Mapping of yield-related QTLs in pepper in an interspecific cross of Capsicum annuum and C. frutescens

An advanced backcross QTL study was performed in pepper using a cross between the cultivated species Capsicum annuum cv. Maor and the wild C. frutescens BG 2816 accession. A genetic map from this cross was constructed, based on 248 BC(2) plants and 92 restriction fragment length polymorphism (RFLP) markers distributed throughout the genome. Ten yield-related traits were analyzed in the BC(2) and BC(2)S(1) generations, and a total of 58 quantitative trait loci (QTLs) were detected; the number of QTLs per trait ranged from two to ten. Most of the QTLs were found in 11 clusters, in which similar QTL positions were identified for multiple traits. Unlike the high percentage of favorable QTL alleles discovered in wild species of tomato and rice, only a few such QTL alleles were detected in BG 2816. For six QTLs (10%), alleles with effects opposite to those expected from the phenotype were detected in the wild species. The use of common RFLP markers in the pepper and tomato maps enabled possible orthologous QTLs in the two species to be determined. The degree of putative QTL orthology for the two main fruit morphology traits-weight and shape-varied considerably. While all eight QTLs identified for fruit weight in this study could be orthologous to tomato fruit weight QTLs, only one out of six fruit shape QTLs found in this study could be orthologous to tomato fruit shape QTLs.

fs3.1: a major fruit shape QTL conserved in Capsicum

fs3.1 is a major fruit shape (defined as the ratio of fruit length to fruit width) quantitative trait locus (QTL) originally detected in an intraspecific cross of Capsicum annuum between the blocky and elongated-fruited inbreds 'Maor' and 'Perennial', respectively. In addition to increasing fruit shape index, the 'Perennial' allele at fs3.1 increased fruit elongation and decreased fruit width and pericarp thickness. We verified the effect of fs3.1 in backcross inbred lines (BILs) derived from crossing 'Perennial' with 'Maor' and with a second blocky-type inbred line of C. annuum. To determine the effect of the fs3.1 region in additional Capsicum species, we constructed an advanced backcross population from the cross of 'Maor' and the oval-fruited Capsicum frutescens BG 2816 and an F2 of the introgression line IL 152 that contains an introgression of the fs3.1 region from Capsicum chinense PI 152225. QTLs for fruit shape, fruit width, and pericarp thickness, but not for fruit length, were detected in both crosses, indicating the conservation of the fs3.1 region as a QTL affecting fruit shape in pepper. We also tested tomato (Lycopersicon spp.) introgression lines containing the corresponding fs3.1 region from L. pennellii and L. hirsutum, but we did not detect a significant fruit shape QTL in these lines. The effect of fs3.1 on the growth of fruit dimensions varied with the genetic background. By measuring the length and width of ovaries and fruits of near-isogenic C. annuum lines that differ in fs3.1 during fruit development, we determined that fs3.1 controls shape predominantly by increasing the growth rate of the longitudinal axis in the first 2 weeks after pollination. However, in the crosses of C. annuum with C. frutescens and C. chinense, fs3.1 predominantly exerted its effect on the width dimension.

Polygalacturonase: a candidate gene for the soft flesh and deciduous fruit mutation in Capsicum

The soft flesh and deciduous fruit of pepper (Capsicum spp.) originated from the wild C. frutescens BG 2816 accession is a complete dominant trait controlled by the S gene. We constructed an F2 population from a cross of BG 2816 (SS) and the bell-type C. annuum cultivar Maor (ss) and determined that S cosegregated with the tomato fruit-specific endo-polygalacturonase (PG) gene. The soft flesh and deciduous fruit phenotypes were observed together in all F2 individuals, indicating a pleiotropic effect of PG on the two traits. We mapped S to pepper chromosome 10 in the region corresponding to that in which PG was previously mapped in tomato. Northern, RT-PCR and western analyses and enzyme activity assays, collectively, indicated that PG is not detected in green, breaker or red fruits of Maor, nor in green fruits of BG 2816. Accumulation of PG mRNA and protein was detected in the fruits of BG 2816, and it increased during ripening from breaker to red stages. The sequence analysis of partial PG cDNA isolated from BG 2816 revealed high homology (87% identity) with the tomato PG. The resemblance of the soft flesh and deciduous fruit phenotypes to PG-associated phenotypes in other fruit crops, the complete linkage between S and PG, and the greater expression of PG in the fruits of BG 2816 than in those of Maor, all strongly indicate that PG is a candidate gene for S.

