Host food choice

The suitability of a host may be influenced by the host s food choice. Smith (1941) found that Habrolepis rouxi developed on the California red scale, Aonidiella aurantii, when the scale was reared on sago palm, but did not develop when the scale was reared on citrus. Campbell and Duffey (1979) reported that a-tomatine, an alkaloid in tomato plants, was toxic to Hyposoter exiguae developing in hosts fed the alkoloid. 

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Feeding. The feeding behavior of phytophagous Insects has been studied much more widely than other aspects of the Insect/plant relationship. The reason for this probably lies In the relative ease with which bloassays can be performed and the results Interpreted. Many Insects can be reared on artificial diets, and the effects of added plant constituents can readily be determined. Some early studies by Dethler (29) demonstrated a correlation between larval food choice and the presence of specific chemicals In the umbelliferous host plants of Paplllo polyxenes. However, many of the compounds typically found In the Umbelliferae are also present in other... 

A number of resistance factors influence behavioral processes and hence determine an insect s preference or non-preference for a particular plant. Hosts which do not contain the proper kairo-monal compounds are often totally rejected as food plants and by ovipositing females. Dethier (29) noted, however, that plants are almost never neutral, but are aTmost always either attractive or repellant. As previously observed, the ovipositional choice of the female imago and the food choice of the larvae usually coincide ( ). 

In conclusion, plastid-based expression systems provide for potentially higher expression levels than the majority of nuclear expression systems, and with a higher level of transgene containment, but the platform provides limited post-translational processing choices. Also, despite reports of successful plastid transformation of new species beyond Nicotiana, the choice of production host is stiU predominantly restricted to the Nicotiana family. However, this hmita-tion does not present a serious drawback for production of pharmaceutical proteins (except perhaps for edible vaccines ) since tobacco is a non-feed/non-food crop with a weU-estabhshed agriculture. 

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