Amanda Lopes Ferreira, Josias Correa de Faria, Matheus da Costa Moura, Antônia Lopes de Mendonça Zaidem, Carolina Senhorinho Ramalho Pizetta, Elínea de Oliveira Freitas, Gesimária Ribeiro Costa Coelho, Jose Francisco Arruda e Silva, José Alexandre Freitas Barrigossi, Lucia Vieira Hoffmann, Thiago Lívio Pessoa Oliveira de Souza, Francisco José Lima Aragão and Patricia Valle Pinheiro

Front. Plant Sci., 25 August 2022

Common bean (Phaseolus vulgaris L.) is a staple food in Brazil with both nutritional and socioeconomic importance. As an orphan crop, it has not received as much research attention as the commodity crops. Crop losses are strongly related to virus diseases transmitted by the whitefly Bemisia tabaci, one of the most important agricultural pests in the world. The main method of managing whitefly-transmitted viruses has been the application of insecticides to reduce vector populations. Compared to chemical vector control, a more sustainable strategy for managing insect-borne viruses is the development of resistant/tolerant cultivars. RNA interference has been applied to develop plant lines resistant to the whitefly in other species, such as tomato, lettuce and tobacco. Still, no whitefly-resistant plant has been made commercially available to date. Common bean is a recalcitrant species to in vitro regeneration; therefore, stable genetic transformation of this plant has been achieved only at low frequencies (<1%) using particle bombardment. In the present work, two transgenic common bean lines were obtained with an intron-hairpin construct to induce post-transcriptional gene silencing against the B. tabaci vATPase (Bt-vATPase) gene, with stable expression of siRNA. Northern blot analysis revealed the presence of bands of expected size for siRNA in leaf samples of the line Bt-22.5, while in the other line (11.5), the amount of siRNA produced was significantly smaller. Bioassays were conducted with both lines, but only the line Bt-22.5 was associated with significant mortality of adult insects (97% when insects were fed on detached leaves and 59% on the whole plant). The expression of the Bt-vATPase gene was 50% lower (p < 0.05) in insects that fed on the transgenic line Bt-22.5, when compared to non-transgenic controls. The transgenic line did not affect the virus transmission ability of the insects. Moreover, no effect was observed on the reproduction of non-target organisms, such as the black aphid Aphis craccivora, the leafminer Liriomyza sp. and the whitefly parasitoid Encarsia formosa. The results presented here serve as a basis for the development of whitefly-tolerant transgenic elite common bean cultivars, with potential to contribute to the management of the whitefly and virus diseases.

See https://www.frontiersin.org/articles/10.3389/fpls.2022.984804/full

FIGURE 2 Analysis of common bean transgenic plants and relative expression of the vATPase gene in the whitefly Bemisia tabaci. (A) Progeny analysis of the transgenic common bean line Bt-22.5 for the marker gene ahas. Numbers 1 to 20 correspond to the 20 T2 plants from seeds collected from plant Bt-22.5, C+ is the positive control and W is water, used as negative control. (B) Northern blot analysis for the detection of Bemisia tabaci vATPase small interfering RNA (siRNA) isolated from transgenic common bean lines Bt-11.5 and Bt-22.5. NT is the non-transgenic common bean cv. Olathe Pinto. SYBR Safe stained RNA served as loading control.