudagrass (Cynodon transvaalensis Burtt-Davy).

African bermudagrass (Cynodon transvaalensis Burtt-Davy) (2n=2x=18) belongs to the genus Cynodon, tribe Cynodonteae, subfamily Chloridoideae in the grass family Poaceae. The species is frequently crossed with common bermudagrass (Cynodon dactylon Pers.) in developing high-quality hybrid turf cultivars. Molecular resources for C. transvaalensis are scarce; thus, its genomic evolution is unknown. Recently, a linkage map consisting of 1278 markers provided a powerful tool for African bermudagrass genomic research. The objective of this study was to investigate chromosome number reduction events that resulted in the nine haploid chromosomes in this species. Tag sequences of mapped single nucleotide polymorphism markers in C. transvaalensis were compared against genome sequences of Oropetium thomaeum (L.f.) Trin. (2n=2x=20), a genomic model in the Cynodonteae tribe. The comparative genomic analyses revealed broad collinearity between the genomes of these two species. The analyses further revealed that two major interchromosomal rearrangements of the paleochromosome ρ12 (ρ1-ρ12-ρ1 and ρ6-ρ12-ρ6) resulted in nine chromosomes in the genome of C. transvaalensis. The findings provide novel information regarding the formation of the initial diploid species in the Cynodon genus.

Changes in Soil Bacterial Community Structure in Bermudagrass Turf under Short-Term Traffic Stress

Bermudagrass (Cynodon dactylon (L.) Pers.) is an extensively utilized turf grass for football fields and golf courses. Traffic stress is one of the most important stresses affecting the life of turf, which leads to a decrease in turf quality and changes in the soil microbial community structure. The structural change in soil bacterial community is an important reference for turf growth, maintenance, and restoration. Tifgreen bermudagrass turf and Common bermudagrass turf were applied with traffic treatment by a traffic simulator with moderate intensity to explore soil bacterial community structural changes in turf under traffic stress. The environmental factors including turf quality indicators and soil properties were measured, and the association of the soil bacterial community diversity with the environment factors was analyzed. As a result, traffic treatments significantly changed the soil properties and bacterial community composition in two bermudagrass species at the phylum and genus level. Actinobacteria, Chloroflexi, and Verrucomicrobia showed significantly high abundance in turf soils under traffic stress. The soil bacterial ACE, Chaol, and Shannon indexes of two bermudagrass species under traffic stress were significantly lower than non-traffic stress. The bacterial community structure was highly correlated with some turf quality indicators and soil properties under traffic stress. Our results illustrate that compared to Common bermudagrass, Tifgreen bermudagrass had better turf quality under traffic stress and less changes in its bacterial community structure, perhaps Tifgreen bermudagrass is a better choice of grass for sports turf as opposed to Common bermudagrass.

Evaluation of South African common bermudagrass germplasm for shade tolerance

AbstractCommon bermudagrass (Cynodon dactylon L. Pers.) is a widely grown warm‐season turfgrass species characterized by a dense, deep‐rooted canopy and high levels of traffic tolerance. However, most cultivars have poor shade tolerance, which limits the use of these grasses in partly‐shaded areas. The identification of new sources of genetic resistance to shade will expand the germplasm pool available to breeders for developing improved bermudagrass cultivars. In this study, 24 common bermudagrass accessions recently introduced from South Africa were evaluated for their ability to persist under shade. Entries were established in a randomized complete block design with three replications at the Lake Wheeler Turfgrass Field Lab (Raleigh, NC) in the spring of 2019. Following full green‐up in summer 2020, entries were evaluated for performance under full sun, and then a 63% shade cloth was installed over the plots. Traits evaluated under shade included: turfgrass quality, turfgrass density, genetic color, ground coverage, turfgrass regrowth and the normalized difference vegetation index (NDVI). A turfgrass performance index (TPI) was calculated to identify the top performers across all traits. Under full sun, seven accessions had comparable performance with ‘Celebration’ and ‘TifTuf’ across traits. Under shade, ‘Stil03’, ‘Q 47620’, ‘TifGrand’, ‘WIN10F’, Celebration, and TifTuf exhibited the highest TPI. Accessions with superior shade tolerance identified in this study represent novel germplasm that can be used in future breeding efforts to improve shade tolerance in bermudagrass.

