Sunday, September 12, 2010

Is anyone breeding tomorrow's heirloom fruit and vegetable varieties?

I've noticed that an increasing number of people seem to be going nuts for heirloom vegetable varieties these days.

An "heirloom" fruit or vegetable is an old (usually 50+ years old, depending on who you ask), pure-bred cultivar that breeds true to type from one generation to the next. Heirloom cultivars are great for home gardeners who want to grow exactly the same vegetable varieties each year, because the seeds can be saved and replanted year after year, and the result will be highly predictable.

Heirloom varieties are also great for people who want to escape the clutches of the world's multinational seed companies - most notably Monsanto, that giant ogre of a corporation which pushes its GMOs and pesticides on farmers and consumers alike, while snapping up gene patents like a greedy child in a lolly shop.   

I totally understand the attraction of growing heirloom cultivars, because I grow a bunch of them myself. I have a particular soft spot for heirloom pumpkins, and this year I'll be planting 5 different heirloom pumpkin/squash varieties, namely:

* Marina di Chioggia (as memorably featured in Barbara Kingsolver's fabulous book, Animal, Vegetable, Miracle)
* Rouge vif d'Etampes (the so-called Cinderella pumpkin)
* Lakota (reportedly a favourite of the Lakota indians)
* Lady Godiva (with nude seeds!), and
* Musquee de Provence (just because).

But, there's a potential problem with heirloom varieties. What's good about them is also what's bad about them. Specifically, heirloom cultivars are thoroughly inbred ... which is why they breed true to type in the first place.

Inbreeding is generally a bad thing, for two main reasons:

1) inbreeding can, and usually does, cause the expression of harmful ("deleterious") recessive genes. This situation is known as inbreeding depression, and it produces offspring with a relatively low level of fitness for survival, and

2) repeated inbreeding inevitably causes a reduction in the resultant offspring's genetic diversity. This reduced genetic diversity may never cause a problem - as long as the environment throws up no unexpected challenges to the offspring's survival. But, inbred plants typically respond poorly to new and unexpected changes in their environment, such as:

* unusually high (or low) temperatures,
* unusually low (or high) rainfall,
* unusually low (or high) nutrient levels,
* a different or unusually severe pest infestation, or
* a new viral, bacterial, or fungal disease.

The fact that we're now experiencing world-wide climate change (a.k.a "global weirding") means that, for example, an heirloom variety of pumpkin which was (in)bred in France two hundred years ago may simply not be able to cope with the environment where I live (i.e. rural Australia) in the year 2020.

That's why, this year, I'll be growing at least one disease-resistant hybrid tomato variety. This summer I'll be testing the taste and productivity of the hybrid/s. But the really interesting test will come next year, when I plant out the seeds of these hybrid tomatoes. I'll be very interested to see what I get.

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