Gardens as Islands of Genetic Diversity
I was standing in the produce section at Albertsons one day
when struck by the uniformity of the produce. All of one kind
of apples looked exactly alike, same with onions, peppers,
potatoes, squash, beans, and even dried beans. I guess I have
known this for years, but just now stopped to wonder why.
Is this a demonstration of loss of diversity or of a sophisticated
state of agriculture, or of the power of “the market”,
or something else?
Diversity in Squash
My inquiry into genetic diversity has
grown during the last three years of incorporating native
food plants into my kitchen garden. I noticed right
off that unlike traditional garden varieties, native
food plants tend to produce edibles parts that do not
all look alike. The first year my Hopi Pumpkin, (Cucurbita
pepo - a summer squash) produced fruits that were either
roundish and stripped, or longish and stripped. On closer
examination, you could see that no two fruits were “look-a-likes”,
as you would expect to see in the zucchini squash, (C.
pepo) bin at the local supermarket.
That year I saved seed from the roundish
form and planted them the next year. The second year
I saw no longish fruit, nor has my seed line produced
any longish fruit since. This year was the first year
that I have seen fruit that is plain pale green without
a single dark stripe. This year I saved seed from the
plain green fruits and will plant them next year. Is
this a case of my selectivity causing a loss of genetic
diversity in my own garden? Obviously, the full range
of genetic diversity would benefit by saving seeds from
as wide a variety of plant characteristics as possible.
Diversity in Beans
When you buy a bag of Pinto Beans, you expect them
to all look the same. When you grow Hopi Black Pinto
Beans, you can expect considerable variety. All Pinto
Beans are the same species (P. vulgaris), share the
same ancestry, but have a very different developmental
history, so what accounts for the genetic diversity
in native beans and the genetic similarity of commercial
I propose that market and cultural forces have created
a general loss of genetic diversity in our produce
while greater genetic diversity survives in the agricultural
islands of native and local farmers and gardeners.
These agricultural islands exist in part because of
physical isolation, in part because of cultural isolation
and in part because of isolation from the impact of
industrial agricultural practices.
It is not just
Pinto Beans where you can see these differences in diversity
between modern varieties and native varieties. It shows
up in Hopi Yellow Limas (P. lunatis) as well –
in a very distinct dark maroon variant as well as an
unmarked yellow variant, with the bulk of seeds falling
somewhere in between those two extremes.
Variation in genetic characteristics is
not limited to color and size in seeds, but shows up
as well in yield characteristics, plant growth and environmental
tolerance. Not surprisingly, these genetic variations
are even greater in Tepary Beans (P. acutifolius). Diversity
research with many genotypes of Teparies has shown wide
variations for plant growth, number of pods per plant
and number of seeds per pod. The published research
studies show only moderate variation in seed weight
per 100 seeds, but the varieties selected did not include
the San Felipe Pueblo White Tepary, which has a huge
seed (for Teparies) and produced as prolifically (in
my garden) as other varieties.
is the Value of Genetic Diversity?
At the highest level, that is what keeps
us safely fed. Consider the Irish
Potato Famine, caused by an airborne fungus (phytophthora
infestans) and a monoculture of the Irish Cobbler potato.
Consider the Southern
corn leaf blight that severely reduced corn production
in the United States in 1970, caused by the lack of
genetic diversity in corn. Consider the current threat
to vast monocultures of Cavendish cultivar bananas caused
Sigatoka, also known as black leaf streak. At the
same time, we have lost many of the native varieties
of bananas that contain genetic resistance to diseases.
It has been demonstrated many times that
the loss of genetic diversity through monoculture leads
to problems with food crops. So why do we keep valuing,
selecting for and producing uniformity? Fortunately,
there are still local and native growers who value and
select for diversity, as well as several organizations
working to preserve localized landraces of food plants.
till next time,
Doña Ana Extension Master Gardener
printable version of this article (pdf)
(1) Changes in the Export Banana Business
garden well - eat local