Assessment of the influence of field size on maize gene flow using SSR analysis

Abstract

One of the factors that may influence the rate of cross-fertilization is the relative size of the pollen donor and receptor fields. We designed a spatial distribution with four varieties of genetically-modified (GM) yellow maize to generate different sized fields while maintaining a constant distance to neighbouring fields of conventional white kernel maize. Samples of cross-fertilized, yellow kernels in white cobs were collected from all of the adjacent fields at different distances. A special series of samples was collected at distances of 0, 2, 5, 10, 20, 40, 80 and 120 m following a transect traced in the dominant down-wind direction in order to identify the origin of the pollen through SSR analysis. The size of the receptor fields should be taken into account, especially when they extend in the same direction than the GM pollen flow is coming. From collected data, we then validated a function that takes into account the gene flow found in the field border and that is very useful for estimating the % of GM that can be found in any point of the field. It also serves to predict the total GM content of the field due to cross fertilization. Using SSR analysis to identify the origin of pollen showed that while changes in the size of the donor field clearly influence the percentage of GMO detected, this effect is moderate. This study demonstrates that doubling the donor field size resulted in an approximate increase of GM content in the receptor field of 7%. This indicates that variations in the size of the donor field have a smaller influence on GM content than variations in the size of the receptor field.

Detection of genetically modified maize in processed products, dry grains, and corn ears intended for fresh consumption in South Brazil

“…Non-transgenic corn crops can be pollinated by transgenic plants grown in neighboring locations (Devos et al, 2009). Good management practice of transgenic crops (use of natural barriers, cultivation of conventional plants in the borders, postponing or advancing sowing to the flowering period) could help to avoid the contamination of non-transgenic crops (Palaudelmàs et al, 2012). Of note, producers have responsibility, especially in organic production, for the accuracy of the information provided about the crop (CIB, 2011).…”

Sampling Strategies for Evaluating the Rate of Adventitious Transgene Presence in Non‐Genetically Modified Crop Fields

“…Sampling methods were tested with data from three field experiments (Fig. ): two experiments carried out in 1998 and 1999 at Montargis, France, and an experiment carried out in 2004 at Mas Cebria in Spain . The three experimental fields studied had different rates of transgene presence (Table ).…”

“…We used a sampling procedure described elsewhere to select 708 points, at each of which we sampled three ears. The locations of the collected ears were recorded . The rate of transgene presence was calculated for each ear as the percentage of grains with a yellow color.…”

“…The locations of the collected ears were recorded. (18) The rate of transgene presence was calculated for each ear as the percentage of grains with a yellow color. The mean transgene ratio was 1.90% yellow grains in the whitemaize field.…”

Asynchronous Flowering or Buffer Zones: Technical Solutions for Small‐scale Farming

“…Of these, cross‐pollination causes most concern to maize growers because it is difficult to control and depends on many factors, including the distance between the GM donor(s) and the conventional receptor fields, type of cultivars, farming practices and climatic conditions. The rate of cross‐fertilsation is highest near the borders and decreases toward the centre of the conventional field (Palaudelmàs et al ., ). Separation distances between GM and conventional fields have been proposed as a strategy to ensure coexistence (Bénétrix and Bloc, 2003; Henry et al ., ; Brookes et al ., 2004; Ma et al ., ; Melé et al ., ; Sanvido et al ., 2005; Bannert, 2006; Della Porta et al ., 2006; Ortega Molina 2006; Pla et al ., ; Weber et al ., ).…”