A High-Quality Haplotype-Resolved Genome of Common Bermudagrass (Cynodon dactylon L.) Provides Insights Into Polyploid Genome Stability and Prostrate Growth

Common bermudagrass (Cynodon dactylon L.) is an important perennial warm-season turfgrass species with great economic value. However, the reference genome is still deficient in C. dactylon, which severely impedes basic studies and breeding studies. In this study, a high-quality haplotype-resolved genome of C. dactylon cultivar Yangjiang was successfully assembled using a combination of multiple sequencing strategies. The assembled genome is approximately 1.01 Gb in size and is comprised of 36 pseudo chromosomes belonging to four haplotypes. In total, 76,879 protein-coding genes and 529,092 repeat sequences were annotated in the assembled genome. Evolution analysis indicated that C. dactylon underwent two rounds of whole-genome duplication events, whereas syntenic and transcriptome analysis revealed that global subgenome dominance was absent among the four haplotypes. Genome-wide gene family analyses further indicated that homologous recombination-regulating genes and tiller-angle-regulating genes all showed an adaptive evolution in C. dactylon, providing insights into genome-scale regulation of polyploid genome stability and prostrate growth. These results not only facilitate a better understanding of the complex genome composition and unique plant architectural characteristics of common bermudagrass, but also offer a valuable resource for comparative genome analyses of turfgrasses and other plant species.

Correlations among Soil, Leaf Morphology, and Physiological Factors with Wear Tolerance of Four Warm-season Turfgrass Species

Traffic resistance of turfgrasses is an essential indicator of urban recreational and sports turf quality (TQ). In our study, four turfgrass species were investigated for their wear resistance. A self-made traffic simulator was used to determine the wear resistance of the study turf area in a 2-year field trial (2019–20). The experimental plots were established using a randomized block design with three replicates. The morphological characteristics, soil physical properties, and physiological indices of the grasses were analyzed. Using the acquired quantitative data, we set the turf cover index (TCI), the turf quality index (TQI), and the shoot density index (SDI) as the wear tolerance index, and assessed the correlations among these morphological characteristics, soil physical properties, physiological indices, and wear tolerance. ‘Lanyin III’ zoysiagrass and ‘Tifgreen’ hybrid bermudagrass provided relatively greater wear tolerance, followed by ‘Qingdao’ zoysiagrass and common bermudagrass after 12 weeks of traffic exposure in 2019 and 2020. Traffic changes the soil physical properties and affects the physiological metabolism of turfgrasses. Leaf morphology characteristics and the mechanical strength of these grasses were related significantly to TCI, TQI, and SDI, and most physiological responses and soil properties correlated significantly with TCI and TQI. Our findings of the correlations among physiological responses, soil properties, leaf morphology, and wear tolerance will allow grass breeders to evaluate their breeding procedures more efficiently.

Adaptive Responses of Common and Hybrid Bermudagrasses to Shade Stress Associated With Changes in Morphology, Photosynthesis, and Secondary Metabolites.

Alteration of ploidy in one particular plant species often influences their environmental adaptation. Warm-season bermudagrass is widely used as forage, turfgrass, and ground-cover plant for ecological remediation, but exhibits low shade tolerance. Adaptive responses to shade stress between triploid hybrid bermudagrass cultivars [“Tifdwarf” (TD), “Tifsport” (TS), and “Tifway” (TW)] and tetraploid common bermudagrass cultivar “Chuanxi” (CX) were studied based on changes in phenotype, photosynthesis, and secondary metabolites in leaves and stems. Shade stress (250 luminance, 30 days) significantly decreased stem diameter and stem internode length, but did not affect the leaf width of four cultivars. Leaf length of CX, TD, or TW showed no change in response to shade stress, whereas shade stress significantly elongated the leaf length of TS. The CX and the TS exhibited significantly higher total chlorophyll (Chl), Chl a, carotenoid contents, photosynthetic parameters [PSII photochemical efficiency (Fv/Fm), transpiration rate, and stomatal conductance] in leaves than the TW and the TD under shade stress. The CX also showed a significantly higher performance index on absorption basis (PIABS) in leaf and net photosynthetic rate (Pn) in leaf and stem than the other three cultivars under shade stress. In addition, the TS maintained higher proantho cyanidims content than the TW and the TD after 30 days of shade stress. Current results showed that tetraploid CX exhibited significantly higher shade tolerance than triploid TD, TS, and TW mainly by maintaining higher effective photosynthetic leaf area, photosynthetic performance of PSI and PSII (Pn and Fv/Fm), and photosynthetic pigments as well as lower Chl a/b ratio for absorption, transformation, and efficient use of light energy under shade stress. For differential responses to shade stress among three triploid cultivars, an increase in leaf length and maintenance of higher Fv/Fm, gas exchange, water use efficiency, carotenoid, and proanthocyanidin contents in leaves could be better morphological and physiological adaptations of TS to shade than other hybrid cultivars (TD and TW).

