Rhizosphere carboxylate concentrations of chickpea are affected by soil bulk density

We investigated whether carboxylate exudation by chickpea (Cicer arietinum L.) was affected by soil bulk density and if this effect was local or systemic. We hypothesised that concentrations of carboxylates would increase with distance from the root apex due to continuous and constitutive accumulation of carboxylates, and that exudate accumulation would be greater in a compacted soil than in a loose soil. Plants were grown in split-root or single cylinders containing loose (1400 kg m (-3)) or compacted (1800 kg m (-3)) soil. Rhizosphere carboxylate concentrations were measured of whole root systems as well as of sections along the root. The root diameter was greatest of plants grown in the compacted soil; however, root diameters were the same for both root halves in the split-root design, whether they grew in loose soil or in compacted soil. Similarly, carboxylate concentrations tended to be lower for the whole root system in the compacted soil, but were the same for both root halves in the split-root design, irrespective of whether the roots were in loose soil or in compacted soil. These results indicate that both root diameter and carboxylate exudation by roots in chickpea is regulated systemically via a signal from the shoot rather than by local signals in the roots. There was no accumulation of carboxylates with increasing distance from the apex, probably because microbial degradation occurred at similar rates as carboxylate exudation. Malonate, previously suggested as deterrent to microorganisms, is likely only a selective deterrent.     

Rhizosphere soil bacterial communities and nitrogen cycling affected by deciduous and evergreen tree species

Deciduous and evergreen trees differ in their responses to drought and nitrogen (N) demand. Whether or not these functional types affect the role of the bacterial community in the N cycle during drought remains uncertain. Two deciduous tree species (Alnus cremastogyne, an N₂‐fixing species, and Liquidambar formosana) and two evergreen trees (Cunninghamia lanceolata and Pinus massoniana) were used to assess factors in controlling rhizosphere soil bacterial community and N cycling functions. Photosynthetic rates and biomass production of plants, 16S rRNA sequencing and N‐cycling‐related genes of rhizosphere soil were measured. The relative abundance of the phyla Actinobacteria and Firmicutes was higher, and that of Proteobacteria, Acidobacteria, and Gemmatimondaetes was lower in rhizosphere soil of deciduous trees than that of evergreen. Beta‐diversity of bacterial community also significantly differed between the two types of trees. Deciduous trees showed significantly higher net photosynthetic rates and biomass production than evergreen species both at well water condition and short‐term drought. Root biomass was the most important factor in driving soil bacterial community and N‐cycling functions than total biomass and aboveground biomass. Furthermore, 44 bacteria genera with a decreasing response and 46 taxa showed an increased response along the root biomass gradient. Regarding N‐cycle‐related functional genes, copy numbers of ammonia‐oxidizing bacteria (AOB) and autotrophic ammonia‐oxidizing archaea (AOA), N₂ fixation gene (nifH), and denitrification genes (nirK, nirS) were significantly higher in the soil of deciduous trees than in that of the evergreen. Structural equation models explained 50.2%, 47.6%, 48.6%, 49.4%, and 37.3% of the variability in copy numbers of nifH, AOB, AOA, nirK, and nirS, respectively, and revealed that root biomass had significant positive effects on copy numbers of all N‐cycle functional genes. In conclusion, root biomass played key roles in affecting bacterial community structure and soil N cycling. Our findings have important implications for our understanding of plants control over bacterial community and N‐cycling function in artificial forest ecosystems.     

