Question
That is very interesting! So it's like the plant has a natural tendency to revert back to it's original genetic state, regardless of who does what to it.  I have heard some opinions about consuming hybridized fruits and veggies, that it is not as good for us, as non- hybrid...would that be considered "organic", or is that another thing altogether?  Do you have an opinion on this issue?
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Followup To

Question -
Regarding a prior question about planting a nectarine seed, you said most citrus sold in stores ar hybrids, not "true from seed". Please explain how hybrids are developed vs. a tree that is "true from seed". Do hybrid plants produce a new hybrid seed?  My logic has always been that if you plant the seed from some produce, you should eventually get the same produce from which the seed came.  So this is new to me.  Thank you.

Answer -
Hi Wendy,
Thanx for your question, however, my expertise is not in genetics it is in basic horticulture.  I understand some of the mechanics of genetics but I am by no means an expert.

What I do know is that a hybrid is created by a breeder selecting two different plants that have characteristics he or she would like to see in the same plant.  This is how many different cultivars of fruit, vegetables, flowers, trees, shrubs etc. have been developed over the years and how the West, in particular the U.S. has developed grains and corn that produce tons and tons more than the ancestor plants.

A plant breeder may develop a hybrid over many, many generations to come up with the exact hybrid s/he is looking for.  These genetic combinations tend to be unstable and seldom will result in a duplicate of the plant after the first generation (after development) and the genetic patterns begin to degrade backwards.  If you understand how the genetic pattern degrades it will make sense to you why a seed from the fruit of a hybrid nectarine will seldom result in a plant that resembles the parent.  Like I said, I am not an expert in genetics and although it makes sense to me, it is difficult for me to explain.

Here is some information from Texas A&M you may find helpful.  You can also do a Google search typing in "hybridization" for a number of explanations that will help you understand why seeds from fruit developed from hybrids seldom come true.  I hope this helps.
Tom

http://plantanswers.tamu.edu/vegetables/seed.html

Answer
Hi Wendy,
Thanx for the follow up.  Many hybrids are genetically unstable and after the first generation will start to degrade.  Hybridization causes mutations and most mutations are lethal which results in the end of the genetic line.  Only the strongest, most stable mutations survive.  If you look at human genetics, that is the theory also.  The current human genome is the result of eons of natural mutations and cross-breeding between different cultures but the same species.  In the plant world, there are also natural mutations that result in stronger, healthier plants. These mutations most often occur as a result of environmental issues.  Natural mutations resulted in plants that are naturally able to survive in desert or drought conditions.  The plant evolved in order to ensure it's survival by either storing water efficiently or developing deep root systems that could access water deep in the soil.

You asked if I had an opinion.  Yes, I have many opinions on the subjects of agriculture/horticulture/hybridizing.  First, let me explain to you what "organic" means.  Organic in general (and this is a very liberal description)means that methods to grow and culture plants are used that do not involve the use of chemical fertilizers or chemical insecticides, pre-emergents, etc.  It also means that certain environmentally-friendly methods are used to cultivate and amend soil (with natural amendments), soil conservation methods are practiced and water management.  The United States Department of Agriculture has an in depth definition of organic practices on its website USDA.gov.  I personally do not use chemical fertilizers (which often are byproducts of petroleum products) and I do not use chemical pesticides which is very difficult sometimes.  I am currently battling cucumber beetle and squash bugs that have resulted in the death of about 1/10th of my plants and a total loss of my Italian Arancino canteloupes which was a great disappointment.  However, organic practices teach us to use varieties of plants that have resistance to disease and pests and there are other organic practices which I have begun to employ which helped save my cucumbers.  An example is that I trellis my cucumbers which has resulted in no plant deaths this year. It is more hygenic and it restricts acces to the plant of the larvae of some of the predatory insects.  Crop rotation is another key organic practice.  This means not planting the same crop in the same place every year.  This cuts down on the chances of a disease or pest infestation.  Removing spent plants at the end of the season and burning them in a place distant from the growing area is another organic safeguard and basic hygiene principles apply to organic farming as it does to human physical health.  I believe organic is healthier and more beneficial to both the land and to consumers but it is labor intensive and it is more expensive.  More and more people however, are willing to pay a premium for organically grown fruits and vegetables.

Let's talk about the safety of hybrids.  As far as I know, most hybrid fruits and veggies unless they have been genetically modified (which all the data are not in on the safety of this, some dangers have been exposed and I am against genetically modified food products) are safe to consume.  A hybrid Better Boy tomato is just as nutritious as an organically grown heirloom/open pollinated Arkansas Traveler tomato.  In my opinion though, most of the open pollinated tomatoes have a more robust taste and are meatier.  This is just my opinion.  There are many parts of the U.S. where it is difficult to grow some varieties of open pollinated tomatoes because they don't have resistance to certain diseases common to tomatoes that have infested the soil.  Many years ago tomato breeders began breeding in disease resistance which became a boon for areas of the country in which it was difficult to grow tomatoes disease-free.  But, many hybridizers have developed tomatoes that are tasteless and mushy because the consumer wants to see uniform fruit.  Many Americans don't care much about the taste as long as the product looks uniform in color and shape.  I often see people at the farmer's market stare in shock at gigantic specimens of Arkansas Traveler or Amish Brandywine tomatoes often weighing up to a pound each.  They are used to the pale orange baseball sized tomatoes packed neatly side-by-side at the grocery store.  These people are often overwhelmed by the magical and haunting aroma that is so intense when one cuts into a freshly picked, open-pollinated tomato.  And the taste, almost always knocks them over.  There is NO comparison between what is bought in the store and what is grown naturally outside the back door.  I assure you that to my knowledge, vegetables and fruits that are not the result of genetically modified practices are just as safe as open-pollinated and are in most cases just as nutritious.  Now, there are some hybrids that have been hybridized to increase certain vitamin, mineral, protein, sugar contents.

Finally, hybridizing isn't bad.  If it weren't for hybridizing, we wouldn't have the corn and potatoes we have now that Native Americans in the New World spent thousands of years developing by selecting plants that had the characteristics they wanted.  Corn at one time was a heavy-seeded grass-type of plant.  Potatoes came from a plant that had small peanut-sized nobs on its roots.  Look what we have now as a result of hybridization.  We are able to feed billions of people with corn and potatoes.  But, we must maintain genetic diversity.  Genetic Diversity ensures the general survival of the species.  One disease may kill several varieties of a species but certain other varieties have a natural resistance.  This characteristic can be used to cross-breed into a disease resistant variety.  Unfortunately, not paying attention to genetic diversity has resulted in at least one great human disaster and another that could have been the second great human disaster involving a lack of genetic diversity.

Example 1:  By the 1800s the potato had become very popular in Europe.  In fact, in Ireland, it was a staple food and often made up most of an Irishman's meal.  But an attack of phytophora infestans (potato blight) all but destroyed the potato crops in the 1840s because the potato varieties used in Ireland did not have resistance to this disease.  Over a million Irish people perished in the potato famine years and caused a huge emigration from Ireland to the United States, Australia and other places around the world.  It is probably one of the most well-known examples of how a lack of genetic diversity in crop growing can result in lethal disaster for humankind.  

Example 2:  In 1970 or so, 15% of the total U.S. corn crop was lost due to corn blight as a result of genetic flaws.  Because the U.S. stores huge amounts of grain very few people probably noticed or even remember this.  However, in some countries like Guatemala where over 50% of caloric intake comes from corn a loss such as that could have had devastating affects.

Anyway, I apologize for being so wordy but I hope this helps.
Tom