Gene flow in genetically modified wheat

Understanding gene flow in genetically modified (GM) crops is critical to answering questions regarding risk-assessment and the coexistence of GM and non-GM crops. In two field experiments, we tested whether rates of cross-pollination differed between GM and non-GM lines of the predominantly self-pollinating wheat Triticum aestivum. In the first experiment, outcrossing was studied within the field by planting "phytometers" of one line into stands of another line. In the second experiment, outcrossing was studied over distances of 0.5-2.5 m from a central patch of pollen donors to adjacent patches of pollen recipients. Cross-pollination and outcrossing was detected when offspring of a pollen recipient without a particular transgene contained this transgene in heterozygous condition. The GM lines had been produced from the varieties Bobwhite or Frisal and contained Pm3b or chitinase/glucanase transgenes, respectively, in homozygous condition. These transgenes increase plant resistance against pathogenic fungi. Although the overall outcrossing rate in the first experiment was only 3.4%, Bobwhite GM lines containing the Pm3b transgene were six times more likely than non-GM control lines to produce outcrossed offspring. There was additional variation in outcrossing rate among the four GM-lines, presumably due to the different transgene insertion events. Among the pollen donors, the Frisal GM line expressing a chitinase transgene caused more outcrossing than the GM line expressing both a chitinase and a glucanase transgene. In the second experiment, outcrossing after cross-pollination declined from 0.7-0.03% over the test distances of 0.5-2.5 m. Our results suggest that pollen-mediated gene flow between GM and non-GM wheat might only be a concern if it occurs within fields, e.g. due to seed contamination. Methodologically our study demonstrates that outcrossing rates between transgenic and other lines within crops can be assessed using a phytometer approach and that gene-flow distances can be efficiently estimated with population-level PCR analyses.     

Influence of physical distance between cultivars on yield,outcrossing rate and selective fruit drop in avocado (Persea americana,Lauraceae)

Avocado shows protogynous dichogamy with two complementary cultivar types (A and B) that differ in their floral behaviour. Because of this peculiar flowering system, mixed plantings of cultivars of complementary flower type have been traditionally recommended to increase yield. However, the effect of planting complementary avocado cultivars on outcrossing rate and yield is a subject of controversy. In this work, we have studied the outcrossing rate with microsatellite markers under the growing conditions of Southern Spain. Outcrossing rate was determined at harvest on several ‘Hass’ trees situated in rows at different distances from a ‘Fuerte’ orchard for two consecutive years (2005 and 2006). Outcrossing rate ranged from 0.31 to 0.74 with an average of 0.47 showing a significant decrease from the first row (in proximity to the pollen source) to the rest of the rows. However, using data of 13 years no significant differences in yield have been recorded with increasing distance to the pollen donor trees. The paternity of abscised fruits was recorded weekly from June to the period of commercial harvest in March the following year. The results obtained indicate that the fruits that dropped during June were mostly derived from self‐fertilisation. However, a high proportion of those fruits were derived from flowers fertilised during the last weeks of the ‘Hass’ blooming season when the cultivar Fuerte presents either few or no flowers. Consequently, most of the late fertilised ‘Hass’ fruits were derived from self‐pollination and those small fruits compete for limited maternal resources with the earlier fertilised fruits derived from cross‐pollination. These results suggest that, under our growing conditions, fruit drop in avocado is rather determined by the fertilisation date and not by the embryo genetic composition.     

Regeneration and characterization of somatic hybrids combining sweet orange and mandarin/mandarin hybrid cultivars for citrus scion improvement