The impact of commercially available microbial inoculants on bermudagrass establishment, aesthetics, and function

AbstractThe production and application of fertilizers are not only costly but can be harmful to the environment if misapplied; therefore, sustainability research has aimed to investigate alternatives to traditional nitrogen fertilizer applications. Biostimulants, including microbial inoculants, have been touted to enhance plant nutrition, growth, and stress tolerance, but research on warm‐season turfgrass is limited. Therefore, the objective of our research was to compare the establishment, quality, and function of bermudagrass (Cynodon spp.) in response to commercially available microbial inoculants (Klebsiella variicola, Gluconacetobacter diazotrophicus, and Azospirillum brasilense) in field and controlled environment experiments. Microbial inoculant applications in the field did not consistently increase the normalized vegetation difference index, turfgrass color, or turfgrass quality of hybrid bermudagrass [Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt Davy] compared with the nontreated check. However, although the difference was not always significant, inoculated hybrid bermudagrass often exhibited higher carbon efflux measurements than the nontreated check, but the results were inoculant‐specific. No microbial inoculant resulted in greater common bermudagrass [Cynodon dactylon (L.) Pers.] root or shoot production in the greenhouse. Perennial cropping systems such as turfgrass may create greater challenges for microbial inoculant use and performance because of the presence of endemic microbial populations that are already adapted to survive and proliferate in turfgrass environments. Consequently, future research should examine inoculation frequency, soil and plant persistence, and the use of microbial blends to determine best management practices leading to the greatest opportunity for colonization and subsequent turfgrass benefits.

Nitrogen requirements for deficit‐irrigated bermudagrass (Cynodon spp.) fairways in South Florida

AbstractSeveral new bermudagrass cultivars are available and commonly used on golf course fairways. However, little is known about their cultural requirements or how these cultivars perform under lower inputs regimes. A 2‐year study was conducted at University of Florida, Fort Lauderdale Research and Education Center, to assess performance of four hybrid bermudagrass [Cynodon dactylon L. Pers. X Cynodon transvaalensis (Burtt‐Davy)] cultivars (‘Latitude 36’, ‘Tifway 419’, ‘TifGrand’ and ‘TifTuf’), and 2 common bermudagrass (Cynodon dactylon L. Pers.) cultivars (‘Bimini’ and ‘Celebration’) irrigated at either 50% or 80% reference evapotranspiration (ETo) and fertilised at either 0, 146, 244, or 342 kg N ha−1 year−1. Plots were evaluated monthly for turfgrass quality, dark green colour index (DGCI), normalised difference vegetation index (NDVI), and Chlorophyll Index, and seasonally for N tissue content. Plots watered at 80% ETo enhanced bermudagrass quality compared to 50% ETo, DGCI and NDVI only in two months out of 24. Latitude 36 and Celebration were the top‐rated cultivars, and their quality was not affected by no N fertilisation. Conversely, TifGrand, TifTuf and Tifway that received no N fertilisation resulted in insufficient quality during the second year of the study. Insufficient quality may be linked to reduced N metabolization compared to the highest rated cultivars. Results show that new cultivars such as Latitude 36 and Bimini could be maintained at sufficient quality levels with reduced water and N inputs in South Florida.