The Significance ofBacillusspp. in Disease Suppression and Growth Promotion of Field and Vegetable Crops

Bacillusspp. produce a variety of compounds involved in the biocontrol of plant pathogens and promotion of plant growth, which makes them potential candidates for most agricultural and biotechnological applications. Bacilli exhibit antagonistic activity by excreting extracellular metabolites such as antibiotics, cell wall hydrolases, and siderophores. Additionally,Bacillusspp. improve plant response to pathogen attack by triggering induced systemic resistance (ISR). Besides being the most promising biocontrol agents,Bacillusspp. promote plant growth via nitrogen fixation, phosphate solubilization, and phytohormone production. Antagonistic and plant growth-promoting strains ofBacillusspp. might be useful in formulating new preparations. Numerous studies of a wide range of plant species revealed a steady increase in the number ofBacillusspp. identified as potential biocontrol agents and plant growth promoters. Among different mechanisms of action, it remains unclear which individual or combined traits could be used as predictors in the selection of the best strains for crop productivity improvement. Due to numerous factors that influence the successful application ofBacillusspp., it is necessary to understand how different strains function in biological control and plant growth promotion, and distinctly define the factors that contribute to their more efficient use in the field

Competitiveness of Bradyrhizobium japonicum inoculation strain for soybean nodule occupancy

The competitiveness of Bradyrhizobium japonicum inoculation strain against indigenous rhizobia was examined in a soil pot experiment. The effect of inoculation strain was evaluated under different soil conditions: with or without previously grown soybean and applied commercial inoculant. Molecular identification of inoculation strain and investigated rhizobial isolates, obtained from nodules representing inoculated treatments, was performed based on 16S rDNA and enterobacterial repetitive intergenic consensus (ERIC) sequencing. Inoculation strain showed a significant effect on the investigated parameters in both soils. Higher nodule occupancy (45% vs. 18%), nodule number (111% vs. 5%), nodule dry weight (49% vs. 9%), shoot length (15% vs. 7%), root length (31% vs. 13%), shoot dry weight (34% vs. 11%), shoot nitrogen content (27% vs. 2%), and nodule nitrogen content (9% vs. 5%) was detected in soil without previously grown soybean and applied commercial inoculant. Soil had a significant effect on the shoot, root and nodule nitrogen content, while interaction of experimental factors significantly altered dry weight and nitrogen content of shoots, roots and nodules, as well as number of nodules. Nodulation parameters were significantly related with shoot dry weight, shoot and nodule nitrogen content. Symbiotic performance of inoculation strains in the field could be improved through co-selection for their competitiveness and effectiveness

Ionic liquids as potentially new antifungal agents against Alternaria species

The fungal genus Alternaria Nees 1816 includes the most prevalent pathogenic species that can cause crop diseases such as blight, black spot, and dark leaf spot. In accordance with the aim of developing modern sustainable approaches in agriculture for the replacement of synthetic and toxic substances with environmentally friendly alternatives, the objective of this study was to examine thein vitro antifungal activities of 18 newly synthesized ionic liquids (ILs) against three Alternaria strains: A. padwickii, A. dauci and A. linicola. The antifungal activities of the ILs were estimated via a microdilution method to establish minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) values. The results confirmed that 17 of the 18 ILs showed strain specificity, including good antifungal activity toward Alternaria strains, with MIC and MFC values in the range of 0.04 to 0.43 mol dm(-3). The strongest antifungal effects toward all analyzed Alternaria strains were displayed by the compounds with long alkyl chains: [omim][Cl] (MIC/MFC: 0.042 mol dm(-3)), [dmim][Cl] (MIC/MFC: 0.043 mol dm(-3)), [ddmim][Cl] (MIC/MFC: 0.053 mol dm(-3)), [ddTSC][Br] (MIC/MFC: 0.053 mol dm(-3)), and [Allyl-mim][Cl] (MIC/MFC: 0.054 mol dm(-3)). The introduction of oxygen as a hydroxyl group resulted in less-pronounced toxicity towards Alternaria compared to the introduction of an ether group, while the contribution of the hydroxyl group was shown to be a more determining factor than the prolongation of the side-chain, resulting in overall fungicidal activity decrease. Our results indicate the possibility that the most effective ILs ([Allyl-mim][Cl], [omim][Cl], [dmim][Cl], [ddmim][Cl], [bTSC][Br], [hTSC][Br], [oTSC][Br], [dTSC][Br], and [ddTSC][Br]) could be applied to the control of plant diseases caused by Alternaria species, based on their potential as an environmentally friendly crop protection approach. Since salts based on TSC cations are significantly cheaper to synthesize, stable under mild conditions, and environmentally friendly after degradation, thiosemicarbazidium-based ILs can be a suitable replacement for commercially available imidazolium ILs

Seed priming treatments to improve heat stress tolerance of garden pea (Pisum sativum L.)