Protoplast fusion between sweet orange and mandarin/mandarin hybrids scion cultivars was performed following the model ??diploid embryogenic callus protoplast?+?diploid mesophyll-derived protoplast??. Protoplasts were isolated from embryogenic calli of ??Pera?? and ??Westin?? sweet orange cultivars (Citrus sinensis) and from young leaves of ??Fremont??, Nules??, and ??Thomas?? mandarins (C. reticulata), and ??Nova?? tangelo [C. reticulata?×?(C. paradisi?×?C. reticulata)]. The regenerated plants were characterized based on their leaf morphology (thickness), ploidy level, and simple sequence repeat (SSR) molecular markers. Plants were successfully generated only when ??Pera?? sweet orange was used as the embryogenic parent. Fifteen plants were regenerated being 7 tetraploid and 8 diploid. Based on SSR molecular markers analyses all 7 tetraploid regenerated plants revealed to be allotetraploids (somatic hybrids), including 2 from the combination of ??Pera?? sweet orange?+???Fremont?? mandarin, 3 ??Pera?? sweet orange?+???Nules?? mandarin, and 2 ??Pera?? sweet orange?+???Nova?? tangelo, and all the diploid regenerated plants showed the ??Pera?? sweet orange marker profile. Somatic hybrids were inoculated with Alternaria alternata and no disease symptoms were detected 96?h post-inoculation. This hybrid material has the potential to be used as a tetraploid parent in interploid crosses for citrus scion breeding.     

Outcrossing rates and their relationship to phenology in Triticum dicoccoides

Summary Outcrossing rates (t) were estimated in natural and garden populations of wild emmer wheat, Triticum dicoccoides. The estimated t from the natural populations was 0 with the 0.95 upper confidence limit ranging from 0.102 to 0.925 depending on the genetic variation within the population. Outcrossing rates for two genotype classes of this species grown in a common garden were 0.0077 and 0.0018. The difference in Outcrossing rates between the two genotypes is ascribed to phenological differences and hence different available pollen pools. Phenological displacement is discussed as a possible bias in the estimation of outcrossing rates in both predominantly selfing and outcrossing plants.     

Surveying of pollen-mediated crop-to-crop gene flow from a wheat field trial as a biosafety measure

Outcrosses from genetically modified (GM) to conventional crops by pollen-mediated gene flow (PMGF) are a concern when growing GM crops close to non-GM fields. This also applies to the experimental releases of GM plants in field trials. Therefore, biosafety measures such as isolation distances and surveying of PMGF are required by the regulatory authorities in Switzerland. For two and three years, respectively, we monitored crop-to-crop PMGF from GM wheat field trials in two locations in Switzerland. The pollen donors were two GM spring wheat lines with enhanced fungal resistance and a herbicide tolerance as a selection marker. Seeds from the experimental plots were sampled to test the detection method for outcrosses. Two outcrosses were found adjacent to a transgenic plot within the experimental area. For the survey of PMGF, pollen receptor plots of the conventional wheat variety Frisal used for transformation were planted in the border crop and around the experimental field up to a distance of 200 m. Although the environmental conditions were favorable and the donor and receptor plots flowered at the same time, only three outcrosses were found in approximately 185,000 tested seedlings from seeds collected outside the experimental area. All three hybrids were found in the border crop surrounding the experimental area, but none outside the field. We conclude that a pollen barrier (border crop) and an additional isolation distance of 5 m is a sufficient measure to reduce PMGF from a GM wheat field trial to cleistogamous varieties in commercial fields below a level that can be detected.     

Pollen-mediated intraspecific gene flow from herbicide resistant oilseed rape (<Emphasis Type="Italic">Brassica napus</Emphasis> L.)

The cultivation of genetically modified (GM) herbicide resistant oilseed rape (Brassica napus) has increased over the past few years. The transfer of herbicide resistance genes via pollen (gene flow) from GM crops to non-GM crops is of relevance for the realisation of co-existence of different agricultural cultivation forms as well as for weed management. Therefore the likelihood of pollen-mediated gene flow has been investigated in numerous studies. Despite the difficulty to compare different experiments with varying levels of outcrossing, we performed a literature search for world-wide studies on cross-fertilisation in fully fertile oilseed rape. The occurrence and frequency of pollen-mediated intraspecific gene flow (outcrossing rate) can vary according to cultivar, experimental design, local topography and environmental conditions. The outcrossing rate from one field to another depends also on the size and arrangement of donor and recipient populations and on the ratio between donor and recipient plot size. The outcrossing levels specified in the presented studies are derived mostly from experiments where the recipient field is either surrounding the donor field (continuous design) or is located as a patch at different distances from the donor field (discontinuous design). Reports of gene flow in Brassica napus generally show that the amount of cross-fertilisation decreases as the distance from the pollen source increases. The evidence given in various studies reveals that the bulk of GM cross-fertilisation occurs within the first 10 m of the recipient field. The removal of the first 10 m of a non-transgenic field facing a GM crop might therefore be more efficient for reducing the total level of cross-fertilisation in a recipient sink population than to recommend separation distances. Future experiments should investigate cross-fertilisation with multiple adjacent donor fields at the landscape level under different spatial distributions of rapeseed cultivars and different cropping systems. The level of cross-fertilisation occurring over the whole field is mainly important for co-existence and has not been investigated in agricultural scale experiments until now. Potential problems with herbicide resistant oilseed rape volunteers arising from intraspecific gene flow can be largely solved by the choice of suitable cultivars and herbicides as well as by soil management.     