Osmotic tolerance and intracellular ion concentrations of bovine sperm are affected by cryopreservation

In this study, the effects of cryopreservation on osmoregulation and ion homeostasis in bovine sperm were studied. We determined: (1) the osmotic tolerance limits and cell volume response upon exposure to anisotonic conditions, (2) the intracellular pH and potassium concentration, and (3) expression and localization of proteins encoding for potassium and chloride ion channels. A flow cytometric approach was used for simultaneous assessment of cell volume and viability of propidium iodide stained sperm in anisotonic media. Osmotic tolerance was found to be decreased after cryopreservation, especially in the 120 to 60 mOsm/kg osmotic range. The critical osmolality at which half of the sperm population survived increased from 55 to 89 mOsm/kg. The osmotic cell volume response for viable sperm was similar before and after cryopreservation, with an osmotic inactive volume of about 70%. The intracellular pH, determined by recording changes in carboxyfluorescein fluorescence of sperm in media with different pH before and after addition of digitonin, decreased from 6.28 in diluted sperm to 6.16 after cryopreservation. The intracellular potassium concentration, determined using the potassium ionophore nigericin and incubation in media with various potassium concentrations, increased from 154 mM to 183 mM before and after cryopreservation, respectively. The levels of the chloride and potassium ion channel proteins chloride channel 3 protein (CLC-3) and two pore domain potassium channel 2 protein (TASK-2), as detected using Western blot analysis, were not affected by cryopreservation. Immunolocalization studies showed that CLC-3 is present in the acrosome and midpiece as well as in the upper and lower tail. In conclusion, cryopreserved sperm exhibit reduced tolerance to hypotonic stress, a decreased intracellular pH, and increased intracellular potassium level.     

Rice grain zinc concentrations as affected by genotype, native soil-zinc availability, and zinc fertilization

The development of rice (Oryza sativa L.) cultivars with a higher Zn content in their grains has been suggested as a way to alleviate Zn malnutrition in human populations subsisting on rice in their daily diets. This study was conducted to evaluate the effects of native soil Zn status and fertilizer application on Zn concentrations in grains of five rice genotypes that had previously been identified as either high or low in grain Zn. Genotypes were grown in field trials at four sites ranging in native soil-Zn status from severely deficient to high in plant available Zn. At each site a −Zn plot was compared to a +Zn plot fertilized with 15 kg Zn ha⁻¹. Results showed that native soil Zn status was the dominant factor to determine grain Zn concentrations followed by genotype and fertilizer. Depending on soil-Zn status, grain Zn concentrations could range from 8 mg kg⁻¹ to 47 mg kg⁻¹ in a single genotype. This strong location effect will need to be considered in estimating potential benefits of Zn biofortification. Our data furthermore showed that it was not possible to simply compensate for low soil Zn availability by fertilizer applications. In all soils fertilizer Zn was taken up as seen by a 50–200% increase in total plant Zn content. However, in more Zn deficient soils this additional Zn supply improved straw and grain yield and increased straw Zn concentrations by 43–95% but grain Zn concentrations remained largely unchanged with a maximum increase of 6%. Even in soils with high Zn status fertilizer Zn was predominantly stored in vegetative tissue. Genotypic differences in grain Zn concentrations were significant in all but the severely Zn deficient soil, with genotypic means ranging from 11 to 24 mg kg⁻¹ in a Zn deficient soil and from 34 to 46 mg kg⁻¹ in a high Zn upland soil. Rankings of genotypes remained largely unchanged from Zn deficient to high Zn soils, which suggests that developing high Zn cultivars through conventional breeding is feasible for a range of environments. However, it may be a challenge to develop cultivars that respond to Zn fertilizer with higher grain yield and higher grain Zn concentrations when grown in soils with low native Zn status.     

Coastal insect herbivore communities are affected more by local environmental conditions than by plant genotype

Abstract.

• 1 We compared the effects of plant genotype and local environment on population densities of a community of coastal insect herbivores in west-central Florida. Reciprocal transplants of four genotypes of three species of coastal plants, Borrichia frutescens, Iva frutescens and Limbricata, were made in July 1992 between a series of off-shore islands.
• 2 For each plant species, phytophagous insects with a wide range of feeding modes including gall-makers, stem borers, leaf miners and sap suckers were affected more by local environment than by plant genotype. Whereas host genotype had a significant effect on the population densities of gall-makers on B.frutescens in the spring of 1993, no significant effect on the denrities of any other insect species was found and the effect on the gall-makers on Borrichia disappeared in the summer, 1 year after the transplants had been made. In our study, local environment had by far the greatest effect on insect population densities among islands. This is an unusual result because in other studies over 80% of the insect species examined have been affected by plant genotype (Karban, 1992). This result is consistent with that reported by Stiling (1994), who censused populations of two phytophagous insects on reciprocal transplantr ot Borrichia in north Florida.
• 3 Local environment also had an effect on insect population densities within islands. This result contrasts with similar studies performed in north Florida (Stiling, 1994), where population densities did not differ within areas, and underlies how some biotic processes may change with in the same community even over relatively small changes in species range.

