Variation in the response of melon genotypes to sudden wilt

Summary Differences in the response of melon genotypes to the sudden wilt disease were observed in several field trials conducted during 1993–1994 in the Arava region of southern Israel. Generally, the disease was more severe in the late summer growing season which is shorter and has higher temperatures than the spring and autumn growing seasons. The Oriental pickling melon breeding line P6a was the most tolerant among the entries tested. The response to the disease was also studied using two segregating families and their progenitors. BSK (tolerant) × P202 (susceptible) and P6a (tolerant) × D17 (susceptible). Wilting percentages of F₁, F₂ and backcross families were intermediate between the parents, suggesting an additive mode of gene action.     

Response by soil nematode populations and the soil microbial biomass to a rain episode in the hot,dry Negev Desert

Since the amount, intensity, and frequency of rainfall in desert regions vary strongly over space and time, the response by soil biota to this variability is of great importance. We conducted a study in the Negev desert in order to examine the immediate response by the soil nematode populations and the microbial biomass to varying amounts of water applied in a single pulse. Soil samples from the 0–10-cm depth were collected from areas undergoing four different wetting treatments, comprising 5, 10, 15, and 20 mm of water, and from a non-irrigated control soil. There was a correlation between diurnal variations in nematode populations and the diurnal fluctuations in soil moisture. The greatest abundance of nematodes was found in the soil treated with 20 mm water (970 individuals 100 g^-1 dry soil) which was 2, 4, 5, and 14 times larger than that found in the soil treated with 15, 10, 5, and 0 mm of water, respectively. Bacterialfeeding and fungal-feeding nematodes accounted for approximately 95% of the total nematode population found in all treatments. The microbial biomass examined in the current study exhibited an immediate response to the wetting which was greater in soil treated with, 10, 15, and 20 mm of water compared with 0 and 5 mm. However, after 4 days (96 hours) the microbial biomass stabilized again at the basic level of the 0-mm control. However, our results indicated that the major trigger for changes in the nematode populations, and in the microbial biomass, was diurnal fluctuations in soil moisture, since peaks in nematode populations and in the microbial biomass were observed at various times of the day.     

Soil biogeochemical properties of Angren industrial area, Uzbekistan

Background, aim, and scope  The present study examined air pollution effects on soil health applying microbiological parameters. It was carried out near the Angren heavy industry complex in a semiarid region of Uzbekistan. This area was selected in order to establish a national monitoring program for assessing environmental condition of areas remote but downwind from greater emission sources. Moreover, little information exists about how air pollution affects microbiological functioning of soils in semiarid and arid regions of the world, and especially those of Central Asia. Materials and methods  Soil samples were collected in May 2005 along a 20-km NE–SW river valley transect downwind from the industrial complex. Soil chemical analyses included electrical conductivity, pH, water soluble Na, Ca, and K, total soluble nitrogen, and mineralizable nitrogen content upon a 1:2 digestion by deionized water. Major elements and heavy metal inventory in solids was measured by X-ray fluorescence and atomic absorption spectrometry. Microbiological ecosystem properties were assessed by biological indicators such as basal respiration (R _B), microbial biomass related C and N contents, and microbial community functioning coefficients like the metabolic quotient qCO₂. Results  There was a significant spatial dependence and differences for all soil chemical and microbiological parameters tested. The highest contents were found for the relatively volatile metals Zn (≤1,136 mg/kg) and Pb (≤373 mg/kg) in upper soil layers near the power station suggesting that the metal pollutants are derived from local stack emissions. Soil microflora was obviously affected by heavy metals. Significant positive correlations (p ≤ 0.001) were found between the metal content, R _B, and qCO₂, while a negative one was found for the mineralizable N and C _mic/C _org ratio. A high total number of nematodes was found only most distant from the industrial emission sources. Discussion  The results disclosed remarkable spatial dependence not only of the heavy metal impact onto the soil but also of microbiological soil properties in the study area. The latter suggests bioavailability of the anthropogenic metals in the soil affecting the soil microbial community. This is suggested by less biomass formation and higher qCO₂ values in heavy metal-contaminated compared to less-polluted soil plots. Conclusions  Knowledge of these spatial ecosystem functioning patterns and dependence could be very useful in determining and delineating specific land use and management programs that would be suited and feasible for the highly polluted area. Results of this study can be utilized to develop a monitoring program that may quantify harmful effects on the soil health and impact of any future remediation activities. Recommendations and perspectives  Studies on the relationship between soil biota and pollution levels have raised the question regarding the status of natural soil microbial health, stressing the importance of background data of environmental conditions, and elucidating the importance of this environmental monitoring approach even in semiarid and arid regions. Soil microbiological parameters, in particular the metabolic quotient qCO₂ as one of the most sensitive bioindicators identified for that region, should clearly become part of the national environmental monitoring program.     

