Comments on: Those naughty plants!

By: Biofortified » Hybrids in Haiti

Biofortified » Hybrids in Haiti — Fri, 04 Jun 2010 22:45:54 +0000

[...] Yes and no. Gene flow is simple and complex at the same time. For the most part, pollen stays near the source, but in a country as small as Haiti (10,714 mi²), wind and pollinators could conceivably carry pollen all over the country. If farmers who choose to plant traditional varieties, they will be able to maintain those varieties. Some percentage of the seed that they harvest at the end of this growing season will be a hybrid between the traditional variety and the new seed, depending on how close they are physically to a farmer who planted the new seed. Conversely, the farmer who planted the new seed will have a certain percentage of his harvest “contaminated” with the traditional variety. They can keep their two varieties separate (for the most part) generation after generation by keeping seeds from plants that are similar to the variety they want and avoiding keeping seeds from plants that look different. Importing heirloom or open-pollinated seeds would “contaminate” the local varieties as much as the seeds from Monsanto. For more details on gene flow, check out Those naughty plants! [...]

By: Anastasia Bodnar

Anastasia Bodnar — Fri, 12 Feb 2010 16:56:17 +0000

Ewan, I just caught that last statement of yours about shifts in flowering time. I’ve always wondered why researchers in places where there are lots of wild relatives, weedy relatives, or landraces for the crop species of interest (like Mexico) aren’t developing crops that flower earlier or later than most of the wild or landrace ones. Seems like a nice low tech way to keep the plants from being so naughty – so they’ll be more likely to stay with their intended mates. It’s not 100% but it could be quite effective.

By: Ewan R

Ewan R — Sat, 23 Jan 2010 13:48:30 +0000

Throughout my college days I used “Allele” as a chracter name on many online games… I suffer worse than most as a result from the allele/gene fallacy.

I wonder to what extent gene flow from hybrids (or inbreds, or any non-native variety)can be expected to infiltrate a landrace and I’d expect (with absolutely no sound empirical backing) that it would be pretty tough although my understanding of how landraces are utilized/grown in Mexico may be somewhat limited – I’d imagine that introgression of foreign alleles into a low input system would in general tip them away from being as resistant to abiotic stress, less acclimated to the specific soil type and dominant weather etc – if inputs are higher this issue would likely go away, but I think it is rather questionable that anyone would use a landrace in anything other than a low input environment.

To a certain extent here I can see why Bt for instance, may impact biodiversity (allele diversity?), as I’d guess you may well get a bunch of semi-deleterious alleles (comparitively) hopping over with a Bt gene and then getting stuck there due to the increased fitness provided by the Bt gene (assuming it does anything in the environment it is in – it won’t always) – one can always hope that genetic drift and potential to shift flowering time would take care of things also (which I’m sure everyone would agree is the scientifically sound way to go)

By: Anastasia Bodnar

Anastasia Bodnar — Fri, 22 Jan 2010 16:26:42 +0000

Ewan, you’re right, of course. I described the extremes here. In real fields, gene flow can positively contribute to genetic diversity, even when the genes are from unwanted sources like modern hybrids or inbreds and weedy relatives. I do worry about places like Mexico, though, where maize landraces are planted nearby hybrid corn year after year. If the landrace population keeps getting pollinated by the hybrids, even if it’s only a small portion of the field, there could very easily be loss of genetic diversity, especially if the alleles confer an advantage. Ah, I wish I remembered my population genetics a little better.

I’m amazed at the tricks plant breeders use to keep those naughty plants from mating with undesirable partners. I live in Ames, IA near a branch of the USDA Agricultural Research Service and it’s so neat to see things like sunflowers protected from pollinators with netting and cucumbers housed in little mesh cubes to keep the pollinators in. Planning parenthood for plants isn’t easy!

By the way, have you noticed that even breeders and geneticists, people who know better, often use the word gene when they mean allele? Even though we know what the differene is, it’s just easier to say gene – but the meaning might not be clear to someone who doesn’t know the difference. We say gene flow, but really we often mean allele flow, except in the case of actually new genes like transgenes.

By: Ewan R

Ewan R — Fri, 22 Jan 2010 15:32:26 +0000

Isn’t gene flow out of a crop species into a landrace (whether it is transgenic or not) likely to result in an actual increase in biodiversity rather than the reverse -at least on a population level, the individual plant may have a more uniform set of chromosomes than one might expect (from the inbred/hybrid parent) but the addition of information into the overall gene pool surely represents an increase in diversity, unless of course the situation you discuss on farmer selection within the field comes in to play – although arguably if a farmer is selecting the best plants to take seed from every year you’d get a local decrease in biodiversity regardless of proximity to hybrids/inbreds (albeit at a slower pace).

As far as I see it the main concerns around gene flow should come from those with the “heirloom” obsession – as any gene flow from any source is going to ruin your variety (or the seeds from that season anyway) – and of course plant breeders in general… although I’ll go out on a limb here and assume that plant breeders are well aware of gene flow issues hence the endless hours in the field/greenhouse/growth chamber with paintbrushes, tweezers and all manner of arcance devices involved in planned parenthood for plants.