Specific biochemical marker-based techniques for the identification of damage to Douglas-fir seed resulting from feeding by the western conifer seed bug, Leptoglossus occidentalis Heidemann (Hemiptera : Coreidae)

Specific biochemical marker-based techniques were tested for their ability to distinguish between seeds of Douglas-fir, Pseudotsuga menziesii (Mirbel) France, that were filled or unfilled (aborted) at maturity and those that were damaged or emptied by the western conifer seed bug, Leptoglossus occid entalis Heidemann. A polyclonal antibody raised against salivary gland extr acts from L. occidentalis successfully identified residual salivary protein s on Western blots containing proteins from Douglas-fir seeds that had sust ained various degrees of seed bug feeding damage. In a single blind experim ent. the polyclonal antibody correctly identified 100% of undamaged control , 97% of unfilled control (aborted), and 98% of seed bug damaged seeds. Pol yclonal antibodies raised against insoluble alfalfa crystalloid storage pro tein (11S globulin) detected the depletion of 11S globulin and the subseque nt appearance of its hydrolyzed fragments in the soluble protein fraction o f Douglas-fir seeds that were fed-upon by the seed bug. Feeding by L. occid entalis nymphs caused ca. 98% depletion of insoluble protein, but only ca. 53% reduction in the amount of soluble protein in seeds that appeared empty on radiographs. By comparison, unfilled (aborted) seeds contained signific antly less insoluble and soluble protein than empty seeds that were fed-upo n by L. occidentalis: moreover, no crystalloid (11S globulin) breakdown pro ducts were generated. The biochemical markers described in this study are r eliable tools that can be used to identify conifer seeds that have sustaine d light to severe damage from L. occidentalis feeding. (C) 2001 Elsevier Sc ience Ltd. All rights reserved.