The identification and characterization of resistance in wild species of Arachis to Spodoptera litura (Lepidoptera: Noctuidae)

Abstract

Fourteen wild species of Arachis (Leguminosae) were investigated under field and laboratory conditions to evaluate their effect on the survival and development of the larvae of Spodoptera litura (Fabricius). All of the species studied were observed to be resistant compared to the susceptible control, Arachis hypogaea (genotype TMV2). Overall, the mortality 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 larvae were fed pulped leaves they gained more weight than when exposed to intact leaves, except in the case of A. chacoensis and Arachis spp. 30007. A penetrometer was used to determine the relative toughness of the 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 was 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-mercadoi, A. paraguariensis, A. appresipila, A. chacoensis, A. glabrata and A. pseudovillosa resulted in low larval weight gain. The physical quality of the leaves and foliar chemicals are implicated as being responsible for the observed resistance. The implications and potential applications of these results are discussed.

Mechanisms of Resistance to Tobacco Cutworm (Spodoptera litura F.) and their Implications to Screening for Resistance in Groundnut

“…Such a mechanism of resistance has been reported in wild Arachis species and chlorogenic acid, quercetin and rutin were shown to impart resistance (Stevenson, 1993). The resistance factors from a wild Arachis species (A. kempff-mercadoi) were transferred to cultivated groundnut (Nalini Mallikarjuna et al, 2004) and high percentage of neonate larval mortality, decrease in pupal size and weights, induction of deformation and reduced fecundity of adults was observed on the interspecific derivatives.…”

Does the size of larval groups influence the effect of metabolic inhibitors on the development of Phormia regina (Diptera: Calliphoridae) larvae?

“…If calliphorid larvae do not receive sufficient nutriment they produce smaller larvae, pupae and adults [for example, Lucilia sericata (L.), Daniels et al, 1991 and L. caesar (L.) Okorie and Okoke, 1990]. Metabolic inhibitors, such as CGA, can similarly retard the growth of insect larvae (Kimmins et al, 1995) by interfering with digestion of protein and absorption of the resulting amino-acids (Felton et al, 1992;Stevenson et al, 1993aStevenson et al, , 1993b. Toxic and antinutritive effects of CGA can be reduced if sufficient quantity of specific amino-acids such as lysine, methionine and/or histidine are present in a substratum (Felton et al, 1992).…”

Examination of the involvement of mechanical strength in antixenotic resistance of subterranean clover cotyledons to the redlegged earth mite (Halotydeus destructor) (Acarina: Penthaleidae)

“…It is therefore regarded as a physical defence mechanism (Bergvinson et al, 1994;Edwards & Wanjura, 1990;Lucas et al, 1991;Stevenson et al, 1993;Tanton, 1962;Waller, 1982). However, the results obtained from penetrometer measurements do not represent fracture toughness, but more precisely the mechanical strength of the plant tissues (Lucas et al, 1991;Vincent 1990).…”