Biological effects of African yam bean lectins on Clavigralla tomentosicollis (Hemiptera : Coreidae)

The biological effects of affinity purified seed lectin from African yam be an, Sphenosnostylis stenocarpa (Harms), were tested on Clavigralla tomentos icollis (Stal) in an artificial seed system. S, stenocarpa was extracted fr om two African)yam bean accessions: Enugu 95-3 and Enugu 98-2. Lectins from both accessions were highly toxic to the insect at 1.0% dry weight. Fur ny mphs feeding on Enugu 95-3 and Enugu 98-2, survival ranged from 16.0 to 21. 0% and 4.0 to 16.0% at 1.0 and 2.0% dry weight dietary lectin levels, respe ctively. From 1.0 to 8.0% dru weight of both lectins. no nymph survived up to 6 d after infestation. At 1.0% 6 d weights of Enugu 95-3 and Enugu 98-2 lectins, there was a significant delay in total developmental time (5.35 an d 5.18 d), reduced survival (24.0% and 16.0%), and, reduced growth (0.15 +/ - 0.02 and 0.14 +/- 0.01) and resistance (61.85 +/- 9.78 and 57.79 +/- 3.80 ) indices, respectively. S. stenocarpa,a from Enugu 98.2 was the most toxic , with an LD50 of 0.43%, compared with an LD50 of 0.65% For S. stenocarpa f rom Enugu 95-3. The results of this investigation indicate that there exist s in C. tomentosicollis physiological systems vulnerable to African yam bea n lectins.