Infection with the fungal endophyte Epichloë festucae may alter the allelopathic potential of red fescue

Red fescue (Festuca rubra) is a perennial grass used as both forage and turfgrass. Asymptomatic plants of this species are systemically infected by the fungal endophyte Epichloë festucae, which has a beneficial effect on the infected plants. The aim of this study was to determine the effect of the endophyte Epichloë festucae on the allelopathic potential of F. rubra against four associated pasture species that are also considered as weeds in lawns, Trifolium pratense, Trifolium repens, Lotus corniculatus and Plantago lanceolata. Two experiments were designed to evaluate the allelopathic effect of extracts from the roots and leaves of endophyte‐infected (E+) and non‐infected (E?) plants on the germination and seedling growth of the four target species. Regardless of the endophyte status of the host plant, leaf extracts elicited a stronger reduction in germination and seedling growth than root extracts. Extracts from E+ plants reduced the speed of germination index of Trifolium spp. to a greater extent than those from E? plants. Radicle length of the target species was the parameter most affected by the presence of the endophyte in F. rubra. Root extracts from E+ plants had a greater inhibitory effect on the radicle growth of the target species than did root extracts from E? plants. A greater concentration in total phenolic compounds was found in the roots of E+ plants than of E?; however, this difference was not observed in the leaves. Thus, the allelopathic potential of F. rubra is altered in infected plants.     

Plantago lanceolata and Plantago rugelii Extracts are Toxic to Meloidogyne incognita but not to Certain Microbes

Extracts from the plants Plantago lanceolata and P. rugelii were evaluated for toxicity to the root-knot nematode Meloidogyne incognita, the beneficial microbes Enterobacter cloacae, Pseudomonas fluorescens and Trichoderma virens, and the plant-pathogenic fungi Fusarium oxysporum f. sp. gladioli, Phytophthora capsici, Pythium ultimum, and Rhizoctonia solani. Wild plants were collected, roots were excised from shoots, and the plant parts were dried and ground to a powder. One set of extracts (10% w/v) was prepared in water and another in methanol. Treatments included extract concentrations of 25%, 50%, 75% and 100%, and water controls. Meloidogyne incognita egg hatch was recorded after 7-day exposure to the treatments, and second-stage juvenile (J2) activity after 48 hours. All extracts were toxic to eggs and J2, with P. lanceolata shoot extract tending to have the most activity against M. incognita. Numbers of active J2 remained the same or decreased in a 24-hour water rinse following the 48-hour extract treatment, indicating that the extracts were lethal. When data from water- and methanol-extracted roots and shoots of both plant species were combined for analysis, J2 tended to be more sensitive than eggs to the toxic compounds at lower concentrations, while the higher concentrations (75% and 100%) were equally toxic to both life stages. The effective concentrations causing 50% reduction (EC₅₀) in egg hatch and in J2 viability were 44.4% and 43.7%, respectively. No extract was toxic to any of the bacteria or fungi in our assays.     

Land use intensification in grasslands: higher trophic levels are more negatively affected than lower trophic levels

Increasing land use intensity and human influence are leading to a reduction in plant and animal species diversity. However, little is known about how these changes may affect higher trophic levels, apart from simply reducing species numbers. Here we investigated, over 3 years, the influence of different land practices on a tritrophic system in grassland habitats. The system consisted of the host plant Plantago lanceolata L. (Plantaginaceae), two monophagous weevils, Mecinus labilis Herbst and Mecinus pascuorum Gyllenhal (Coleoptera: Curculionidae), and their parasitoid Mesopolobus incultus Walker (Hymenoptera: Pteromalidae). At over 70 sites across three geographic regions in Germany, we measured plant species diversity and vegetation structure, as well as abundance of P. lanceolata, the two weevils, and the parasitoid. Land use intensity (fertilization) and type (mowing vs. grazing) negatively affected not only plant species richness but also the occurrence of the two specialized herbivores and their parasitoid. In contrast, land use had a mostly positive effect on host plant size, vegetation structure, and parasitization rate. This study reveals that intensification of land use influences higher trophic organisms even without affecting the availability of the host plant. The observed relationships between land use, vegetation complexity, and the tritrophic system are not restricted locally; rather they are measureable along a broad range of environmental conditions and years throughout Germany. Our findings may have important implications for the conservation of insect species of nutrient‐poor grasslands.     