Emission factors of carbon monoxide and size-resolved aerosols from biofuel combustion

This study reports emission factors of carbon monoxide and size-resolved aerosols from combustion of wood, dung cake, and biofuel briquette in traditional and improved stoves in India. Wood was the cleanest burning fuel, with higher emissions of CO from dung cake and particulate matter from both dung cake and briquette fuels. Combustion of dung cake, especially in an improved metal stove, resulted in extremely high pollutant emissions. Instead, biogas from anaerobic dung digestion should be promoted as a cooking fuel for public health protection. Pollutant emissions increased with increasing stove thermal efficiency, implying that thermal efficiency enhancement in the improved stoves was mainly from design features leading to increased heat transfer but not combustion efficiency. Compared to the traditional stove, the improved stoves resulted in the lower pollutant emissions on a kW h-1 basis from wood combustion but in similar emissions from briquette and dung cake. Stove designs are needed with good emissions performance across multiple fuels. Unimodal aerosol size distributions were measured from biofuel combustion with mass median aerodynamic diameters of 0.5-0.8 micron, about a factor of 10 larger than those from fossil fuel combustion (e.g. diesel), with potential implications for lung deposition and health risk.

Production of hybrids, amphiploids and backcross progenies between a cold-tolerant wild species, Erucastrum abyssinicum and crop brassicas

Three intergeneric hybrids were produced between a cold-tolerant wild species, Erucastrum abyssinicum and three cultivated species of Brassica, B. juncea, B. carinata and B. oleracea, through ovary culture. The hybrids were characterized by morphology, cytology and DNA analysis. Amphiploidy was induced in all the F1 hybrids through colchicine treatment. Stable amphiploids and backcross progenies were obtained from two of the crosses, E. abyssinicum x B. juncea and E. abyssinicum x B. carinata. The amphiploid, E. abyssinicum x B. juncea was successfully used as a bridge species to produce hybrids with B. napus, B. campestris and B. nigra. These hybrids and backcross progenies provide useful genetic variability for the improvement of crop brassicas.

Tissue doses in the upper gastrointestinal fluoroscopy examination

A method was developed to estimate tissue doses from the upper gastrointestinal fluoroscopy examination. It involved measuring the technical parameters of the clinical examination, partitioning the dynamic examination into a set of discrete x-ray fields, and generating corresponding tissue does tables with an existing computer program. Knowledge of the radiation exposures associated with each of the fields enabled the calculation of tissue doses for the entire dynamic examination. In this limited sample (eight patients), fluoroscopy times ranged from 108 to 183 seconds. Radiation exposures ranged from 2.3 to 7.2 mC/kg (9.1-28 R), thyroid doses from 0.15 to 3.5 mGy (15-350 mrad), uterine doses from 0.16 to 1.0 mGy (16-100 mrad), lung doses from 0.90 to 4.2 mGy (90-420 mrad), and active bone marrow doses from 0.81 to 5.4 mGy (81-540 mrad).

Predicting femoral neck strength from bone mineral data. A structural approach

An interactive computer program was developed to derive femoral neck geometry from raw bone mineral image data for an estimate of hip strength using single plane engineering stress analysis. The program, which we call Hip Strength Analysis (HSA), was developed as an attempt to improve the predictive value of hip bone mineral data for osteoporosis fracture risk assessment. We report a series of experiments with an aluminum phantom and with cadaver femora, designed to test the accuracy of derived geometric measurements and strength estimates. Using data acquired with both Lunar DP3 (DPA) and Hologic QDR-1000 (x-ray) scanners, HSA computed femoral neck cross-sectional areas (CSA) and cross-sectional moments of inertia (CSMI) on an aluminum phantom were in excellent agreement with actual values (r greater than .99). Using Lunar DP3 data, CSA and CSMI measurements at mid-femoral necks of 22 cadaver specimens were in good general agreement with literature values. HSA computed cross-sectional properties of three of these specimens were compared with measurements derived from sequential CT cross-sectional images. Discrepancy between the two methods averaged less than 10% along the length of the femoral neck. Finally, breaking strengths of 20 of the femora were measured with a materials testing system, showing better agreement with HSA predicted strength (r = .89, percent standard of the estimate (%SEE) = 21%) than femoral neck bone mineral density (r = .79, %SEE = 28%).