Pollen dispersal from two field trials of transgenic cotton in the Namoi Valley,Australia

The testing of transgenic crops in the field is a necessary part of the validation of genetically engineered cultivars, but in the early stages of testing, biosafety procedures must be carefully monitored to ensure that the modified plants do not have deleterious effects on the environment. This study was carried out over two seasons to determine the effectiveness of containment procedures under australian environmental conditions by measuring the dispersal of pollen amay from a test plot of transgenic cotton into a surrounding buffer field of non-transgenic cotton plants whose function was to act as a sink for pollen carried by nectar feeding and pollen-gathering insects. Dispersal was estimated by measuring the frequency of the dominant selectable marker transgene, neomycin phosphotransferase (NptII) in the progeny of the buffer plants. The presence of nptii was determined by a sensitive radioactive enzyme assay. Pollen dispersal was low in both years, but increased with an increase in the size of the source plot in the second year. In the first year outcrossing averaged from 0.15% of progeny at 1 m to below 0.08% at 4 m from the test plot. Outcrossing was highest within the central test plot where progeny from non-transgenic control plants, immediately adjacent to transgenic plants, had transgenic progeny at frequencies of up to 1.7%. In the second year, with a bigger source of transgenic plants, outcrossing declined on average from 0.4% at 1 m to below 0.03% at 16 m into the buffer zone. These results indicate that 20 m buffer zones would serve to limit dispersal of transgenic pollen from small-scale field tests.     

Identification, Distribution and Vector Population Dynamics of Barley Yellow Dwarf Virus in Three Cereal-Producing Areas of Spain

ELISA-based surveys during 1985–87 in three major cereal-growing areas of Spain confirmed the presence of barley yellow dwarf virus (BYDV). Samples of small grain cereals and grasses with and without BYDV-like symptoms were collected in the central, southwestern, and northeastern Spain. Infections were found in all cereal species sampled and in some grasses. About 37 % of the samples collected in 1985 were infacted with isolates of the PAV serotype. Isolates of the RPV serotype were less common, and were detected only in samples from the central region at El Encin, Madrid. Only a single sample, collected from El Encin in 1987, was unequivocally diagnosed as containing an isolate of the MAV serotype. Aphid vector population dynamics was monitored during fall and winter of 1984–87 in the central region. Rhopalosiphum padi L. appeared to be the most abundant species during fall and winter months, infesting grasses and volunteer wheat. Other species present were Sitobion avenae (F.), Metopolophium dirhodum (Walker) and Rhopalosiphum maidis (Fitch). Both R. padi and S. avenae seem to be anholocyclic in the central region of Spain, and are able to remain and reproduce on wheat volunteers and grasses until the beginning of spring. S, avenae populations increase quickly on wheat volunteers in April, while populations of R. padi remain low. Therefore, spread of S. avenae-transmitted BYDV types to neighbouring cereal fields seem more likely to occur than spread of other types. Other possible virus reservoirs, such as maize, also need investigation for a better understanding of BYDV epidemiology in the central and other cercal-growing areas of Spain.     

