Diversity of Arbuscular Mycorrhizal fungi under different agroforestry practices in the drylands of Southern Ethiopia.

The conversion of an agroforestry based agricultural system to a monocropping farming system influences the distribution and composition of arbuscular mycorrhizal fungi (AMF). The aim of this paper was to analyze AMF species diversity, spore density, and root colonization across different agroforestry practices (AFP) in southern Ethiopia. Soil and root samples were collected from homegarden, cropland, woodlot, and trees on soil and water conservation-based AFP. AMF spores were extracted from the soil and species diversity was evaluated using morphological analysis and root colonization from root samples. The AMF spore density, root colonization and composition were significantly different among the AFP (P < 0.05). In this study, 43 AMF morphotypes belonging to eleven genera were found, dominated by Acaulospora (32.56%), followed by Claroideoglomus (18.60%). Home gardens had the highest spore density (7641.5 spore100 g- 1 dry soil) and the lowest was recorded in croplands (683.6 spore100 g- 1 dry soil). Woodlot had the highest root colonization (54.75%), followed by homegarden (48.25%). The highest isolation frequency (63.63%) was recorded for Acaulospora scrobiculata. The distribution of AMF species and diversity were significantly related to soil total nitrogen and organic carbon. The homegarden and woodlot AFP were suitable for soil AMF reserve and conservation.

Infection Prevalence of Microsporidia Vairimorpha (Nosema) spp. in Japanese Bumblebees.

Microsporidia are spore-forming intracellular parasites of various invertebrates and vertebrates. Vairimorpha bombi negatively affects the fitness of bumblebees and its prevalence correlates with declining bumblebee populations. The invasive alien species Bombus terrestris colonized Japan and possibly introduced new parasites. To assess the infection prevalence of V. bombi in Japanese bumblebees and B. terrestris, we investigated V. bombi infections using PCR and microscopy. The prevalence of sporulating V. bombi infections in three Bombus s. str. species/subspecies was low, whereas that of non/low-sporulating Vairimorpha sp. infections in three Diversobombus species/subspecies was high. Invasive B. terrestris showed low prevalence of non/low-sporulating V. bombi infections and shared the same V. bombi haplotype with B. hypocrita found in Hokkaido, where B. terrestris is present, and in Honshu, where B. terrestris is absent. Although V. bombi may have been introduced with B. terrestris colonies imported from Europe, it seems to be originally distributed in Japan. Furthermore, a new Vairimorpha sp. was found in Japanese bumblebee species. V. bombi and Vairimorpha sp. showed different organ and host specificities in bumblebees. There are no reports on the specific effects of other Vairimorpha spp. on bumblebees; further studies are needed to clarify the individual characteristics of Vairimorpha spp.

Root Colonization and Spore Abundance of Arbuscular Mycorrhizal Fungi Along Altitudinal Gradients in Fragmented Church Natural Forest Remnants in Northern Ethiopia.

Arbuscular mycorrhizal fungi (AMF) spore density and root colonization are considered sensitive to host species and abiotic factors such as climate and soil. However, there is a knowledge gap about how fragmented native forest remnants might contribute to AMF conservation, what is the AMF spore density and root colonization, and to what extent climate change, particularly warming, might impact AMF. The aim of the study was to quantify the AMF spore density and root colonization along altitudinal gradients in three agro-ecological zones of nine church forests in northern Ethiopia. Data were collected from 45 plots. All the surveyed church forest species were colonized by AMF. However, we found a significant (p < 0.05) decrease in root colonization and AMF abundance in forests at high elevation. The topsoil had significantly (p < 0.05) higher root colonization and AMF abundance than subsurface soil. We found strong negative correlations between altitude and both spore density and root colonization and soil fertility. While we cannot separate whether spore density was temperature or soil limited, we can demonstrate the importance of conserving certain tree species, particularly Ficus species, which harbor high spore densities, in both lowland and midland church forests. In the highland, no Ficus species were found. However, Hagenia abyssinica, another Rosales, had the highest spore density in the highland ecoregion.

Greenhouse Evaluation of Clubroot Resistant-Brassica napus cv. Mendel and Its Efficacy Concerning Virulence and Soil Inoculum Levels of Plasmodiophora brassicae.

