The effect of host mycorrhizal status on host plant–parasitic plant interactions

Two pot experiments were conducted to examine three-level interactions between host plants, mycorrhizal fungi and parasitic plants. In a greenhouse experiment, Poa annua plants were grown in the presence or absence of an AM fungus (either Glomus lamellosum V43a or G. mosseae BEG29) and in the presence or absence of a root hemiparasitic plant (Odontites vulgaris). In a laboratory experiment, mycorrhizal infection (Glomus claroideum BEG31) of Trifolium pratense host plants (mycorrhizal versus non-mycorrhizal) was combined with hemiparasite infection (Rhinanthus serotinus) of the host (parasitized versus non-parasitized). Infection with the two species of Glomus had no significant effect on the growth of P. annua, while hemiparasite infection caused a significant reduction in host biomass. Mycorrhizal status of P. annua hosts (i.e. presence/absence of AM fungus) affected neither the biomass nor the number of flowers produced by the attached O. vulgaris plants. Infection with G. claroideum BEG31 greatly increased the biomass of T. pratense, but hemiparasite infection had no effect. The hemiparasitic R. serotinus plants attached to mycorrhizal hosts had higher biomass and produced more flowers than plants growing with non-mycorrhizal hosts. Roots of T. pratense were colonized by the AM fungus to an extent independent of the presence or absence of the hemiparasite. Our results confirm earlier findings that the mycorrhizal status of a host plant can affect the performance of an attached root hemiparasite. However, improvement of the performance of the parasitic plant following attachment to a mycorrhizal host depends on the extent to which the AM fungi is able to enhance the growth of the host. Accepted: 23 February 2001     

Age-Related Incidence and Family History in Frontotemporal Dementia: Data from the Swedish Dementia Registry

Objectives

Frontotemporal dementia (FTD) is considered to be a mainly early-onset neurodegenerative disorder with a strong hereditary component. The aim of the study was to investigate age-related incidence and family history in FTD compared to other dementia disorders, especially Alzheimer''s disease (AD).

Methods

The Swedish Dementia Registry (SveDem) registers all new cases of dementia diagnosed by the participating centres, including data on demographics, diagnosis, and investigations used. Data for the period 2008–2011 were extracted and compared with age-related population data on a regional and national level.

Results

There were 20 305 patients registered in SveDem during 2008–2011, whereof 352 received a diagnosis of FTD. Mean age at diagnosis for FTD was 69.6 years and almost 70% of FTD cases were 65 years or older at the time of diagnosis. Both FTD and AD showed an increased incidence with age, which reached a maximum in the age group 80–84 years at 6.04 and 202 cases per 100 000 person-years, respectively. The proportion of cases with a positive family history was significantly lower in FTD than in AD.

Conclusions

Contrary to general opinion within the field, data from SveDem show that the incidence of FTD increases with age, and that the majority of cases are diagnosed after the age of 65 years. In addition, data from SveDem might suggest that the importance of hereditary factors in general is similar in FTD and AD. The recognition of these findings has important consequences for the diagnosis, treatment and care of patients with FTD.     

Occurrence of some Glomales in Finland

By using trap plants, 17 species of arbuscular mycorrhizal fungi (AMF) belonging to the order Glomales were identified in 266 soil samples collected in the period 1987–1989. Of the identified isolates, 87.1% belonged to the genus Glomus Tulasne & Tulasne, 8.5% to Acaulospora Gerdemann & Trappe, 4.1% to Scutellospora Walker & Sanders and 0.3% to Entrophospora. Of the individual species identified, Glomus hoi Berch & Trappe was the most frequently identified, followed by G. fistulosum Skou & Jakobsen and G. mosseae (Nicol. & Gerd.) Gerdemann & Trappe. Only small differences in AMF trapping ability were observed between the four trap plants used, Trifolium pratense L., Zea mays L., Allium cepa L. var. cepa and Fragaria x ananassa Duch. T. pratense was chosen for further study because it had the highest AMF sporulation index in trap cultures and it also performed better than the other plants when grown in soils with different physical and chemical properties. The proportion of soil samples where AMF were identified decreased from close to 100% in the southern and central parts of Finland to about 50% in northern Finland.     

Infection of hairy roots of strawberry (Fragaria x Ananassa Duch.) with arbuscular mycorrhizal fungus

Summary Hairy root cultures of strawberry (Fragaria x ananassa Duch.) were induced with the Agrobacterium rhizogenes strain A4. Cultures were maintained on B50 medium but could also grow on a minimal medium, which did not inhibit the growth of arbuscular mycorrhizal fungi. The growth and nutrient uptake were characterized in shake flasks and in a bioreactor. Spores of the native Finnish arbuscular mycorrhizal fungus Glomus fistulosum V128 were used to infect strawberry (Fragaria x ananassa Duch. Senga Sengana) hairy roots in vitro. During cultivation, vegetative spore formation was observed. At the end of the cultivation, hyphae and arbuscules were observed in the stained roots.Abbreviations AM arbuscular mycorrhiza - AMF arbuscular mycorrhizal fungus     

