Direct and indirect detection of 2n eggs in hybrid diploid families derived from haploid tbr × wild species crosses

The analytic-synthetic scheme makes use of haploidization and 2n gametes-mediated sexual polyploidization to incorporate genetic diversity from wild related species in potato breeding. Whereas 2n pollen can be directly screened by microscopy, 2n eggs are routinely screened indirectly by interploid crosses, a time-consuming and inaccurate technique. In five haploid tbr × wild diploid species families with variability for agronomic characters, 2n eggs were screened indirectly to incorporate this germplasm into a useful form and directly by microscopy to establish the feasibility of this approach. For the indirect screening, at least 15 flowers of each of 49 genotypes/family were crossed with a commercial cultivar. Eighty-five fruits were produced; only 15 of them had seeds (1–25). Chromosome numbers were determined in a random sample of five seeds/fruit, resulting diploid in two genotypic combinations and tetraploid in another two. For the direct screening, eight combinations of staining and destaining (times and concentrations) were evaluated in detached ovules to adjust a clarification technique. The best combination was one day of staining and one day of destaining in 0.5 % acetic acid. In an indirectly detected diplogynoid, the average diameters of the central cell nuclei (CCN) and nucleoli (CCNu) were, respectively, 9.3 μ and 3.4 μ. Gametophytes with diametres 1.26 times the average were considered 2n. By crosses, eleven seeds were obtained in one fruit of this clone whereas the 2n egg frequency determined by microscopy was 7%. The direct technique is easy to carry out once the eye is trained and its results better reflect actual 2n gamete frequencies.     

Responses to water withdrawal of tobacco plants genetically engineered with the AtTPS1 gene: a special reference to photosynthetic parameters

We have previously obtained several lines of tobacco transformed with a trehalose-6-phosphate synthase gene of plant origin (Arabidopsis thaliana), involved in the first step of the biosynthesis of trehalose, a known osmoprotectant. Two showed distinct intensity of expression: high (B5H) and low (B1F). Such lines were analyzed for trehalose-6-phosphate content and the obtained results demonstrated to be in accordance with the expression results. In order to study the responses of photosynthesis to water deficit of transgenic lines in comparison to wild type (WT), three experiments were performed under different conditions: (1) Relative water (2) Leaf gas exchange (3) Modulated Chlorophyll a Fluorescence. Different responses in RWC of plant lines to water withdrawal were detected, with transgenic line B5H indicating less water loss after the water withdrawal period. Similar responses to water deficit regarding the leaf gas exchanges were recorded for the three lines. When subjected to water deficit stress situations, higher F _v/F _m, Φ_PSII and qP were detected for the transgenic lines. Under a SWC of 20% where higher values for such parameters were detected with special relevance for the B5H line, indicating a possible higher ability to withstand severe drought stress and to resist to prolonged periods without water than the B1F and WT lines.     

Genetic variability measures among Bromus catharticus Vahl. populations and cultivars with RAPD and AFLP markers

The objectives of this study were to optimize RAPD and AFLP techniques in B. catharticus, and to determine the genetic variability of populations and commercial prairie grass cultivars with the aforementioned molecular markers. Two populations with contrasting morphological characteristics were evaluated from individual and bulked DNA samples using RAPD markers. Both analyses showed a similar information about inter population variability. Each accession was sampled by a single leaf bulk of 10 plants. Accession similarities were established with 276 RAPD and 714 AFLP bands using Jaccard similarity coefficient. The dendrogram of the accessions using RAPD markers showed that they shared high similarity values (>94%). A similar result was obtained with AFLP markers (similarity values >98%), revealing a narrow genetic basis in the analyzed accessions. Consequently, molecular characterization of germplasm should be considered in addition to morphological criteria, to choose the parental genotypes for breeding programs of this forage crop. The AFLP technique was more efficient to detect DNA polymorphism in our experiments and unique fingerprints were detected for all the accessions. RAPD is a simple and non expensive technique, suitable to estimate genetic similarity. This revised version was published online in August 2006 with corrections to the Cover Date.     

Ecuador, 1991 potato germplasm collecting expedition: taxonomy and new germplasm resources

Summary We conducted a joint Ecuador/Colombia/United States wild potato (Solanum sect. Petota) germplasm collecting expedition in Ecuador from April 13–July 1, 1991. The goals of the expedition were to collect germplasm and study the species boundaries of all of the 25 Ecuadorian taxa accepted by current taxonomists. We made 126 collections of 24 of these 25 taxa, 113 as germplasm samples, 13 only as herbarium collections. We synonymize six of these 25 names (S. baezense Ochoa, S. cyanophyllum Correll, S. pichinchense Bitter & Sodiro, S. serratoris Ochoa, S. suffrutescens Correll as synonyms of S. andreanum Baker; S. correllii Ochoa as a synonym of S. regularifolium Correll). Four other names (S. chomatophilum f. angustifoliolum Correll, S. moscopanum Hawkes, S. solisii Hawkes, S. tundalomense Ochoa) could not be consistently distinguished from S. colombianum Dunal in the field. We are currently investigating them to determine their species status.     

