Arbuscular mycorrhizal fungi as support systems for seedling establishment in grassland

Recruitment of new seedlings into the vegetation is essential for maintaining species rich plant communities. Hence it is of pivotal importance to understand factors determining seedling recruitment. Here it is tested whether arbuscular mycorrhizal fungi (AMF) promote seedling recruitment in perennial grassland communities. Seeds of four plant species (two grasses and two forbs) were added to patches within 1‐year old grassland microcosms that were inoculated with different AMF taxa or to control microcosms that were not inoculated. The seedlings grew larger and obtained more phosphorus when AMF were present. Moreover, the seedlings obtained different amounts of phosphorus in microcosms inoculated with different AMF taxa. The results indicate that AMF promote seedling establishment by integrating emerging seedlings into extensive hyphal networks and by supplying nutrients to the seedlings. AMF, thus, act as a symbiotic support system that promotes seedling establishment and reduces recruitment limitation in grassland.     

Mycorrhization of the Commercially Important Micropropagated Plants

Abstract

In the last few years, urbanization and changes in eating habits have caused a significant shift toward the consumption of fresh fruits, leafy green salads, and vegetables. This has been followed by a growing commercialization of ornamental plants. These products come from a labor- and capital-intensive activity, where chemical inputs play an essential role but also brings with it a set of problems linked to the degradation of the natural environment and resource base. The present review presents new developments in the potential use of biological tools such as arbuscular mycorrhizal fungi (AMF), which should ensure adequate levels of food production with satisfactory reduction of chemical fertilizer and pesticides, in the context of technologies needed for sustainable agriculture. The potential of mycorrhizal fungi as biofertilizers and bioprotectors to enhance crop production is well recognized, but not well exploited because of the current agronomic practices, with their implications for the environment. To clarify a few salient points, we discuss a case experiment conducted on tissue culture-raised plantlets in association with mycorrhizal fungi grown in a controlled growth house (phytotron) and then transferred to the field for follow-up response under natural conditions.

For rooting, the genetic, developmental, positional, and physiological conditions of the microcutting are essential. Propagation in vitro offers an excellent possibility to study the factors that determine the rooting ability of a shoot. The major leap forward in the study of rooting was made 60 years ago with the discovery of the effect of auxin. (Thimann and Went, 1934). Since then, progress has been slow and no other major factor has been found to achieve rooting of recalcitrant crops. It has been postulated that redirection of research is required. We have established the positive influence of endomycorrhizal fungi (possibly Glomus mosseae Schenck and Perez) on the excessive root proliferation in the maize seedlings in in situ experiments. Evidence was documented for the secretion of growth-promoting metabolites like indole acetic acid (IAA) and kinetin on associative growth and development of maize roots and fungal symbionts. Such a study under controlled conditions with micropropagated plants will allow identification of the promoters involved and accurate determination of which step in the rooting process is blocked in recalcitrant crops. This review highlights such a novel approach for future biotechnology.     

Nicotiana occidentalis 37 B als Viruswirt

An der endrotrophen vesikular‐arbuskulären Mykorrhiza (VAM) des Spargels sind vor allem Pilzarten der Gattung Glomus beteiligt. Sie bewirken eine gesicherte Förderung des Wurzel‐ und Sproßwachstums der Spargelpflanzen. Die Besiedelung der VAM‐Pilze wird durch mehrere Standortfaktoren beeinflußt. Das VAM‐Pilzinokulum kann aus mykorrhizalen Wurzelstücken, Pilzsporen und Feinerde bestehen. Die Methode ist billig und kann überall angewendet werden. Pflanzen, die mit VAM und Fusarium oxysporum f. sp. asparagi infiziert waren, erkrankten weniger als Pflanzen ohne Mykorrhiza.     

Der Einfluß von Insektiziden und Akariziden auf die Parasitierung der Apfelblattminiermotte Stigmella malella Stainton (Lepidoptera,Nepticulidae)

SEM studies were conducted on VAM associations in three ferns. Dense intracellular mycelia, terminal and intercalary vesicles were observed in cortical cells of Christella. VAM invasion in the stelar region of Microsorium and Nephrolepis is being reported for the first time.     

Mycorrhizal colonization in cowpea is host dependent and heritable

Cowpea genotypes (101) of diverse origin were evaluated for their endomycorrhizal colonization under natural field conditions in an alfisol soil. There was considerable variation in colonization ranging from 0 to 28.6%. The genetic coefficient of variability was high (55.9), heritability moderate (46.2) with high genetic advance (78.3) revealing that mycorrhizal colonization is not only host dependent but heritable.