Genetic Diversity in Adults of Cowpea Aphid, Aphis craccivora (Koch) Produced from Treatments of Photosensitizing Compounds

Abstract

The present investigation aimed to evaluate the efficacy of four photosensitizing compounds, namely, rose Bengal, rhodamine B, methyl violet, and methylene blue, against the adults of the cowpea aphid, Aphis craccivora (Koch), under laboratory conditions. The obtained results indicated that rose Bengal was the most effective photosensitizer compound. The corresponding LC₅₀ and LC₉₀ values against the tested adults of cowpea aphid, Aphis craccivora were 0.024 and 0.143 %; followed by methyl violet, where the LC₅₀ and LC₉₀ levels recorded 0.125 and 0.620 %, on the other hand rhodamine B exhibited least efficient against tested adult of the pest, the corresponding LC₅₀ and LC₉₀ values recorded 1.49 and 4.50 %; LC₅₀ and LC₉₀ values for methylene blue were0.140 and 0.660 %; respectively. The molecular changes, after treatment with photosensitizers were tracked using RAPD-PCR with five arbitrary DNA primers. The obtained results showed that the fingerprints generated in adults resulted from treating the aphid adults with each primer, OP-B3, OP-A3, OP-A5, OP-C3, and OP-C9 recorded polymorphic, monomorphic, and unique profiles for the pest exposed to photosensitizing compounds. It was found that DNA of good quality is a prerequisite to have reproducible results from the RAP-PCR technique. The highest number of amplified fragments was 35 generated from primer Op-B3, whereas the lowest number of amplified fragments was 20 detected from primer OP-A5.

The RAPD-PCR patterns resulted from amplification of DNA of untreated adults as well as adults of A. craccivora revealed the lowest value of mean of similarity index was noticed in case of treatment with rose Bengal (0.70), the highest toxicity compound, which reflects the highest degree of change in DNA structure and sequence.