Biofertilizing Effects of Anabaena cylindrica Biomass on the Growth and Nitrogen Uptake of Wheat

There are a substantial number of studies on the biofertilization effects of cyanobacteria in rice paddy fields, mainly attributed to biological fixation of N2, but not much attention has been given to their fertilizing capacity in aerobic soils. Few studies have used solid media (i.e. a soil) when testing the plant-growth-promoting effects of microalgae on plants, and particularly on wheat. The purpose of this study was to test the biofertilizing effect of a filamentous cyanobacterium, previously isolated from an agricultural soil, in order to evaluate the potential substitution of chemical fertilizers and to test its phyto-stimulating capacity. Seedlings of Triticum aestivum were grown in pots with a peat-vermiculite mixture (1:1 weight basis) in an experiment designed as a complete randomized block, consisting of four treatments and with four replicates each: a pure culture of Anabaena cylindrica concentrated by centrifugation to 2 g dry matter L−1 (treatment B); spent cyanobacteria growth medium filtered at 0.22 µm (treatment F); harvested cyanobacterial mat re-suspended in distilled water (treatment WB); and distilled water as a control (treatment W). Aboveground wheat plant mass was improved by 40% in both treatments with cyanobacterial biomass (B and WB), as compared to the control (W) and filtrate (F), demonstrating that the co-cultivation with living cyanobacterial biomass was key to plant improvement. Chlorophyll contents were also increased by nearly 50% and nitrogen by over 10% in the treatment WB, clearly indicating that nutrients in the filtrate were irrelevant to the beneficial effects on plant growth.This work was financed by LIFE13 ENV/ES/001251 EU Project. Rajaa Kholssi benefits from a grant of the AECID (Foreign Office of Spanish Government)

A consortium of cyanobacteria and plant growth promoting rhizobacteria for wheat growth improvement in a hydroponic system

Biofertilizers containing living organisms are attractive because of their potential positive impact on plant growth and reduced environmental effect compared to mineral fertilizers. Many studies have reported the potential of plant growth-promoting rhizobacteria (PGPR) and cyanobacteria, applied singly or in combination. In the present study, the combined effect of PGPR and cyanobacteria on Triticum aestivum L. was examined in a hydroponic growth system. Calothrix sp. and Anabaena cylindrica were used as cyanobacterial strains, and Chryseobacterium balustinum, Pseudomonas simiae and Pseudomonas fluorescens were used as PGPR strains. In addition to growth parameters, total nutrients in each treatment and the ability to produce indole acetic acid (IAA) were measured after 17 days of treatments. The study results indicate that the consortium of the five isolates gave the best performance in terms of growth parameters. It increased by 36% for plant height in the combination of Calothrix sp. and P. simiae, and the dry shoot mass was increased by 80%, 77%, and 76% under the combinations of A. cylindrica with C. balustinum, P. simiae, and P. fluorescens, respectively. The ability to produce IAA was confirmed in the treatments with cyanobacteria, with PGPR strains, and in treatments combining the different microorganisms, using both colorimetric and chromatographic methods. Thus, biofertilizers containing the consortia cyanobacteria and PGPR used in this study are recommended for improved growth of wheat plants.This work was financed by LIFE13 ENV/ES/001251 EU Project. Rajaa Kholssi benefits from a grant of the AECID (Foreign Office of Spanish Government)

Inhibitory Activity of Shrimp Waste Extracts on Fungal and Oomycete Plant Pathogens

(1) Background: This study was aimed at determining the in vitro inhibitory effect of new natural substances obtained by minimal processing from shrimp wastes on fungi and oomycetes in the genera Alternaria, Colletotrichum, Fusarium, Penicillium, Plenodomus and Phytophthora; the effectiveness of the substance with the highest in vitro activity in preventing citrus and apple fruit rot incited by P. digitatum and P. expansum, respectively, was also evaluated. (2) Methods: The four tested substances, water-extract, EtOAc-extract, MetOH-extract and nitric-extract, were analyzed by HPLC-ESI-MS-TOF; in vitro preliminary tests were carried out to determine the minimal inhibitory/fungicidal concentrations (MIC and MFC, respectively) of the raw dry powder, EtOAc-extract, MetOH-extract and nitric-extract for each pathogen. (3) Results: in the agar-diffusion-assay, nitric-extract showed an inhibitory effect on all pathogens, at all concentrations tested (100, 75, 50 and 25%); the maximum activity was on Plenodomus tracheiphilus, C. gloeosporioides and Ph. nicotianae; the diameters of inhibition halos were directly proportional to the extract concentration; values of MIC and MFC of this extract for all pathogens ranged from 2 to 3.5%; the highest concentrations (50 to 100%) tested in vivo were effective in preventing citrus and apple fruit molds. (4) Conclusions: This study contributes to the search for natural and ecofriendly substances for the control of pre- and post-harvest plant pathogens

Inhibitory Activity of Shrimp Waste Extracts on Fungal and Oomycete Plant Pathogens

(1) Background: This study was aimed at determining the in vitro inhibitory effect of new natural substances obtained by minimal processing from shrimp wastes on fungi and oomycetes in the genera Alternaria, Colletotrichum, Fusarium, Penicillium, Plenodomus and Phytophthora; the effectiveness of the substance with the highest in vitro activity in preventing citrus and apple fruit rot incited by P. digitatum and P. expansum, respectively, was also evaluated. (2) Methods: The four tested substances, water-extract, EtOAc-extract, MetOH-extract and nitric-extract, were analyzed by HPLC-ESI-MS-TOF; in vitro preliminary tests were carried out to determine the minimal inhibitory/fungicidal concentrations (MIC and MFC, respectively) of the raw dry powder, EtOAc-extract, MetOH-extract and nitric-extract for each pathogen. (3) Results: in the agar-diffusion-assay, nitric-extract showed an inhibitory effect on all pathogens, at all concentrations tested (100, 75, 50 and 25%); the maximum activity was on Plenodomus tracheiphilus, C. gloeosporioides and Ph. nicotianae; the diameters of inhibition halos were directly proportional to the extract concentration; values of MIC and MFC of this extract for all pathogens ranged from 2 to 3.5%; the highest concentrations (50 to 100%) tested in vivo were effective in preventing citrus and apple fruit molds. (4) Conclusions: This study contributes to the search for natural and ecofriendly substances for the control of pre- and post-harvest plant pathogens