Estimating yields of tropical maize genotypes from non-destructive,on-farm plant morphological measurements

Maize is the main grain crop grown in the highlands of sub-Saharan Africa, on a broad range of soil fertility and management conditions. Important yield variability has been reported at different scales, reflecting the intensity and spatial distribution of growth-limiting and growth-reducing factors. Maize yield estimation represents a valuable tool to assess within-farm variability in soil fertility through crop performance. The objective of this study was to develop mathematical relationships between plant morphological attributes and grain yield of tropical maize genotypes, based on plant allometric characteristics. These models were used to estimate maize yields and the estimates were validated against independent data collected from experimental and farmers’ fields in western Kenya. Three commercial hybrids and three local varieties were considered. Multiple linear regression models including plant height and either ear length or ear diameter as explanatory variables, and simple linear regressions including only plant height, were the most accurate to estimate both total aboveground biomass and grain dry matter yields per plant (r²: 0.76–0.91). Average values for the harvest index ranged between 0.34 and 0.42, varying with the total aboveground biomass produced per plant. Yield estimations on ground area basis for farmers’ fields were acceptably accurate. Plant height measurements can be easily taken at any moment after maize flowering and used in simple models to estimate maize yield. This approach proved also a valuable tool to discuss yield variability with farmers.     

First-trimester prenatal diagnosis in quintuplets: A practical approach using step-by-step embryo reduction

A multiple pregnancy of high rank may occur in a couple at risk for a Mendelian disorder. Prenatal diagnosis is hampered by the difficulty of (1) obtaining chorionic villi from each zygote arid (2) unequivocally relating each sample to the corresponding embryo. The calculation of the genetic risk according to the number of zygotes led us to propose a diagnostic strategy based on embryo reduction, a technique initially designed to improve the perinatal outcome of multiple pregnancies with normal embryos. We report a case in which this approach allowed rational use of first-trimester chorionic villus sampling in a quintuplet pregnancy at risk for non-ketotic hyperglycinaemia, resulting in the selective birth of unaffected twins.     

Prenatal diagnosis of congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency by steroid analysis in the amniotic fluid of mid-pregnancy: Comparison with HLA typing in 17 pregnancies at risk for CAH

Amniotic fluid (AF) levels of 17-hydroxyprogesterone (17OHP) and testosterone (T) were determined at 16–17 weeks in 17 pregnancies at risk for CAH and results compared to 75 normal controls. The fetus was predicted to be unaffected in 12 cases on the findings of normal AF levels of both 17OHP and T and the latter allowed a correct prediction of fetal sex in all instances. HLA typing confirmed normality in 12 cases revealing 5 carriers, 5 homozygous normal and 2 indeterminate. Steroid levels of the 2 groups were similar. Three fetuses were predicted to be CAH affected on unambiguously high levels of 17OHP and T (in female only). HLA typing was in agreement, and the diagnosis was confirmed in 2 abortuses and a female newborn by physical and hormonal studies. In the last 2 cases AF levels of OHP and T were normal but HLA (A/B/C) genotypes were identical to the CAH affected siblings. Normal physical and hormonal findings in the 2 aborted fetuses would exclude the possibility of an in utero virilizing form of CAH. The discrepancy could be explained on the basis that the fetuses had an allelic form of 21-hydroxylase deficiency or on the basis of recombination (not fully tested). It is concluded that a fully informative prenatal diagnosis of CAH should not rely entirely on HLA typing but on hormonal studies.     

Organic versus conventional arable farming systems: Functional grouping helps understand staphylinid response

The response of different feeding groups of staphylinid beetles to organic management, distance to perennial boundary and landscape context was studied in 42 paired organic and conventional winter wheat fields. Management effects were found to strongly depend on feeding group. While the activity-density of predators was higher in the conventional fields, both activity-density and species richness of detritivores were higher in the organic fields. Activity-density and species richness of detritivores were positively correlated to crop yield in the conventional but not in the organic fields. Unexpectedly, species richness as high as in the less productive organic fields was thus found in intensified conventional systems. No significant effects of landscape context could be found on activity-density or species richness of the different feeding groups. More species were caught near the field edge than in the middle, showing the importance of spill-over from field boundaries into arable crops for diversity. In conclusion, separation of species into feeding groups revealed patterns that have not been shown before. Decomposer diversity (but not that of predators and fungivores) was higher in organic fields, but reached similar levels in high-yielding conventional fields. Thus resource quality (purely organic or organic/synthetic fertiliser) and quantity appear to play a major role for this functional group.     

