Characterization and analysis of simple sequence repeat (SSR) loci in seashore paspalum (Paspalum vaginatum Swartz)

A size-fractionated TaqI genomic library of seashore paspalum (Paspalum vaginatum Swartz) was screened for the presence of (GA) _n and (CA) _n simple sequence repeats (SSRs). A total of 54 clones with a positive signal were detected among 13,000 clones screened. Forty-seven clones having repeats of n 3 were identified, of which 85% were perfect, 13% were imperfect and 2% were compound repeat sequences. Five of ten primer pairs synthesized to amplify selected loci resulted in a product in the expected size range and were subsequently used to examine SSR polymorphisms among 46 ecotypes of P. vaginatum. The number of alleles resolved on agarose or polyacrylamide gels were similar and ranged from 6 to 16 with an average of 14 per locus. Phenetic analysis of SSR polymorphisms revealed genetic relationships among the P. vaginatum ecotypes that were in general agreement with relationships determined previously by RAPD analysis of the same plant materials. Further screening of the genomic library did not identify (AT) _n , trimeric or tetrameric repeats. Hybridization of an (ATT)₈ oligonucleotide probe to genomic DNA isolated from I. batatas, E. coli, Citrullis lanatus and P. vaginatum suggested that the P. vaginatum genome contained significantly fewer ATT repeats than either the I. batatas or C. lanatus genome.     

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.     

The effect of auxin type and cytokinin concentration on callus induction and plant regeneration frequency from immature inflorescence segments of seashore paspalum (<Emphasis Type="Italic">Paspalum vaginatum</Emphasis> Swartz)

Seashore paspalum (Paspalum vaginatum Swartz) is a salt tolerant, fine textured turfgrass used on golf courses in coastal, tropical, and subtropical regions. A callus induction and plant regeneration protocol for this commercially important turfgrass species has been developed. Induction of highly regenerable callus with approximately 400 shoots per cultured immature inflorescence (1 cm in length) was achieved by culturing 0.2 cm segments on media with 3 mg l⁻¹ 3,6-dichloro-2-methoxybenzoic acid (dicamba) and 0.1 or 1.0 mg l⁻¹ benzylaminopurine (BA). A multifactorial experiment demonstrated the combination of 3 mg l⁻¹ dicamba and 1.0 mg l⁻¹ BA for induction of callus resulted in 12 times higher plant regeneration frequency compared to 3 mg l⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D) alone or ten times higher plant regeneration frequency than the combination of 3 mg l⁻¹ 2,4-D and 1.0 mg l⁻¹ BA. These results are expected to support the development of a genetic transformation protocol for seashore paspalum.     

Synthesis of organic osmolytes and salt tolerance mechanisms in Paspalum vaginatum

Synthesis of organic compounds in response to salinity stress and their contribution to organic osmotic adjustment were investigated in seashore paspalum (Paspalum vaginatum Swartz). Nine genotypes exhibiting the widest range of salt tolerance were grown in sea-salt amended nutrient solution in a greenhouse. Salinity ranges were 1.1 (EC_w0, control) to 49.7 dS m⁻¹ (EC_w50) based on electrical conductivity of the solution (EC_w). Organic osmolytes most important within seashore paspalum under salinity stress were proline, Gly-betaine, and trigonelline in terms of explaining intraspecific salt tolerance differences and, therefore, should be the focus of biotechnology approaches to enhance these traits. While these osmolytes differed in accumulation with increasing salinity and absolute concentrations among salt tolerant and intolerant genotypes, the magnitude of responses was not sufficiently large to suggest use for salt screening as physiological/biochemical markers. Fructose concentration increased with salinity, especially for salt sensitive ecotypes, and may have potential as a marker. Glucose, sucrose, and myo-inositol tended to increase with salinity, but changes did not relate to intraspecific salt tolerance, while mannitol and sorbitol were not affected by salinity. Proline demonstrated a 20.8-fold increase averaged across genotypes from EC_w0 to EC_w50 salinity. Proline was the primary organic osmolyte for osmotic adjustment accounting for an average of 9.3% to total solute potential (Ψ_s) at EC_w50 and 56% of the organic solute contribution to Ψ_s. In the salt tolerant genotype, SI 93-2, proline and Gly-betaine exhibited greater absolute concentration and accumulation rate relative to the least salt tolerant, Adalayd. The intraspecific role of Gly-betaine did not relate to osmotic adjustment differences, suggesting another role perhaps in protection of the thylakoid membrane.     

