▪ Abstract Domesticated plant taxa cannot be regarded as evolutionarily discrete from their wild relatives. Most domesticated plant taxa mate with wild relatives somewhere in the world, and gene flow from crop taxa may have a substantial impact on the evolution of wild populations. In a literature review of the world's 13 most important food crops, we show that 12 of these crops hybridize with wild relatives in some part of their agricultural distribution. We use population genetic theory to predict the evolutionary consequences of gene flow from crops to wild plants and discuss two applied consequences of crop-to-wild gene flow–the evolution of aggressive weeds and the extinction of rare species. We suggest ways of assessing the likelihood of hybridization, introgression, and the potential for undesirable gene flow from crops into weeds or rare species.

Gene flow and introgression from domesticated plants into their wild relatives.

The intertidal copepod Tigriopus californicus was used as a model organism to look at effects of crossing distance on fitness and to investigate the genetic mechanisms responsible. Crosses were conducted between 12 pairs of populations spanning a broad range of both geographic distance (5 m to 2007 km) and genetic distance (0.2% to 22.3% sequence divergence for a 606-bp segment of the mitochondrial COI gene). For each pair of populations, three fitness components (hatching number, survivorship number, and metamorphosis number) were measured in up to 16 cohorts including parentals, reciprocal F1 , F2 , F3 , and first-generation backcross hybrids. Comparisons of each set of cohorts allowed estimation of within- and between-locus gene interaction. Relative to parentals, F1 hybrids showed a trend toward increased fitness, with no correspondence with population divergence, and a decrease in variance, which in some cases correlated with population divergence. In sharp contrast, F2 hybrids had a decrease in fitness and an increase in variance that both corresponded to population divergence. Genetic interpretation of these patterns suggests that both the beneficial effects of dominance and the detrimental effects of breaking up coadaptation are magnified by increasing evolutionary distance between populations. Because there is no recombination in T. californicus females, effects of recombination can be assessed by comparing F1 hybrid males and females backcrossed to parentals. Both recombinant and nonrecombinant backcross hybrids showed a decline in fitness correlated with population divergence, indicating that segregation among chromosomes contributes to the breakup of coadaptation. Although there was no difference in mean fitness between the two backcross types, recombinational backcrosses showed greater variance for fitness than nonrecombinational backcrosses, suggesting that the breakup of parental gene ombinations within chromosomes has both beneficial and detrimental effects.

Heterosis and outbreeding depression in interpopulation crosses spanning a wide range of divergence.

Transgenes engineered into annual crops could be unintentionally introduced into the genomes of their free-living wild relatives. The fear is that these transgenes might persist in the environment and have negative ecological consequences. Are some crops or transgenic traits of more concern than others? Are there natural genetic barriers to minimize gene escape? Can the genetic transformation process be exploited to produce new barriers to gene flow? Questions abound, but luckily so do answers.

/pdf/transgene-introgression-from-genetically-modified-crops-to-4xgv1kuvm5.pdf

Transgene introgression from genetically modified crops to their wild relatives.

Glyphosate [N-(phosphonomethyl) glycine]-resistant crops (GRCs), canola (Brassica napus L.), cotton (Gossypium hirsutum L.), maize (Zea mays L.), and soybean [Glycine max (L.) Merr.] have been commercialized and grown extensively in the Western Hemisphere and, to a lesser extent, elsewhere. Glyphosate-resistant cotton and soybean have become dominant in those countries where their planting is permitted. Effects of glyphosate on contamination of soil, water, and air are minimal, compared to some of the herbicides that they replace. No risks have been found with food or feed safety or nutritional value in products from currently available GRCs. Glyphosate-resistant crops have promoted the adoption of reduced- or no-tillage agriculture in the USA and Argentina, providing a substantial environmental benefit. Weed species in GRC fields have shifted to those that can more successfully withstand glyphosate and to those that avoid the time of its application. Three weed species have evolved resistance to glyphosate in GRCs. Glyphosate-resistant crops have greater potential to become problems as volunteer crops than do conventional crops. Glyphosate resistance transgenes have been found in fields of canola that are supposed to be non-transgenic. Under some circumstances, the largest risk of GRCs may be transgene flow (introgression) from GRCs to related species that might become problems in natural ecosystems. Glyphosate resistance transgenes themselves are highly unlikely to be a risk in wild plant populations, but when linked to transgenes that may impart fitness benefits outside of agriculture (e.g., insect resistance), natural ecosystems could be affected. The development and use of failsafe introgression barriers in crops with such linked genes is needed.

/pdf/the-current-status-and-environmental-impacts-of-glyphosate-10h5knp6fz.pdf

The current status and environmental impacts of glyphosate-resistant crops: a review.

