White y (Bemisia tabaci) is a polyphagous insect that causes huge damage in several horticultural crops, including tomato, by sucking nutrients from the phloem and transmitting viruses. White ies are particularly di cult to manage and the use of chemicals remains the common practice, which causes the development of insecticidal resistance. Thus, there is considerable interest in the introduction of white y resistance by classical and molecular breeding. Here, we explored the concept of using an RNA interference construct to silence a v-ATPase gene in white ies interacting with transgenic tomato plants that express siRNA molecules corresponding to a fragment from the B. tabaci vATPase. PCR analyses revealed the presence of both ΔATPase and nptII transgenes in all transgenic lines. siRNA expressing lines were challenged against white y and revealed a mortality rate of 57.1% in transgenic line 4.4.1, while in the control the mortality was 7.6%. Mortality of 2nd instar nymphs was higher on the transgenic plants and the development of 3rd instar nymphs was slightly longer than on the control plants. Although the attraction of insects was not signi cantly different between treatments, the number of eggs laid by the insects on the transgenic plants was signi cantly lower, compared to the controls. RT-qPCR revealed a decreased expression level of endogenous v-ATPase gene in white ies feeding on transgenic plants. No unexpected effect was observed on the non-target insects Myzus persicae or Tuta absoluta. Results presented here may form the foundation for the generation of elite tomato varieties resistant to white y, a devastating insect pest.
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.
Buriti (Mauritia flexuosa) is a palm tree widely distributed in South America. The oil extracted from its fruit is an added value product for its high carotenoids content. The aim of this work was to evaluate the alkaline (magnesium oxide-MgO) and enzymatic (lipase B from Candida antarctica immobilized on macroporous acrylic resin) glycerolysis of buriti oil to obtain non-ionic emulsifiers and evaluate the carotenoids degradation during this process. Alkaline glycerolysis was carried out using a 3:1 glycerol/oil molar ratio, temperatures of 170 and 210 C, and MgO contents of 0.5 and 1%wt. Enzymatic glycerolysis reactions were performed using 3%wt. of a lipase catalyst and varying the following parameters: glycerol: oil molar ratio (3:1, 6:1, and 9:1), solvent (tert-butyl alcohol) concentration (50%, 150%, and 250%, vol./substrate mass), and temperature (40, 55 and 70 C). The products were analyzed by liquid chromatography and UV-visible spectroscopy (370-520 nm). Enzymatic glycerolysis was superior in terms of conversion and selectivity to monoacylglycerols (MAG). MAG yields were close to 80% or higher for most conditions tested for enzymatic glycerolysis, while the maximum yield for alkaline glycerolysis was of 58%. UV-Vis data showed that carotenoids were severally degraded in alkaline glycerolysis, while the enzymatic product exhibited high preservation of carotenoids and color and odor similar to those of the pure buriti oil. Based on the final composition of the non-ionic emulsifiers obtained from buriti oil by enzymatic glycerolysis, they can be considered potential raw materials for cosmetic and food industries.
The most important viruses infecting common bean (Phaseolus vulgaris L.) in Brazil are BCMV, BGMV and CPMMV, the last two transmitted by the whitefly Bemisia tabaci, occurring simultaneously and causing severe yield losses. Genetically modified progenies of common bean, from carioca market class and multiple virus resistance (BCMV, BGMV and CPMMV), have been developed using conventional breeding and molecular tools. Agronomic performance and virus disease severity (VS) evaluated in two field trials, selected 39 elite progenies out of 477. Molecular analyses identified the presence of BCMV and BGMV resistance alleles in plants. CPMMV resistance was measured on mechanically inoculated plants using a VS scoring scale. Among the lowest VS average scores, five progenies showed resistance to BCMV, BGMV and CPMMV, and upright plant architecture, resistance to plant lodging and carioca market class grains, presenting potential to be developed into a new transgenic cultivar, with multiple virus resistance. Additionally, the resistant progenies may also contribute to reduce virus spread in the field, as they were a less efficient inoculum source of CPMMV in insect transmission assays.
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