Comparison of PCR-based molecular marker analyses of Musa breeding populations

Progress in the breeding of plantain and banana has been restricted by the complex genetic structure and behaviour of cultivated polyploid Musa. Genetic improvement has been hindered due to the large amount of space required for growth and maintenance of plant populations, in addition to the long growth cycle and the low levels of fertility and seed viability characteristic of cultivated genotypes. Molecular marker assisted breeding has the potential to dramatically enhance the pace and efficiency of genetic improvement in Musa. This study was conducted to compare different PCR-based marker systems (RAPD, VNTR and AFLP) for the analysis of breeding populations generated from two diverse Musa breeding schemes. All three assays detected a high level of polymorphism between parental genotypes and within progeny populations. As expected, AFLP assays had by far the highest multiplex ratio while VNTR analysis detected the highest levels of polymorphism. AFLP analysis of a full-sib tetraploid hybrid population confirmed previous reports based on VNTR analysis, of a high frequency of recombination during 2n (3x) gamete formation by a triploid plantain landrace. In addition, both VNTR and RAPD analyses of a full-sib triploid hybrid population suggested a high frequency of homoeologous recombination during n (2x) gamete formation by tetraploid hybrids. In general, there was a poor correlation between estimates of genetic similarity based on different types of marker. The implications of these findings for the molecular breeding of Musa crops are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Amplified somatic embryogenesis from male flowers of triploid banana and plantain cultivars (Musa spp.)

Summary Somatic embryogenesis and plant regeneration of banana and plantain cultivars (Musa spp.) were obtained by culturing young male flowers. Multiplication and maintenance of embryogenic cultures were achieved by culturing somatic embryos in a temporary immersion system (SIT). A multiplication rate of 40 allowed us to obtain more than 6000 somatic embryos after 6 mo. of subculture. Plant recovery frequencies were 60 to 70%. This method was expanded to different banana and plantain genomic groups.     

Rapid decarboxylation of the products of dark fixation of CO2 in roots of pisum and Plantago

Seedlings of Pisum sativum and excised roots of Plantago major and P. lanceolata were given, in the dark, a pulse of ¹⁴CO₂ in air followed by a chase in ¹²CO₂ in air. A very substantial proportion of the ¹⁴C fixed into organic compounds in the pulse was lost from the tissues in the chase. The activity of NAD malic enzyme in extracts of roots of all three species exceeded their rate of respiration. Azide, 2-n-butylmalonate, and salicylhydroxamic acid each inhibited CO₂ fixation by excised roots of pea. The first two compounds inhibited respiratory gas exchange, but the third stimulated it. Arguments are presented for the widespread diversion of phosphoenolpyruvate from glycolysis to oxaloacetate and thence to malate in the cytosol followed by transport of the malate into the mitochondria for conversion to pyruvate via NAD malic enzyme. No differences, in the above respects, were found between the two species of Plantago.     

Recovery and regeneration of embryogenic cultures from female flowers of False Horn Plantain

Somatic embryogenesis from immature male flowers in Musa is only suitable for genotypes with a male bud. Six friable embryogenic cultures were obtained from 28 cultured buds of female flowers of the AAB False Horn Plantains, ‘Curraré’ and ‘Curraré Enano’. Embryogenic suspensions were established from these embryogenic cultures. Somatic embryogenesis was demonstrated histologicaly. Regeneration of plants was obtained either from somatic embryos directly isolated from embryogenic cultures or from suspensions after plating on a semi-solid medium. This study demonstrates that somatic embryogenesis from immature flowers is suitable for genotypes of Musa with or without male buds. This revised version was published online in June 2006 with corrections to the Cover Date.     

A new hydroxyolefinic acid from Plantago major seed oil

A new isomer of ricinoleic acid has been found as a minor constituent (1.5%) of the seed oil of Plantago major. This previously unknown β-hydroxyolefinic acid, 9-hydroxy-cis-11-octadecenoic, was characterized by IR, ¹H NMR and oxidative cleavage, and the structure was supported by MS.