GMO alone does not affect the genetic diversity of the variety.
GMO just affects how the first plant(s) of a variety are obtained; in the case of GMO, you shoot a gene gun (or use some other technique) to modify one or more starting seeds. In non-GMO crop development, you simply observe an interesting individual (or cross some number of existing varieties and look for interesting individuals among the offspring). A math teacher of mine once found an exceptionally fuzzy soybean plant he thought might be insect resistant.
What happens next is what affects the genetic diversity of the crop.
So you have one special plant. How do you turn that into a field?
Well, you breed it and hope its offspring are also special. Some plants are self-fertilizing; you may do that, to try to avoid introducing non-special genes into the germ-line. You may also use the pollen from your special plant to pollinate a large number of other plants and hope at least some of their offspring are special. In the case of GMO, you might use your gene gun to shoot the same modification into a reasonably diverse set of initial seeds.
Your goal as a seed breeder - GMO or non-GMO - is to get the genes that produce the characteristics of the variety you are trying to produce (flavor or size or color of the fruit; speed of growth; hardiness or resistance) as uniformly as you can into a breeding population of plants, so that all of the offspring of all of the plants can reasonably be expected to express the traits.
There will necessarily be a weak point there: if a new virus attacks the gene that is needed to make your new corn variety super-delicious, all the plants will inherently be susceptible to that disease, regardless of how that gene got there. This sort of susceptibility isn't too troubling, however, because it's always there: corn shares a great number of genes with other corn; that's what makes it corn and not wheat or beans.
What will vary is how much diversity will be in the rest of the plant's genome. There could be very little, if you simply breed your exemplar starting plant against it self, and then its children against themselves, over and over until you have enough seeds to plant a field. There could be a lot, if you can find or produce a number of unrelated exemplars or you first breed your exemplars against a more diverse gene pool.
This second sort of a lack of genetic diversity is more troubling, but it isn't a product of genetic engineering: it's a result of going through a population bottleneck in the recent past; this can happen to non-GMO varieties just as easily.
GMO just affects how the first plant(s) of a variety are obtained; in the case of GMO, you shoot a gene gun (or use some other technique) to modify one or more starting seeds. In non-GMO crop development, you simply observe an interesting individual (or cross some number of existing varieties and look for interesting individuals among the offspring). A math teacher of mine once found an exceptionally fuzzy soybean plant he thought might be insect resistant.
What happens next is what affects the genetic diversity of the crop.
So you have one special plant. How do you turn that into a field?
Well, you breed it and hope its offspring are also special. Some plants are self-fertilizing; you may do that, to try to avoid introducing non-special genes into the germ-line. You may also use the pollen from your special plant to pollinate a large number of other plants and hope at least some of their offspring are special. In the case of GMO, you might use your gene gun to shoot the same modification into a reasonably diverse set of initial seeds.
Your goal as a seed breeder - GMO or non-GMO - is to get the genes that produce the characteristics of the variety you are trying to produce (flavor or size or color of the fruit; speed of growth; hardiness or resistance) as uniformly as you can into a breeding population of plants, so that all of the offspring of all of the plants can reasonably be expected to express the traits.
There will necessarily be a weak point there: if a new virus attacks the gene that is needed to make your new corn variety super-delicious, all the plants will inherently be susceptible to that disease, regardless of how that gene got there. This sort of susceptibility isn't too troubling, however, because it's always there: corn shares a great number of genes with other corn; that's what makes it corn and not wheat or beans.
What will vary is how much diversity will be in the rest of the plant's genome. There could be very little, if you simply breed your exemplar starting plant against it self, and then its children against themselves, over and over until you have enough seeds to plant a field. There could be a lot, if you can find or produce a number of unrelated exemplars or you first breed your exemplars against a more diverse gene pool.
This second sort of a lack of genetic diversity is more troubling, but it isn't a product of genetic engineering: it's a result of going through a population bottleneck in the recent past; this can happen to non-GMO varieties just as easily.