Tips for co-existence between RR and conventional alfalfa
At the Alfalfa and Forage Meeting held at the Kearney Agricultural Center in September, we provided a demonstration of the co-existence of Roundup Ready (RR) and conventional alfalfa hay fields. The demonstration took place between two hay fields – one of them RR and the other conventional – that were in their third year of production and separated only by a one-lane dirt road.
The demonstration showed what is meant by “co-existence”; the RR trait has not transferred to the adjacent conventional hay field or to a nearby organic hay field. All of the fields are co-existing in close proximity, and the RR trait is only found in the RR field. We used commercially-available test strips that detect the CP4 EPSPS protein unique to RR alfalfa to confirm that transfer had not occurred.
The test strips are reported to detect the presence of the protein in a hay sample that contains at least five percent RR hay by weight.
Roundup Ready alfalfa became commercially available in 2005. The genetically-engineered RR trait allowed alfalfa to tolerate the broad-spectrum, post-emergence herbicide, glyphosate. A lawsuit in 2007, however, stopped any further planting. It was not until January 2011 that RR alfalfa was granted non-regulated status and planting resumed.
There are concerns among growers, marketers, and the general public about the ability of RR and conventional alfalfa to co-exist. Key among the concerns is the possibility for the RR trait to transfer by pollen to conventional alfalfa, known as adventitious presence (AP). While transfer of the RR trait has been measured between alfalfa fields grown for seed production (the likelihood depending on the distance between fields), it is largely prevented between fields grown for hay due to management barriers to AP and plant and pollinator biology.
The primary management barrier is that hay is generally cut well before 10% flowering, so seed is rarely allowed to form, let alone mature. Biological limitations that make the transfer of the RR trait to conventional hay highly unlikely include the necessity of simultaneous flowering between fields, the presence of pollinators, successful pollen movement via a pollinator to a receptive flower (known as cross-pollination), successful fertilization resulting in viable seed, and viable seed falling to the ground and having the proper conditions for germination and survival.
Any grower who has ever tried seeding alfalfa into an existing alfalfa stand knows how difficult it can be to establish new alfalfa plants in an old stand due to competition and autotoxicity. Nevertheless, despite the odds, it is courteous and wise to employ practices that allow the co-existence of RR and conventional alfalfa.
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