Distribution of voltage-gated sodium channel and acetylcholinesterase mutations in Bemisia tabaci species from the Democratic Republic of the Congo

The intensive use of insecticides can result in the emergence of resistant genotypes, as observed globally in the B. tabaci species complex. Two well-studied/known cases of resistance mechanisms in B. tabaci involve mutations in the voltage-gated sodium channel (Kdr) and acetylcholinesterase (Ace 1) genes. However, no studies have surveyed these resistance mechanisms in whitefly populations from Central Africa. To study the frequency of these mutations in whitefly species on cassava, 1315 individuals were collected from 60 fields across 12 provinces of the Democratic Republic of the Congo. Species were identified molecularly, and then the frequencies of Kdr and Ace 1 mutations were assessed. Four species were found: SSA1-SG1 ∪ SG2 (71.48 %); SSA1-SG3 (0.31 %); SSA2 ∪ SSA3 (15.51 %), and MED ASL (12.70 %). For the Kdr mutation, 9 % of individuals of SSA1-SG1 ∪ SG2, 6 % of MED ASL, and 3 % of SSA2USSA3 carried at least one resistant allele. For the Ace 1 mutation, resistance alleles were found in 0.1 % of SSA1-SG1 ∪ SG2, 6 % of MED ASL, and 1 % of SSA2 ∪ SSA3 individuals. The geographical distribution of resistant genotypes remains limited to certain regions. However, there is a long-term risk that resistance becomes established around areas where insecticides are used on cotton and vegetable crops. Appropriate strategies for the management of these vectors of phytoviruses are discussed.