Chloroplast-localized PvBASS2 regulates salt tolerance in the C4 plant seashore paspalum.

BILE ACID: SODIUM SYMPORTER FAMILY PROTEIN 2 (BASS2) is localized within chloroplast membranes, facilitating the translocation of pyruvate and Na+ from the cytosol to the plastid, where pyruvate supports isopentenyl diphosphate (IPP) synthesis via the methylerythritol phosphate pathway in C3 plants. Nevertheless, the biological function of BASS2 in C4 plants has not been well defined. This study unveils a previously unidentified role of PvBASS2 in Na+ and pyruvate transport in seashore paspalum (Paspalum vaginatum), a halophytic C4 grass, indicating a specific cellular function within this plant species. Data showed that overexpression of PvBASS2 in seashore paspalum attenuated salt tolerance, whereas its RNAi lines exhibited enhanced salt resistance compared to wild-type plants, suggesting a negative regulatory role of PvBASS2 in seashore paspalum salt tolerance. The constitutive overexpression of PvBASS2 was also found to reduce salt tolerance in Arabidopsis. Further study revealed that PvBASS2 negatively regulates seashore paspalum salt tolerance, possibly due to elevated Na+/K+ ratio, disrupted chloroplast structure, and reduced photosynthetic efficiency following exposure to salinity. Importantly, our subsequent investigations revealed that modulation of PvBASS2 expression in seashore paspalum influenced carbon dioxide assimilation, intermediary metabolites of the tricarboxylic acid cycle, and enzymatic activities under salinity treatment, which in turn led to alterations in free amino acid concentrations. Thus, this study reveals a role for BASS2 in the C4 plant seashore paspalum and enhances our comprehension of salt stress responses in C4 plants.

A calmodulin-like protein PvCML9 negatively regulates salt tolerance.

Calmodulin-like proteins (CMLs) are unique Ca2+ sensors and play crucial roles in response to abiotic stress in plants. A salt-repressed PvCML9 from halophyte seashore paspalum (Paspalum vaginatum O. Swartz) was identified. PvCML9 was localized in the cytoplasm and nucleus and highly expressed in roots and stems. Overexpression of PvCML9 led to reduced salt tolerance in rice and seashore paspalum, whereas downregulating expression of PvCML9 showed increased salt tolerance in seashore paspalum as compared with the wild type (WT), indicating that PvCML9 regulated salt tolerance negatively. Na+ and K+ homeostasis was altered by PvCML9 expression. Lower level of Na+/K+ ratio in roots and shoots was maintained in PvCML9-RNAi lines compared with WT under salt stress, but higher level in overexpression lines. Moreover, higher levels of SOD and CAT activities and proline accumulation were observed in PvCML9-RNAi lines compared with WT under salt stress, but lower levels in overexpression lines, which altered ROS homeostasis. Based on the above data, mutation of its homolog gene OsCML9 in rice by CRISPR/Cas9 was performed. The mutant had enhanced salt tolerance without affecting rice growth and development, suggesting that OsCML9 gene is an ideal target gene to generate salt tolerant cultivars by genome editing in the future.

Overexpression of PvWAK3 from seashore paspalum increases salt tolerance in transgenic Arabidopsis via maintenance of ion and ROS homeostasis.

Seashore paspalum (Paspalum vaginatum O. Swartz) is an important warm-season turfgrass species with extreme salt tolerance, but investigations on its salt tolerance mechanism are limited. A salt induced PvWAK3 from halophyte seashore paspalum was identified in this study. Overexpression of PvWAK3 in Arabidopsis led to increased salt tolerance. Transgenic plants had higher levels of seed germination rate, root length, number of lateral roots, shoot weight, survival rate, Fv/Fm, ETR, and NPQ compared with the wild type (WT) under salt stress. Na+ content was increased and K+ content was decreased after salinity treatment, with lower levels of Na+ and Na+/K+ ratio but higher level of K+ in transgenic plants than in WT under salt stress. The improved maintenance of Na+ and K+ homeostasis was associated with the higher transcript levels of K + -Uptake Permease 4 (KUP4), Potassium Transport 2/3 (AKT2), Salt Overly Sensitive 1 (SOS1) and High-Affinity K + Transporter 5 (HAK5) in transgenic plants compared with WT. Superoxide dismutase (SOD), catalase (CAT) and ascorbate-peroxidase (APX) activities, proline concentration, and P5CS1 transcript were increased after salinity treatment, with higher levels in transgenic lines compared with WT, which led to reduced accumulation of O2·- and H2O2 under salt stress. It is suggested that PvWAK3 regulates salt tolerance positively, which is associated with promoted Na+ and K+ homeostasis, activated antioxidant enzymes, and proline biosynthesis under salt stress.

