Effects of Cultivation Conditions for Apples on Growth Rates of Fruit Fly Larvae and Contents of Phenolics

Summary

Apples were grown with 3 different alleyway groundcover management strategies, providing a wide range of nutrient availabilities to the trees, spanning the ranges normally found in both conventional and organic orchards. These treatments had significant effects on both yields and incidence of fungal diseases. However, the differences in yields and disease incidence cancelled each other out, resulting in identical average yields of marketable fruit, as reported earlier (Lindhard Petersen & Bertelsen 2002).
These results indicated that the composition of the fruit may also differ, and that this material is useful as a model for investigating how growth conditions influence the content of nutritionally relevant compounds, and thus may affect the health of humans and animals.
In a preliminary study, two species of fruit flies were reared on material from each of the 3 cultivation treatments, and the time when 50% of the flies in each vial had emerged was calculated.
Development duration, hours
Treatment: Annual clovergrass Perennial clovergrass Perennial grass
(high N availability) (medium N availability) (low N availability)
Species:
D. melanogaster: 256 271 286
Drosophila hydei: 456 475 557
The fruit from each treatment, as well as corresponding fruit treated with pesticides, was analysed for contents of phenolic compounds.
The number of flies produced in each treatment did not differ systematically, but observations indicate that the fastest development also resulted in the heaviest animals. It should be pointed out that excessive growth rates (obesity) is a major health risk in affluent human societies. This material is also used in ongoing rat feeding experiments.