Tryptophan dimer produced by water-stressed bahia grass is an attractant for Gigaspora margarita and Glomus caledonium

Stimulation of Hyphal Ramification and Sporulation in Funneliformis mosseae by Root Extracts Is Host Phosphorous Status-Dependent

A simulation of the environment inhabited by arbuscular mycorrhizal (AM) fungi could provide clues as to how to cultivate these obligate biotrophs axenically. Host intraradical and rhizospheric environments, root extracts and exudates in particular, would be crucial for AM fungi to complete their life cycles. In this study, we analyzed and compared the effects of root exudates (RE) and root extracts (RET) of white clover (Trifolium repens) on the asymbiotic growth of the AM fungus Funneliformis mosseae in vitro, and furtherly analyzed the chemical components of different RET with the LC-MS/MS technique in order to establish an asymbiotic cultivation system for this important and hardly domesticated AM fungus. RET is superior to RE in stimulating spore germination, hyphal elongation and branching, and secondary spore formation (p < 0.05). RET-induced effects were dependent on phosphate supplement levels, and the RET obtained following the treatment with low levels of phosphorus significantly promoted hyphal growth and sporulation (p < 0.05). A few newly formed secondary spores showed limited colonization of white clover roots. The low phosphorus-induced effects could be ascribed to the metabolic adjustment (mainly lipids and organic acids) of white clover roots under low phosphate conditions. Our findings demonstrate that the low phosphate-induced RET boosts the asymbiotic growth of AM fungus, and thus offers an alternative way to fulfill the life cycle of AM fungi asymbiotically.

Scanning electron microscopy indicates Pseudomonad strains facilitate AMF mycorrhization in litchi (Litchi chinensis Sonn.) air-layers and improving survivability, growth and leaf nutrient status

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Co-inoculation of pseudomonad R62 and R81 (PGPR) with Glomus intraradices (AM fungi) was tested at two different stages of litchi air-layering technique.

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The process of mycorrhization was enhanced with co-inoculation of these pseudomonad strains.

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This co-inoculation treatment reduced the mortality and increased the growth of the litchi air-layers.

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The leaf primary (N, P, and K) and micro (Zn, Cu and Fe) nutrient status in the litchi air-layers were also improved under this co-inoculation treatment.

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Inoculation after detachment of the air-layers from the mother tree was more productive.

The efficacy of two plant growth promoting rhizobacteria (PGPR) viz. Pseudomonas jessenni strain R62 and Pseudomonas synxantha strain R81 was examined for mycorrhization of arbuscular mycorrhizal (AM) fungi (Glomus intraradices), survivability, growth and leaf nutrient status in litchi air-layer system. Therefore, the litchi air-layers were inoculated with PGPR i.e., Pseudomonad strains and AM fungi alone and with combination during the preparation of air-layers on the mother tree and planting of air-layers in root trainers just after detachment of the fresh air-layers from the mother tree. The scanning electron microscopy of the litchi roots indicated that Pseudomonad strains enhanced the process of mycorrhization of AM fungi and accounted near about 11.5 (tree inoculation) to 14.5 (root trainer inoculation) per cent increase in colonization over the sole inoculation of AM fungi in respective air-layers. No sign of mortality in any air-layered plants was noted in PGPR + AM fungi and sole AM fungi inoculated air-layers up to 18 months of growing. Significantly the highest shoot and root dry weight, and root length were recorded in the air-layers inoculated with both PGPR and AM fungi. This co-inoculation of PGPR with AM fungi was also responsible for the significant enrichment of the primary (N, P and K) and micro (Zn, Cu and Fe) nutrient concentration of the leaves in the litchi air-layers. However, the inoculation of air-layers with these microorganisms failed to produce any significant effects on leaf secondary (Ca, Mg and S) nutrient content. Further, the inoculation treatments had an adverse impact on leaf Mn content. The fresh air-layers inoculated after detachment from the mother tree were performed better for most of the studied parameters than the tree inoculated air-layers.

Soil fungal resources in annual cropping systems and their potential for management

Soil fungi are a critical component of agroecosystems and provide ecological services that impact the production of food and bioproducts. Effective management of fungal resources is essential to optimize the productivity and sustainability of agricultural ecosystems. In this review, we (i) highlight the functional groups of fungi that play key roles in agricultural ecosystems, (ii) examine the influence of agronomic practices on these fungi, and (iii) propose ways to improve the management and contribution of soil fungi to annual cropping systems. Many of these key soil fungal organisms (i.e., arbuscular mycorrhizal fungi and fungal root endophytes) interact directly with plants and are determinants of the efficiency of agroecosystems. In turn, plants largely control rhizosphere fungi through the production of carbon and energy rich compounds and of bioactive phytochemicals, making them a powerful tool for the management of soil fungal diversity in agriculture. The use of crop rotations and selection of optimal plant genotypes can be used to improve soil biodiversity and promote beneficial soil fungi. In addition, other agronomic practices (e.g., no-till, microbial inoculants, and biochemical amendments) can be used to enhance the effect of beneficial fungi and increase the health and productivity of cultivated soils.