Comparative genomics and transcriptome analysis reveals potential pathogenic mechanisms of Microdochium paspali on seashore paspalum.

The sparse leaf patch of seashore paspalum (Paspalum vaginatum Sw.) caused by Microdochium paspali seriously impacts the landscape value of turf and poses a challenge to the maintenance and management of golf courses. Little is known about the genome of M. paspali or the potential genes underlying pathogenicity. In this study, we present a high-quality genome assembly of M. paspali with 14 contigs using the Nanopore and Illumina platform. The M. paspali genome is roughly 37.32 Mb in size and contains 10,365 putative protein-coding genes. These encompass a total of 3,830 pathogen-host interactions (PHI) genes, 481 carbohydrate-active enzymes (CAZymes) coding genes, 105 effectors, and 50 secondary metabolite biosynthetic gene clusters (SMGCs) predicted to be associated with pathogenicity. Comparative genomic analysis suggests M. paspali has 672 species-specific genes (SSGs) compared to two previously sequenced non-pathogenic Microdochium species, including 24 species-specific gene clusters (SSGCs). Comparative transcriptomic analyses reveal that 739 PHIs, 198 CAZymes, 40 effectors, 21 SMGCs, 213 SSGs, and 4 SSGCs were significantly up-regulated during the process of infection. In conclusion, the study enriches the genomic resources of Microdochium species and provides a valuable resource to characterize the pathogenic mechanisms of M. paspali.

Spraying Zinc Sulfate to Reveal the Mechanism through the Glutathione Metabolic Pathway Regulates the Cadmium Tolerance of Seashore Paspalum (Paspalum vaginatum Swartz).

Cadmium (Cd) is considered to be one of the most toxic metals, causing serious harm to plants' growth and humans' health. Therefore, it is necessary to study simple, practical, and environmentally friendly methods to reduce its toxicity. Until now, people have applied zinc sulfate to improve the Cd tolerance of plants. However, related studies have mainly focused on physiological and biochemical aspects, with a lack of in-depth molecular mechanism research. In this study, we sprayed high (40 mM) and low (2.5 mM) concentrations of zinc sulfate on seashore paspalum (Paspalum vaginatum Swartz) plants under 0.5 mM Cd stress. Transcriptome sequencing and physiological indicators were used to reveal the mechanism of Cd tolerance. Compared with the control treatment, we found that zinc sulfate decreased the content of Cd2+ by 57.03-73.39%, and that the transfer coefficient of Cd decreased by 58.91-75.25% in different parts of plants. In addition, our results indicate that the antioxidant capacity of plants was improved, with marked increases in the glutathione content and the activity levels of glutathione reductase (GR), glutathione S-transferase (GST), and other enzymes. Transcriptome sequencing showed that the differentially expressed genes in both the 0.5 Zn and 40 Zn treatments were mainly genes encoding GST. This study suggests that genes encoding GST in the glutathione pathway may play an important role in regulating the Cd tolerance of seashore paspalum. Furthermore, the present study provides a theoretical reference for the regulation mechanism caused by zinc sulfate spraying to improve plants' Cd tolerance.

Lipid metabolism and antioxidant system contribute to salinity tolerance in halophytic grass seashore paspalum in a tissue-specific manner.

