Aspectos agronômicos, metabólicos e moleculares associados às respostas de genótipos de mandioquinha-salsa ao calor

Abstract

The mandioquinha-salsa, originating from the Andes, boasts roots of high economic value and nutritional quality. As a long-cycle vegetable, its development is significantly influenced by climatic factors, with productivity highly sensitive to elevated temperatures. Due to climate change-induced temperature increases, mandioquinha- salsa production in Brazil falls below demand. Plantings during hot and rainy seasons often result in high rates of seedling and root rot, leading to substantial losses from bacterial diseases. Current projections suggest that the anticipated temperature rise due to climate change may further reduce production, rendering cultivation unfeasible in certain regions. Thus, identifying genotypic variations adapted to these unfavorable climatic conditions becomes crucial for ensuring sustainable production. Against this backdrop, this study aimed to analyze the agronomic performance, metabolic responses, and in silico exploration of heat tolerance genes in mandioquinha-salsa genotypes cultivated in Pato Branco, Paraná. Two experiments, simulating commercial field cultivation, were conducted at the Experimental Area of the Federal Technological University of Paraná (UTFPR), Campus Pato Branco. Additionally, a third experiment in pots, within a controlled environment, exposed plants to two temperature conditions (30°C and 20°C in phytotron chambers). Commercially cultivated plants underwent analysis for growth, pest and disease incidence, agronomic performance, root quality, gas exchange, and metabolic profiling. Plants grown in a controlled environment were evaluated for metabolic parameters and gas exchange. Lastly, an in silico study was performed to prospect genes involved in the response to heat stress in plants, aiming to identify homologous sequences in Apiales order species. Analyzing the agronomic performance, growth, incidence of pests and diseases, and root quality of the genotypes studied during the experimental period, Amarela de Senador Amaral, Branca Comum, and Amarela Comum obtained unsatisfactory performances. Conversely, the genotypes SCS380 Inca and SCS381 Coqueiral generally demonstrated the best results, showing adaptability to the region's soil and climatic conditions. Overall, the genotypes BRS Rubia 41 (first cultivation period) and SCS380 Inca (second cultivation period) showed the best results for gas exchange evaluations, with the highest rates of CO2 assimilation, higher internal CO2 concentrations in the leaves, and consequently, a suggested higher photosynthetic capacity when cultivated in the field. In the controlled environment experiment, the genotypes BRS Acarijó 56 and SCS380 Inca stood out, with surviving plants until the end of the experiment. Additionally, surviving and stressed plants exhibited higher average stomatal conductance and internal CO2 concentration compared to plants in the control environment. Regarding biochemical data, analysis of the first cultivation period highlighted genotypes BRS Rubia 41 and BRS Catarina 64 for the accumulation of pigments, total proteins, and free amino acids in both the aerial and root systems. Conversely, the sugar content exhibited an opposite pattern, with higher levels of starch and sucrose in genotypes BRS Acarijó 56 and SCS380 Inca, with the added distinction of BRS Acarijó 56 accumulating higher levels of reducing sugars (glucose and fructose) compared to other genotypes. Analyses for the second cultivation period indicated that genotype BRS Acarijó 56 had a higher content of pigments and total proteins in its root system, while these metabolites accumulated in leaves for genotypes SCS381 Coqueiral and SCS380 Inca. Total phenol analysis indicated higher levels in the leaves of BRS Acarijó 56, while the roots of SCS381 Coqueiral and SCS380 Inca exhibited higher accumulation. In assessing the impact on the primary metabolism of A. xanthorrhiza genotypes under thermal stress, genotype BRS Rubia 41 stood out, with plants under thermal stress exhibiting higher contents of chlorophylls a and b, total chlorophylls, proteins, starch (glucose equivalent), and fructose. In contrast, genotype SCS380 Inca showed a higher content of the osmoregulator proline, as well as free amino acids, compared to others. The in silico study identified 29 genes associated with heat stress tolerance caused by high temperatures in various species, with the model species Arabidopsis thaliana playing a prominent role in these studies. Notably, the results indicated a crucial role for the Heat Shock Proteins (HSPs) family, underscoring their essentiality in preserving cellular integrity, especially under thermal stress conditions induced by high temperatures. Furthermore, aligning nucleotide sequences against Apiales order sequences identified 19 species with similar sequences, with carrot (Daucus carota) standing out for returning a higher quantity of results.