Porcine SWC1 is CD52--final determination by the use of a retroviral cDNA expression library

During the last decades for several species--e.g. swine--many mAb to leukocyte-specific molecules have been developed and clusters of differentiation corresponding to human CD could be established. However, for a significant amount of the raised mAb the corresponding antigens were not characterized on the molecular level and therefore preliminary clusters--in swine so-called Swine workshop clusters (SWC)--were established. These clusters contain antigens with currently no obvious orthologs to human leukocyte differentiation antigens. In this study, we describe the generation of a eukaryotic cDNA expression library from in vitro activated porcine peripheral blood mononuclear cells. Screening of this library with an antibody recognizing SWC1 enabled isolation and sequencing of cDNAs coding for the porcine SWC1 molecule. A BLAST search of the obtained sequence revealed that SWC1 is the orthologous molecule of human CD52. Therefore, our study provides the basis for comparative studies on the role of CD52 in different mammalian species. In addition, the established cDNA library can be used for investigation of additional SWC-defined molecules.     

What do we learn from neutrinos?

Each type of particle, by definition, is special. The special property of neutrinos is that they are penetrating. This has made their discovery and the understanding of their properties elusive, but it has also made them a useful tool in the study of particles and their interactions. In astrophysics, on account of this property, neutrinos provide an important means for energy transfer and permit insight into the interior of stars hidden to other radiation. The special conditions in space permit, in turn, the study of neutrino properties not possible in the laboratory.     

Genetic Variation and Yield Performance of Jerusalem Artichoke Germplasm Collected in China

Jerusalem artichoke (Helianthus tuberosus L.) is a perennial tuberous plant rich in inulin and is a potential energy crop.This study was conducted in a semiarid region of the Loess Plateau to investigate variations in morphological and agronomic characteristics and yield performance of 59 Jerusalem artichoke clones collected from 24 provinces in China.The germplasm we collected exhibited variations either in qualitative or in quantitative traits. Substantial genetic variations (genotype coefficient of variation ＞20%) in the main stem diameter, main stem number per plant, branch number per main stem, tuber number per plant, tuber size, tuber yield, and top yield (i.e., aboveground biomass) were found as well. Seven clones had a tuber yield ranging between 9.1-10.6 t ha-1, 7 clones had a top yield ranging between 18.1-31.3 t ha-1, and 15clones had a total biomass yield (i.e., tuber and top weight) between 25.0-35.0 t ha-1 on an oven-dried weight basis under the drought soil and climatic condition in the semiarid region. The 59 Jerusalem artichoke clones were clustered into 8groups based on 17 quantitative traits, and indicated that the most prevalent clones planted by farmers exhibited relatively low variation. Correlation analysis was conducted on the morphology and agronomy of the clones. This investigation suggests possible genetic improvement of Jerusalem artichoke for a higher tuber yield or a top biomass yield, and as a promising application for inulin or bioenergy in semiarid regions.     