Therapeutic vaccination of active arthritis with a glycosylated collagen type II peptide in complex with MHC class II molecules

In both collagen-induced arthritis (CIA) and rheumatoid arthritis, T cells recognize a galactosylated peptide from type II collagen (CII). In this study, we demonstrate that the CII259-273 peptide, galactosylated at lysine 264, in complex with Aq molecules prevented development of CIA in mice and ameliorated chronic relapsing disease. In contrast, nonglycosylated CII259-273/Aq complexes had no such effect. CIA dependent on other MHC class II molecules (Ar/Er) was also down-regulated, indicating a bystander vaccination effect. T cells could transfer the amelioration of CIA, showing that the protection is an active process. Thus, a complex between MHC class II molecules and a posttranslationally modified peptide offers a new possibility for treatment of chronically active autoimmune inflammation such as rheumatoid arthritis.     

Creation of a non-mycorrhizal control for a bioassay of AM effectiveness

γ -irradiation of soil by 10 and 3 kGy, and the use of a myc⁻ mutant. The methods were examined on clay and loam. Two management histories were included with both soils to study the ability of the methods to differentiate AM effectiveness. For each soil type, two pot experiments were conducted in field soil, one to investigate the effects of the methods on soil nutrient status, and the other to study the effects on mycorrhization and plant response. The test plants, flax (Linum usitatissimum) and pea (Pisum sativum) myc⁺ and myc⁻ mutants, were grown in 1-l pots for 4 weeks in a growth chamber. To test the ability of the bioassay to reflect differences in AM effectiveness in the field, the mutants and benomyl were also studied in the field from which the loam for the pot experiments was obtained. The bioassay accurately represented the situation in the field and the use of benomyl appeared to be the most appropriate method currently available. The advantages were the ability to use a test plant responsive to AM, the use of less elevated nutrient concentrations than with irradiation, and thus the possibility to use untreated soil as the mycorrhizal treatment. The pea mutants proved unresponsive to AM, and reinoculation to irradiated soil resulted in only half the colonization rate in untreated soil. Benomyl may, however, lead to an underestimation of AM effectiveness because the control is not totally non-mycorrhizal. Its use also carries with it health and environmental risks. Received: 9 February 1999 / Accepted: 27 September 1999     

Arbuscular mycorrhizal fungal diversity and species dominance in a temperate soil with long-term conventional and low-input cropping systems

The aim of this work was to study the effect of long-term contrasting cropping systems on the indigenous arbuscular mycorrhizal fungal (AMF) spore populations in the soil of a field experiment located in western Finland. Conventional and low-input cropping systems were compared, each with two nutrient management regimes. The conventional cropping system with a non-leguminous 6-year crop rotation (barley–barley–rye–oat–potato–oat) was fertilized at either full (rotation A) or half (rotation B) the recommended rate. In the low-input cropping system, plant residues were returned to the plots either as such (rotation C) or composted (rotation D). In the rotation of this system, 1 year with barley was replaced by clover, and oat was cultivated mixed with pea. Thus, the 6-year rotation was barley–red clover–rye–oat + pea–potato–oat + pea. Each rotation was replicated three times, starting the 6-year rotation in three different years, these being designated point 1, point 2, and point 3, respectively. In the low-input system, biotite and rock phosphate were used to compensate for K and P in the harvested yield, while animal manure was applied at the start only. After 13 years, rotation points 1 and 3 were studied. Barley was the standing crop in all plots of rotation point 1, while oat and oat + pea were grown in rotations C and D, respectively. AMF spores were studied by direct extraction and by trapping, sampled on 15 June and 15 August. In addition, a special assay was designed for isolation of fast colonizing, dominating AMF. The cropping system did not significantly affect AMF spore densities, although the low-input cropping system with composted plant residues had the highest density with 44 spores on average and the conventional system with full fertilization 24 spores per 100 cm³ soil in the autumn samples. Species richness was low in the experimental area. Five Glomus spp., one Acaulospora, and one Scutellospora were identified at the species level. In addition to these, three unidentified Glomus spp. were found. Species richness was not affected by cropping system, rotation point, or their interactions. The Shannon–Wiener index of AMF spore distributions was significantly higher in the fully fertilized than in the half-fertilized conventional plots. Glomus claroideum was the most commonly identified single species in the experimental area. It occurred in all the cropping systems and their various rotation points, representing about 30% of the total number of identified spores. In August, G. claroideum accounted for as much as 45–55% of the total numbers of spores identified in the conventional system with halved fertilization. In contrast, Glomus mosseae occurred more commonly in June (26%) than in August (9%). A bioassay using roots as inoculum for isolation and culture of dominating AMF was successfully developed and yielded only G. claroideum. This indicates a high probability of being able to more generally identify, isolate, and culture fast colonizing generalist AMF for use as inoculants in agriculture and horticulture.     

