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AG Hybrid Theory 2 By Joe Ailts - Dec 2002
 

B.S. Biotechnology, University of Wisconsin-River Falls

This is a long overdue update to a previous article I wrote concerning hybrid vigor. In the two years since I wrote the first article, I have had plenty of time to toss around the possibility of hybrid vigor in Atlantic Giants. But before I dive into the gory details of what I’ve found, I’d suggest reading or re-reading the first version of this article. (It can be found on my website and at the AGGC.) There you will find the basic idea behind hybrid vigor and my initial analysis as it applies to AG’s.

In this update, I will once again offer data that supports the possibility of hybrid vigor in AG’s. I will also use the same data to possibly disprove hybrid vigor. Sounds contradictory, eh? Frustratingly so, this is true. Read on…

Scientific literature states that C. maxima can and does experience hybrid vigor, but this was found to be true in other varieties of C. maxima, not Atlantic Giants specifically. The million-dollar question then becomes: is there enough genetic variation within particular lines of AG seeds, that when crossed, will exhibit a measurable degree of hybrid vigor? By looking at the family trees of specific lines, it is too hard to tell. Most trees become empty when tracing 5 or more generations back. Without knowing the ancestry of the particular seeds, there is no way of determining if they are related. Remember, in order to observe hybrid vigor, you would need to cross two significantly different sources of genetics within the same species. When the family trees led me to a dead end, I began compiling some numbers, based on data collected from the AGGC. I investigated a number of different AG seed histories, and one still stands out heads and tails above the rest- the Lloyd lineage. I reported on the significance of this line in the first article, and am standing by it in this one as well. Only this time, I have included the 876.5 Lloyd in my calculations, rather than singling out the 935 Lloyd. Onto the numbers…

What I did was calculate the average weight of fruit where the matriarchal grandma or grandpa was the 935 Lloyd or 876.5 Lloyd, and the opposite grandparent was not either of these fruit. This is the basic “vigor cross”, where one grandparent is the 935 or 876.5, and the other grandparent is any other seed that does not have Lloyd genetics in its background. Common “vigor crosses” just “happen” to be the 723 & 845 Bobier, 846 Calai, and 712 Kuhn. After doing the math, I was left with 362 fruit resulting from a “vigor cross”, with an average weight of 721.5 lbs. I then took the average weight of all non-vigor cross fruit registered at the AGGC between 1999 and the present. (I chose 1999 because that was the first year a “vigor cross” seed was planted.) This average was calculated at 634.9 lbs. Dividing this number by 721.5 gave a difference of 12.0%. That’s right, 12%. To me that’s big! The most basic interpretation of this data is simple, “vigor crosses” yield fruit that are an average of 12% heavier than other seeds.

Initially, this sounds great. Who wouldn’t plant a seed that offered an extra 12%? But unfortunately, we cannot conclusively interpret the data in this manner. Here’s where the data begins to contradict itself, and the possibility of the theory goes down the toilet. The reason the “vigor cross” average is so high is because it contains fruit from seeds like the 723, 845 and 846, which have performed very well recently. Have they performed well because it’s in their genetics, or because they receive favor from the growers who plant them, due to seed reputation? If an unknown seed grows a 1000lber, growers will jump on the bandwagon and grow the heck out of it the next year, often giving it favored attention in their patches based on its past. This may boost the average weight of fruit this seed produces, regardless of its genetics. Another problem I encountered was the fact that heavy hitters have greater access to seeds with excellent track records than average growers. Typically, a seed will do better in an experienced grower’s patch than a grower with less experience. Its possible that a no-name seed could produce great results in the patch of a heavy hitter, and a 723 or 846 could be a dud in the hand of a newbie. Situations like these really skew the data, and makes it almost impossible to solidify hybrid vigor.

However, I would like to offer some additional data that helps give hybrid vigor theory a boost. I did similar a similar analysis for other proven seeds, such as the 801 Stelts and 567 Mombert. In each case, not one of them came close the average shown by the “vigor crosses”. This suggests that increased weights may be due to something special in the seeds, and not just gardener favoritism.

In order to conclusively prove or disprove hybrid vigor, we would need to have all types of growers plant “vigor crosses” and non-vigor crosses side by side, treat them exactly the same, and record the results.

Until that day comes, we have to work with what we got, and hybrid vigor will remain just a loosely put together theory. And here is where I make my disclaimer: what I offer in this article is simply an organized presentation of data. I myself am not convinced that current AG seeds can express hybrid vigor, however the data is significant enough to warrant consideration. The take home message is this: when pondering your seed selections for next year, don’t overlook the potential of the “vigor cross”, if hybrid vigor indeed is present in these crosses, that 12% might mean the difference between a personal best or just another big pumpkin.

Constructive criticism is always welcome.

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