Investigating Pollen and Gene Flow of WYMV-Resistant Transgenic Wheat N12-1 Using a Dwarf Male-Sterile Line as the Pollen Receptor

Pollen-mediated gene flow (PMGF) is the main mode of transgene flow in flowering plants. The study of pollen and gene flow of transgenic wheat can help to establish the corresponding strategy for preventing transgene escape and contamination between compatible genotypes in wheat. To investigate the pollen dispersal and gene flow frequency in various directions and distances around the pollen source and detect the association between frequency of transgene flow and pollen density from transgenic wheat, a concentric circle design was adopted to conduct a field experiment using transgenic wheat with resistance to wheat yellow mosaic virus (WYMV) as the pollen donor and dwarf male-sterile wheat as the pollen receptor. The results showed that the pollen and gene flow of transgenic wheat varied significantly among the different compass sectors. A higher pollen density and gene flow frequency was observed in the downwind SW and W sectors, with average frequencies of transgene flow of 26.37 and 23.69% respectively. The pollen and gene flow of transgenic wheat declined dramatically with increasing distance from its source. Most of the pollen grains concentrated within 5 m and only a few pollen grains were detected beyond 30 m. The percentage of transgene flow was the highest where adjacent to the pollen source, with an average of 48.24% for all eight compass directions at 0 m distance. Transgene flow was reduced to 50% and 95% between 1.61 to 3.15 m, and 10.71 to 20.93 m, respectively. Our results suggest that climate conditions, especially wind direction, may significantly affect pollen dispersal and gene flow of wheat. The isolation-by-distance model is one of the most effective methods for achieving stringent transgene confinement in wheat. The frequency of transgene flow is directly correlated with the relative density of GM pollen grains in air currents, and pollen competition may be a major factor influencing transgene flow.     

Variation in the breeding behavior of the dry forest tree Enterolobium cyclocarpum (guanacaste) in Costa Rica

We studied the breeding systems of four populations of Enterolobium cyclocarpum (guanacaste, earpod tree) in Costa Rica. Multilocus estimates of the outcrossing rate indicate that E. cyclocarpum is a predominant outcrossing species (t(m) ranged between 0.881 and 0.901) and biparental inbreeding is low (range between 0.058 and 0.079). Overall, our analyses showed significant differences in the gene frequencies between pollen and ovules and significant differences in pollen gene frequencies between the four populations. We also found significant differences in the pollen gene frequencies calculated for single trees in the same population. Outcrossing rates and pollen gene frequencies varied in two consecutive years in two populations of E. cyclocarpum. The correlated mating model revealed that there are differences in the correlation of paternity between populations and years. These findings indicate that there is variation in the average number of trees that father the seed crop of each tree and/or that some fathers are overrepresented in the seed crop of each tree. The implication of these findings for the development of strategies for conservation and management of this species are discussed.     

Efficiency of direct and indirect shoot organogenesis in different genotypes of Rosa hybrida

To optimize indirect regeneration (IR) and direct regeneration (DR) in Rosa hybrida cv. Apollo different explant types and different concentrations of plant growth regulators were investigated. Among the different auxins studied and over all explant types, 10???M 2,4-dichlorophenoxyacetic acid (2,4-D) promoted the highest frequency of callus production for IR. The highest frequency of regeneration (60.8?%) was obtained when calli were transferred to Murashige and Skoog medium supplemented with 2.5???M thidiazuron (TDZ) and 2???M gibberellic acid. The highest frequency of regeneration (80.2?%) for DR was obtained from leaves cultured on the medium containing 10???M TDZ. The efficiency of IR and DR were compared in four different rose cultivars including ??Apollo??, ??Black Baccara??, ??Maroussia?? and ??Amanda??. The frequency of regeneration in all four cultivars was significantly higher in DR compared to IR. Also shoots regenerated by DR appeared earlier than the shoots regenerated by IR. The results of flow cytometry showed that the shoots derived from IR to DR were tetraploid like the original cultivars.     