Soil salinization is a growing issue that limits agriculture globally. Understanding the mechanism underlying salt tolerance in halophytic grasses can provide new insights into engineering plant salinity tolerance in glycophytic plants. Seashore paspalum (Paspalum vaginatum Sw.) is a halophytic turfgrass and genomic model system for salt tolerance research in cereals and other grasses. However, the salt tolerance mechanism of this grass largely unknown. To explore the correlation between Na+ accumulation and salt tolerance in different tissues, we utilized two P. vaginatum accessions that exhibit contrasting tolerance to salinity. To accomplish this, we employed various analytical techniques including ICP-MS-based ion analysis, lipidomic profiling analysis, enzyme assays, and integrated transcriptomic and metabolomic analysis. Under high salinity, salt-tolerant P. vaginatum plants exhibited better growth and Na+ uptake compared to salt-sensitive plants. Salt-tolerant plants accumulated heightened Na+ accumulation in their roots, leading to increased production of root-sourced H2O2, which in turn activated the antioxidant systems. In salt-tolerant plants, metabolome profiling revealed tissue-specific metabolic changes, with increased amino acids, phenolic acids, and polyols in roots, and increased amino acids, flavonoids, and alkaloids in leaves. High salinity induced lipidome adaptation in roots, enhancing lipid metabolism in salt-tolerant plants. Moreover, through integrated analysis, the importance of amino acid metabolism in conferring salt tolerance was highlighted. This study significantly enhances our current understanding of salt-tolerant mechanisms in halophyte grass, thereby offering valuable insights for breeding and genetically engineering salt tolerance in glycophytic plants.

Genome-wide analysis of tandem duplicated genes and their expression under salt stress in seashore paspalum.

Seashore paspalum (Paspalum vaginatum) is a halophytic, warm-season grass which is closely related to various grain crops. Gene duplication plays an important role in plant evolution, conferring significant plant adaptation at the genomic level. Here, we identified 2,542 tandem duplicated genes (TDGs) in the P. vaginatum genome and estimated the divergence time of pairs of TDGs based on synonymous substitution rates (Ks). Expression of P. vaginatum TDGs resulted in enrichment in many GO terms and KEGG pathways when compared to four other closely-related species. The GO terms included: "ion transmembrane transporter activity," "anion transmembrane transporter activity" and "cation transmembrane transport," and KEGG pathways included "ABC transport." RNA-seq analysis of TDGs showed tissue-specific expression under salt stress, and we speculated that P. vaginatum leaves became adapted to salt stress in the earlier whole-genome duplication (WGD; ~83.3 million years ago; Ma), whereas the entire P. vaginatum plant acquired a large number of TDGs related to salt stress in the second WGD (~23.3 Ma). These results can be used as a reference resource to accelerate salt-resistance research in other grasses and crops.

Evaluation of the tolerance and forage quality of different ecotypes of seashore paspalum.

Seashore paspalum is a halophytic, warm-season grass with wide applications. It is noted for its superior salt tolerance in saline environments; however, the nutritive value of seashore paspalum and the effect of salinity remains to be determined. Therefore, this study aimed to evaluate the relationship between agronomic traits and forage quality and identified the effects of short-term high-salt stress (1 week, 700 mM NaCl) on the growth and forage nutritive value of 16 ecotypes of seashore paspalum. The salt and cold tolerances of the seashore paspalum ecotypes were assessed based on the survival rate following long-term high-salt stress (7 weeks, 700 mM NaCl) and exposure to natural low temperature stress. There were significant genetic (ecotype-specific) effects on plant height, leaf-stem ratio, and survival rate of seashore paspalum following salt or low temperature stress. Plant height was significantly negatively correlated with the leaf-stem ratio (r = -0.63, P<0.01), but the heights and leaf-stem ratios were not significantly correlated with the fresh weight (FW) and dry weight (DW) of the shoots. High salinity decreased the FW and DW of the shoots by 50.6% and 23.6%, respectively, on average. Seashore paspalum exhibited outstanding salt tolerance and forage quality at high salinity. The survival rate of the different ecotypes of seashore paspalum varied from 6.5% to 49.0% following treatment with 700 mM NaCl for 7 weeks. The crude protein (CP) content of the control and treatment groups (700 mM NaCl) was 17.4% and 19.3%, respectively, of the DW on average, and the CP content of most ecotypes was not significantly influenced by high salinity. The average ether extract (EE) content ranged from 4.6% to 4.4% of the DW under control and saline conditions, respectively, indicating that the influence was not significant. The neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents of the control group were 57.4% and 29.8%, respectively, of the DW on average. Salt stress reduced the content of NDF and ADF to 50.2% and 25.9%, respectively, of the DW on average. Altogether, the results demonstrated that stress did not have any significant effects on the CP and EE content of most ecotypes, but reduced the NDF and ADF content and improved relative feed value (RFV). The results obtained herein support the notion that seashore paspalum is a good candidate for improving the forage potential of saline soils and can provide useful guidelines for livestock producers.

