From Jacob van Etten.
Uncorking a big bottle of agrobiodiversity, that is what Mexico’s first farmers did when they domesticated maize. Not only is maize enormously malleable, genetic diversity also goes everywhere through cross-pollination. That is in traditional farming systems. Modern maize improvement has been about sorting out this abundance by “freezing” it into breeding lines, to get some control over the diversity feast. But what happens when the hybrids are released into the dance room again?
An Italian study just out quantifies the gene flow from hybrids to traditional varieties. It finds different degrees of purity in the traditional varieties, but no genetic erosion. This is an interesting finding in the light of writings about “creolisation” in Mesoamerican agriculture. Creolisation, the mixing of modern and traditional varieties, is thought to lead to plants that combine their benefits. I have always wondered if the creolised varieties of Mesoamerica are not modern varieties “creolised” by selection instead of mixing with traditional varieties. Something similar to the Italian study would be needed to find this out.
The question is only one step removed from the issue of gene flow from transgenic crops to traditional varieties. Perhaps you remember the Quist and Chapela paper published in Nature in 2001 on the presence of transgenes in Mexican traditional maize, and the controversy it generated. A new study confirms the presence of transgenes in Mexico with an improved study design. Through genetic population simulations it also explains why detection of transgenes is erratic and prone to giving false negatives. The distribution of the transgenes is likely to be very skewed. A few fields will have much of them, but most will have very few. This has to be taken into account and therefore authors call for more rigorous sampling methods to detect transgene presence.
There is little discussion or speculation about the effects of transgenes on maize diversity. Will the transgenes just add to the existing diversity, like the hybrids in Italy? Will they perhaps produce some benefits, like the creolized varieties? Or will, in some Monty Python-like scenario, the big seed companies pick up the message about rigorous sampling and start to trace transgenes in Mexico in order to charge farmers for unlicensed use of their technology?
Gallesio gives a curious account of the naturalisation of the Orange in Italy. During many centuries the sweet orange was propagated exclusively by grafts, and so often suffered from frosts that it required protection. After the severe frost of 1709, and more especially after that of 1763, so many trees were destroyed that seedlings from the sweet orange were raised, and, to the surprise of the inhabitants, their fruit was found to be sweet. The trees thus raised were larger, more productive, and hardier than the former kinds; and seedlings are now continually raised. Hence Gallesio concludes that much more was effected for the naturalisation of the orange in Italy by the accidental production of new kinds during a period of about sixty years, than had been effected by grafting old varieties during many ages. I may add that Risso describes some Portuguese varieties of the orange as extremely sensitive to cold, and as much tenderer than certain other varieties.
