Efficient selection intensity in early generation index selection in groundnut (Arachis hypogaea L.)

Summary The F₂ potential of single and three-way crosses was evaluated using a set of physiological and yield components. Results were based on an index of selection using (a) only yield components and (b) both physiological and yield components. The indices were constructed using the percentage improvement of F₂ over the better parent of the corresponding F₁ cross for every character. The performance of F₂ plants assessed by the expected value of the regression index was ranked in descending order to provide a ranked F₂ distribution (FRD). The FRD was divided into four equal parts, T₂₅ (top 25%), T₅₀ (26–50%), T₇₅ (51–75%) and T₁₀₀ (76–100%). F₃ families derived from F₂ plants in T₂₅ were found to provide a higher frequency of selections for pod number than T₅₀, T₇₅ and T₁₀₀. The frequency of selections was higher in three-way than single crosses. Selection index based on physiological and yield components was more efficient in trapping F₂ plants providing selections in F₃ than the index based on yield components only. The results brought out the importance of bunch x bunch crosses as a complement to the usually advocated bunch x runner ones.     

Effects of random and non-random errors on phenotypic selection in autotetraploids

Summary A theoretical investigation was made to ascertain the effects of random and non-random deviations, called errors, of phenotypic from genotypic values on population means and on the response to phenotypic recurrent selection. The study was motivated as a selection experiment for disease resistance where there was either variability in the inoculation or environment (the random errors) or where the inoculation was above or below the the optimum rate where genetic differences in resistance are maximized (the non-random errors). The study was limited to the genetics at a diallelic locus (alleles B and b) in an autotetraploid population in random mating equilibrium. The response to selection was measured as the covariance of selection and compared to the exact covariance which was the covariance of selection without errors in phenotype. The random errors were modeled by assuming that a given percentage () of the population was uniformly distributed among the five possible genotype classes independent of their true genotypes. This model was analyzed numerically for a theoretical population with the frequency of the B allele (p) ranging from 0.0 to 1.0 and assumed errors of=0.1 and 0.5 for the following six types of genic action of the B allele: additive, monoplex dominance, partial monoplex dominance, duplex dominance, partial duplex dominance, and recessive. The effect of random error was to consistently reduce the response to selection by a percentage independent of the type of genic action at the locus. The effect on the population mean was an upward bias when p was low and a downward bias when p approached unity. In the non-random error model below optimum inoculations altered the phenotypes by systematically including percentage of susceptible genotypes into one or more other genotype classes with more genetic resistance (a positive shift). With above optimum inoculations, some resistant genotypes are classed with the non-resistant genotypes (a negative shift). The effects on the covariance of selection were found by numerical analysis for the same types of genic action and's as investigated for random error. With a negative shift and a low p, the covariance of selection was always reduced, but for an increasing p the covariance approached and exceeded the exact covariance for all types of genic action except additive. With a positive shift and a low p, response to selection was greatly improved for three types of genic action: duplex dominance, partial duplex dominance, and recessive. The effect of a non-random error on population means was to greatly bias the means upwards for a low p and positive shift, but with increasing p the bias decreased. A relatively slight decrease in the mean occurred with a negative shift. This study indicated check varieties commonly used to monitor selection pressures in screening programs are very responsive to positive non-random shifts, but are relatively unresponsive to negative shifts. The interaction of selection pressure, types of genic action, and genotypes in the class shift models was suggested as a partial explanation for the lack of response to increasing selection pressures observed in some breeding programs.Cooperative investigations of the Alfalfa Production Research Unit, United States Department of Agriculture, Agricultural Research Service, and the Nevada Agricultural Experiment Station, Reno, Nevada. Paper No. 404 Scientific Journal Series. Nevada Agricultural Experiment Station     

A sodium ion gradient as energy source for Peptostreptococcus asaccharolyticus

The determination of enzymatic activities in cell-free extracts of Acidaminococcus fermentans and Peptostreptococcus asaccharolyticus led to a refined scheme for the pathway of glutamate fermentation via (R)-2-hydroxyglutarate to acetate and butyrate. From the ratio of these products the amount of ATP generated by substrate level phosphorylation was calculated. Growth experiments with the organisms including Clostridium symbiosum and Clostridium tetanomorphum indicated that a sodium gradient contributed additional energy for growth. The high growth yields found in organisms containing the biotin dependent sodium pump glutaconyl-CoA decarboxylase could be reduced by the sodium ionophor monensin. In P. asaccharolyticus energy equivalent up to 0.6 mol ATP per mol of glutaconyl-CoA decarboxylated was conserved via the Na⁺ gradient. The data may explain the growth promoting effects of monensin in cattle.     

A biological sampling problem illustrated by the population structure and growth patterns of Sardinella aurita at Tripoli,Libya

Synopsis Sardinella aurita were sampled from catches of the lampara fishery at Tripoli, Libya during October 1979 through to September 1980. Landings consisted mainly of adult fish with large (mode 21–26 cm total length), relatively fast growing 3–5-group individuals in winter and spring and smaller (mode 14–20 cm total length), slow growing 2- and 3-group fish in summer. Gonad growth commenced in April, when the fish were feeding on zooplankton, and continued at the expense of mesenteric fat until July. It is suggested that the older and bigger fish spawn first, probably after having moved westwards, and that this results in spatial and temporal differences in length at age within the population. There was no consistent difference in growth rate between the sexes, but because first maturity in males tends to occur earlier than in females, there were length distribution differences between the sexes in the youngest (2+) age group as sampled.     