     

Crude and purified proteasome activity assays are affected by type of microplate

Measurement of proteasome activity is fast becoming a commonly used assay in many laboratories. The most common method to measure proteasome activity involves measuring the release of fluorescent tags from peptide substrates in black microplates. Comparisons of black plates used for measuring fluorescence with different properties show that the microplate properties significantly affect the measured activities of the proteasome. The microplate that gave the highest reading of trypsin-like activity of the purified 20S proteasome gave the lowest reading of chymotrypsin-like activity of the 20S proteasome. Plates with medium binding surfaces from two different companies showed an approximately 2-fold difference in caspase-like activity for purified 20S proteasomes. Even standard curves generated using free 7-amino-4-methylcoumarin (AMC) were affected by the microplate used. As such, significantly different proteasome activities, as measured in nmol AMC released/mg/min, were obtained for purified 20S proteasomes as well as crude heart and liver samples when using different microplates. The naturally occurring molecule betulinic acid activated the chymotrypsin-like proteasome activity in three different plates but did not affect the proteasome activity in the nonbinding surface microplate. These findings suggest that the type of proteasome activity being measured and sample type are important when selecting a microplate.     

The effect of soil pH on chickpea (Cicer arietinum) genotype sensitivity to isoxaflutole

A glasshouse experiment was conducted to investigate the effect of soil pH on chickpea (Cicer arietinum) tolerance to isoxaflutole applied pre-emergence at 0, 75 (recommended rate) and 300 g a.i. ha⁻¹. For this study, the variables examined were two desi chickpea genotypes (97039-1275 as a tolerant line and 91025-3021 as a sensitive line) and four pH levels (5.1, 6.9, 8.1, and 8.9). The results demonstrated differential tolerances among chickpea genotypes to isoxaflutole at different rates and soil pH levels. Isoxaflutole applied pre-emergence resulted in increased phytotoxicity with increases in soil pH and herbicide rate. Even the most tolerant chickpea genotype was damaged when exposed to higher pH and herbicide rates, as indicated by increased leaf chlorosis and significant reductions in plant height, and shoot and root dry weight. The effects were more severe with the sensitive genotype. The susceptibility of chickpea to this herbicide depends on genotype and soil pH which should be taken into account in breeding new lines, and in the agronomy of chickpea production.     

Rhizosphere concentrations of zinc and cadmium in a metal contaminated soil after repeated phytoextraction by Sedum plumbizincicola

A growth chamber pot experiment and a field plot experiment were conducted with the installation of rhizobags to study the effects of repeated phytoextraction by Sedum plumbizincicola on the bioavailability of Cd and Zn in the rhizosphere and bulk soil Repeated phytoextraction gave significantly lower Cd and Zn concentrations in both rhizosphere and bulk soil solutions compared with soil without repeated phytoextraction. The depletion rates of NH40Ac-extractable Zn in rhizosphere soil in each treatment (L-PS, L-NPS, H-PS, and H-NPS) were 59.7, 18.0, 16.3, and 18.6%, respectively. For NH40Ac-extractable Cd, the depletion rates in treatments L-PS, L-NPS, H-PS, and H-NPS were 6.67, 29.4, 40.3, and 41.4%, respectively. Plant shoot biomass decreased in the order H-PS > H-NPS > L-PS > L-NPS, with dry weights of 0.56, 0.42, 1.43, and 1.21 g pot(-1), respectively. Plant Cd uptake increased with increasing aqua-regia extractable metal concentrations. The NH4OAc extraction procedure was satisfactory to predict the bioavailability of Cd and Zn in rhizosphere soil in terms of shoot uptake by S. plumbizincicola with positive correlation coefficients of 0.545 (p < 0.05) and 0.452 (p < 0.05), respectively. The field study results show a slight decrease in water soluble and NH4OAc-extractable metals, a trend similar to that found in the pot experiment.     

