Comprehensive transcriptional analysis reveals salt stress-regulated key pathways, hub genes and time-specific responsive gene categories in common bermudagrass (Cynodon dactylon (L.) Pers.) roots

Background Despite its good salt-tolerance level, key genes and pathways involved with temporal salt response of common bermudagrass (Cynodon dactylon (L.) Pers.) have not been explored. Therefore, in this study, to understand the underlying regulatory mechanism following the different period of salt exposure, a comprehensive transcriptome analysis of the bermudagrass roots was conducted. Results The transcripts regulated after 1 h, 6 h, or 24 h of hydroponic exposure to 200 mM NaCl in the roots of bermudagrass were investigated. Dataset series analysis revealed 16 distinct temporal salt-responsive expression profiles. Enrichment analysis identified potentially important salt responsive genes belonging to specific categories, such as hormonal metabolism, secondary metabolism, misc., cell wall, transcription factors and genes encoded a series of transporters. Weighted gene co-expression network analysis (WGCNA) revealed that lavenderblush2 and brown4 modules were significantly positively correlated with the proline content and peroxidase activity and hub genes within these two modules were further determined. Besides, after 1 h of salt treatment, genes belonging to categories such as signalling receptor kinase, transcription factors, tetrapyrrole synthesis and lipid metabolism were immediately and exclusively up-enriched compared to the subsequent time points, which indicated fast-acting and immediate physiological responses. Genes involved in secondary metabolite biosynthesis such as simple phenols, glucosinolates, isoflavones and tocopherol biosynthesis were exclusively up-regulated after 24 h of salt treatment, suggesting a slightly slower reaction of metabolic adjustment. Conclusion Here, we revealed salt-responsive genes belonging to categories that were commonly or differentially expressed in short-term salt stress, suggesting possible adaptive salt response mechanisms in roots. Also, the distinctive salt-response pathways and potential salt-tolerant hub genes investigated can provide useful future references to explore the molecular mechanisms of bermudagrass.

Comprehensive transcriptional analysis reveals salt stress-regulated key pathways, hub genes and time-specific response categories in common bermudagrass (Cynodon dactylon (L.) Pers.) roots

Background: Despite its good salt-tolerance level, key genes and pathways that are involved with temporal salt response of common bermudagrass (Cynodon dactylon (L.) Pers.) have not been explored. Therefore, in this study, to understand the underlying regulatory mechanism following the different period of salt exposure, a comprehensive transcriptome analysis of the bermudagrass roots was conducted.Results: The transcripts regulated after 1 h, 6 h, or 24 h of hydroponic exposure to 200 mM NaCl in the roots of bermudagrass were investigated. Dataset series analysis revealed 16 distinct salt-responsive temporal transcripts. Enrichment analysis identified common and distinct stress response themes such as hormonal metabolism, secondary metabolism, misc, cell wall, transcription factors and genes encoded a series of transporters. Weighted gene co-expression network analysis (WGCNA) revealed that lavenderblush2 and brown4 modules were significantly positively correlated with the proline content and peroxidase activity and hub genes within these two modules were further determined. Besides, after 1 h of salt treatment, categories such as signalling receptor kinase, transcription factors, tetrapyrrole synthesis and lipid metabolism were immediately and exclusively up-enriched compared to the subsequent time points, which indicated fast-acting and immediate physiological responses. Other specific categories involved in secondary metabolite biosynthesis such as simple phenols, glucosinolates, isoflavones and tocopherol biosynthesis were exclusively up-regulated after 24 h of salt treatment, suggesting a slightly slower reaction of metabolic adjustment.Conclusion: Here, we revealed salt response themes that were commonly or differentially expressed in short-term salt stress, suggesting possible adaptive salt response mechanisms in the roots. Also, the distinctive salt-response pathways and potential salt-tolerant hub genes investigated can provide useful future references to explore the molecular mechanisms of bermudagrass.

The Spectral Reflectance Response of ‘Riviera’ Common Bermudagrass to Increasing Saline Irrigation Concentrations

