Stylet penetration activities by Aphis craccivora (Homoptera : Aphididae) on plants and excised plant parts of resistant and susceptible cultivars ofcowpea (Leguminosae)
Ib. Annan et al., Stylet penetration activities by Aphis craccivora (Homoptera : Aphididae) on plants and excised plant parts of resistant and susceptible cultivars ofcowpea (Leguminosae), ANN ENT S A, 93(1), 2000, pp. 133-140
Direct current electrical penetration graphs (DC-EPGs) were used to analyze
the styler penetration activities of cowpea aphid, Aphis craccivora Koch,
on plants of aphid-resistant (ICV-12) and aphid-susceptible (ICV-1) cultiva
rs of cowpea, Vigna unguiculata (L.) Walpers. Aphid stylet penetration on w
hole plants at seedling, flowering, and podding stages were studied in one
experiment, and in another experiment excised leaves from seedling plants,
excised flowers, and. excised polls were tested. Electrical signals depicti
ng the aphid stylet penetration activities on their host plants were amplif
ied, recorded onto a paper chart recorded, and scored for specific waveform
patterns. Compared with similar tissues of ICV-1, intact leaves and excise
d seedling foliage of ICV-12 plants caused severe disruption of aphid style
r penetration activities. This was manifested in frequent penetration attem
pts that were abruptly terminated or unsustained, and in shorter' penetrati
on times, signifying antixenosis resistance in ICV-12. There was reduced oc
currence of E waveforms, which represent stylet activity in plant vascular
tissues. Also, prior. exposure of lest aphids to plants of one cultivar did
not significantly influence the expected stylet penetration activities on
plants of the other cultivar. Overall, ICV-12 exhibited high levels of resi
stance against A. craccivora.