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Bt pesticide resistance
On Wed, 13 Aug 2003 11:09:54 GMT, Mooshie peas
wrote: On Fri, 08 Aug 2003 17:30:28 +0200, Torsten Brinch posted: On Fri, 08 Aug 2003 05:48:09 GMT, "Moosh:}" wrote: On Fri, 8 Aug 2003 06:18:46 +0100, Oz posted: Someone wrote: They fed resistant larvae of the diamondback moth - an increasingly troublesome pest in the southern US and in the tropics - on normal cabbage leaves and ones that had been treated with a Bt toxin. The larvae eating the treated leaves grew much faster and bigger - with a 56 per cent higher growth rate. .. Plants attacked by pests will elevate their toxin levels as a response. If the untreated plants were under attack (or their neighbours were) then they would increase their toxin level. .. It amazed me that such a tiny amount of one protein could produce such growth differences. Your explanation of growth inhibition from a predated crop certainly fits. It doesn't fit or explain anything at all, since the same cabbage leaf material was fed in all treatment groups in the experiment. The researchers grew a single cabbage crop, cut discs from its leaves, and fed the discs to different groups of larvae kept in petri dishes, with or without Bt toxin fortification. You obviously have the advantage of reading the full paper. Care to share? So how do you explain the marked growth increase from this tiny amount of one protein? You mean the 56% increase? It is beyond me where the authors get that particular figure from. On the face of it the data shows a growth rate increase of only about 30 %, and I would be wary to accept even that. The main observation in the experiment IMO is that feeding BT fortified substrate (10ppm) to larvae, re-selected to yield high Bt resistance (LC50~200 ppm), increased their mean pupae weight significantly - about 20% - relative to feeding them non-BT fortified substrate -- while leaving their time to pupation unchanged or perhaps a bit shorter. Has the experiment been replicated? I don't know, Jack. You can ask the authors if they are working on that or something similar, email: h dot cerda at ic dot ac dot uk If not, perhaps we should wait until the attempt has been made? Funny you did not get that thought while you and Oz were happily explaining the findings. Boy, you couldn't even wait until you'd read the article :-) |
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