RESPONSE OF NP MUTANT OF PEA (PISUM-SATIVUM L) TO PEA WEEVIL (BRUCHUS-PISORUM L) OVIPOSITION AND EXTRACTS

The Np mutant of pea (Pisum sativum L.) is characterized by two physio logical responses: growth of callus under pea weevil (Bruchus pisorum L., Coleoptera: Bruchidae) oviposition on pods, and formation of neopl astic callus on pods of indoor-grown plants. Although these two respon ses are conditioned by Np, they are anatomically and physiologically d istinguishable, based on sites of origin, distribution pattern, and se nsitivity to plant hormones. Further characterization of the response to extracts of pea weevil showed that response of excised pods, measur ed by callus formation, was log-linear, and treatment with as little a s 10(-4) weevil equivalents produced a detectable response. Mated and unmated females contained similar amounts of callus-inducing compound( s), and immature females contained significantly less of the compound( s). Female vetch bruchids (Bruchus brachialis F., Coleoptera: Bruchida e), a related species, contained callus-inducing compound(s), but usua lly less than pea weevils on a per weevil basis. Males of both species contained less than 10% of the activity of the mature females. Extrac ts of female black vine weevils, a nonbruchid species, did not stimula te callus formation. Based on partitioning and TLC analysis, the biolo gically active constituent(s) was stable and nonpolar. Thus, the Np al lele probably conditions sensitivity to a nonpolar component of pea we evil oviposition as a mechanism of resistance to the weevil.