Distribution Pattern of N6-Methyladenine DNA Modification in the Seashore Paspalum (Paspalum vaginatum) Genome.

N6-methyladenine (6mA) DNA modification has been detected in several eukaryotic organisms, in some of them, it plays important role in the regulation process of stress-resistance response. However, the genome-wide distribution patterns and potential functions of 6mA DNA modification in halophyte Seashore paspalum (Paspalum vaginatum) remain largely unknown. Here, we examined the 6mA landscape in the P. vaginatum genome by adopting single molecule real-time sequencing technology and found that 6mA modification sites were broadly distributed across the P. vaginatum genome. We demonstrated distinct 6mA methylation levels and 6mA distribution patterns in different types of transcription genes, which hinted at different epigenetic rules. Furthermore, the moderate 6mA density genes in P. vaginatum functionally correlated with stress resistance, which also maintained a higher transcriptional level. On the other hand, a specific 6mA distribution pattern in the gene body and near TSS was observed in gene groups with higher RNA expression, which maybe implied some kind of regularity between 6mA site distribution and the protein coding genes transcription was possible. Our study provides new insights into the association between 6mA methylation and gene expression, which may also contribute to key agronomic traits in P. vaginatum.

Seasonal Paspalum vaginatum Physiological Characteristics Change with Agricultural Byproduct Biochar in Sandy Potting Soil.

A plastic pot open-air trial was conducted with the Paspalum vaginatum (seashore paspalum) using different rates of biochar or compost addition to sandy loam soil and two water treatments (60% and 20% of the water-holding capacity of the control) during three seasons (winter, spring, and summer). Paspalum growth, physiological characteristics, and physicochemical properties of soil were investigated. The effect of biochar on soil properties was assessed using factor analysis of mixed data (FAMD). Additionally, multiple factorial designs (MFA) were used to examine the impact of three biochars on physiological functions. Peanut hull biochar application increased soil fertility and chlorophyll concentration of paspalum leaves significantly compared to the other biochars. Physiological characteristics were significantly improved with peanut hull biochar under summer compared to winter and spring due to the accumulation of nutrients in the soil by the decomposition of biochar. The application rate of the three biochars reduced the water requirements of paspalum. The best result was obtained by incorporating 6% peanut hull biochar into the soil, which resulted in better soil quality and healthy grass in dryland conditions while using 47.5% less water. These findings can be suitable for golf managers and can serve as a solution for dry zones.

Tolerance of some warm-season turfgrasses to compaction under shade and sunlight conditions in Riyadh, Saudi Arabia.

We evaluated the compaction tolerance of some warm-season turfgrasses under shade and sunlight conditions in Riyadh, Saudi Arabia. Hybrid bermudagrass, Cynodon dactylon, cultivars 'Tifway' and 'Tifsport,' seashore paspalum (Paspalum vaginatum) and its cultivar 'Sea Isle 2000' were used. The study area was divided into two sections: one was exposed to sunlight and the other was maintained under 70% shade using a green plastic grille. Turfgrasses were planted using "sods" in beds containing a mixture of sand, silt, and peat moss (4: 1: 1, v/v). The soil was compacted using a locally-made 250 kg cylindrical roll, passing four times over the grown turfgrasses for 3 days/week. The results showed that plant height, leaf area, grass quality and color were decreased by compaction in both the shade and sunlight areas. Plant height in the shaded area with or without compaction was higher than in the sunlight area. Under compaction, 'Sea Isle 2000' was the shortest: 8.8 cm in the sunlight and 14.3 cm in the shade. For grasses grown in sunlight, compaction decreased grass height, and height was lowest (4.0 cm) for paspalum 'Sea Isle 2000' in January. In the shaded area, paspalum turfgrass retained its high quality (4.0) in April, May, and June. In the sunlight area, the grass quality was highest (4.0) in 'Sea Isle 2000' and the lowest (3.0) in 'Tifsport.' Paspalum turfgrass showed a higher color degree (4) than bermudagrass (2.5) in April, May, and June. Compaction also led to a decline in leaf area and fresh and dry weights of all grown turfgrasses. The grass density was high for paspalum turfgrasses, indicating that their resistance to compaction was greater than bermudagrasses. It can be concluded that the best compaction and shade-tolerant turfgrasses are 'Sea Isle 2000' and seashore paspalum.