The availability of freshwater is a growing concern throughout the world as it is an increasingly valuable and limited resource. Alternative water resources such as recycled water low in quality and high in salinity are now frequently used to irrigate turfgrass. However, irrigating with highly saline water can affect the growth, performance, appearance, and quality of turfgrass. Bermudagrass (Cynodon sp.) is the most commonly used turfgrass throughout the southern United States. In this study, the spectral reflectance and visual response of ‘Riviera’ common bermudagrass (Cynodon dactylon) were evaluated by consecutively irrigating with 12 salinity concentrations (4–48 dS·m−1) in increments of 4 dS·m−1 via manual overhead irrigation for 30 days. The experiment was replicated in time in a controlled environment with four replications for each salinity treatment and control. ‘Riviera’ maintained a leaf firing (LF) value above 5 (rated on a scale from 1 to 9) when irrigated with 28 dS·m−1 for 30 days. Also, the LF value did not fall below 2 when irrigated with a salinity concentration of 48 dS·m−1 for 30 days, suggesting high salinity tolerance of ‘Riviera’. However, in this study, the normalized difference vegetation index (NDVI) had a lower ability to detect the increase in salinity stress due to the limited area measured by the NDVI measuring device used. An increase in sodium ion concentration was observed in the shoot with increasing salinity concentrations. The NDVI was highly correlated (r = 0.93) to LF, indicating the usefulness of NDVI as a tool to measure the magnitude of salinity stress. The multiple linear regression analysis revealed that the data showed a linear response to salinity stress with LF (r2 = 0.86) and NDVI (r2 = 0.76) decreasing linearly as the salinity concentration and days of treatment increased. This study provides an accurate depiction of the spectral and visual responses of ‘Riviera’ when exposed to multiple salinity concentrations with narrow increments.

PSVIII-24 Evaluating supplementation programs for growing calves grazing bermudagrass pastures

Operational time constraints limit producer’s ability to manage supplement delivery, thus we aimed to determine gain response to self-fed (SF) or hand-fed (HF) summer supplementation programs at the University of Arkansas Livestock and Forestry Research Station on 20, 0.81-ha common bermudagrass pastures stocked with 5 growing calves per pasture (BW ± SD = 247 ± 24.6). This research was a 2 × 2 + 1 factorial arrangement of treatments, including: Control (CON) – only free choice mineral; HF 1.13 kg/d corn gluten feed/soybean hull supplement offered all summer (AS) or only late summer (LS); SF tub supplement (PVM Cattle Tub, Positive Feed Ltd., Sealy, TX) either AS or LS. Supplement costs (US dollars) were $0.82/kg for SF and $0.23/kg for HF supplements. Consumption of SFAS was 0.44 kg/day in the early summer, while late summer intakes were 0.25 and 0.38 kg/d for SFLS and SFAS, respectively. In early summer HF increased (P < 0.01) ADG compared with CON and SFAS. During the late summer, HF increased ADG compared with CON (P ≤ 0.05) and HFAS tended (P = 0.08) to have greater ADG than both SFAS and SFLS. Added gain:supplement in the early summer did not differ (P = 0.38), 0.17 for SFAS and 0.31 for HFAS. Late summer gain:supplement did not differ (P = 0.56) averaging 0.58, 0.23, 0.17, and 0.23 for SFLS, SFAS, HFLS, HFAS. Cost of added gains in LS were SFLS and HFLS at $1.45 and $1.36/kg, respectively. Providing supplements AS resulted in $4.38 and $0.84/kg cost of added gain for SFAS and HFAS. Providing HF supplements all summer is a cost effective way to increase gains of growing calves grazing bermudagrass, providing supplements only during the late summer may be cost effective for both SF and HF supplements depending on economic conditions.

95 Impact of daily movement with low or higher target residue on ewe weight gain and parasite infestation

Impact of grazing method on ewe performance, parasite infestation, and soil, was examined using mature, non-lactating Katahdin ewes. Pasture consisting of primarily common bermudagrass/crabgrass mixture previously grazed by sheep was divided into four, approximately one acre paddocks [two with a target of 3 cm residue (SR; short residue) and two with a target of 13 cm residue (LR; long residue)] and soil sampled. On May 17 (d 0), 5 ewes were placed on each paddock and provided with daily grazing allocation using temporary electric fence. Body weight and fecal egg count (FEC) was recorded biweekly beginning on d 0. On alternate weeks, ewe body condition score (BCS) and FAMACHA score was recorded. After 84 days of grazing, final data and soil samples were collected. BCS, FAMACHA, FEC, body weight, and soil test results were tested for effect of treatment (SR vs LR), day, and treatment by day interaction using procedures for repeated measures with JMP software (version 10, SAS Inst. Inc., Cary, NC). There was an effect of treatment (P = 0.0345) and day (P < 0.0001) on BCS such that BCS was greater for LR than SR, and d 63 and 77 was greater than 35 and 49. There was an effect of day on body weight (P = 0.0008) such that body weights were greater on d 70 and 84 than d 0, 14, and 28. There was a tendency for a treatment by day interaction (P = 0.0766) on FEC such that FEC was greater for SR on d 70 and 84 than all other treatment days except SR on d 56 and LR on d 0. No effects on FAMACHA score or soil parameters were significant. These data indicate daily rotation with a higher target residue can result in improved body condition and lower FEC.