Systematic errors in bone-mineral measurements by quantitative computed tomography

Bone-mineral measurements using quantitative computed tomography (QCT) are commonly based on comparisons with solutions in water of known concentrations of K2HPO4. In this paper are described theoretical and experimental studies that have led to the conclusion that large systematic errors can arise in these measurements, depending on the soft-tissue and fat concentrations in the vertebral spongiosa. In the case of single energy scanning, such large errors have been identified to be due to the varying water content (displacement effect) in the calibration samples and the varying fat content in the region of interest (ROI) within the patient. In the case of dual energy scanning, the error arises because when normalized to that of water, the mass attenuation coefficient of fat increases with photon energy while the reverse is true for K2HPO4. Our studies have also revealed that total trabecular bone density (which includes the mineral, soft tissue, and fat) can be much more accurately determined by the dual energy QCT method than bone mineral alone. This finding is especially interesting since there have been several reports in the literature suggesting that bone density rather than bone-mineral content is a better predictor of the risk of osteoporosis-related fractures.

Regional cerebral blood flow measurements using stable xenon enhanced computed tomography: a theoretical and experimental evaluation

Several theoretical and practical aspects of regional cerebral blood flow measurements using stable xenon gas and CT are discussed. It is shown that by comparing the enhancement at any time T1 with that at saturation or any other time T2, the need to use arbitrary means to bring the arterial concentration data and the CT enhancement data to the same system of measurement units can be eliminated. If CT is performed continuously during the washin phase, say at intervals of 1 min, least squares analysis of the enhancement data can be used to obtain the best possible estimates for the flow rate constant kappa and the saturation enhancement. However, if only a limited number of scans can be performed, as may be the case in human studies, it is also possible to get a good estimate of kappa from a knowledge of the ratio of the enhancement at any time T1 with that at any other time T2. Combinations of T1 = 2.0 min and T2 = 4.0 min, T1 = 1.0 min and T2 = 6.0 min, or T1 = 2.0 min and T2 = 5.0 min were found to be the most convenient. It is also shown that the end-tidal xenon concentration in the exhaled air can be accurately assessed indirectly by measuring the oxygen, CO2, and water vapor concentrations, thereby eliminating the need for more expensive methods involving the use of a mass spectrometer or a thermal conductivity gas analyzer.

A comparison of carbon-fiber and aluminum front plates in rapid film changers

The radiation transmission characteristics of 2-mm-thick aluminum front plates and 2-mm-thick carbon-fiber-reinforced plastic front plates for rapid film changers were compared. While the carbon-fiber plates were found to be intrinsically more radiolucent than the aluminum plates, the decrease in patient exposure with the carbon-fiber plates was only approximately 25%. No measurable differences in image quality were observed in carefully controlled experiments on the two types of front plates.

Xeromammographic image quality

Xeroradiography is a diagnostic modality whose image-forming properties are fundamentally different from those of the conventional silver halide process. In this work, the xeromammographic process, representing the low-constrast limit of xeroradiography, is analyzed in detail. A step by step approach is taken, whereby th eimiting factors in the exposure and development stages are identified and quantified. The sensitivity of the Se layer is also computed and the concept of optimal exposure introduced. The paper concludes by considering a simple model for xeroradiographic noise.

Evaluation of a new x-ray film with reduced crossover

The improvement in MTF that can be obtained by the reduction of crossover exposures is evaluated using an experimental film supplied by the 3M Company (3M XUD). It was found that image resolution, as measured by the equivalent passband (2 integral of infinity 0 [M(f)]2df), of 3M Trimax 8 screens when used with the experimental 3M XUD film was 2.9 c/mm as compared to 1.8 c/mm when used with a conventional double coated film such as Kodak Ortho G or 3M XD. On the other hand, system speed with 3M XUD film was only 1.6 mR-1 as compared to 3.2 mR-1 with 3M XD film and 2.4 mR-1 with Kodak Ortho G film. These findings were substantiated by phantom studies as well.

Quantum fluctuations in radiographic screen-film systems

With the recent introduction of fast rare-earth screens into the market, the question of noise and how it influences image quality becomes particularly important. In this paper a compact formula involving familiar and measurable quantities is derived for the specification of the noise arising from the spatial fluctuations of the x-ray quanta absorbed in the screens. Experimental evidence in support of this concept is also given.