Physiological responses and tolerance mechanisms of seashore paspalum and centipedegrass exposed to osmotic and iso-osmotic salt stresses.

Osmotic stresses caused by reduced water availability or the accumulation of salts in the soil can be highly damaging to plants. The objective of this study was to investigate physiological responses and tolerance mechanisms of two turfgrass species (seashore paspalum and centipedegrass) with distinct differences in salinity tolerance exposed to osmotic and iso-osmotic salt stresses. Three turfgrass genotypes including seashore paspalums 'Seastar' and 'UGP113', and centipedegrass 'TifBlair' were grown in ½ strength Hoagland's solution with three different treatment conditions; control (no external addition), salt stress (-0.4 MPa by adding NaCl) and osmotic stress [-0.4 MPa by adding polyethylene glycol (PEG)]. Osmotic stress damages were more severe with greater reductions in turf quality, photochemical efficiency (Fv/Fm), relative water content (RWC) and leaf water potential (Ψw) compared to iso-osmotic salt stress in both seashore paspalum and centipedegrass. Greater osmotic adjustment (OA) with greater accumulation of metabolically inexpensive inorganic osmolytes (Na+) helped turfgrasses to lessen damages in salt stress compared to osmotic stress. However, such accumulation of Na+ resulted ion-toxicity and triggered some damages in terms of increased electrolyte leakage (EL) and reduced total protein in salt-sensitive centipedegrass. Seashore paspalum had better ion regulation and also maintained greater antioxidant enzyme activities compared to centipedegrass; therefore it was able to avoid ion-specific damages under salt stress. Differences in the utilization of specific solutes for osmotic adjustment and antioxidant metabolism are partially responsible for the differences in salt versus osmotic stress responses in these species; the regulation of these defense mechanisms requires further investigation.

Up-regulation of lipid metabolism and glycine betaine synthesis are associated with choline-induced salt tolerance in halophytic seashore paspalum.

Choline may affect salt tolerance by regulating lipid and glycine betaine (GB) metabolism. This study was conducted to determine whether alteration of lipid profiles and GB metabolism may contribute to choline regulation and genotypic variations in salt tolerance in a halophytic grass, seashore paspalum (Paspalum vaginatum). Plants of Adalayd and Sea Isle 2000 were subjected to salt stress (200-mM NaCl) with or without foliar application of choline chloride (1 mM). Genotypic variations in salt tolerance and promotive effects of choline application on salt tolerance were associated with both the up-regulation of lipid metabolism and GB synthesis. The genotypic variations in salt tolerance associated with lipid metabolism were reflected by the differential accumulation of phosphatidylcholine and phosphatidylethanolamine between Adalayd and Sea Isle 2000. Choline-induced salt tolerance was associated with of the increase in digalactosyl diacylglycerol (DGDG) content including DGDG (36:4 and 36:6) in both cultivars of seashore paspalum and enhanced synthesis of phosphatidylinositol (34:2, 36:5, and 36:2) and phosphatidic acid (34:2, 34:1, and 36:5), as well as increases in the ratio of digalactosyl diacylglycerol: monogalactosyl diacylglycerol (DGDG:MGDG) in salt-tolerant Sea Isle 2000. Choline regulation of salt tolerance may be due to the alteration in lipid metabolism in this halophytic grass species.

Overexpression of a NF-YC Gene Results in Enhanced Drought and Salt Tolerance in Transgenic Seashore Paspalum.

Seashore paspalum (Paspalum vaginatum O. Swartz) is an important warm-season turfgrass species. In this study we generated transgenic seashore paspalum overexpressing CdtNF-YC1, a nuclear factor Y transcription factor from hybrid bermudagrass (Cynodon dactylon × Cynodon transvaalensis). DNA blot hybridization and qRT-PCR analysis showed that CdtNF-YC1 was integrated into the genomes of transgenic seashore paspalum plants and expressed. Reduced relative water content (RWC) and survival rate and increased ion leakage were observed in both wild type (WT) and transgenic plants after drought stress, while transgenic plants had higher levels of RWC and survival rate and lower ion leakage than the WT. Maximal photochemical efficiency of photosystem II (F v/F m), chlorophyll concentration and survival rate were decreased after salt stress, while higher levels were maintained in transgenic plants than in WT. In addition, an increased Na+ content and decreased or unaltered K+ in leaves and roots were observed after salt treatment, while lower level of Na+ and higher levels of K+ and K+/ Na+ ratio were maintained in transgenic plants than in WT. The results indicated that overexpressing CdtNF-YC1 resulted in enhanced drought and salt tolerance in transgenic plants. Transcript levels of stress responsive genes including PvLEA3, PvP5CS1, PvABI2, and PvDREB1B were induced in response to drought and salt stress, and higher levels were observed in transgenic seashore paspalum than in WT. The results suggest that the enhanced drought and salt tolerance in transgenic seashore paspalum is associated with induction of a series of stress responsive genes as a result of overexpression of CdtNF-YC1.