Infection and development of Nosema bombycis (Microsporida: Protozoa) in a cell line of Antheraea eucalypti

Spores of Nosema bombycis derived from diseased insects were highly purified by Urografin density gradient centrifugation. Antheraea eucalypti cells were inoculated with the purified spores primed with 0.1 n KOH solution to start a continuous propagation of N. bombycis in cell culture. The first increase in the number of infected A. eucalypti cells was observed at 48 hr postinoculation, and it was caused by the secondary infective forms of N. bombycis. The secondary infective forms were produced during the course of sporoblast differentiation. The parasites in cell cultures divided synchronously until 36 hr postinoculation. Mature spores were observed initially 6 days postinoculation at 27°C. The infected cultures were subcultured extensively for more than 1 year with the addition of healthy A. eucalypti cells.     

Transport by reconstituted lactose carrier from parental and mutant strains ofEscherichia coli

Summary The lactose transport carrier from parental (X71/F'W3747) and mutant cells (54/F'5441) was reconstituted into proteoliposomes. Transport by the counterflow assay showed slightly greater activity in proteoliposomes prepared from extracts of the mutant membranes compared with that for the parental cell. The mutant carrier showed a threefold lowerK _m but similarV _max compared to the parent. On the other hand proteoliposomes from the mutant showed a defect in protonmotive force-driven accumulation, compared with the parent. With a pH gradient (inside alkaline) plus a membrane potential (inside negative) the parental proteoliposomes accumulated lactose 25-fold over the medium concentration while the mutant proteoliposomes accumulated sixfold. In a series of experiments proteoliposomes were exposed to proteolytic enzymes. Chrymotrypsin treatment resulted in 30% inhibition of counterflow activity for the reconstituted carrier from both parent and mutant. Papain produced 84% inhibition of transport by the reconstituted parental carrier but only 41% of that of the mutant. Trypsin and carboxypeptidase Y treatment had no effect on counterflow activity of either parent or mutant. Exposure of purified lactose carrier in proteoliposomes to carboxypeptidase Y resulted in the release of alanine and valine, the two C-terminal amino acids predicted from the DNA sequence.     

Bulk separation and long-term culture of oligodendrocytes from adult pig brain. I. Morphological studies

Abstract: A method is described by which oligodendrocytes from adult pig brains can be isolated. It results in a cellular preparation suitable for long-term culture. The entire procedure can be accomplished within 2–3 h. The purity of oligodendrocytes ranges between 80 and 95% depending on the Percoll gradient used and on the time in vitro . Yields between 2.5 and 4 × 10⁷ cells per brain and plating efficiencies on the order of 60% make the system very useful for biochemical investigations. It was shown by immunocytochemical studies that oligodendrocytes produce extensive networks of processes, some of them having elaborate membranous expansions. Anti-galactocerebroside (GC) antibodies as well as anti-myelin basic protein (MBP), anti-Wolfgram protein (WP), antiglial fibrillary acidic protein (GFAP), and monoclonal antibodies O1 and O4 are used to identify the cell types and to characterize the cellular composition of the cultures. Anti-GC and O1 are suitable markers for these oligodendrocytes. Both antibodies label similar cells, and the staining intensities are equally strong. In the case of O4, variable staining intensities are observed, and a few additional cells are labeled that are anti-GC⁻. After 3¹/2 weeks in culture, about 60% of the cells can be labeled by anti-MBP. Here too differences in staining intensities are observed. The anti-WP stain is too weak to be defined as positive. The percentage of GFAP⁺ cells lies in the range 15–20% at maximum. Cells were also mixed into collagen gels. This method appears to be more useful for outgrowth and branching of fibers than are monolayer systems. Drawbacks, however, include limited access for the antibodies and poor recovery of undamaged cells with their fibers.     

Uptake of Magnesium by Chromaffin Granules In Vitro: Role of the Proton Electrochemical Gradient

Abstract: The chromaffin granule membrane in vitro is impermeable to protons as well as to Mg²⁺; however, when granules are incubated in the presence of the proton ionophore carbonyl cyanide p -trifluoromethoxy-phenylhydrazone or an inhibitor of the granule membrane Mg²⁺-dependent ATPase, the metal ion is accumulated inside the granules. This accumulation is dependent upon the granule transmembrane potential. The simultaneous presence of the ATPase inhibitor and the proton ionophore markedly increases metal ion incorporation. Mg²⁺ incorporation is also promoted by nigericin in the presence of potassium or sodium ions, indicating that Mg²⁺ accumulation is also dependent upon the transmembrane pH gradient. Concomitant with the Mg²⁺ accumulation, there is a significant loss of endogenous catecholamines. It is concluded that Mg²⁺ accumulation is determined by the electrochemical gradient maintained across the membrane. Once the metal ion has accumulated into the granules it displaces catecholamines from their storage sites.     

Selection for yield and yield components in the early generations of a potato breeding programme

Summary A number of unselected potato (Solanum tuberosum L.) clones were grown at two locations (a seed site and a ware site) in three consecutive years. The repeatability of total yield and yield components in the first two clonal years was compared with the same characters recorded in the third clonal year. Selection for yield in the first clonal year was only marginally more effective than a random reduction in number of genotypes, while selection in the second clonal year appeared to be somewhat more effective as judged by performance in the third clonal year. The inefficiency of selection in the first clonal year was ascribed, at least in part, to the inaccuracy of yield assessment as well as the carry-over effect of the mother tubers. Correlations of total yield were higher between different years in the same location than between different locations. Selection under growing conditions suitable for production of seed tubers tended to result in selection of early maturing clones which would not necessarily be optimal for ware growing conditions.