96 Impact of daily movement with low or higher target residue on ewe weight gain and parasite infestation

Impact of grazing method on ewe performance, parasite infestation, and soil, was examined using mature, non-lactating Katahdin ewes. Pasture consisting of primarily common bermudagrass/crabgrass mixture previously grazed by sheep was divided into four, approximately one acre paddocks (two with a target of 3 cm residue [SR; short residue) and two with a target of 13 cm residue (LR; long residue)] and soil sampled. On May 17 (d 0), 5 ewes were placed on each paddock and provided with daily grazing allocation using temporary electric fence. Body weight and fecal egg count (FEC) was recorded biweekly beginning on d 0. On alternate weeks, ewe body condition score (BCS) and FAMACHA score was recorded. After 84 days of grazing, final data and soil samples were collected. BCS, FAMACHA, FEC, body weight, and soil test results were tested for effect of treatment (SR vs LR), day, and treatment by day interaction using procedures for repeated measures with JMP software (version 10, SAS Inst. Inc., Cary, NC). There was an effect of treatment (P = 0.0345) and day (P < 0.0001) on BCS such that BCS was greater for LR than SR, and d 63 and 77 was greater than 35 and 49. There was an effect of day on body weight (P = 0.0008) such that body weights were greater on d 70 and 84 than d 0, 14, and 28. There was a tendency for a treatment by day interaction (P = 0.0766) on FEC such that FEC was greater for SR on d 70 and 84 than all other treatment days except SR on d 56 and LR on d 0. No effects on FAMACHA score or soil parameters were significant. These data indicate daily rotation with a higher target residue can result in improved body condition and lower FEC.

Complete chloroplast genome sequence of a vegetative Bermudagrass cultivar Tifeagle (Cynodon dactylon × Cynodon transvaalensis)

Hybrid (Cynodonn dactylon × C. transvaalensis) is a widely distributed turfgrass and shows a great value of environment, horticulture and economic. Though, the chloroplast genome of C. dactylon has been reported, it might be helpful finding reasons that triploid bermudagrass shows a better drought and trampling tolerance than common bermudagrass through comparing chloroplast genome analysis. The present results showed the complete chloroplast genome of the C. dactylon × C. transvaalensis is 134655 bp in length. The tetramerous genome contained a large single copy (LSC) region (79,998 bp), a small single copy (SSC) region (12,517 bp), and a pair of inverted repeat (IR) regions (42,140 bp). In the chloroplast genome, 116 genes were predicted, including 83 protein-coding, 29 tRNA and 4 rRNA genes. Furthermore, a total of 80 repeat sequences were identified. Only 0.23% intergenicnon-collinear sequences were found between the chloroplast genome of Cynodon dactylon × C. transvaalensis and Cynodon dactylon.

The Salinity Tolerance of Seeded-type Common Bermudagrass Cultivars and Experimental Selections

Turfgrass managers are using reclaimed water as an irrigation resource because of the decreasing availability and increasing cost of fresh water. Much attention, thereby, has been drawn to select salinity-tolerant turfgrass cultivars. An experiment was conducted to evaluate the relative salinity tolerance of 10 common bermudagrasses (Cynodon dactylon) under a controlled environment in a randomized complete block design with six replications. ‘SeaStar’ seashore paspalum (Paspalum vaginatum) was included in this study as a salinity-tolerant standard. All entries were tested under four salinity levels (1.5, 15, 30, and 45 dS·m−1) consecutively using subirrigation systems. The relative salinity tolerance among entries was determined by various parameters, including the normalized difference vegetation index (NDVI), percentage green cover determined by digital image analysis (DIA), leaf firing (LF), turf quality (TQ), shoot vertical growth (VG), and dark green color index (DGCI). Results indicated that salinity tolerance varied among entries. Except LF, all parameters decreased as the salinity levels of the irrigation water increased. ‘Princess 77’ and ‘Yukon’ provided the highest level of performance among the common bermudagrass entries at the 30 dS·m−1 salinity level. At 45 dS·m−1, the percent green cover as measured using DIA varied from 4.97% to 16.11% among common bermudagrasses, where ‘SeaStar’ with a DIA of 22.92% was higher than all the common bermudagrass entries. The parameters LF, TQ, NDVI, DGCI, VG, and DIA were all correlated with one another. Leaf firing had the highest correlation with other parameters, which defined its value as a relative salinity tolerance measurement for common bermudagrass development and selection.