Transmissão de Begomovirus a leguminosas e ação inseticida de extratos de Annona sobre Bemisia tabaci

Abstract

The begomoviruses (genus Begomovirus, family Geminiviridae) stand out as viral agents of extreme relevance to plants, causing economic and social losses on a global scale. In the Brazilian agricultural scenario, the bean golden mosaic virus (BGMV) stands out as one of the major concerns for bean cultivation, while the macroptilium yellow spot virus (MaYSV) is emerging as a potential threat to beans in the Northeast region. These viruses are transmitted in a persistent-circulative manner by insects of the Bemisia spp. complex (whiteflies) and have the ability to infect a wide variety of dicotyledonous plants. Resistance to a variety of chemical groups of insecticides has been a significant challenge in whitefly control. Given this scenario, plant-derived insecticides emerge as sustainable options for pest management, helping to reduce indiscriminate dependence on synthetic insecticides in crops. One of the objectives of this study was to evaluate the insecticidal action of ethanolic extracts from Annona muricata (soursop) and A. squamosa (sugar apple) on adult whiteflies. Concentrations of 2, 4, 6, 8, and 10 g/L were used in bioassays to evaluate the lethal effect by contact, lethal time, and systemic effect on Sida sp. plants. Overall, the A. squamosa extract proved to be more toxic compared to A. muricata. After 72 hours, mortality was 72% in adult insects treated with A. muricata extract and 99% in those treated with A. squamosa extract. The A. squamosa extract also showed a faster action, with 50% mortality in 4.67 hours, while the A. muricata extract took 5.24 hours. In the systemic evaluation, the A. squamosa extract demonstrated considerably superior efficacy at lower concentrations compared to the A. muricata extract. However, after 72 hours, there was no significant difference in observed mortality, which was 81% for soursop and 84% for sugar apple in adult whiteflies. The results indicate that the A. squamosa extract acts more quickly and effectively, resulting in higher and faster mortality in adult whiteflies, demonstrating the potential of these extracts as a promising alternative for whitefly control. Additionally, another objective was to evaluate the ability of infectious clones of BGMV and MaYSV to cause systemic infection in common bean (Phaseolus vulgaris), lima bean (P. lunatus), and Macroptilium lathyroides. For this purpose, both single and mixed infection assays were conducted. The experiments involved the inoculation of infectious clones of the BGMV and MaYSV viruses using the biolistic technique. Furthermore, transmission assays were conducted using the whitefly B. tabaci Middle East-Asia Minor 1 (MEAM1), using infected common bean plants with each virus, both in single and mixed infections, for healthy host plants. The results indicated that BGMV ability to cause systemic infection in the three host plants was superior to that of MaYSV. The transmission rate of BGMV to bean plants was 60%, while for M. lathyroides, it was 70%. Additionally, mixed infections were only observed in common bean plants. These results indicate that BGMV remains a more relevant threat, possibly more widespread, and with a moresignificant impact on these host plants.

Keywords: Adaptability, Begomovirus, Annonaceae, alternative control, whitefly.