Heat stress seriously affects the production of cool-season food legume crops such as garden peas. Seed priming is a widely used technique that increases germination and improves plant growth and development, resulting in better field performance and higher yield of crops. In the current study, we investigated three seed priming treatments—hydropriming (dH2O), osmopriming (2.2% w/v CaCl2), and hormopriming (50 mg L-1 salicylic acid - SA)—and their effect on germination, initial seedling development, and physiological traits of two novel garden pea cultivars, under optimal conditions and heat stress. Seed priming with H2O, CaCl2, and SA enhanced garden pea performance under both optimal and stress conditions via significant improvements in germination energy, final germination, mean germination time, mean germination rate, seedling vigor index, shoot length, root length, fresh seedling weight, dry seedling weight, shoot elongation rate, root elongation rate, relative water content, chlorophyll content, and membrane stability index, as compared to control. The highest effect on the examined parameters was achieved by osmopriming and hormopriming in both cultivars, suggesting that these treatments could be used to improve the heat stress tolerance of garden pea, after extensive field trial

Screening of Bacillus spp. as potential biocontrol agents against sunflower pathogens

Sunflower (Helianthus annuus L.) is one of the most important oilseed crops worldwide. Numerous pathogens can affect sunflower cultivation and production, causing serious yield losses. The control of sunflower pathogens is conditioned by the limited management strategies, and it is focused on genetic resistance and chemical treatments. However, the excessive usage of agrochemicals leads to the loss of soil fertility and gradual decrease of microbial diversity, which is subsequently reflected in reduced growth and yield. For as much, the use of Bacillus spp. is becoming more frequent in modern agriculture as an environmentally sustainable and safe alternative to synthetic pesticides and fertilizers. Spore-forming Bacillus spp. are well known to protect plants from seed or soil-borne pathogens by the synthesis of various metabolites with antifungal activity, such as hydrolytic enzymes and antibiotics. These bacteria are also reported to enhance plant growth through the phytohormone production and nutrient acquisition. This study aimed to select the most effective Bacillus spp. from a group of ten antagonistic strains by antifungal activity assay

Molecular characterization of Fusarium proliferatum and F. equiseti of Pisum sativum seed

Backgraund: The presence or absence of fungi on the seed surface is an important aspect that determines the quality of seeds. Since the data on the presence of Fusarium spp. and other seed-borne pathogens on vegetable pea in Serbia are scarce, the aim of this study was to isolate seed-borne pathogens and identify the disease-causing Fusarium spp. from the infected pea seed. Methods: Colony morphology and microscopic characters of isolated Fusarium species were recorded from the cultures grown on PDA and CLA, respectively. In order to confirm the morphological identification at the species level, a single-spore culture of the representative isolates was subjected to genomic DNA extraction and gene amplification using the translational elongation factor 1α(TEF-1α) region. The PCR products were sequenced and the sequences were compared against the GenBank nucleotide database by using the BLAST alignment. Result: Based on morphological and microscopic characteristics, as well as molecular identification by sequencing the TEF gene, the presence of Fusarium equiseti and F. proliferatum was confirmed on the representative isolates Ps18, Ps19 and Ps1, Ps36 obtained from vegetable pea seeds, respectively. According to our knowledge and research, this is the first report of F. equiseti and F. proliferatum on vegetable pea seeds in Serbia

The effect of biostimulants on parsnip seed germination and initial growth

Biostimulants are used for seed quality and performance improvement. However, the impact of biostimulants on parsnip seed quality has not been examined. Slow germination of parsnip is often further impeded by stress conditions. This study therefore aimed to assess whether treatments with different biostimulants could enhance seed germination and the initial seedling growth of parsnip. Amino acid and micronutrient-based biostimulants (0.2% solutions (v/v) of Technokel Amino Mix® and Megafol®) improved germination of parsnip seeds under optimal conditions, while biostimulant treatments with humic acid, fulvic acid and micronutrients (0.02% solution (v/v) of Organiko®) enhanced the initial growth. Our findings validate the potential of biostimulant application as a seed treatment. Determination of the main physiological causes of parsnip germination enhancement is needed in further research

