Metagenomic analysis of rhizosphere microbiome provides insights into occurrence of iron deficiency chlorosis in field of Asian pears

Background Fe-deficiency chlorosis (FDC) of Asian pear plants is widespread, but little is known about the association between the microbial communities in the rhizosphere soil and leaf chlorosis. The leaf mineral concentration, leaf subcellular structure, soil physiochemical properties, and bacterial species community and distribution had been analysed to gain insights into the FDC in Asian pear plant. Results The total Fe in leaves with Fe-deficiency was positively correlated with total K, Mg, S, Cu, Zn, Mo and Cl contents, but no differences of available Fe (AFe) were detected between the rhizosphere soil of chlorotic and normal plants. Degraded ribosomes and degraded thylakloid stacks in chloroplast were observed in chlorotic leaves. The annotated microbiome indicated that there were 5 kingdoms, 52 phyla, 94 classes, 206 orders, 404 families, 1,161 genera, and 3,043 species in the rhizosphere soil of chlorotic plants; it was one phylum less and one order, 11 families, 59 genera, and 313 species more than in that of normal plant. Bacterial community and distribution patterns in the rhizosphere soil of chlorotic plants were distinct from those of normal plants and the relative abundance and microbiome diversity were more stable in the rhizosphere soils of normal than in chlorotic plants. Three (Nitrospira defluvii, Gemmatirosa kalamazoonesis, and Sulfuricella denitrificans) of the top five species (N. defluvii, G. kalamazoonesis, S. denitrificans, Candidatus Nitrosoarchaeum koreensis, and Candidatus Koribacter versatilis). were the identical and aerobic in both rhizosphere soils, but their relative abundance decreased by 48, 37, and 22%, respectively, and two of them (G. aurantiaca and Ca. S. usitatus) were substituted by an ammonia-oxidizing soil archaeon, Ca. N. koreensis and a nitrite and nitrate reduction related species, Ca. K. versatilis in that of chlorotic plants, which indicated the adverse soil aeration in the rhizosphere soil of chlorotic plants. A water-impermeable tables was found to reduce the soil aeration, inhibit root growth, and cause some absorption root death from infection by Fusarium solani. Conclusions It was waterlogging or/and poor drainage of the soil may inhibit Fe uptake not the amounts of AFe in the rhizosphere soil of chlorotic plants that caused FDC in this study.

Evaluation of Water Content in Soils of Žitný Ostrov from the Point of View of Its Exploitation for Biosphere

The lithospheric zone between the soil surface and the first ground water horizon, respectively the ground water table, has a character of three-phase system. It consists of solid phase having fine to rough disperse granularity. This creates a structure of porous environment with characters that can be physically determined. The water occurs in pores in different forms of state and its bond with solid phase. Its energetic bond is clearly quantified by means of moisture retention curve. The gas phase fills pores with the water up to the value of the full porosity, i.e. it fills the part of pores that is not saturated with water. Therefore, this lithospheric zone is called the soil aeration zone. The volume of water occurring in the soil aeration zone corresponds to the concentration of water in the framework of hydrological cycle components. This water serves as the water resource for the vegetation cover. The data used for calculation were particular soil types in the area, depth of ground water table, hydrolimits (wilting point, point of decreased availability, field water capacity) and aeration zone thickness. The water content in the soil aeration zone between hydrolimits field water capacity (FWC) and wilting point (WP) is the critical interval of water content for vegetation cover in a given locality. Water from this interval is available for the vegetation cover. This water has no properties of free water, and plants have to have a developed root system and such suction pressure, that is able to overcome the bond between water and soil. Calculated results were verified with the help of monitored water content. Both calculated and measured values of soil water content in the aeration zone show that the water content is affected by appurtenant soil type. The human activity in a landscape directly affects the dynamics of this water resource, either from quantitative or qualitative viewpoint. This affect is demonstrated by changes of the ground water regime, i.e. changes of ground water table and amplitude of its fluctuation. The paper brings results of water content evaluation in the soil aeration zone in the Žitný ostrov area.

Biodegradation of Natural Rubber: Microcosm Study

In the present work, natural rubber (NR) biodegradation, by means of a microbial consortium, naturally selected in a tyre dump soil, has been evaluated. To this purpose, prepared soil microcosms were incubated for 236 days, at room temperature, and natural light/dark cycles. The effect of primary C-source and fresh soil addition, soil aeration, and humidity maintenance has been monitored by means of microbiological and respirometric analysis, dry weight loss determinations, and SEM micrographs. During the incubation, in biodegradation microcosms (BD), containing NR samples, the produced CO2 was significantly higher than that of biotic controls (BC). Furthermore, after 236 days, a NR dry weight loss of 15.6%, in BD microcosms, was registered, about four-fold higher than that registered in BC control (3.7%). Obtained results confirmed that the naturally selected microbial consortium was able to use NR as the only C-source and to biodegrade it. The positive effect of soil mixing evidenced that the biodegradation process was mainly carried out by aerobic biomass, especially filamentous fungi, as confirmed by microbial counts and SEM observations. Results obtained in the microcosm study provided useful information in terms of soil aeration and nutrient amendment in view of a future biodegradation process scale-up.

Soil aeration and plastic film mulching increases the yield potential and quality of tomato (Solanum lycopersicum)

The aim of this study was to investigate plant growth, fruit yields, IWUE and fruit quality in response to a micro/nano-bubble aeration (MNBA) system and a subsurface artificial air layer aeration system (SAALA) under different treatments. The results indicated that both MNBA and SAALA can positively influence plant dry weight, fruit yield, IWUE and, to some degree, fruit quality indices. In comparison with the no-aeration treatment, the MNBA treatment increased the dry matter accumulation, fruit yield, IWUE, lycopene content and soluble protein content by 7.1%, 9.0%, 7.1%, 6.2% and 16.2%, respectively, during the spring, while those during autumn increased by 4.0%, 14.4%, 4.0%, 3.8% and 1.7%, respectively. During the spring, the SAALA increased the dry matter accumulation, fruit yield, IWUE, lycopene content and soluble protein content by 13.0%, 25.1%, 13.0%, 2.9% and 15.1%, respectively, while those during autumn increased by 12.8%, 19.5%, 12.8%, 5.2% and 4.1%, respectively. PFM significantly improved the total dry weight, fruit yield and IWUE during both the spring and autumn seasons. Nevertheless, the soluble protein content decreased in response to the mulch treatment. The increased yield in response to soil aeration during autumn was significantly greater than that during the spring, and the yield increase in response to PFM was significantly greater in the spring than in autumn. Moreover, the nutrition indices in response to both soil aeration and PFM were more significant during spring than during autumn. Taking into account costs, efficiency and benefits, the optimal treatment was the MNBA and full PFM combination