Melhoramento de Artemisia annua L.: indução de poliploidia expressão gênica e seleção de genótipos de alto rendimento

Abstract

Artemisia annua L. is a native herbaceous plant species from Asia that has aromatic leaves containing artemisinin, a sesquiterpene lactone that has shown efficacy against diseases such as cancer and malaria. To meet the demand for the molecule, management techniques and genetic improvement can be used to obtain superior genotypes. The objectives of this study were: to obtain A. annua genotypes with high yield of artemisinin and biomass by inducing polyploidy using colchicine; to analyze the genes expression related to artemisin biosynthesis pathways in plants under different nutritional levels; to perform a field assay to identify high yield genotypes for artemisinin and biomass. The polyploidy induction was tested in A. annua seeds and Artemis F2 variety with colchicine solution in 1% on doses of 0%, 0.05%, 0.1%, 0.15% and 0.2% for 0, 6, 12, 18, 24 and 30 hours, totaling 25 treatments. For gene expression analysis, a semi-quantitative RT-PCR technique was used, where the B23, B24, C23, C32 genotypes were submitted to different doses of nutrient solution in a greenhouse, using 25%, 50% and 100% of the complete dose (Hoagland's solution), with 3 replicates in a completely randomized design. To the field assay the same genotypes and variety Artemis F2 were tested in randomized block design with four replications. Agronomic, physiological and phytochemical evaluations were performed in all experiments. It has been found colchicine effect on artemisinin content, with maximum 0.60% for 0.10% dose, and it was not possible to confirm if polyploidization occurred. In the assessment of the production of secondary metabolites and the genes expression of enzymes involved in the synthesis of artemisinin from A. annua genotypes submitted to different levels of nutrition, it was observed the application of increasing doses of nutrient solution to A. annua plants allows linear increase for the production of biomass, with a contrary relation in the artemisinin production. Genotypes submitted to nutrition levels of 50% present better relation for the production of biomass, artemisinin and essential oil. The genes ADS1 and CYP71AV increase transcription in plants submitted to 50% levels of nutrient solution. These enzymes are directly involved in the artemisinin biosynthesis pathway. In the experiment of selecting superior genotypes, it was observed the variety Artemis F2 showed better performance in productivity of biomass and essential oil than other genotypes. The increased production of biomass for Artemis F2 justifies the higher oil yield. This variety has a differentiated plant architecture from the others, with greater height and greater density of branches.