Sunday, January 25, 2009

Brassica oleracea: Artificial Selection is Delicious!

Just a quick post...

While reading through a few abstracts at the Journal of Insect Science - looking for information regarding introduced predators as biological controls for invasive insect species - I came across an article discussing Delphastus catalinae (ladybird beetles, image below) as a control agent for Bemisia tabaci (whiteflies).

Whiteflies are major pests, and have recently gained infamy for attacks in Florida.

A good description from a recent Florida news article:

“The whitefly is not a fly, but a flying insect that is very similar to some scale insects. It has sucking mouthparts and some species are known to cause sooty mold, but this species does not. Heavy feeding by the adult and the immature stages — which are immobile, flattened and translucent with red eyes — cause yellowing of the foliage and significant defoliation. The undersides of leaves are coated with a pebbly like, whitish residue, which is the empty casings or “skins” left behind by the immature stages as they molt and develop into the adult stage.”

Luckily, D. catalinae is a voracious predator and both its larval and adult stages feed on B. tabaci’s eggs, larvae and adults. A couple of courting B. tabaci are pictured below.

At any rate, moving on to the intended point of this post - although the mentioned research centered on the affects of temperature variation on Delphastus’ predatory capabilities, the article happened to mention that one of the plant species that may most benefit from Delphastus’ protection is Brassica oleracea.

Rummaging through my mental file cabinet in an attempt to reference B. oleracea, I soon came to the realization that the species has undergone a tremendous amount of artificial selection and is a mainstay of modern diets.

In its wild state B. oleracea is known as “wild cabbage” and looks rather like a common weed you might find in your backyard, here's a photo:

However, through artificial selection the plant has proven to be highly flexible and has been bred for its delicious leaves, inflorescence, stalks, leaf buds and roots. Some of the common names for varieties of B. oleracea include; broccoli, cauliflower, brussel sprouts, kale, kohlrabi and cabbage.

What an amazing variety from one species of plant!

Legaspi J, Legaspi BC, Simmons AM, Soumare M (2008). Life table analysis for immatures and female adults of the predatory beetle, Delphastus catalinae, feeding on whiteflies under three constant temperatures Journal of Insect Science