PREMISE OF THE STUDY Archaeological and genetic analyses of seed-propagated annual crops have greatly advanced our understanding of plant domestication and evolution. Comparatively little is known about perennial plant domestication, a relevant topic for understanding how genes and genomes evolve in long-lived species, and how perennials respond to selection pressures operating on a relatively short time scale. Here, we focus on long-lived perennial crops (mainly trees and other woody plants) grown for their fruits. KEY RESULTS We reviewed (1) the basic biology of long-lived perennials, setting the stage for perennial domestication by considering how these species evolve in nature; (2) the suite of morphological features associated with perennial fruit crops undergoing domestication; (3) the origins and evolution of domesticated perennials grown for their fruits; and (4) the genetic basis of domestication in perennial fruit crops. CONCLUSIONS Long-lived perennials have lengthy juvenile phases, extensive outcrossing, widespread hybridization, and limited population structure. Under domestication, these features, combined with clonal propagation, multiple origins, and ongoing crop-wild gene flow, contribute to mild domestication bottlenecks in perennial fruit crops. Morphological changes under domestication have many parallels to annual crops, but with key differences for mating system evolution and mode of reproduction. Quantitative trait loci associated with domestication traits in perennials are mainly of minor effect and may not be stable across years. Future studies that take advantage of genomic approaches and consider demographic history will elucidate the genetics of agriculturally and ecologically important traits in perennial fruit crops and their wild relatives.

From forest to field: Perennial fruit crop domestication

ABSTRACT Background Lung cancer is a principal cause of death worldwide, and its treatment is very challenging. Nebulization offers a promising means of targeting drugs to their site of action in the lung. Research design and methods In the present study, nebulizable oil in water nanoemulsion formulations was co-loaded with naringin/celecoxib and tested for pulmonary administration by different nebulizer types. Results The translucent appearance of nanoemulsion formulations was revealed, with particle size (75–106 nm), zeta potential (−3.42 to −4.86 mV), and controlled in-vitro release profiles for both drugs. The nanoemulsions showed favorable stability profiles and superior cytotoxicity on A549 lung cancer cells. Aerosolization studies on the selected nanoemulsion formulation revealed its high stability during nebulization, with the generation of an aerosol of small volume median diameter and mass median aerodynamic diameter lower than 5 µm. Moreover, it demonstrated considerable safety and bioaccumulation in lung tissues, in addition to accumulation in the brain, liver, and bones, which are the main organs to which lung cancer metastasizes. Conclusions Nanoemulsion proved to be a promising nebulizable system, which paves the way for treatment of pulmonary diseases other than lung cancer.

Simultaneous pulmonary administration of celecoxib and naringin using a nebulization-friendly nanoemulsion: A device-targeted delivery for treatment of lung cancer

A strategy of DNA pooling aimed at identifying markers linked to quantitative trait loci (QTLs), ‘Sequential Bulked Typing’ (SBT), is presented. The method proposed consists in pooling DNA from consecutive pairs of individuals ranked phenotypically, i.e., pools are formed with individuals ranked (1st, 2nd), (3rd, 4th),…, (N-1st, Nth). The N/2 pools are subsequently amplified using the polymerase chain reaction (PCR). If the whole population is typed the number of PCRs per marker is halved with respect to individual typing (IT). But if this strategy is combined with selective genotyping of extreme individuals savings can be further increased. Two extreme cases are considered: in the first one (SBT0), it is assumed that only presence or absence of a given allele can be ascertained in a pool; in the second one (SBT1), it is further assumed that differences between allele band intensities can be distinguished. The theory to estimate by maximum likelihood the QTL effect and its position with respect to flanking markers is presented. The behaviour of IT and SBT was studied using stochastic computer simulation in backcross and F2 populations. Three percentages of subpattern distinction (0, 50 and 100%) two population sizes (n=1200 and 600) and two QTL effects (a=0.1 and 0.25 standard deviations) were considered. SBT1 had the same power as individual genotyping at half the genotyping costs in all situations studied. Accuracy of QTL location is not increased with a dense number of markers, as opposed to individual typing. As a result DNA pooling is not useful for accurate location of the QTL but rather to pick up genome regions containing QTLs of at least moderate effect. The theory developed provides the general theoretical framework to deal with any DNA pooling strategy aimed at detecting QTLs.

Long-term introgression of crop genes into wild sunflower populations

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Simultaneous pulmonary administration of celecoxib and naringin using a nebulization-friendly nanoemulsion: A device-targeted delivery for treatment of lung cancer

Long-term introgression of crop genes into wild sunflower populations