Clubroot resistance of oilseed rape (OSR) cultivars frequently relies on a major resistance gene originating from cv. Mendel. The efficacy of this resistance was studied in greenhouse experiments using two Plasmodiophora brassicae isolates, which were either virulent (P1(+)) or avirulent (P1) on Mendel. Seeds of clubroot-susceptible cultivar Visby and clubroot-resistant cultivar Mendel were sown in soil mixtures inoculated with different concentrations of resting spores (101, 103, 105, and 107 resting spores/g soil). Clubroot severity, plant height, shoot and root weight as well as resting spore propagation were assessed for each isolate and cultivar separately at four dates after sowing. The OSR cultivars behaved significantly different in the measured parameters. The threshold of inoculum density to cause disease depended strongly on the virulence of the pathogen and susceptibility of the host plant. In Visby grown in soil infested with P1, clubroot symptoms and increases in root weight and the number of propagated resting spores occurred at inoculum levels of 101 resting spores and higher, whereas Mendel was not affected in soils under the three lowest inoculum densities. In contrast, the P1(+) isolate led to earlier and more severe symptoms, heavier galls, and a significantly higher number of new resting spores in both cultivars.

[Responses of the germinability of Sphagnum spores in peat to drainage in Baijianghe Peatland, China]. / 白江河泥炭地泥炭藓孢子萌发力对排水的响应.

Drainage severely changes the environment and ecological process in peatlands, but how does it affect the germinability of Sphagnum spores in peat remains unclear. In this study, we took two peat cores from a near-pristine stand dominated by Sphagnum and a drained stand dominated by dwarf shrubs in Baijianghe Peatland in the Changbai Mountains as experimental materials. Those peat cores were cut into slices. Physicochemical characteristics were measured while Sphagnum spores from each slice were extracted to count spore density and test spore germinability. After dating and determining relationship between peat depth and age, we tried to figure out the mechanism underlying the responses of Sphagnum spore germinability to drainage. The average number of spores in the near-pristine stand was slightly higher than that in the drained stand. There was no difference in average spore germinability between the two stands. The drained stand showed higher peat bulk density, total carbon and total nitrogen relative to the near-pristine stand. Upper peat core showed no significant difference in spore accumulation rate between the two stands after drainage (in 1987), with lower average spore germinability (34%) in the near-pristine stand relative to the drained stand (72%). For the whole peat cores, C/N was positively correlated with spore ger-minability in the near-pristine stand while total carbon, pH and burial time were negatively correlated with spore germinability in the drained stand. The drainage 30 years ago had limited effect on spore accumulation, but improved germinability of spores in shallow peat by changing physicochemical properties of peat due to accelerating decomposition, and thus reduced the persistence of spore bank. This may reduce the persistent regeneration potential of Sphagnum after catastrophic distur-bances.

Diversity and abundance of arbuscular mycorrhizal fungi (Glomeromycota) associated with Ilex paraguarensis in Northeastern Argentina / Diversidad y abundancia de hongos micorrízicos arbusculares (Glomeromycota) asociados con Ilex paraguarensis en el noreste de Argentina

Introduction: The expansion and intensification of agriculture causes profound changes at a global scale, which generates a strong impact on crop productivity and consequently, a decrease in the biodiversity associated. Ilex paraguariensis, known as yerba mate, is a native species from South America and it has been introduced in the world market (e.g. Middle East, Europe, and United States) due to its multiple nutritional benefits and antioxidant properties. The association of plants of I. paraguarensis with arbuscular mycorrhizal fungi (AMF), especially under field conditions, has been scarcely reported so far. Objective: The aim of this work was to assess the species composition, richness, spore density and diversity of Glomeromycota communities of yerba mate under different crop and natural conditions, seasonally over a 2-year period. Methods: Soil samples were extracted in winter and summer from five productive sites (situations 1-5), with contrasting crop conditions with regard to historical management, as a reference situation (situation 6). Spores were identified following morphological criteria. Results: Acaulosporaceae and Glomeraceae presented the highest spore densities in all sampling sites/ seasons/years. The lowest spore density and diversity index was recorded in 2014, when rainfall was higher than in 2013. Discussion: We reported Acaulospora capsicula detected by morphological analysis, for the first time in South America. Differences between years could be attributed to rainfall. This study contributes to the knowledge of the dynamics and factors that influence the structure of AMF communities over time. This information would be valuable to generate conservation strategies for this group of microorganisms, which are key to the sustainable development of yerba mate cultivation systems.

