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Soilborne pathogens reduce 60% of the yield of onion crops. A common fungal pathogen causing wilt disease and severe losses is Fusarium basal rot (FBR). In this study, the combination of Arbuscular Mycorrhizal Fungi (AMF) with Trichoderma harzianum was investigated against FBR. Onion samples were collected from the Ankara–Polatlı region. Among the isolates, isolate S6 was identified as F. oxysporum f. sp. cepae (FOC) using morphological and molecular methods and pathogenicity tests. Different combinations of AMF (Funneliformis mosseae pure strain and the commercial AMF) and T. harzianum were inoculated on susceptible onion cultivars (Seç, Gence, and Şampiyon). The effects of the treatments on FOC biocontrol were studied under growth chamber conditions. The results showed that Şampiyon was the most resistant, while Gence was the most susceptible to basal rot disease. Different colonization rates (8.91–24%), spore densities (16.4–50.4 spore/10 g soil), and the extent to which a plant needs mycorrhizal conditions to grow to its maximum potential (i.e., mycorrhizal dependencies—18.3–51.9%) were recorded by treatment. Both single and combined applications of AMF and Trichoderma applications suppressed FOC. Suppressive effects were more pronounced when the F. mosseae pure strain was used alone (when F. mosseae was used, disease severity decreased from 90 to 68%, p < 0.05). The F. mosseae pure strain also showed the best plant growth promotion and phosphorus content release. The results indicate an interesting potential use of F. mosseae and the combination of AMF with T. harzianum in the management of FOC in onions. [ABSTRACT FROM AUTHOR]

Numerous microbial species participate in precipitation of carbonates in various natural environments, including soils, geological formations, freshwater biofilms and oceans. Despite the geochemical interest of such a biomineralization process, its molecular mechanisms and adaptive aspects remain poorly known. Many Gram-negative bacteria use cell-to-cell communication systems relying on N-acylhomoserine lactone (AHLs) signal molecules to express certain phenotypic traits in a density-dependent manner, a phenomenon referred as to quorum-sensing (QS). In this work, bacterial isolates collected from cave and rhizosphere soil were analyzed to study the occurrence of the AHL-mediated QS in bacterial calcium carbonate (CaCO3) precipitation. To test the production of AHLs signal molecules, we cross-streaked Gram-negative calcifying strains, selected among the environmental strains studied, with the AHL-negative mutant Chromobacterium subtsugae strain CV026. Only Burkholderia ambifaria LMG 11351 was able to restore violacein production in CV026 among the tested strains. The constructed AHL-negative mutant of B. ambifaria LMG 11351 could not precipitate CaCO3 on B-4 agar. Scanning Electron Microscopy (SEM) analysis on CaCO3 crystals obtained in vitro shows crystals of different morphologies, calcified biofilms and bacteria in close contact with the precipitated crystals. In the inner layers of the bioliths deposited by B. ambifaria LMG 11351, a stream-like organization of the Burkholderia imprints was not detected by SEM. Our data provide preliminary evidence that the activation of AHL-regulated genes may be a prerequisite for in vitro bacterial carbonatogenesis, in some cases, confirming the specific role of bacteria as CaCO3 precipitating agents. We enhance the understanding of bacterial CaCO3 biomineralization and its potential biotechnology implications for QS-based strategies to enhance or decrease CaCO3 precipitation through specific bacterial processes. The AHL-negative mutant of B. ambifaria LMG 11351 (a well-known plant growth-promoting bacterium) could also be used to study plant-bacteria interactions. The adaptive role of bacterial CaCO3 biomineralization was also discussed. [ABSTRACT FROM AUTHOR]

Primary Trans Chromosomal Tritipyrum (PTCT) amphiploid is a new cereal grown in saline soil and brackish water for grain and forage production. We evaluated the tolerance to seed deterioration in 13 promising PTCT lines, assessing accelerated aging (AA) tests by using AA boxes with 100% relative humidity at 40 °C for 72 h. The (Ma/b)(Cr/b)F4 and (St/b)(Cr/b)F4) PTCT lines, more sensitive to seed aging, were primed with NaCl, Salicylic Acid (SA), and Polyethylene Glycol (PEG) to increase the seed vigor of artificially aged seeds. Germination and emergence traits, biochemical parameters, and chromosomal abnormalities induced by artificial aging were measured in deteriorated and not-deteriorated seeds. The highest reduction percentages related to seed vigor were observed in (Ka/b)(Cr/b)F2 (34.52) and La(4B,4D)/b (28.15) lines, while the lowest was found in (Ma/b)(Cr/b)F4 (7.65) and (St/b)(Cr/b)F4 (7.46) lines. Seed aging also increases electrolytes, potassium, and protein leakages. Chromosomal abnormalities are caused by seed aging that interferes with chromosome behaviors during cell division. Seed priming on aged seeds revealed an increase in the germination percentage (GP) with PEG treatment, while the priming by SA showed an increase in seedling traits, such as the seedling length (SL2). In conclusion, we highlighted the potential use of different PTCT lines and the effective use of seed priming on deteriorated seed to enhance seed viability and seedling vigor as a useful tool for sustainable agriculture. [ABSTRACT FROM AUTHOR]