The Megophthalmidia (Diptera,Mycetophilidae) of North America including eight new species

Megophthalmidia Dziedzicki is a small leiine genus (Mycetophilidae) with seven species described from the Neotropics and ten species from the Palearctic region. Two species of Megophthalmidia have been reported for North America. Recent collecting of Mycetophilidae in California and Arizona, however, shows current North American diversity of Megophthalmidia is at least on par to other regions of the world. Eight new species of Megophthalmidia are described here, increasing the number of Nearctic Megophthalmidia species to nine. Included is a particularly atypical member of the genus, M. saskia sp. n., which expands the genus concept of Megophthalmidia. Of the two species previously recorded for North America, only one actually belongs in the genus. Megophthalmidia occidentalis Johannsen, is fully described and illustrated. The other named species, M. marceda (Sherman) is illustrated and transferred to the genus Ectrepesthoneura Enderlein. A lectotype is designated for this species. A key to the species of Megophthalmidia of North America is provided. The biology of these flies is not yet known. Three of the new Megophthalmidia species – M. lenimenta, M. misericordia, and M. radiata – are only known to occur within small protected areas within the California State Park and UC Natural Reserve systems.     

Responses of periphyton to artificial nutrient enrichment in freshwater kettle ponds of Cape Cod National Seashore

Nutrient enrichment bioassays, in conjunction with sampling and analysis of surface water chemistry, were conducted in freshwater lakes (kettle ponds) of Cape Cod National Seashore (Massachusetts, USA) to ascertain the importance of nitrogen (N) and phosphorus (P) in regulating the growth of periphyton. Arrays of nutrient diffusing substrata (NDS) were suspended 0.5 m below the water surface in a total of 12 ponds in July and August 2005. Algal biomass developing on each NDS after ~3 weeks of exposure in each month was assessed by quantifying chlorophyll a + phaeophyton pigments. In both July and August, strong responses to N + P and N enrichments were observed in the majority of ponds, while P had no stimulatory effect. These responses correspond well with low atomic ratios (1–18) of dissolved inorganic nitrogen (DIN) to total phosphorus (TP) in ambient surface waters. The results suggest that conditions in the kettle ponds develop whereby nitrogen is the primary limiting nutrient to periphyton growth. While this may be a seasonal phenomenon, it has implications for nutrient management in individual ponds and within the larger watershed.     

苯噻草胺与水稻DNA和稗草DNA作用的谱学研究

提出了苯噻草胺用于水田除草的新除草机理 ,BTMPA在DNA和RNA分子表面堆积 ,抑制DNA复制 ,阻止RNA参与植物体内的蛋白质合成 ,造成稗草等杂草细胞不能分裂 ,从而杀除杂草。发现水稻DNA对BTMPA有解毒作用。用苯噻草胺除草时 ,在植物体内的有效浓度为 1 7× 10 - 5mol L - 5 1× 10 - 5mol L ,最宜施药期为芽期至三叶期 ,最宜施药温度为 2 0℃ - 2 5℃。     

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 ≤ 0.05) by 35% to 45% at 120 days after inoculation on both grasses. In 2003, higher inoculum levels of H. galeatus reduced root growth (P ≤ 0.05) by 19.4% in seashore paspalum and by 14% in bermudagrass after 60 and 120 days of exposure, respectively. Percentage reductions in root length caused by H. galeatus and B. longicaudatus indicated no differences between grass species, although Tifdwarf bermudagrass supported higher soil population densities of both nematodes than SeaIsle 1 seashore paspalum.     

A study of germination inhibition in fruits

The procedure described here for the extraction and bioassay of natural germination inhibitors, requires only inexpensive equipment and minimal experimental skill. The method has been successfully used to demonstrate germination inhibition in a qualitative manner and to provide a framework for quantitative investigations