Pollen‐Mediated Gene Flow in California Cotton Depends on Pollinator Activity

Abstract

on the location, the time period, and how measurements are taken. In the 1950s comprehensive studies using vis-Many cotton (Gossypium hirsutum L.) pollination studies have ual phenotypic traits reported 10% outcrossing in Texas been performed in the southern USA, but no data exist for California. In this study, we measured pollen-mediated gene flow (PGF) in four to 47% in Tennessee (Simpson, 1954; Simpson and Dundirections over 2 yr from herbicide-resistant source plots in upland can, 1956). These studies reported 28% outcrossing in cotton in the California cotton growing region and in a region with Mississippi, but a mean of 2% outcrossing was reported high pollinator activity. In addition, samples were taken from fields in similar locations in Mississippi 20 yr later (Meredith of conventional varieties at varying distances from fields planted with and Bridge, 1973). The authors suggested the differherbicide-resistant varieties to assess PGF under commercial producences were due to a reduction in wooded areas and the tion conditions. A seedling herbicide bioassay confirmed by DNA tests heavy use of pesticides resulting in a decrease in bee was used to measure PGF. PGF was independent of direction from pollinators. Also in Mississippi, Umbeck et al. (1991) the source plot and declined exponentially with increasing distance measured pollen transfer to non-transgenic rows of cotfrom 7.65% at 0.3 m to less than 1% beyond 9 m when there was high ton planted up to 25 m from a 4 ha field of cotton carpollinator activity. In the absence of high pollinator (honeybee, Apis mellifera L.) populations, PGF was less than 1% beyond 1 m. Pollen rying the nptII gene. PGF dropped below 1% at disflow in commercial fields was consistent with the experimental plot tances beyond 7 m, but continued to be detectable at a data, with only 0.04% PGF detected at 1625 m (1 mile). This study distance of 25 m in solid-seeded cotton. Studies sumconfirms that PGF decreases exponentially with distance in cotton marizing data (Ͼ15 000 samples) in Arizona, Arkansas, grown under California conditions and is low in the absence of polli-Mississippi, and North Carolina showed that PGF denators, although sporadic occurrence of PGF can be detected up to creased exponentially with increasing distance from the 1625 m.Published in Crop Sci. 45:1565Sci. 45: -1570Sci. 45: (2005.

Scientific Opinion on applications (EFSA-GMO-UK-2008-57 and EFSA-GMO-RX-MON15985) for the placing on the market of insect-resistant genetically modified cotton MON 15985 for food and feed uses, import and processing, and for the renewal of authorisation o

“…The main cultivated cotton species (G. hirsutum), which has been present in Southern Europe since the 19 th century, is an annual self-pollinator. In the absence of insect pollinators (such as wild bees, honeybees, bumblebees), cotton flowers are self-pollinating, but when these pollinators are present low frequencies of cross-pollination can occur (McGregor, 1959;Moffett and Stith, 1972;Moffett et al, 1975;Van Deynze et al, 2005).…”

“…Because cotton pollen is very large (120-200 µm), heavy and sticky, wind-mediated dispersal of pollen to cross-pollinate other cotton varieties is considered negligible (Vaissiere and Vinson, 1994). In addition, cross-pollination percentages rapidly decrease with increasing distance from the pollen source (Umbeck et al, 1991;Kareiva et al, 1994;Llewellyn and Fitt, 1996;Xanthopoulos and Kechagia, 2000;Zhang et al, 2005;Van Deynze et al, 2005Hofs et al, 2007;Llewellyn et al, 2007;Heuberger et al, 2010).…”

Hybridization rates between lettuce (Lactuca sativa) and its wild relative (L. serriola) under field conditions

“…Moreover, recent studies have shown that low outcrossing rates do not prevent cultivated genes from moving in sympatric wild populations. These studies include both, autogamous and/or predominantly insect-pollinated species like soybean, bean or cotton (Ibarra Perez et al, 1997;Nakamaya and Yamaguchi, 2002;Van Deynze et al, 2005), as well as windpollinated autogamous species as rice or foxtail millet (Chen et al, 2004;Song et al, 2003;Wang et al, 1997;Zhang et al, 2003).…”

“…These factors include the number of flowers produced per plant, the seasonal or annual changes in meteorological conditions, the spatial patterns of distribution of the wild population, and their position relative to the crop pollen source (Schmitt, 1983;Van Deynze et al, 2005). Insect visitation rates and therefore possible hybridization rates might depend on the amount of flowers available from Lactuca, but surely also on the availability of other plant species, since all observed visitors were generalists.…”

Response to Bagavathiannan and Van Acker's “Transgenes and national boundaries – The need for international regulations”: Biotechnology developers and regulators already consider transgene movement across national boundaries and the environmental risks posed by adventitious presence of unapproved events are overstated

“…Other scientific information is presented in an incomplete and unsatisfactory manner. For example, the conclusion presented in Table 2 that soybean is a crop "in which international gene flow may be a potential concern" is doubtful given its limited potential for outcrossing (e.g., Ahrent and Caviness, 1994;Ray et al, 2003); similarly, the potential for pollen mediated gene flow in cotton is also limited (e.g., Umbeck et al, 1991;Van Deynze et al, 2005). One must also question the basis for identifying borders like India and China as well as Egypt and Libya to be areas where "international gene flow may be of potential concern" (see their Tab.…”