Evaluating the influence of different aspects of habitat fragmentation on mating patterns and pollen dispersal in the bird-pollinated Banksia sphaerocarpa var. caesia

Habitat fragmentation can significantly affect mating and pollen dispersal patterns in plant populations, although the differential effects of the various aspects of fragmentation are poorly understood. In this study, we used eight microsatellite loci to investigate the effect of fragmentation on the mating system and pollen dispersal within one large and eight small population remnants of Banksia sphaerocarpa var. caesia, a bird-pollinated shrub in the southern agricultural region of Western Australia. The large population had a much larger neighbourhood size and lower selfing rate, maternal pollen pool differentiation and within-plot mean pollen dispersal distance than the small populations. Outcrossing was consistently high and ranged from 85.7% ± 2.6 to 98.5% ± 0.9, and mating patterns suggested nearest-neighbour pollination. Pollen immigration into small populations ranged from 2.8% ± 1.8 to 16.5% ± 3.2. Using the small populations, we tested for correlations between various fragmentation variables and mating system and pollen dispersal parameters. We found significant negative linear relationships between population isolation and outcrossing rate; population shape and neighbourhood size; and conspecific density and mean pollen dispersal distance. There were significant positive linear relationships between population shape and pollen pool differentiation and between population size and number of different fathers per seed crop. Our results suggest that birds may use a series of fragmented populations as a vegetation corridor while foraging across the landscape and that population connectivity is a critical determinant of pollinator visitation. Our results also suggest that the effect of a linear population shape on the mating system and pollen dispersal is routinely underestimated.     

Variation in pollen dispersal between years with different pollination conditions in a tropical emergent tree

We examined differences in pollen dispersal efficiency between 2 years in terms of both spatial dispersal range and genetic relatedness of pollen in a tropical emergent tree, Dipterocarpus tempehes. The species was pollinated by the giant honeybee (Apis dorsata) in a year of intensive community-level mass-flowering or general flowering (1996), but by several species of moths in a year of less-intensive general flowering (1998). We carried out paternity analysis based on six DNA microsatellite markers on a total of 277 mature trees forming four spatially distinct subpopulations in a 70 ha area, and 147 and 188 2-year-old seedlings originating from seeds produced in 1996 and 1998 (cohorts 96 and 98, respectively). Outcrossing rates (0.93 and 0.96 for cohorts 96 and 98, respectively) did not differ between years. Mean dispersal distances (222 and 192 m) were not significantly different between the 2 years but marginally more biased to long distance in 1996. The mean relatedness among cross-pollinated seedlings sharing the same mothers in cohort 96 was lower than that in cohort 98. This can be attributed to the two facts that the proportion of intersubpopulations pollen flow among cross-pollination events was marginally higher in cohort 96 (44%) than in cohort 98 (33%), and that mature trees within the same subpopulations are genetically more related to each other than those between different subpopulations. We conclude that D. tempehes maintained effective pollen dispersal in terms of outcrossing rate and pollen dispersal distance in spite of the large difference in foraging characteristics between two types of pollinators. In terms of pollen relatedness, however, a slight difference was suggested between years in the level of biparental inbreeding.     

NMR spectroscopy and chemometrics as a tool for anti-TNFα activity screening in crude extracts of grapes and other berries

The identification of active ingredients in crude plant extracts offers great advantages. In this study, nuclear magnetic resonance and chemometrics were used for the screening of in vitro anti-TNF?? activity in different berry types. Solid phase extraction was applied and the resulting water, methanol?Cwater (1:1), and methanol fractions were tested for the activity. The methanol?Cwater fraction contained most of the phenolics and showed significantly higher activity than the other two fractions. In the second phase of this study, grapes from ??Trincadeira??, ??Touriga Nacional??, and ??Aragonês??, at four developmental stages were metabolically classified and tested for the TNF?? inhibition. The initial stages of grape development, green and veraison, were found more active against TNF?? production as compared to the later ripe and harvest stages. Among the cultivars, ??Touriga Nacional?? was found to be the most potent inhibitor. Different multivariate data analyses algorithms based on projections to latent structures were applied to correlate the NMR and TNF?? inhibition data. The variable importance in the projections plot showed that phenolics like quercetin, myricetin, (+)-catechin, (?)-epicatechin, caftarate, and coutarate, were positively correlated with high activity. This work demonstrates the great potential of NMR spectroscopy in combination with chemometrics for the screening of large set of crude extracts, to study the effects of different variables on the activity, and identifying active compounds in complex mixtures like plant extracts.     