Accumulation and partitioning of nitrogen,phosphorus and potassium in different varieties of sweet sorghum

This study investigated changes in accumulation and partitioning of nitrogen (N), phosphorus (P), and potassium (K) with harvest dates of early, middle, and late maturity sweet sorghum varieties in 2006 and 2007 in North China. All the varieties exhibited an obvious trend of decrease in concentrations of N, P and K in aboveground plants from elongation to 60 days after anthesis (DAA). The reduction in nutrient concentrations was found in the order of K (14.5 − 4.5 g kg⁻¹) > N (13.3 − 7.4 g kg⁻¹) > P (2.40 − 0.96 g kg⁻¹). Conversely, N, P, and K accumulation significantly increased from elongation to anthesis, and continued to increase until 40 DAA. The accumulation of N, P, and K at maturity (40 DAA) was 128–339 kg ha⁻¹, 30–75 kg ha⁻¹ and 109–300 kg ha⁻¹, respectively. Between elongation and anthesis, the middle and late maturity varieties had a higher ratio of N (50–82%), P (55–83%), and K (62–88%) accumulation than the early varieties (51–64% for N, 40–62% for P, and 55–75% for K). Sweet sorghum exhibited only one important K uptake stage from elongation to thesis according to the accumulation ratio (percentage of the nutrient accumulated at a given stage relative to that at physiological maturity) and rate (kilogram of nutrient accumulated per day per hectare). The stage from anthesis to grain maturity was the second important N and P uptake period. During the delay harvest period between 40 and 60 DAA, the early varieties exhibited significant increases in N accumulation; and the late varieties exhibited the reverse. P accumulation did not decrease significantly, whereas K accumulation decreased for all varieties in both years. Although of the N and P concentrations in straw were significantly lower than in grains, the N, P and K accumulation in straw was 2.2–9.3, 1.7–7.7, and 8.1–30.5 times higher than in grains, respectively. The concentrations of N and P in leaves were higher than in stems after anthesis. We found significantly higher accumulation of P and K in stems than in leaves, with a comparable N accumulation. The findings are helpful to make a fertilization regime recommendation for sweet sorghum production as a bioethanol crop in North China. It also suggests a further genetic improvement for optimizing nutrient use.     

Soil carbohydrates along a topoclimatic gradient in a Judean desert ecosystem

Soil carbohydrates, which include polysaccharides, are partly of microbial origin, contributing to soil structure and improving soil aggregates. This study examined the effect of climate along a topoclimatic gradient in the Judean desert. Soil was sampled at four locations representing different abiotic environments along the transect during the 1994 and 1995 study period. Significant differences in soil organic matter between the locations were obtained, decreasing towards the dry extreme desert sites. Carbohydrates, which probably are mainly composed of microbial extracellular polysaccharides, were found to increase during the dry season reaching maximum values by the end of autumn. The spatial and temporal changes in carbohydrate content are of great importance, representing biological activity that contributes to bonding between soil particles and helps promote nutrient accessibility to microorganisms. Copyright © 1999 John Wiley & Sons, Ltd.     

Substrate utilization patterns of desert soil microbial communities in response to xeric and mesic conditions

The Negev Desert is characterized by low soil moisture and organic matter content and an unpredictable rainfall amount, dispersion, and intensity. Water and nutrient availability are, therefore, the major limiting factors of biological activity in arid and semi-arid ecosystems. Plants have developed different ecophysiological adaptations in order to cope with the harsh conditions in this xeric environment, e.g., excretion of salt (Reaumuria negevensis) and chemical compounds (Artemisia sieberi) through the leaves. Microorganisms constitute a major part of these ecosystems' total biomass, and are diverse members of the soil food web, being primarily responsible for breaking down complex organic compounds, which are then recycled. They are also known to be very sensitive to abiotic changes and can time their activity to the environmental conditions.Soil samples were collected monthly from a 0 to 10 cm depth, under the canopies of A. sieberi, Noaea mucronata, and R. negevensis. Samples collected from inter-shrub spaces served as control. CO₂ evolution, microbial biomass, microbial functional diversity, and the physiological profile of the community, were determined by MicroResp™ analysis. A significant difference was found between the two dry periods in most of the examined parameters. The values of water, organic matter content, and total soluble nitrogen were higher in soil samples collected in the vicinity of R. negevensis than in samples collected in the vicinity of N. mucronata, A. sieberi, and the open area. A similar trend was found in CO₂ evolution, microbial biomass, and H' values, in which soil samples collected beneath the canopies of N. mucronata and R. negevensis and from open area had higher values during the wet periods (which were characterized by a mesic environment) and in samples collected beneath the A. sieberi in the wet 2006 and dry 2007 periods.