Interactive effects of defoliation and an AM fungus on plants and soil organisms in experimental legume–grass communities

We established a 13‐week greenhouse experiment based on replicated microcosms to test whether the effects of defoliation on grassland plants and soil organisms depend on plant species composition and the presence of arbuscular mycorrhizal (AM) fungi. The experiment constituted of three treatment factors – plant species composition, inoculation of an AM fungus and defoliation – in a fully factorial design. Plant species composition had three levels: (1) Trifolium repens monoculture (T), (2) Phleum pratense monoculture (P) and (3) mixture of T. repens and P. pratense (T+P), while the AM inoculation and the defoliation treatment had two levels: (1) no inoculation of AM fungi and (2) inoculation of the AM fungus Glomus claroideum BEG31, and (1) no trimming, and (2) trimming of all plant material to 6 cm above the soil surface three times during the experiment, respectively. At the final harvest, AM colonization rate of plant roots differed between the plant species compositions, being on average 45% in T, 33% in T+P and 4% in P. Defoliation did not affect the colonization rate in T but raised the rate from 1% to 7% in P and from 20% to 45% in T+P. Shoot production and standing shoot and root biomass were 48%, 85% and 68% lower, respectively, in defoliated than in non‐defoliated systems, while the AM fungus did not affect shoot production and root mass but reduced harvested shoot mass by 8% in non‐defoliated systems. Of the plant quality attributes, defoliation enhanced the N concentration of harvested shoot biomass by 129% and 96% in P and T+P, respectively, but had no effect in T, while the C concentration of shoot biomass was on average 2.7% lower in defoliated than in non‐defoliated systems. Moreover, defoliation reduced shoot C yield (the combined C content of defoliated and harvested shoot biomass) on average by 47% across all plant species compositions and shoot N yield by 37% in T only. In contrast to defoliation, the AM fungus did not affect shoot N and C concentrations or shoot N yield, but induced 10% lower C yield in non‐defoliated systems and 17% higher C yield in defoliated T. In roots, defoliation led to 56% and 21% higher N concentration in P and T+P, respectively, and 28% higher C concentration in P, while the mycorrhizal fungus lowered root N concentration by 9.7% in defoliated systems and had no effect on root C concentrations. In the soil, the nematode community was dominated by bacterivores and the other trophic groups were found in a few microcosms only. Bacterivores were 45% more abundant in defoliated than in non‐defoliated systems, but were not affected by plant species composition or the AM fungus. Soil inorganic N concentration was significantly increased by defoliation in T+P, while the mycorrhizal fungus reduced NH₄–N concentration by 40% in T. The results show that defoliation had widespread effects in our experimental systems, and while the effects on plant growth were invariably negative and those on bacterivorous nematodes invariably positive, most effects on plant C and N content and soil inorganic N concentration varied depending on the plant species present. In contrast, the effects of defoliation did not depend on the presence of the AM fungus, which suggests that while the relative abundance of legumes and grasses is likely to have a significant role in the response of legume–grass communities to defoliation, the role of AM fungi may be less important. In line with this, the AM fungus had only a few significant effects on plant and soil attributes in our systems and each of them was modified by defoliation and/or plant species composition. This suggests that the effects of AM fungi in legume–grass communities may largely depend on the plant species present and whether the plants are grazed or not.     

Potential to improve transfer of N in intercropped systems by optimising host-endophyte combinations

Possibilities for improving N transfer from N2-fixing plants to non-N2-fixing plants by mycorrhiza have been investigated. Initially, the genetic variability with respect to N uptake was assessed by screening five varieties of chicory (Cichorium intybus L.), four of peas (Pisum sativum L.) and three of red clover (Trifolium pratense L.) in combination with eight isolates of arbuscular mycorrhizal fungi. The most promising plant - fungi combinations identified through the cultivar screening were used to optimise conditions for N transfer between intercropped N2-fixing plants (peas and clover) and non-N2-fixing chicory. In the first experiment, the recovery of fixed legume N was investigated using three cultivars, of chicory intercropped with pea variety, and inoculated with one of four mycorrhizal isolates. Roots of the N2-fixing pea and the non-N2-fixing chicory were separated by a root-free soil layer in a three-compartment container. A section of the legume roots was forced to grow into a separate compartment which received four split applications of ¹⁵N. The percentage of N in the chicory derived from transfer ranged between 3% and 50%. In a second experiment one chicory variety was intercropped with one red clover variety and inoculated with four mycorrhizal isolates respecetively. A harvest regime was chosen in which the shoots were harvested from intercropped plants at 3,4.5 and 6 months of age. At three months the percentage of N in the chicory derived from transfer ranged between 15% and 18% and at a plant age of 4.5 months from 46 to 77%. At six months the percentage of N in the chicory roots derived from transfer of legume N ranged from 20 to 34% and varied with fungal isolate. Our results show that there is potential for improving N transfer in intercropped plant systems through the methodological selection of suitable plant and mycorrhizal partners.