Tissue concentrations of vasoactive intestinal peptide are affected by peritonitis-induced sepsis and hemofiltration in pigs

Vasoactive intestinal peptide (VIP) is a neuropeptide released from the autonomic nerves exerting multiple antiinflammatory effects. The aim of the present study was to investigate the impact of severe sepsis and hemofiltration in two settings on plasma and tissue concentrations of VIP in a porcine model of sepsis. Thirty-two pigs were divided into 5 groups: 1) control group; 2) control group with conventional hemofiltration; 3) septic group; 4) septic group with conventional hemofiltration; 5) septic group with high-volume hemofiltration. Sepsis induced by faecal peritonitis continued for 22 hours. Hemofiltration was applied for the last 10 hours. Hemodynamic, inflammatory and oxidative stress parameters (heart rate, mean arterial pressure, cardiac output, systemic vascular resistance, plasma concentrations of tumor necrosis factor-alpha, interleukin-6, thiobarbituric acid reactive species, nitrate + nitrite, asymmetric dimethylarginine) and the systemic VIP concentrations were measured before faeces inoculation and at 12 and 22 hours of peritonitis. VIP tissue levels were determined in the left ventricle, mesenteric and coronary arteries. Sepsis induced significant increases in VIP concentrations in the plasma and mesenteric artery, but it decreased peptide levels in the coronary artery. Hemofiltration in both settings reduced concentrations of VIP in the mesenteric artery. In severe sepsis, VIP seems to be rapidly depleted from the coronary artery and, on the other hand, upregulated in the mesenteric artery. Hemofiltration in both settings has a tendency to drain away these upregulated tissue stores which could result in the limited secretory capacity of the peptide.     

Daily changes of GABA and taurine concentrations in various hypothalamic areas are affected by chronic hyperprolactinemia

This study was designed to characterize, in anterior, mediobasal, and posterior hypothalamic and median eminence, the 24h changes of gamma aminobutyric acid (GABA) and taurine (TAU) contents in adult male rats and to analyze whether chronic hyperprolactinemia may affect these patterns. Rats were turned hyperprolactinemic by a pituitary graft. Plasma prolactin (PRL) levels increased after pituitary grafting at all time points examined. A disruption of the circadian rhythm was observed in pituitary-grafted rats, whereas GABA and TAU content followed daily rhythms in all areas studied in controls. In the mediobasal hypothalamus, two peaks for each amino acid were found at midnight and midday. In the anterior hypothalamus, GABA and TAU showed only one peak of concentration at midnight. In the posterior hypothalamus, the values of both GABA and TAU were higher during the light as compared to the dark phase of the photoperiod. In the median eminence GABA content peaked at 20:00h, the time when TAU exhibited the lowest values. Hyperprolactinemia abolished the 24h changes of GABA in the mediobasal hypothalamus and reduced its content as compared to controls. Hyperprolactinemia advanced the diurnal peak of TAU to 12:00h in the mediobasal hypothalamus and did not modify the 24:00h peak. In the anterior hypothalamus, hyperprolactinemia increased GABA and TAU contents during the light phase while it decreased them during the dark phase of the photoperiod. In the posterior hypothalamus hyperprolactinemia did not modify GABA or TAU patterns as compared to controls. In the median eminence hyperprolactinemia increased the 20:00h peak of GABA and shift advanced the decrease in TAU content at 20:00h and its maximum at 24:00h as compared to controls. These data show that GABA and TAU content exhibit specific daily patterns in each hypothalamic region studied. PRL differentially affects the daily pattern of these amino acids in each hypothalamic region analyzed.     

