Glyphosate-tolerant corn: the composition and feeding value of grain from glyphosate-tolerant corn is equivalent to that of conventional corn (Zea mays L.).

Glyphosate-tolerant (Roundup Ready) corn line GA21 has been developed by genetic modification to tolerate glyphosate, the active ingredient in Roundup herbicide. The purpose of this study was to evaluate the compositional and nutritional safety of corn line GA21 compared to that of conventional corn. Compositional analyses were conducted to measure proximate, fiber, amino acid, fatty acid, and mineral contents of grain and proximate, fiber, and mineral contents of forage collected from 16 field sites over two growing seasons. The nutritional safety of corn line GA21 was evaluated in a poultry feeding study conducted with 2-day old, rapidly growing broiler chickens, at a dietary concentration of 50-60% w/w. Compositional analysis results showed that, except for a few minor differences that are unlikely to be of biological significance, the grain and forage of GA21 corn were comparable in their composition to that of the control corn line and to conventional corn. Results from the poultry feeding study showed that there were no differences in growth, feed efficiency, adjusted feed efficiency, and fat pad weights between chickens fed with GA21 grain or with parental control grain. These data taken together demonstrate that Roundup Ready corn is as safe and nutritious as conventional corn for food and feed use.

Human ocular effects from self-reported exposures to Roundup herbicides.

We evaluated ocular effects from reported human exposures to Roundup herbicides based on 1513 calls to an American Association of Poison Control Centers (AAPCC) certified regional poison center during the years 1993 through 1997. The preponderance of reported exposures were judged by poison center specialists to result in either no injury (21%) or transient minor symptoms (70%). There was some temporary injury in 2% of cases; one injury took more than 2 weeks to resolve. In no instance did exposure result in permanent change to the structure or function of the eye. Since the representativeness of calls to poison control centers is unknown, several interpretations of these findings are possible. The most conservative interpretation is that there were no serious ocular effects from exposure to Roundup herbicides during a 5 year period among callers to a single regional poison center. A less conservative interpretation would be that severe ocular effects from Roundup exposures are rare among users of these products.

The composition of glyphosate-tolerant soybean seeds is equivalent to that of conventional soybeans.

One important aspect of the safety assessment of genetically engineered crops destined for food and feed uses is the characterization of the consumed portion of the crop. One crop currently under development, glyphosate-tolerant soybeans (GTS), was modified by the addition of a glyphosate-tolerance gene to a commercial soybean cultivar. The composition of seeds and selected processing fractions from two GTS lines, designated 40-3-2 and 61-67-1, was compared with that of the parental soybean cultivar, A5403. Nutrients measured in the soybean seeds included macronutrients by proximate analyses (protein, fat, fiber, ash, carbohydrates), amino acids and fatty acids. Antinutrients measured in either the seed or toasted meal were trypsin inhibitor, lectins, isoflavones, stachyose, raffinose and phytate. Proximate analyses were also performed on batches of defatted toasted meal, defatted nontoasted meal, protein isolate, and protein concentrate prepared from GTS and control soybean seeds. In addition, refined, bleached, deodorized oil was made, along with crude soybean lecithin, from GTS and control soybeans. The analytical results demonstrated the GTS lines are equivalent to the parental, conventional soybean cultivar.

Transmission and recombination of chloroplast genes in asexual crosses of Chlamydomonas reinhardtii. II. Comparisons with observations of sexual diploids.

Patterns of biparental chloroplast gene transmission in Chlamydomonas reinhardtii diploids produced by polyethylene glycol (PEG) fusion were found to be similar to those seen in sexual diploids (VanWinkle-Swift and Birky 1978). Examination of the phenotypes of diploid clones showed that the PEG diploids produced a heterogeneous set of allelic frequencies. Neither the frequencies of parental nor recombinant phenotypes were normally distributed. In addition, frequencies of reciprocal recombinant phenotypes showed no significant correlation in the clones from individual PEG diploids. The frequencies of parental phenotypes, on the other hand, were significantly negatively correlated. Like the data from sexual diploids, this is evidence that recombinant frequencies from clones of PEG diploids are not directly related to frequencies of reciprocal recombination. The similarity of results obtained in sexual and PEG diploids supports the hypothesis that the mechanisms operating during biparental chloroplast gene inheritance in PEG diploids are identical to those in sexual diploids.

Transmission and recombination of chloroplast genes in asexual crosses of Chlamydomonas reinhardii : I. Flagellar agglutination prior to fusion does not promote uniparental inheritance or affect recombinant frequencies.

Chlamydomonas reinhardii diploids homozygous for the plus mating-type (mt (+)) allele were constructed via polyethylene glycol (PEG)-induced cell fusion to investigate the transmission of chloroplast genes.We used two methods to determine whether the fusion products (PEG diploids) had inherited chloroplast markers uniparentally or biparentally. One method (multiple clone analysis) was found to markedly improve the detection of biparental transmission. With this method the frequency of biparental PEG-induced diploids was comparable to that seen in sexual diploids. Multiple clone analysis also demonstrated that fusion products which showed biparental inheritance were an extremely heterogeneous group.In some crosses, pre-treatment of one parent with isolated flagella from cells of the opposite mating type was used. This pre-treatment has been reported to promote chloroplast gene transmission from the mt (+) parent in diploids produced by PEG fusion (Adams 1982). In our crosses flagellar pretreatment had no significant effect on chloroplast gene transmission or recombination frequences. A significant bias was found for the date a cross was performed, but neither parent preferentially transmitted its alleles in all crosses. This indicates the necessity of comparing data from treated and control crosses done on the same day. We conclude from our data that separate hypotheses are not required to explain biparental inheritance in sexual versus PEG-induced diploids. The absence of biased parental allelic ratios with PEG-induced biparental diploid clones underscores their usefulness for the study of biparental gene transmission.

New properties of the two-locus partial selfing model with selection.

Analytic solutions are obtained for the equilibria of a simple two-locus, heterotic selection model with mixed selfing and random outcrossing. Two general phenomena are possible, depending upon the viabilities and the degree of selfing: (1) Negative disequilibrium potential, under which only gametic disequilibrium is possible; and (2) positive disequilibrium potential, which can result in permanent gametic disequilibrium provided that linkage is sufficiently tight. Under random mating (s = 0), these two situations correspond to negative and positive additive epistasis, respectively. With partial self-fertilization, however, this is no longer true, and a more appropriate measure of gametc disequilibrium potential, Delta(s), is introduced. A numerically aided examination of the model results in the discovery of two new properties of partial selfing with selection: (1) With negative disequilibrium potential (Delta(s) < 0), the equilibrium mean fitness increases with increasing recombination. With positive disequilibrium potential (Delta(s) > 0), the opposite is true. (2) Gametic disequilibrium can increase or decrease as the degree of selfing is increased. Therefore, it is apparent that partial selfing and linkage are not analogous as regards the maintenance of disequilibrium.