Introducción: La expansión e intensificación de la agricultura provoca profundos cambios a escala mundial, lo que genera un fuerte impacto en la productividad de los cultivos y, en consecuencia, una disminución de la biodiversidad asociada. Ilex paraguariensis, conocida como yerba mate, es una especie nativa de América del Sur y se ha introducido en el mercado mundial (por ejemplo, Medio Oriente, Europa y Estados Unidos) debido a sus múltiples beneficios nutricionales y propiedades antioxidantes. La asociación de plantas de I. paraguarensis con hongos arbusculares (AMF), especialmente en condiciones de campo, ha sido escasamente documentada. Objetivo: El objetivo de este trabajo fue evaluar estacionalmente durante un período de 2 años: la composición de especies, la riqueza, la densidad de esporas y la diversidad de las comunidades Glomeromycota de yerba mate en diferentes cultivos y condiciones naturales. Métodos: Se extrajeron muestras de suelo en invierno y verano de cinco sitios productivos con condiciones de cultivo (situaciones 1-5), en contraste conal manejo histórico como situación de referencia (situación 6). Las esporas se identificaron siguiendo criterios morfológicos. Resultados: Acaulosporaceae y Glomeraceae presentaron las mayores densidades de esporas en todos los sitios de muestreo / estaciones / años. El índice más bajo de densidad y diversidad de esporas se registró en 2014, cuando las precipitaciones fueron más altas que en 2013. Discusión: Se registra por primera vez para América del Sur a Acaulospora capsicula identificada por caracteres morfológicos. Las diferencias entre años podrían atribuirse a las precipitaciones. Este estudio contribuye al conocimiento de la dinámica y los factores que influyen en la estructura de las comunidades AMF a lo largo del tiempo. Esta información sería valiosa para generar estrategias de conservación para este grupo de microorganismos, que son clave para el desarrollo sostenible de los sistemas de cultivo de yerba mate.

Characterizing and handling different kinds of AM fungal spores in the rhizosphere.

Spores are important propagules as well as the most reliable species-distinguishing traits of arbuscular mycorrhizal (AM) fungi. During surveys of AM fungal communities, spore enumeration and spore identification are frequently conducted, but generally little attention is given to the age and viability of the spores. In this study, AM fungal spores in the rhizosphere were characterized as live or dead by vital staining and by performing a germination assay. A considerable proportion of the spores in the rhizosphere were dead despite their intact appearance. Furthermore, morphological and molecular analyses of spores to determine species identity revealed that both viable spores and dead spores with contents were identified. The accurate identification of spores at different developmental stages on the basis of morphology requires considerable experience. Our findings suggest that surveys of AM fungal communities based on spore enumeration and morphological and molecular identification are likely to be inaccurate, primarily because of the large proportion of dead spores in the rhizosphere. A viability check is recommended prior to spore molecular identification, and the use of trap cultures would give more reliable morphological identification results. We show that the abundance and activity of AM fungi in the rhizosphere can be determined by calculating the density of viable spores and the density of spores that could germinate. The adoption of these methods should provide a more reliable basis for further AM fungal community analysis.

Mass production of spores of lactic acid-producing Rhizopus oryzae NBRC 5384 on agar plate.

Mass production of sporangiospores (spores) of Rhizopus oryzae NBRC 5384 (identical to NRRL 395 and ATCC 9363) on potato-dextrose-agar medium was studied aiming at starting its L(+)-lactic acid fermentation directly from spore inoculation. Various parameters including harvest time, sowed spore density, size of agar plate, height of air space, and incubation mode of plate (agar-on-bottom or agar-on-top) were studied. Ordinarily used shallow Petri dishes were found out to be unsuitable for the full growth of R. oryzae sporangiophores. In a very wide range of the sowed spore density, the smaller it was, the greater the number of the harvested spores was. It was also interesting to find out that R. oryzae grown downward vertically with a deep air space in an agar-on-top mode gave larger amount of spores than in an agar-on-bottom mode at 30°C for 7-day cultivation. Scale-up of the agar plate culture from 26.4 to 292 cm(2) was studied, resulting in the proportional relationship between the number of the harvested spores/plate and the plate area in the deep Petri dishes. The number of plates of 50 cm in diameter needed for 100 m(3) industrial submerged fermentation started directly from 2 × 10(5) spores/mL inoculum size was estimated as about 6, from which it was inferred that such a fermentation would be feasible. Designing a 50 cm plate and a method of spreading and collecting the spores were suggested. Bioprocess technological significance of the "full-scale industrial submerged fermentation started directly from spore inoculation omitting pre-culture" has been discussed.