FLORAL BIOLOGY AND REGULATION OF SEED SET AND SEED SIZE IN THE LILY,CLINTONIA BOREALIS

We studied the reproductive ecology of Clintonia borealis, a clonal understory species, in eastern Ontario. Flowers are protogynous and require insect pollination for outcrossing and maximum seed set. Most pollination is done by nectar-gathering bumble bees. We recorded pollen deposition and flowering patterns in 1983. Flowering lasted for about 10 days in mid-June. Stigmatic pollen loads were lowest at the onset of blooming, reflecting the scarcity of male-phase flowers. Pollination increased significantly by peak bloom and subsequently remained high. However, since bees fly mostly between neighboring stems, much of the pollen transferred may have been geitonogamous. In 1983, seed set per flower was not increased by supplementing pollination or by reducing the number of fruits competing for resources per stem. Rather, flowers set more seeds (14%) only if both treatments were performed simultaneously. Seed size was increased by 25% when competitive fruits were removed and by 5% more when pollen was added under the removal treatment. Further work in 1984 showed that pollination effects may be related to changes in pollen source. Selfed flowers set fewer and smaller seeds than outcrossed ones when screened from insects and hand pollinated. Outcrossing distance had little effect on seed set or seed size. Thus, in C. borealis seed number and seed size are limited by a balance between maternal resource availability and the amount of outcrossing provided by pollinators.     

Do inbreeding depression and relative male fitness explain the maintenance of androdioecy in white mangrove, Laguncularia racemosa (Combretaceae)?

Mathematical models predict that to maintain androdioecious populations, males must have at least twice the fitness of male function in hermaphrodites. To understand how androdioecy is maintained in Laguncularia racemosa (white mangrove), outcrossing, inbreeding depression, and relative male fitness were estimated in two androdioecious populations and one hermaphroditic population. Outcrossing was estimated based on length of pollinator foraging bout and pollen carryover assumptions. Inbreeding depression was measured at three life stages: fruit set, seedling emergence, and seedling survivorship. The relative fitnesses of males and the male component of hermaphrodites were compared at these three stages and at the pollen production stage. Male frequency predictions generated by Lloyd's model were compared with observed frequencies in two androdioecious subpopulations. Outcrossing estimates were moderate for all populations (0.29-0.66). Inbreeding depression varied among populations (-0.03-0.86), but the strength of inbreeding depression did not increase with male frequency. Males produced significantly more flowers/inflorescence than hermaphrodites, but pollen production/flower did not differ. Male and hermaphroditic progeny did not differ significantly at other life stages. Populations of white mangrove with male plants were functionally androdioecious. Lloyd's model accurately predicted male frequency in one androdioecious subpopulation, but underestimated male frequency in the second subpopulation.     

Pollen limitation and distance-dependent fecundity in females of the clonal gynodioecious herb Glechoma hederacea (Lamiaceae)

Summary Pollen movement is often restricted in natural populations, and insufficient pollination is a potential constraint on sexual reproduction in outcrossing species. Seed-set should decrease with increased distance from the pollen source in outcrossing plants. This prediction was tested using females of the clonal, gynodioecious herb Glechoma hederacea in three natural populations. In controlled pollinations, both hermaphrodites and females had similar high percentages of fruit-set and seed-set. In a natural population where a female clone was isolated from the nearest hermaphroditic clone by c. 100 m, fruit-set was low (1%). In another population where hemaphroditic clones were rare and female clones had a patchy distribution, fruit-and seed-set in females were pollen-limited and decreased with increased distance from the nearest pollen source. The estimated mean pollen dispersal distance was 5.9 m when calculated on fruit-set and 5.3 m when calculated on seed-set. The most frequent pollinators were bumblebees. The mean and median distances moved by pollinators between ramets were 0.13 m and 0.05 m. In a third population where female clones were isolated from the nearest hermaphrodites by more than 200 m, fruit-set was 0%. After introduction of 16 hermaphroditic ramets in the center of the female clone, fruit-set varied between 0% and 100% in individual female ramets. Fruit-set decreased with increased distance from the pollen source. The mean and median pollen movement distances were 1.06 m and 0.54 m.     

