Genetically modified (GMO) food - are we consuming it without knowing it?

I love food - I love to cook it and eat it. It is obvious from this blog. One of the issues related to food that often intrigues me is genetically modified (GMO) food and how people are opposed to eating it. I am not a botanist nor a plant geneticist, just someone who is curious. I have some questions, I searched for some answers and I have compiled them here to share with you. I'm not pro GMO nor am I vehemently against it. I just think we need a sensible approach to see what is good and what is bad about "modifying" food producing plants, plants and animals.

Seedless Fruits - GMO or not?
From what I know and understand, this is the natural way of getting a fruit:
Plant a seed and wait for it to grow into a plant. Pray and hope for the plant to have lots of flowers. Once flowers start to bloom, pray and hope again that they get fertilized. Flowers that get fertilized mature into fruits that contain seeds and the whole cycle starts again. Therefore, naturally, a grape should contain seeds.

So, how do we get seedless grapes?
I hate seeds in grapes - get into the way of my enjoyment of the fruit. I remember studying about parthenocarpy during secondary school. That was a long, long time ago - don't ask me why I still remember it till today. Maybe the thought of eating seedless grapes when I was a child intrigued me. Anyway, I remember my biology teacher telling us that seedless grapes are produced via parthenocarpy. Actually, she was inaccurate - seedless grapes are seedless because of stenospermocarpy - the abortion of the embryo - not parthenocarpy. But I won't hold it against her.

In parthenocarpy, fruit is developed without fertilization or use of seeds. Parthenocarpy happens in nature - some sort of mutation happens and the fruit becomes seedless. Sometimes, parthenocarpy is man made - use of hormones to induce parthenocarpic fruit. This means use of hormones to cause a mutation that will leave a fruit seedless. So, that means a GMO fruit, yes? When was the last time you ate an orange that was seedless?

How about high yield rice?
I have always believed that high yield rice has been genetically modified because I learnt from my Geography teacher that rice used to be low yield - producing crop annually. According to Wikipedia, "Rice, like corn and wheat, was genetically manipulated to increase its yield." I wonder if the popular Thai Hom Mali rice has been GMO? How many of us eat rice, and wheat based products that come from high yield cereals? and how many people complain?

Will grafting a plant modify genetics?
I can't access Stegmann and Bock's (2009) article. So this was taken from the abstract available from Pubmed:

"We grafted tobacco plants from two transgenic lines carrying different marker and reporter genes in different cellular compartments, the nucleus and the plastid. Analysis of the graft sites revealed the frequent occurrence of cells harboring both antibiotic resistances and both fluorescent reporters. Our data demonstrate that plant grafting can result in the exchange of genetic information via either large DNA pieces or entire plastid genomes. This observation of novel combinations of genetic material has implications for grafting techniques and also provides a possible path for horizontal gene transfer."

Aren't many new breeds of fruits and flowers obtain via grafting? Logically thinking, grafting bud A to plant B producing plant C requires some change to happen genetically, doesn't it? Of course there will be people who will say "oh, GMO has to do with cloning, protein engineering or use of molecular genetic techniques, not grafting that produces a new hybrid." Oh, come on...

Reference:

1. Rotino et al (2005) Open field trial of genetically modified parthenocarpic tomato: seedlessness and fruit quality. http://www.biomedcentral.com/1472-6750/5/32
2. Parthenocarpy. http://en.wikipedia.org/wiki/Parthenocarpy
3. Polyploidy & Hybridization In San Diego County. http://waynesword.palomar.edu/hybrids1.htm#parthenocarpy
4. Genetic engineering. http://en.wikipedia.org/wiki/Genetic_engineering
5. Stenospermocarpy. http://en.wikipedia.org/wiki/Stenospermocarpy
6. Acciarri et al (2002). Genetically modified parthenocarpic eggplants: improved fruit productivity under both greenhouse and open field cultivation.
7. Wikipedia - Rice.
8. Stegemann S, Bock R. Exchange of genetic material between cells in plant tissue grafts.