Identification and Validation of Reference Genes for Seashore Paspalum Response to Abiotic Stresses.

Seashore paspalum (Paspalum vaginatum) is among the most salt- and cadmium-tolerant warm-season perennial grass species widely used as turf or forage. The objective of this study was to select stable reference genes for quantitative real-time polymerase chain reaction (qRT-PCR) analysis of seashore paspalum in response to four abiotic stresses. The stability of 12 potential reference genes was evaluated by four programs (geNorm, NormFinder, BestKeeper, and RefFinder). U2AF combined with glyceraldehyde-3-phosphate dehydrogenase (GAPDH) showed stable expression in Cd-treated leaves and cold-treated roots. U2AF and FBOX were the most stable reference genes in Cd-treated roots and cold-treated leaves. In Polyethylene Glycol (PEG)- or salt-treated roots, the reference gene U2AF paired with either ACT or CYP were stable. SAND and CACS exhibited the most stability in salt-treated leaves, and combining UPL, PP2A, and EF1a was most suitable for PEG-treated leaves. The stability of U2AF and instability of UPL and TUB was validated by analyzing the expression levels of four target genes (MT2a, VP1, PIP1, and Cor413), and were shown to be capable of detecting subtle changes in expression levels of the target genes in seashore paspalum. This study demonstrated that FBOX, U2AF, and PP2A could be used in future molecular studies that aim to understand the mechanisms of abiotic stress tolerance in seashore paspalum.

Functional Identification and Characterization of Genes Cloned from Halophyte Seashore Paspalum Conferring Salinity and Cadmium Tolerance.

Salinity-affected and heavy metal-contaminated soils limit the growth of glycophytic plants. Identifying genes responsible for superior tolerance to salinity and heavy metals in halophytes has great potential for use in developing salinity- and Cd-tolerant glycophytes. The objective of this study was to identify salinity- and Cd-tolerance related genes in seashore paspalum (Paspalum vaginatum), a halophytic perennial grass species, using yeast cDNA expression library screening method. Based on the Gateway-compatible vector system, a high-quality entry library was constructed, which contained 9.9 × 10(6) clones with an average inserted fragment length of 1.48 kb representing a 100% full-length rate. The yeast expression libraries were screened in a salinity-sensitive and a Cd-sensitive yeast mutant. The screening yielded 32 salinity-tolerant clones harboring 18 salinity-tolerance genes and 20 Cd-tolerant clones, including five Cd-tolerance genes. qPCR analysis confirmed that most of the 18 salinity-tolerance and five Cd-tolerance genes were up-regulated at the transcript level in response to salinity or Cd stress in seashore paspalum. Functional analysis indicated that salinity-tolerance genes from seashore paspalum could be involved mainly in photosynthetic metabolism, antioxidant systems, protein modification, iron transport, vesicle traffic, and phospholipid biosynthesis. Cd-tolerance genes could be associated with regulating pathways that are involved in phytochelatin synthesis, HSFA4-related stress protection, CYP450 complex, and sugar metabolism. The 18 salinity-tolerance genes and five Cd-tolerance genes could be potentially used as candidate genes for genetic modification of glycophytic grass species to improve salinity and Cd tolerance and for further analysis of molecular mechanisms regulating salinity and Cd tolerance.

Interaction Between Belonolaimus longicaudatus and Helicotylenchus pseudorobustus on Bermudagrass and Seashore Paspalum Hosts.

