Metodologias e seleção de genótipos de Passiflora spp. para tolerância à salinidade

Abstract

The yellow passion fruit (Passiflora edulis Sims) holds great economic and social relevance in Brazil. However, the progressive salinization of soils and water resources represents a serious threat to its production, especially in semiarid regions. The development of tolerant cultivars is essential to ensure the sustainability of this crop in these areas. Nevertheless, knowledge about the mechanisms of salinity tolerance in Passiflora L. is still scarce, hindering the adoption of efficient screening strategies for use in breeding programs. In this study, the objective was to establish effective methodologies to evaluate salinity stress tolerance in accessions from the Active Germplasm Bank (AGB) of Passiflora spp. at Embrapa Cassava and Fruits, and to conduct the first screening of the genus aiming at the identification of contrasting genotypes. The experiments were carried out under controlled conditions, in laboratory and greenhouse, in Cruz das Almas – BA. Initially, the critical salinity dose for P. edulis was determined using five accessions subjected to different levels of electrical conductivity of the nutrient solution + NaCl (ECw = 3, 6, 9, 12, and 15 dS m⁻¹), in addition to controls (0 dS m⁻¹ – distilled water and 2 dS m⁻¹ – nutrient solution). These evaluations were performed at different phenological stages: seeds and seedlings (Chapter 1) and plants with two and five fully expanded leaves (Chapter 2), under stress exposure for 28 and 21 days, respectively. Based on these results, an ECw of 9 dS m⁻¹ was established as the critical dose for screening. This concentration was then used to evaluate 86 accessions of Passiflora spp. from the BAG of Embrapa, under a hydroponic system (Chapter 3). Throughout the study, variables related to germination, morphophysiology, nutrition, biochemistry, and salinity symptomatology were analyzed. The results revealed that salinity tolerance in Passiflora varies according to the plant’s developmental stage, with seeds, seedlings, and young plants of P. edulis being especially sensitive from 3 dS m⁻¹, and showing critical reductions from 9 dS m⁻¹ onwards. The tested methodologies proved efficient in identifying early toxicity symptoms through scoring scales, as well as in indicating the ideal salinity threshold for screening under controlled conditions. The hydroponic system used for plants aged 20 to 30 days proved effective for the characterization of tolerance mechanisms. The multivariate approach, combined with tolerance indices such as the Yield Stability Index (YSI), allowed for a robust assessment of the wide intra- and interspecific variability within the genus. A total of 22 accessions belonging to 13 Passiflora spp., including P. alata and P. edulis (cultivated species), were classified as tolerant. These materials displayed greater morphological, physiological, and ionic stability under stress conditions. The results highlight these species as promising candidates for use in breeding programs aimed at salinity tolerance, either through interspecific crosses with P. edulis, use as rootstocks, or cloning of superior materials. This research provides valuable insights for the development of tolerant hybrids and guides future biochemical, genetic, and physiological investigations. It is expected that the integration of this knowledge will directly benefit breeding programs and production systems located in regions of increasing salinity, such as the Brazilian semiarid region.