On optimizing the xeromammographic image

This work undertakes a detailed system-based analysis of the xeromammographic process starting from basic considerations. Both the edge enhancement and wide-recording latitude, the two principal characteristics of xeroradiography, are shown to bear an intimate relationship to the electric-field distribution. Criteria and methods are formulated for optimizing xeromammographic image quality and a procedure is developed for calculating the white gap. Densitometric curves are derived for both positive- and negative-mode xeroradiography and found to be in excellent agreement with experiment. The question of image linearity is examined carefully and a threshold value of the electrostatic contrast is established, which sets a natural criterion for the application of Fourier analysis. Furthermore, it is shown that, in xeromammography with its inherently low-contrast structures, an optimal exposure exists which optimizes simultaneously all low-contrast edges. This last finding, coupled with experimental results, suggest immediately the possibility of an automatic exposure termination in xeromammography. Beam hardening is also investigated and it is shown that increased filtration combined with a lower bias potential leads to substantial dose reduction without significant loss of image quality. The paper concludes with a discussion of scattered radiation and how it affects xeromammographic image quality.

Autoradiographic enhancement of mammograms. Investigation of a new dose reduction technique

Autoradiographic image enhancement using thiourea labeled with 35S was investigated as a means of reducing dose in mammography. It was found that mammograms underexposed as much as tenfold can be autoradiographically intensified so that the enhanced image is comparable with a normal exposure. Limitations to routine use include cost, processing time, and disposal of radioactive solutions.

Physical characteristics of modern radiographic screen-film systems

The most important characteristics that determine the performance of a screen-film system are system sensitivity (speed), slope or the average gradient of the characteristic curve, latitude of the film, system resolution (MTF) and system noise. In addition to these, one has to consider secondary characteristics such as the base plus fog level, the base tint, safelight sensitivity, reciprocity law failure and film granularity while evaluating performance. A comprehensive study of many of these characteristics has been made for a number of film-screen systems on the market. The data has been tabulated in the form of what are called "characteristic tables of radiographic film-screen systems." In these tables, characteristics such as average gradient, base plus fog level, etc. which depend on film alone, appear along the horizontal axis and MTF values which essentially depend on screens only appear along the vertical axis. The body of the table contains the absolute speeds in units of mR-1 at 80 KVP (heavy filtration) and a quantum mottle index of the various film-screen combinations tested, since these depend both on the film as well as on the screens.

The relationship between resolution and speed of x-ray intensifying screens

Two important physical characteristics of x-ray intensifying screens, speed and resolution, are inversely related. However, the exact mathematical relationship, if any, between them is not known. To investigate this matter, a simple model is considered, which predicts that the product of the equivalent passband Ne and the square root of the speed is constant for a given phosphor material and given film. This relationship is found to be in excellent agreement with experimental data. The papper concludes with a discussion of the generalized validity of this relationship.

Negative-mode soft-tissue xeroradiography

Positive-mode xeroradiography is an excellent method of visualizing soft-tissue structures in mammography and other procedures; however, toner deletions over a large area may preclude adequate delineation of the soft tissues near high-density structures such as bone. Use of the negative mode in the development cycle provides excellent demonstration of the soft tissues without toner deletions and requires only about 70% of the exposure needed in the positive mode. Negative-mode images also exhibit greater changes in radiographic contrast than those observed with the positive mode. The extent of achilles tendon lacerations was shown particularly well by this technique.

Evaluation of xeroradiographic image quality

A theory of edge enhancement has been developed to describe xeroradiographic images of linear step objects. The theory is shown to give an accurate description of the relationship between edge enhancement, subject contrast, radiation exposure, selenium charging potential and developer bias potential. An optimal transmitted x-ray exposure exists which gives the maximum edge enhancement. For low contrast structures, this same optimal exposure was found to yield the most acceptable images as judged subjectively. This finding has led to the successful application of automatic exposure termination in mammographic examinations using xeroradiography.

A circular test pattern for evaluating x-ray tube focal spots

The design and use of a circular x-ray resolution test pattern is presented. This pattern is shown to yield equivalent focal spot dimensions equal to those obtained with the more commonly used star pattern. The advantage of using the circular pattern is that it obviates the necessity of positioning the pattern strictly along the x-ray beam central axis. A major source of experimental error in making focal spot measurements is therefore circumvented, especially in the case of x-ray tubes with a small target angle.

Collimator misalignment in high energy therapy machines

Measurements of the intensity distribution of a 60-Co beam revealed a significant field distortion caused by minor misalignment of the collimator assembly which was not detected by routine methods. Accurate monitoring of radiation intensity distribution and periodic visual inspection of collimators are suggested for early detection of this problem.