Invasive Species Compendium

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Abstract

Influence of foliar glucosinolates in oilseed rape and mustard on feeding and growth of the Bertha armyworm, Mamestra configurata Walker.

Abstract

The relationship between host plant glucosinolate profile and feeding, and growth of Mamestra configurata was investigated using 8 cultivated rape and mustard varieties. The mean weight of neonate larvae reared on intact rosette-stage plants were significantly different with Brassica juncea [Indian mustard] < Sinapis alba < B. napus [sarson] < B. campestris. While Indian mustard was least preferred, S. alba was significantly more attractive to neonate larvae in choice tests. The relative consumption and growth rates of 4th-instar larvae were also reduced on Indian mustard foliage. Other differences were dependent on the plant growth stage. Neonate preference was not correlated to total glucosinolate levels, but rather to the concn of isothiocyanate-releasing glucosinolates. However, the relationship between consumption and glucosinolate levels was inconsistent. Relative growth rate was negatively correlated to total glucosinolate content for stage 3 and 4 foliage, due mainly to the concn of isothiocyanate-releasing glucosinolates. The relative importance of isothiocyanate-releasing glucosinolates was verified by rearing neonate larvae on meridic diets containing equimolar concn of sinigrin, its metabolite allyl isothiocyanate, and indole-3-carbinol, a metabolite of 3-indolylmethyl glucosinolate. Sinigrin and allyl isothiocyanate in the diet produced virtually identical negative weight vs. concn regression lines. No such dose-response effect was observed with indole-3-carbinol. The data suggest that foliar isothiocyanate-releasing glucosinolates may provide some degree of plant protection from polyphagous insects.