Pc. Stevenson et al., THE IDENTIFICATION AND CHARACTERIZATION OF RESISTANCE IN WILD-SPECIESOF ARACHIS TO SPODOPTERA-LITURA (LEPIDOPTERA, NOCTUIDAE), Bulletin of entomological research, 83(3), 1993, pp. 421-429
Fourteen wild species of Arachis (Leguminosae) were investigated under
field and laboratory conditions to evaluate their effect on the survi
val and development of the larvae of Spodoptera litura (Fabricius). Al
l of the species studied were observed to be resistant compared to the
susceptible control, Arachis hypogaea (genotype TMV2). Overall, the m
ortality and development of larvae recorded in the field were similar
to those recorded for larvae on excised leaves of the same species in
the laboratory. When neonate larvae were exposed to excised leaves of
A. batizogaea, A. kemph-mercadoi, A. appresipila, A. paraguariensis, A
. stenophyla and A. villosa mortality was greater than 94% compared to
less than 20% on TMV2. Third stadium larvae lost weight when exposed
to both field plants and excised leaves of eight of the wild species,
whereas larvae feeding on TMV2 gained weight. When third stadium larva
e were fed pulped leaves they gained more weight than when exposed to
intact leaves, except in the case of A. chacoensis and Arachis spp. 30
007. A penetrometer was used to determine the relative toughness of th
e leaves. The leaves of most of the wild species were shown to require
a greater biting effort for feeding than the leaves of TMV2. There wa
s a negative correlation between toughness of whole leaves and larval
development. Observations of larval behaviour indicated that, overall,
larvae were deterred from feeding on the leaves of the wild species.
Diets containing the chemical extracts of dried leaves of A. kemph-mer
cadoi, A. paraguariensis, A. appresipila, A. chacoensis, A. glabrata a
nd A. pseudozillosa resulted in low larval weight gain. The physical q
uality of the leaves and foliar chemicals are implicated as being resp
onsible for the observed resistance. The implications and potential ap
plications of these results are discussed.