Nitrogen transformation rates are affected by cover soil type but not coarse woody debris application in reclaimed oil sands soils

Forest floor mineral soil mix (FMM) and peat mineral soil mix (PMM) are cover soils commonly used for reclamation of open‐pit oil sands mining disturbed land in northern Alberta, Canada; coarse woody debris (CWD) is another source of organic matter for land reclamation. We investigated net nitrogen (N) transformation rates in FMM and PMM cover soils near and away from CWD 4–6 years after oil sands reclamation. Monthly net nitrification and N mineralization rates varied over time; however, mean rates across the incubation periods and microbial biomass were greater (p < 0.05) in FMM than in PMM. Net N mineralization rates were positively related to soil temperature (p < 0.001) and microbial biomass carbon (p = 0.045). Net N transformation rates and inorganic N concentrations were not affected by CWD; however, the greater ¹⁵N isotope ratio of ammonium near CWD than away from CWD indicates that CWD application increased both gross N mineralization/nitrification (causing N isotope fractionation) and gross N immobilization (no isotopic fractionation). Microbial biomass was greater near CWD than away from CWD, indicating the greater potential for N immobilization near CWD. We conclude that (1) CWD application affected soil microbial properties and would create spatial variability and diverse microsites and (2) cover soil type and CWD application had differential effects on net N transformation rates. Applying FMM with CWD for oil sands reclamation is recommended to increase N availability and microsites.     

Growth and internal ion concentrations in seedlings of winter wheat are affected by 1 pM tentoxin

The long-term effect of tentoxin on K^+;, Ca²⁺ and total phosphorus (P) concentrations in the roots and shoots of 7- and 14-day-old seedlings of winter wheat ( Triticum aestivum L. cv. Martonvásári-8) was studied. Growth (dry weight) and shoot to root ratios (dry weight and mineral concentrations) were also estimated. One p M tentoxin increased the shoot to root ratio for dry weight after a 14-day period of application. The concentration of Ca²⁺ slightly increased in the shoot. In roots, tentoxin caused a 30% higher accumulation of Ca²⁺ after 7 days, which did not change with treatment during the following 7 days. The accumulation of Ca²⁺ was enhanced by increasing concentrations of tentoxin. K⁺ and total P levels increased in roots but decreased in shoots after 7 days. However, they were redistributed between root and shoot during days 8–14 of tentoxin treatment. The effect of tentoxin is explained as a stimulation of ion transport mainly into the vacuoles of the immature metaxylem elements. It is suggested that tentoxin and other microbial products effective at very low concentrations may have a general significance in promoting plant infection or symbiosis via the modification of physiological or biochemical processes.     

Maize grain concentrations and above-ground shoot acquisition of micronutrients as affected by intercropping with turnip, faba bean, chickpea, and soybean

Most research on micronutrients in maize has focused on maize grown as a monocrop. The aim of this study was to determine the effects of intercropping on the concentrations of micronutrients in maize grain and their acquisition via the shoot. We conducted field experiments to investigate the effects of intercropping with turnip (Brassica campestris L.), faba bean (Vicia faba L.), chickpea (Cicer arietinum L.), and soybean (Glycine max L.) on the iron (Fe), manganese (Mn), copper (Cu) and zinc (Zn) concentrations in the grain and their acquisition via the above-ground shoots of maize (Zea mays L.). Compared with monocropped maize grain, the grain of maize intercropped with legumes showed lower concentrations of Fe, Mn, Cu, and Zn and lower values of their corresponding harvest indexes. The micronutrient concentrations and harvest indexes in grain of maize intercropped with turnip were the same as those in monocropped maize grain. Intercropping stimulated the above-ground maize shoot acquisition of Fe, Mn, Cu and Zn, when averaged over different phosphorus (P) application rates. To our knowledge, this is the first report on the effects of intercropping on micronutrient concentrations in maize grain and on micronutrients acquisition via maize shoots (straw+grain). The maize grain Fe and Cu concentrations, but not Mn and Zn concentrations, were negatively correlated with maize grain yields. The concentrations of Fe, Mn, Cu, and Zn in maize grain were positively correlated with their corresponding harvest indexes. The decreased Fe, Mn, Cu, and Zn concentrations in grain of maize intercropped with legumes were attributed to reduced translocation of Fe, Mn, Cu, and Zn from vegetative tissues to grains. This may also be related to the delayed senescence of maize plants intercropped with legumes. We conclude that turnip/maize intercropping is beneficial to obtain high maize grain yield without decreased concentrations of Fe, Mn, Cu, and Zn in the grain. Further research is required to clarify the mechanisms underlying the changes in micronutrient concentrations in grain of intercropped maize.     

