Wheat pollen dispersal under semiarid field conditions: potential outcrossing with Triticum aestivum and Triticum turgidum

Abstract

Isolation distance is the main barrier to crop-to-crop gene-flow. A 3-year study assessed the maximum potential outcrossing under field conditions between two wheat cultivars (Triticum aestivum L.) and between wheat and durum wheat (Triticum turgidum L. var. durum). Outcrossing was measured by seed set on emasculated recipient plants placed at four sides with different distances from a 3 m · 3 m T. aestivum (cultivar Chinese Spring) pollen source. Frequencies of seed set at 0 m distance were 45% (37-56%) for T. aestivum cultivars and 18% (5-30%) with T. turgidum. These values agree with hybridization in non-limiting pollen conditions measured by manual crosses in greenhouse. The number of pollen grains and the outcrossing frequencies decreased at increasing distances influenced by the prevailing wind direction. Under semiarid conditions of this assay, viable pollen was found 14 m from the pollen source, with a maximum distance of 8 m at which crosspollination decreases below 1%. Ambient conditions affect pollen viability, hybridization and pollen dispersal. Data presented in this paper emphasize the major role played by environmental conditions in outcrossing. Data obtained in one area may therefore not coincide with the prevailing situation in different locations and climates.

Gene flow between wheat and wild relatives: empirical evidence from Aegilops geniculata, Ae. neglecta and Ae. triuncialis

“…2004; Hanson et al. 2005; Loureiro et al. 2007b), this observation is not surprising and indicates that wheat to Aegilops gene flow might be a local‐scale phenomenon.…”

“…As pollen-mediated gene flow from wheat is expected to be more important along wheat fields than in remote locations (i.e. 20-30 m pollen is a commonly reported range for pollen movements, Matus-Cadiz et al 2004;Hanson et al 2005;Loureiro et al 2007b), this observation is not surprising and indicates that wheat to Aegilops gene flow might be a local-scale phenomenon. Nevertheless, a several admixed individuals were observed in populations distant from wheat cultivations (i.e.…”

Testing coexistence and genetic containment for an autogamous crop

“…In the case of certified seed nurseries, however, it could be recommended to avoid growing GM and non-GM cultivars side by side in order to prevent any detectable gene flow. Compared to other autogamous cereals, gene flow between foxtail millet fields was lower than in the case of wheat (Waines and Hedge 2003;MatusCadiz et al 2007;Loureiro et al 2007), but higher than in rice (Messeguer et al 2001;Shivrain et al 2007;Rong et al 2007), although experimental designs, cultivars, and environmental conditions could be the source of great variations.…”

Pollen Mediated Gene Flow in GM Crops: the Use of Herbicides as Markers for Detection. the Case of Wheat

“…Outcrossing was detected at the very low level of 0.07% at 100 m from the source. These outcrossing rates are in the range of published frequencies averaging 1%, but that can vary between 0 to 6.7% at distances below 1 m (Griffin, 1987;Hucl, 1996;Zhao et al, 2000;Hucl & Matus-Cadiz, 2001;Loureiro et al, 2005), although hybrid seed set is also possible at greater distances.…”