Seasonal changes in surface aggregate stability under different tillage and crops

Temporal changes in the surface aggregate stability of an Oxic Paleustalf under different tillage practices (direct drilled/stubble retained versus conventional cultivated/stubble burnt) and under different crops (wheat (Triticum aestivum L.) versus lupin (Lupinus angustifolius L.)) were monitored at a 10-year-old rotation site in Wagga Wagga, N.S.W., Australia.

Seasonal fluctuations in aggregate stability were observed under all treatments and were greater than the differences detected between the different tillage and cropping treatments. The seasonal variation was significantly related to the soil water content at the time of sampling and the lowest stability occurred during the autumn/winter period. Cropping under direct drilling and stubble retention resulted in significantly higher stability and lower seasonal fluctuations in stability than under conventional tillage and stubble burning. Despite the seasonal fluctuation, water stability over the season of both of the macroaggregate (more than 250 μm) and microaggregate (less than 50 μm) fractions increased significantly.

While the mean (temporal) stability of the different treatments was significantly related to the mean organic carbon content (r = 0.91) and polysaccharide content, the temporal changes were not related to the soil organic carbon content nor the living root length density.

Lupin had a more beneficial effect on promoting macroaggregate stability than wheat under the conventional tillage/stubble burnt treatment but no significant difference was found under the direct drilled/stubble retained treatment.     

Copper toxicity in tropical barnacles,Balanus Amphitrite amphitrite and Balanus tintinnabulum tintinnabulum

The effect of Cu on survival time, O₂ consumption and accumulation of Cu in barnacles, Balanus amphitrite amphitrite and Balanus tintinnabulum tintinnabulum was studied. B. amphitrite amphitrite were found to survive longer than B. tintinnabulum tintinnabulum at all concentrations of Cu. Copper reduced the O₂ consumption of both barnacles, but the reduction was greater with B. tintinnabulum tintinnabulum. Copper accumulation in soft parts of the barnacles increased with increasing Cu concentration and time. The barnacles accumulated Cu up to a particular limit (166.7 ± 8.98 μg g^?1 in B. amphitrite amphitrite and 173.6 ± 12.17 μg g^?1 in B. tintinnabulum tintinnabulum) at all Cu concentrations beyond which they died.     

Reverse phase liquid chromatographic determination and confirmation of aflatoxin M1 in cheese

A systematic method is proposed for determination and confirmation of aflatoxin M1 in cheese by liquid chromatography (LC). A sample of cheese is extracted with chloroform, cleaned up on 2 silica gel columns followed by a Sep-Pak C18 cartridge, and chromatographed on a 5 microns octadecyl silica column with fluorometric detection. The sample extract or standard is treated with n-hexane-trifluoroacetic acid (TFA) (4 + 1) for 30 min at 40 degrees C. Analysis by LC with TFA-treatment of the extract provides quantitative data. Multiple assays of 5 samples of Gouda cheese spiked with aflatoxin M1 at levels of 0.5, 0.1, and 0.05 ng/g showed average recoveries of 93.2, 91.6, and 92.4%, with coefficients of variation of 2.63, 3.97, and 4.52%, respectively. Assay of 5 naturally contaminated cheeses resulted in 0.051-0.448 ng/g of aflatoxin M1. Limit of quantitation is about 0.01 ng/g. The identity of aflatoxin M1 is confirmed by treating aflatoxin M1 or the M2a derivative with TFA-methanol (or ethanol) (3 + 1). The TFA-methanol reaction products of M2a could be detected quantitatively.     

Marker-assisted backcross selection in an interspecific <Emphasis Type="Italic">Cucumis</Emphasis> population broadens the genetic base of cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L.)