Systemic but not intraovarian concentrations of insulin-like growth factor-I are affected by short-term fasting.

To determine whether systemic and/or intraovarian concentrations of insulin-like growth factor-I (IGF-I) are affected by short-term fasting, 24 heifers were blocked by weight and, within block, were assigned to one of three treatments: fasted for 0 h (controls; n = 8), fasted for 24 h (n = 8), or fasted for 48 h (n = 8). Blood plasma was collected every 8 h from -64 h to 0 h before ovariectomy (OVEX). OVEX was performed per vagina under local anesthesia during the follicular phase of an estrous cycle (36-42 h after synchronization with prostaglandin-F2 alpha). Follicular fluid (FFL) and granulosa cells were collected individually from follicles greater than or equal to 6 mm (large), and FFL was pooled from follicles 1.0-5.9 mm (small) in diameter. Fasting did not affect (p greater than 0.20) the number (mean +/- SE) of small (52 +/- 7) or large (1.5 +/- 0.4) follicles per heifer, specific binding of 125I-hCG to granulosa cells of follicles greater than or equal to 8 mm in diameter, or concentrations of progesterone in FFL of small follicles. At OVEX, body weight was less (p less than 0.01) for 24 h- and 48 h-fasted heifers (412 +/- 7 kg and 399 +/- 7 kg, respectively) than for 0 h-fasted heifers (442 +/- 7 kg). At OVEX, plasma concentrations of IGF-I were lower (p less than 0.05) in the 48 h-fasted group (105 +/- 8 ng/ml) than in the 0 h-fasted group (140 +/- 8 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)     

Viability of frozen-thawed mouse embryos is affected by genotype

Embryos from mice of five different genotypes were evaluated for their ability to survive cryopreservation as measured by post-thaw in vitro development. In Study 1, ovulation was induced with a standardized pregnant mares' serum gonadotropin (PMSG)/human chorionic gonadotropin (hCG) regimen, after which females were mated with males of the same genotype to produce incrossed embryos. Four- to 8-cell embryos were frozen in 1.5 M dimethyl sulfoxide (DMSO) at a rate of 0.5 degrees C/min to -80 degrees C and stored in liquid nitrogen. Following thawing at room temperature, embryos were cultured and development was evaluated 24 h later. The mean (+/- SEM) number of 4- to 8-cell embryos/pregnant female by stock/strain were: N:NIH(S), 6.8 +/- 0.8; N:NIH(S)-B, 5.8 +/- 0.5; N:GP(S), 6.5 +/- 0.6; C57BL/6N, 9.7 +/- 1.0; C3H/HeN MTV-, 9.5 +/- 0.9 (P less than 0.05). Post-thaw in vitro development was related to genetic background; the proportion of embryos culturing after thawing was: N:NIH(S), 49%; N:NIH(S)-B, 61%; N:GP(S), 66%; C57BL/6N, 75%; C3H/HeN MTV-, 56% (P less than 0.05). Study 2 was conducted to evaluate the influence of mating various females to males of a genotype known to have a lower post-thaw embryo survival rate. N:NIH(S)-B, N:GP(S), C57BL/6N, and C3H/HeN MTV- female mice were mated with N:NIH(S) males to produce hybrid embryos. Post-thaw embryo survival was reduced (P less than 0.05) in three of the four hybrid groups. Fresh incrossed and hybrid embryos from each study were cultured for 24 h and yielded culture rates ranging from 95% to 99% (P greater than 0.05) among all groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Decomposition and element concentrations of silver birch leaf litter as affected by boron status of litter and soil