Cladosporium cladosporoides, pathogen of sunflower seed

The sunflower (Helianthus annuus L.) is one of the most important oil crops in the world and the most important cultivated oil crop in Serbia, where it is grown on about 160,000 to 210,000 ha and the seed yield ranging from 1.7 to 2.3 t/ha. Several seed-borne fungi including species of Alternaria, Aspergillus, Cladosporium, Drechslera, Epicoccum, Fusarium and Penicillium, have been reported from sunflower seeds and could cause different levels of losses in its production. During the routine seed quality control and seed health testing analysis of sunflower, according to ISTA Rules, Cladosporium spp. infection was observed on an average of 5%. The aim of this study was the isolation and identification of Cladosporium spp. based on their morphological characteristics and molecular analyses. Isolation of the pathogen was carried out by transferring infected seeds onto a potato dextrose agar (PDA), and incubated for 5 days at 25 °C. Cladosporium-like colonies were transferred onto fresh PDA and water agar (WA, 17 g agar and 1 liter of distilled H2O) to obtain monosporial isolates. Seven days later, five isolates formed grey-greyish brown, velvet-like colony with apically and laterally branched conidiophores. Margin of the colony was white to grey-olivaceous. Conidias were mostly globose to subglobose, 3-4.5 µm in diameter, mild to dark olivaceous brown

Presence and molecular characterization of cucumber mosaic virus on safflower in Serbia [Prisustvo i molekularna karakterizacija virusa mozaika krastavca u usevu šafranike u Srbiji]

Safflower (Carthamus tinctorius L.) is an important oilseed crop belonging to the family Asteraceae. A total of 46 safflower samples were collected from Srbobran locality (South Bačka District) in Serbia in 2015 and analysed for the presence of cucumber mosaic virus (CMV), alfalfa mosaic virus (AMV), and lettuce mosaic virus (LMV), using commercial double-antibody sandwich (DAS)-ELISA kits. Both viruses, CMV and AMV, were detected serologically in the collected samples. None of the analysed samples was found to be positive for LMV. The presence of CMV was further confirmed by mechanical transmission to test the plants including Chenopodium quinoa, C. amaranticolor, Nicotiana glutinosa, and Datura stramonium as well as C. tinctorius, confirming the infectious nature of the disease. Molecular detection of CMV was performed by amplification of a 871 bp fragment in all the tested samples, using the specific primers CMVCPfwd/CMVCPrev that amplify the entire coat protein (CP) gene and part of 3'- and 5'-UTRs of CMV RNA 3. The RT-PCR products derived from the isolates 290Saff and 294Saff were sequenced (MH577791 and MH577792, respectively) and compared with the CMV sequences available in GenBank. Phylogenetic analysis based on CP gene sequences showed clustering of the selected isolates into three subgroups: IA, IB and II. Serbian CMV isolates found in safflower belong to subgroup II. To our knowledge, this is the first report on CMV infection of safflower in Serbia, which has the potential to cause substantial damage to safflower production and pose a threat to other economic crops grown in Serbia

Bio-priming of soybean with Bradyrhizobium japonicum and Bacillus megaterium: strategy to improve seed germination and the initial seedling growth

Bio-priming is a new technique of seed treatment that improves seed germination, vigor, crop growth and yield. The objective of this study was to evaluate the effectiveness of Bradyrhizobium japonicum (commercial strains) and Bacillus megaterium (newly isolated strains) as a single inoculant and co-inoculant during seed bio-priming to improve seed germination and initial seedling growth of two soybean cultivars. The treated seeds were subjected to germination test (GT), cold test (CT) and accelerated aging test (AAT). B. megaterium significantly improved all parameters in GT and CT; final germination, shoot length, root length, root dry weight, and seedling vigor index in AAT, as compared to control. In addition, co-inoculation significantly increased all parameters except shoot dry weight in GT; all parameters in CT; germination energy, shoot length, root length, and seedling vigor index in AAT, in comparison to the control. Moreover, Br. japonicum significantly improved the germination energy, shoot length, shoot dry weight, root dry weight, and seedling vigor index in GT; all parameters in CT; shoot length, root length, and seedling vigor index in AAT, compared with non-primed seeds. Thus, B. megaterium strains could be used in soybean bio-priming as a potential single inoculant and co-inoculant, following proper field evaluation