Outcrossing potential between 11 important genetically modified crops and the Chilean vascular flora

The potential impact of genetically modified (GM) crops on biodiversity is one of the main concerns in an environmental risk assessment (ERA). The likelihood of outcrossing and pollen‐mediated gene flow from GM crops and non‐GM crops are explained by the same principles and depend primarily on the biology of the species. We conducted a national‐scale study of the likelihood of outcrossing between 11 GM crops and vascular plants in Chile by use of a systematized database that included cultivated, introduced and native plant species in Chile. The database included geographical distributions and key biological and agronomical characteristics for 3505 introduced, 4993 native and 257 cultivated (of which 11 were native and 246 were introduced) plant species. Out of the considered GM crops (cotton, soya bean, maize, grape, wheat, rice, sugar beet, alfalfa, canola, tomato and potato), only potato and tomato presented native relatives (66 species total). Introduced relative species showed that three GM groups were formed having: a) up to one introduced relative (cotton and soya bean), b) up to two (rice, grape, maize and wheat) and c) from two to seven (sugar beet, alfalfa, canola, tomato and potato). In particular, GM crops presenting introduced noncultivated relative species were canola (1 relative species), alfalfa (up to 4), rice (1), tomato (up to 2) and potato (up to 2). The outcrossing potential between species [OP; scaled from ‘very low’ (1) to ‘very high’ (5)] was developed, showing medium OPs (3) for GM–native relative interactions when they occurred, low (2) for GMs and introduced noncultivated and high (4) for the grape‐Vitis vinifera GM–introduced cultivated interaction. This analytical tool might be useful for future ERA for unconfined GM crop release in Chile.     

SEX ALLOCATION AND OUTCROSSING RATE: A TEST OF THEORETICAL PREDICTIONS USING BROMEGRASSES (BROMUS)

Predictions of sex-allocation theory were tested by comparisons among hermaphroditic bromegrass (Bromus) species that differed in outcrossing rate. Relative maternal and paternal investment were calculated using both the ratio of pollen to seed production, and absolute allocations in units of energy, nitrogen, phosphorus, potassium, magnesium, and calcium. Outcrossing rate had a large effect on sex allocation; species having greater outcrossing rates had relatively more paternal reproductive effort. Bromus inermis was obligately outcrossing, and nearly half of its reproductive effort was devoted to pollen production. Three partially outcrossed species, B. kalmii, B. ciliatus, and B. latiglumis, invested between 5% and 11% of reproductive effort in pollen production. Paternal investment was less than 2% in the selling species B. tectorum. Estimates of sex allocation were relatively unaffected by the resource currency used in calculation. The differences among species in sex allocation were mostly due to differences in anther size and seed set.>     

Transgene flow to hybrid rice and its male-sterile lines

Gene flow from genetically modified (GM) crops to the same species or wild relatives is a major concern in risk assessment. Transgenic rice with insect and/or disease resistance, herbicide, salt and/or drought tolerance and improved quality has been successfully developed. However, data on rice gene flow from environmental risk assessment studies are currently insufficient for the large-scale commercialization of GM rice. We have provided data on the gene flow frequency at 17 distances between a GM japonica line containing the bar gene as a pollen donor and two indica hybrid rice varieties and four male-sterile (ms) lines. The GM line was planted in a 640m² in an isolated experimental plot (2.4 ha), which simulates actual conditions of rice production with pollen competition. Results showed that: (1) under parallel plantation at the 0-m zone, the transgene flow frequency to the ms lines ranged from 3.145 to 36.116% and was significantly higher than that to hybrid rice cultivars (0.037–0.045%). (2) Gene flow frequency decreased as the distance increased, with a sharp cutoff point at about 1–2 m; (3) The maximum distance of transgene flow was 30–40 m to rice cultivars and 40–150 m to ms lines. We believe that these data will be useful for the risk assessment and management of transgenic rice lines, especially in Asia where 90% of world's rice is produced and hybrid rice varieties are extensively used. Shirong Jia, Feng Wang and Lei Shi contributed equally to this investigation.