Cucumber (Cucumis sativus L.) is a major cucurbit vegetable species whose genetic base has been drastically reduced during its domestication. The crop’s narrow genetic base (3–12% DNA polymorphism) has resulted from the use of limited genetic material and intense selection during plant improvement. Recently, however, interspecific hybridization has been successful in Cucumis via mating of C. hystrix Chakr. and C. sativus, which resulted in the amphidiploid C. hytivus. We report herein a marker-assisted strategy for increasing genetic diversity in cucumber through introgression backcrossing employing C. hytivus. The comparatively late-flowering but high-yielding, indeterminate, monoecious line WI 7012A (P₁; donor parent) derived from a C. hytivus × C. sativus-derived line (long-fruited Chinese C. sativus cv. Beijingjietou) was initially crossed to the determinate, gynoecious C. sativus line WI 7023A (P₂; recurrent parent 1), and then advanced backcross generation progeny (BC₂) were crossed with the gynoecious indeterminate line WI 9-6A (P₃; recurrent parent 2). More specifically, a single F₁ individual (P₁ × P₂) was backcrossed to P₂, and then BC progeny were crossed to P₂ and P₃, where marker-assisted selection (MAS) for genetic diversity (8 mapped and 16 unmapped markers; designated Sel) or no selection (designated NSel) was applied to produce BC₃P₂ (Sel) and BC₃P₃ (Sel), and BC₂P₂ (NSel) and BC₂P₂S₁ (NSel) progeny. Relative vegetative growth, number of lateral branches (LB), days to flowering (DF), yield (fruit number), and fruit quality [as measured by length:diameter (L:D) and endocarp:total diameter (E:T) ratios] were assessed in parents and cross-progeny. DF varied from ~20 (BC₃P₂Sel) to ~25 days (BC₂P₃Sel) among the populations examined, where progeny derived from P₂ possessed the shortest DF. Differences in cumulative yield among the populations over six harvests were detected, varying from ~8 fruits per plant in BC₃P₂ (Sel) to ~39 fruits per plant in BC₂P₃ (Sel). Although the vigorous vegetative growth of line P₁ was observed in its backcross progeny, highly heterozygous and polymorphic backcross progeny derived from P₃ were comparatively more vigorous and bore many high-quality fruit. Response to selection was detected for LB, DF, L:D, and E:T, but the effectiveness of MAS depended upon the parental lines used. Data indicate that the genetic diversity of commercial cucumber can be increased by introgression of the C. hystrix genome through backcrossing.     

Rapid and high-precision marker assisted backcrossing to introgress the <Emphasis Type="Italic">SUB1</Emphasis> QTL into BR11, the rainfed lowland rice mega variety of Bangladesh

Flooding is one of the major hazards of rice production for the rainfed lowland rice ecosystem, and tolerant cultivars are urgently needed to help protect farmers from submergence damage. A quick and efficient strategy was implemented to introgress SUB1, a major QTL for submergence tolerance, into a rainfed lowland mega variety BR11 of Bangladesh by only two backcrosses and one selfing generation. In marker-assisted backcrossing (MABC), one tightly-linked simple sequence repeat (SSR) and two gene-based markers, four flanking SSR and 116 background SSR markers were used for foreground, recombinant and background selection, respectively, in backcrosses between a SUB1 donor IR40931-33-1-3-2 and BR11. BR11-Sub1, identified in a BC₂F₂ plant, possessed BR11 type SSR alleles on all fragments analyzed except the SUB1 QTL. The introgression size in BR11-Sub1 was 800 Kb indicating approximately 99.8% identity to BR11. BR11-Sub1 along with other introgression lines showed submergence tolerance similar to the tolerant parent. Yield, yield-component parameters and grain physico-chemical properties showed successful recovery of the BR11 traits in BR11-Sub1, with yield potential ranging from 5.2 to 5.6 t/ha, not significantly different from the recurrent parent mega variety BR11. Producing a large number (~1000) of backcross F₁ plants was considered essential to achieve recombination on both sides of the gene, limiting linkage drag with only two backcrosses. A large number of background markers ensured proper recovery of the recurrent parent genome in the BC₂F₂ generation. The study demonstrates a rapid and highly precise strategy to introgress a major QTL by BC₂F₂ generation into a modern rice variety using an unadapted donor. The variety can replace BR11 on more than 2 million of ha in Bangladesh and provide major increases in rice production.     

Carrier state in human acatalasemia

The heterozygous carrier state of a rare hereditary disease, acatalasemia, has been defined biochemically. Affected homozygotes have no blood catalase activity, whereas heterozygotes show activities intermediate between this inactivity and the activity of normal controls, without overlap. Pedigrees show a high frequency of consanguineous marriages.     

Identification and characterization of a neuron-specific nuclear antigen in Drosophila

An antigen found only in neuronal nuclei of Drosophila melanogaster is revealed by staining with a monoclonal antibody (Mab44C11). This antigen appears early in development, before neurons show any other signs of antigenic or morphologic differentiation, and persists throughout development. This nuclear staining permits reliable detection of neurons in developmental studies of wild-type and mutant flies. Protein immunoblot analyses and immune precipitation experiments show that the neuronal nuclear antigen is a 50-kilodalton polypeptide.