Inadequate boron (B) nutrition can affect the structural integrity and chemical composition of plant tissues. The changes in mass and element concentrations were studied using silver birch (Betula pendula Roth) leaf litter from seedlings grown with or without added B (B_litter+ or B_litter?). The litter was produced in a growth room, and it was incubated in either B fertilised or control forest plots (B_soil+ or B_soil?) between the moss and humus layers in two Norway spruce stands for 13 months. Additionally, the field decomposition experiment included long-term N and P application treatments (N_soil and P_soil). B_litter+ somewhat reduced the remaining litter mass. In contrast, B_soil+ increased it, possibly because of lower soil pH. The +N_soil treatment reduced the remaining mass. B_litter+ increased the remaining P, S, Cu, Cd, Ni and Zn but reduced Pb. Remaining B was high in the B_litter– which also accumulated B from soil. B_soil increased remaining Ca, Cd, Mg, Na, Pb, and slightly reduced N (in N fertilised plots). These changes in decomposition and element release have a potential to affect nutrient, carbon, and heavy-metal cycles in areas where B deficiencies are common, and where B fertilisation is practised.     

Soil and root populations of fluorescent Pseudomonas spp. associated with seedlings and field-grown plants are affected by sorghum genotype

Sorghum [Sorghum bicolor (L.) Moench] is valued for bioenergy, feed and food. Potential of sorghum genotypes to support differing populations of root- and soil-associated fluorescent Pseudomonas spp. or Fusarium spp., in two soils, was assessed. Culturable pseudomonads were enumerated from roots and soil of sorghum (Redlan and RTx433) and wheat (Lewjain) seedlings repeatedly grown in cycled soils in the growth chamber. Pseudomonads and Fusarium spp. were assessed from roots and soil of field-grown sorghum along with biological control traits hydrogen cyanide (HCN) and 2,4-diacetylphlorogluconol (phl) production. After four 4-week cycles, soil associated with Redlan seedlings had greater numbers of fluorescent pseudomonads than Lewjain. In dryland field conditions, RTx433 roots had greater numbers of pseudomonads than Redlan before anthesis but similar numbers after. There were no differences in numbers of pseudomonads from dryland soil or roots or soil of irrigated plants. Percentages of HCN-producing root isolates and phl soil isolates declined on irrigated Redlan plants, but percentages of HCN-producers increased in dryland conditions. Redlan roots had greater percentages of Fusarium isolates in the Gibberella fujikuroi complex. Results indicated that sorghum genotype affected root-associated populations of fluorescent Pseudomonas spp. and Fusarium spp. across soil environments.     

Role of soil type and macrosymbiont genotype in aftereffect of biological nitrogen

Aftereffect of biological nitrogen produced by different plant genotypes was studied in gray forest and chernozem meadow soils. High efficiency was established for availability of fixed nitrogen by oats after super nodular form of peas. In the second year of aftereffect, the yield gain with regard to the breed amounted to 11 and 49% on gray forest and chernozem meadow soils, respectively.     

Infection density of Wolbachia endosymbiont affected by co-infection and host genotype

Infection density is among the most important factors for understanding the biological effects of Wolbachia and other endosymbionts on their hosts. To gain insight into the mechanisms of infection density regulation, we investigated the adzuki bean beetles Callosobruchus chinensis and their Wolbachia endosymbionts. Double-infected, single-infected and uninfected host strains with controlled nuclear genetic backgrounds were generated by introgression, and infection densities in these strains were evaluated by a quantitative polymerase chain reaction technique. Our study revealed previously unknown aspects of Wolbachia density regulation: (i) the identification of intra-specific host genotypes that affect Wolbachia density differently and (ii) the suppression of Wolbachia density by co-infecting Wolbachia strains. These findings shed new light on symbiont-symbiont and host-symbiont interactions in the Wolbachia-insect endosymbiosis and strongly suggest that Wolbachia density is determined through a complex interaction between host genotype, symbiont genotype and other factors.