Feasibility Study of 316L Stainless Steel for the Ultrasonic Consolidation Process

The viability of using 316L stainless steel in the ultrasonic consolidation process was examined in this work. Ultrasonic consolidation is an additive, free-form manufacturing process that employs ultrasonic welding and machining to form a part. The process ultrasonically joins layers of metal together by welding them one at a time. Once four layers of metal foil are welded together, welding is suspended and the system machines the part outline, and repeats this cycle until a component is completed. Experiments were conducted to determine the feasibility and processing parameters for ultrasonically welding stainless steel. Mechanical testing and optical microscopy were conducted. 316L stainless steel was successfully welded. Increasing welding amplitude and decreasing welding speed were the most effective way to increase weld peel strength. Unlike work in aluminum alloys, these experiments found no relationship between horn force and peel strength. Rough processing windows for ultrasonically welding 316L were identified.     

Rapid modification in the olfactory signal of ants following a change in reproductive status

In insect societies, the presence and condition of egg-layers can be assessed with pheromones. Exocrine secretions are expected to vary in time in order to give up-to-date information on an individuals reproductive physiology. In the queenless monogynous ant Streblognathus peetersi, we allowed a previously infertile high-ranking worker to accede to the alpha rank, thus triggering the onset of her oogenesis (15 replicates). We then studied her interactions with an established egg-layer from the same colony after different durations, ranging from 20 h to several days. Even though her eggs are only ready to be laid after 30 days, the new alpha was recognised within 1–2 days. Detection occurred at a distance of a few millimetres, suggesting the involvement of a pheromone with low volatility, such as cuticular hydrocarbons. When the new alpha had differentiated for >48 h, she was attacked by the established egg-layer. In all cases, low-ranking workers eventually immobilised one of the two alphas: the new alpha was the target if she had differentiated only recently, suggesting that police workers select the dominant worker with the less fertile odour. Using the behaviour of ants as our measure, we demonstrate that a dominants olfactory signal changes rapidly with a modification in her social status, and it occurs well before the onset of egg-laying.     

Is the Newly Described Vietnamese Bovid Pseudonovibos spiralis a Chamois (Genus Rupicapra)?

 The “Linh Duong” (Pseudonovibos spiralis), a newly described Vietnamese bovid, has been shown to be related to the Caprinae on the basis of the mitochondrial cytochrome b gene sequencing from horn fragments. To integrate the greatest available biodiversity we performed a new phylogenetic analysis including all genera of Caprinae. Unexpectedly, Pseudonovibos is found to be robustly associated with Rupicapra, and closer to the Alpine than to the Pyrenean chamois. Several clues led us to interpret this result as a carry-over DNA contamination of Pseudonovibos by Rupicapra. Received: 19 July 1999 / Accepted in revised form: 20 October 1999     

Meckel-Gruber syndrome: Prenatal diagnosis at 10 menstrual weeks using embryoscopy

A case of Meckel—Gruber syndrome was diagnosed by embryoscopy at 10 menstrual weeks, allowing for early termination of pregnancy. Post-mortem examination confirmed the presence of polydactyly and bilateral cystic lesions of the mesonephros and metanephros. Both the forming nephrons and the collecting ducts were involved in the formation of renal cysts.     

Prenatal diagnosis of β thalassaemia by reverse phase HPLC

Reverse phase HPLC of radioactive globin chains has been compared to classical carboxy methyl cellulose chromatography for the prenatal diagnosis of β thalassaemia. The two methods correlated highly (r = 0.97 p < 0.0005) and provided an identical diagnosis for 40 fetal blood samples of fetuses homozygous or heterozygous for β thalassaemia. The HPLC procedure was much faster and required fewer biochemical steps (no globin preparation). It was at least as accurate and more sensitive than the classical chromatography. A single column can be used for 150 analyses and is always ready to be used. Last but not least it is much less expensive than CMC chromatography.