Screening of wild Ipomoea genotypes for resistance against sweet potato weevil Cylas formicarius F. based on multiple choice bioassay and phytochemical constituents

Abstract

Screening of wild Ipomoea sp. and identification of new sources of resistance to the sweet potato weevil (Cylas formicarius Fabricius) with I. palmata, I. mauritiana, I. obscura, I. triloba were carried out. The leaves, vines and tubers of the different Ipomoea sp. were screened using multiple choice bioassay. The insect feeding holes on I. mauritiana leaves (1.67+1.528), vines (7.67±2.96) and tubers (12.67+2.309) was significantly less compared with other Ipomoea sp. Further, the two-choice bioassay was done, using I. batatas and I. mauritiana for comparison. Based on the morphological screening different phytochemical constituents was identified using GC-MS analysis of the methanolic extract of roots of selected Ipomoea sp. (I. mauritiana, I. palmata and I. batatas). The results indicated that the phytochemical constituent of I. mauritiana viz., undecane, quinic acid which is to have insecticidal activity. The major constituent of I. batatas comprises of melezitose (38.53%) and alpha-I-rhamnopyranose (21.26%). It can be concluded that the phytochemical constituents of I. mauritiana was responsible for the antibiosis.