Mapping of genes involved in glutathione, carbohydrate and COR14b cold induced protein accumulation during cold hardening in wheat

Using some of the chromosome substitution lines developed from thecrosses of the donor Cheyenne to Chinese Spring we showed that theaccumulation of water soluble carbohydrates during different stages ofhardening was time dependent. Moreover there was a significantcorrelation between the rate of carbohydrate accumulation and the frosttolerance. The expression and regulation of a wheat gene homologous tothe barley cold regulated cor14b gene was compared in frost sensitiveand frost tolerant wheat genotypes at different temperatures. Studies madewith chromosome substitution lines showed that the threshold inductiontemperature polymorphism of the cor14b wheat homologous genewas controlled by loci located on chromosome 5A of wheat, while cor14b gene was mapped, in Triticum monococcum, onto the longarm of chromosome 2A^m. Our study on the effect of cold hardeningon glutathione (GSH) metabolism showed that chromosome 5A of wheathas an influence on the GSH accumulation and on the ratio of reduced andoxidised glutathione as part of a complex regulatory function during coldhardening. In addition, the level of increase in GSH content duringhardening may indicate the degree of the frost tolerance of wheat.     

Sclerotinia resistance in sunflower: I. Genotypic variations of hybrids in three environments of Argentina

Sclerotinia sclerotiorum infections on sunflower capitula produce white rot, one of the most dangerous diseases sunflower bears in all humid areas. Therefore, disease quantification on developed genetic materials is a very important action in sunflower breeding. Given the horizontal type of resistance these evaluations should be made in different environments. Several hybrids obtained after crossing seven female × seven male sunflower inbred lines in a factorial mating design were evaluated for resistance to white rot in two locations in the southeast of the province of Buenos Aires, Argentina. Disease incidence and the symptom appearance index indicated significant genotypic effects and genotype × environment (G × E) interactions. Genotypic effects were a greater source of variance than the G × E interaction effects. The G × E interactions only represented changes in magnitude. These results were used to identify the best genotypes for both resistance factors. Four hybrids showed low disease incidence values under both artificial and natural infections, of which only two had high values of the symptom appearance index at both locations. These hybrids are considered to have adequate resistance attributes for the ascosporic penetration and the mycelium extension in the capitulum tissue and could therefore be sown in the province of Buenos Aires without increasing risks of S. sclerotiorum attacks.     

Transformation of organoarsenical species by the microflora of freshwater crayfish

A study of the transformation of arsenic species by the microflora of the freshwater crayfish Procambarus clarkii was carried out. The study of the degradation of AB (arsenobetaine) was performed in aerobic conditions in two culture media (tryptic soy broth and saline medium) at two temperatures (30 and 8 degrees C). The microflora transformed AB into TMAO (trimethylarsine oxide), DMA (dimethylarsinate), MA (methylarsonate), and an unidentified compound (U1). The quickest transformations were carried out by microflora from hepatopancreas incubated in saline medium at 30 degrees C. The individualized study of other arsenic species [AC (arsenocholine), TETRA (tetramethylarsonium ion), TMAO, DMA, and MA] was also performed in saline medium. The only transformation observed was of AC into AB. The bacteria possibly responsible for AB degradation were isolated, identified by phenotypic and genotypic methods, and individually assayed for AB transformation. Only isolates allocated to the species Pseudomonas putida were able to metabolize AB.     

Heavy metal, total arsenic, and inorganic arsenic contents of algae food products

The total arsenic, inorganic arsenic, lead, cadmium, and mercury contents of 18 algae food products currently on sale in Spain were determined. The suitability of the analytical methodologies for this type of matrix was confirmed by evaluating their analytical characteristics. The concentration ranges found for each contaminant, expressed in milligrams per kilogram of dry weight, were as follows: total arsenic, 2.3-141; inorganic arsenic, 0.15-88; lead, < 0.05-1.33; cadmium, 0.03-1.9; and mercury, 0.004-0.04. There is currently no legislation in Spain regarding contaminants in algae food products, but some of the samples analyzed revealed Cd and inorganic As levels higher than those permitted by legislation in other countries. Given the high concentrations of inorganic As found in Hizikia fusiforme, a daily consumption of 1.7 g of the product would reach the Provisional Tolerable Weekly Intake recommended by the WHO for an average body weight of 68 kg. A more comprehensive study of the contents and toxicological implications of the inorganic As present in the algae food products currently sold in Spain may be necessary, which might then be the basis for the introduction of specific sales restrictions.     

Color quality of pigments in cochineals (Dactylopius coccus Costa). Geographical origin characterization using multivariate statistical analysis

The commercial value of a cochineal (Dactylopius coccus Costa) sample is associated with its color quality. Because the cochineal is a legal food colorant, its color quality is generally understood as its pigment content. Simply put, the higher this content, the more valuable the sample is to the market. In an effort to devise a way to measure the color quality of a cochineal, the present study evaluates different parameters of color measurement such as chromatic attributes (L*, and a*), percentage of carminic acid, tint determination, and chromatographic profile of pigments. Tint determination did not achieve this objective because this parameter does not correlate with carminic acid content. On the other hand, carminic acid showed a highly significant correlation (r = - 0.922, p = 0.000) with L* values determined from powdered cochineal samples. The combination of the information from the spectrophotometric determination of carminic acid with that of the pigment profile acquired by liquid chromatography (LC) and the composition of the red and yellow pigment groups, also acquired by LC, enables greater accuracy in judging the quality of the final sample. As a result of this study, it was possible to achieve the separation of cochineal samples according to geographical origin using two statistical techniques: cluster analysis and principal component analysis.