Belonolaimus longicaudatus and Helicotylenchus pseudorobustus are among the most common nematode parasites of turfgrasses in Florida. Bermudagrass (Cynodon dactylon × C. transvaalensis) and seashore paspalum (Paspalum vaginatum) are the two turf species most commonly used on Florida golf courses. This paper explores the interactions between B. longicaudatus and H. pseudorobustus on bermudagrass and seashore paspalum hosts. Data collected from thousands of nematode samples submitted to the Florida Nematode Assay Lab over a 8-yr period revealed a negative relationship between B. longicaudatus and H. pseudorobustus on bermudagrass, but not seashore paspalum. In a multi-year field plot experiment using multiple cultivars of bermudagrass, and seashore paspalum B. longicaudatus and H. pseudorobustus were negatively related on both turf species. Greenhouse trials where multiple cultivars of both turf species were inoculated with different combinations of B. longicaudatus and H. pseudorobustus found that each nematode species was inhibitory to the other on both host species. Belonolaimus longicaudatus and H. pseudorobustus clearly impact each other on turfgrass hosts, although the mechanism of the nematode-nematode interactions is unknown.

Field Responses of Bermudagrass and Seashore paspalum Cultivars to Sting and Spiral Nematodes.

Belonolaimus longicaudatus and Helicotylenchus spp. are damaging nematode species on bermudagrass (Cynodon spp.) and seashore paspalum (Paspalum vaginatum) in sandy soils of the southeastern United States. Eight bermudagrass and three seashore paspalum cultivars were tested for responses to both nematode species in field plots for two years in Florida. Soil samples were taken every three months and nematode population densities in soil were quantified. Turfgrass aboveground health was evaluated throughout the growing season. Results showed that all bermudagrass cultivars, except TifSport, were good hosts for B. longicaudatus, and all seashore paspalum cultivars were good hosts for H. pseudorobustus. Overall, bermudagrass was a better host for B. longicaudatus while seashore paspalum was a better host for H. pseudorobustus. TifSport bermudagrass and SeaDwarf seashore paspalum cultivars supported the lowest population densities of B. longicaudatus. Seashore paspalum had a higher percent green cover than bermudagrass in the nematode-infested field. Nematode intolerant cultivars were identified.

Saline Irrigation Affects Belonolaimus longicaudatus and Hoplolaimus galeatus on Seashore Paspalum.

Seashore paspalum (Paspalum vaginatum) has great potential for use in salt-affected turfgrass sites. Use of this grass on golf courses, athletic fields, and lawns in subtropical coastal areas may aid in conservation of freshwater resources. Belonolaimus longicaudatus and Hoplolaimus galeatus are considered among the most damaging root pathogens of turfgrasses in Florida. Glasshouse experiments were performed in 2002 and 2003 to examine the effects of increasing levels of irrigation salinity on B. longicaudatus and H. galeatus. Irrigation treatments were formulated by concentrating deionized water to six salinity levels (0, 5, 10, 15, 20, and 25 dS/m). Final population densities of H. galeatus followed a negative linear regression (r(2) = 0.92 and 0.83; P <= 0.01) with increasing salinity levels. Final population densities of B. longicaudatus were quadratically (r(2) = 0.72 and 0.78; P <= 0.01) related to increasing salinity levels from 0 to 25 dS/m. An increase in population densities of B. longicaudatus was observed at moderate salinity levels (10 and 15 dS/m) compared to 0 dS/m. Root-length comparisons revealed that B. longicaudatus caused root stunting at low salinity levels, 0 to 10 dS/m, but roots were not affected at 15 to 25 dS/m. These results indicate that the ability of B. longicaudatus to feed and stunt root growth was negatively affected at salinity levels of 15 dS/m and above.

Host Status of 'SeaIsle 1' Seashore Paspalum (Paspalum vaginatum) to Belonolaimus longicaudatus and Hoplolaimus galeatus.

Belonolaimus longicaudatus and Hoplolaimus galeatus are considered among the most damaging pathogens of turfgrasses in Florida. However, the host status of seashore paspalum (Paspalum vaginatum) is unknown. Glasshouse experiments were performed in 2002 and 2003 to determine the tolerance of 'SeaIsle 1' seashore paspalum to a population of B. longicaudatus and a population of H. galeatus, and to compare to 'Tifdwarf' bermudagrass for differences. Both nematode species reproduced well on either grass, but only B. longicaudatus consistently reduced root growth as measured by root length. Belonolaimus longicaudatus reduced root growth (P