Estudio poblacional en vid (Alicante Bouschet cv. X Itumfifteen cv.)caracterización en campo, calidad fisicoquímica y compuestos bioactivos

Résumé

In the last 20 years, the cultivated area of table grapes worldwide has experienced a significant increase. Currently, nearly the same number of grapes are produced globally for table grape consumption as for winemaking, which is historically unprecedented. The Region of Murcia is a national benchmark in both wine grape cultivation and table grape cultivation, being the leading producer and main national exporter of table grapes. It has breeding programs for obtaining new seedless varieties of table grapes that are cultivated both in the Region and around the world. The growth in the consumption of table grapes in Spain, Europe, and worldwide is primarily due to it being an attractive fruit, with excellent flavour, easy to consume, absence of seeds, thin skin, and crunchy texture. Grapes are associated with significant nutritional value, primarily due to the presence of bioactive compounds. These nutritional and phytochemical compounds, distinct but acting together, contribute beneficial properties for humans and are presented as essential for a healthy lifestyle. Bioactive compounds, with diverse chemical structures, are secondary metabolites of plants that play a crucial role in their growth and reproduction. They are essential for the plant's survival and defence, protecting it from oxidation and ultraviolet radiation. The main bioactive compounds of interest in table grapes are phenolic compounds, which are classified into two major groups based on their chemical structure: flavonoids (flavonols, anthocyanins, and flavan-3-ols) and non-flavonoids (phenolic acids, stilbenes). These phytochemical compounds are primarily found in the skin and seeds of the berries, with only a small amount present in the flesh. However, teinturier grapes, with coloured or flesh, exhibit elevated levels of phenols not only in their skin and seeds but also in their flesh, making them of great nutraceutical interest for the development of new varieties. The main objective of the thesis is the study of the population behaviour in grapevines (Vitis vinifera L.) of 131 hybrids and their parentals ‘Alicante Bouschet cv.’, a parent with coloured flesh, and ‘Itumfifteen cv.’, a parent of table grape with excellent organoleptic characteristics. The specific objectives encompass studies of population traits, the evaluation of physicochemical quality, and the main bioactive compounds of the best individuals in the population. Parameters of interest studied for field quality characterization included seed presence, skin and flesh colour, taste, texture, and acceptability, all of which are relevant to the selection of plant material in table grape genetic improvement. Following this initial study, the best hybrids were identified, leading to a comprehensive examination of physicochemical quality and the determination of bioactive compounds. Outstanding heritability results were obtained in the study population, with 67% of hybrids showing seed traces (without lignified seeds), 98% of hybrids exhibiting a soft texture, 54% of hybrids having an acidic taste, 65% of hybrids displaying black skin colour, and 51% of hybrids showing partial or total flesh coloration. After field characterization, 19 hybrids were selected and classified into 3 groups: hybrids with non-coloured flesh and pink-violet skin colour (PSC), hybrids with partially coloured flesh and black skin colour (PCP), and hybrids with total coloured flesh and black skin colour (PCT). Among these hybrids, AB×IT_17 (within PCT) stood out with a higher total antioxidant capacity (TAC), reporting 34.6 ± 5.7 g TE kg-1 dw, 19.4 ± 3.0 g TE kg-1 dw, and 32.2 ± 6.9 g TE kg-1 dw for FRAP, DPPH, and ABTS assays, respectively. It also stood out for its higher total phenolic content (TPC) with 17.0 ± 5.1 g GAE kg-1 dw. PCP and PCT hybrids exhibited higher TAC, increasing from 0.9 to 2.3- fold compared to the AB parent and from 2.3 to 7.2-fold compared to the IT-15 parent. Similarly, PCP and PCT hybrids showed a higher TPC, ranging from 1.0 to 2.1-fold more than the AB parent and from 3.0 to 6.2-fold more than the IT-15 parent. Phenolic compounds were determined by U-HPLC, and their total was calculated as the sum of phenolic acids, stilbenes, flavonols, and anthocyanins, consistent with previous spectrophotometric results. For PSC hybrids, TPC corresponded to 74% phenolic acids, 2% stilbenes, 17% flavonols, and 6% anthocyanins, with the flesh representing 53% of the total. For their part, the TPC in PCP and PCT hybrids corresponded to 52% phenolic acids, 1% stilbenes, 16% flavonols, and 31% anthocyanins, with the flesh representing 55% of these compounds. It is particularly noteworthy that, in PCP and PCT hybrids the anthocyanins were 9.5 times higher than in PSC hybrids. Thus, the generation of new hybrids with enhanced nutritional quality to meet consumer demands is achievable through the crossbreeding of Vitis vinifera AB and IT-15, which adapt well to the studied growing conditions in the Region of Murcia. Particularly, PCP and PCT grapes exhibited 0.8 to 2.3-fold higher in phenolic acids, 0.4 to 2.2-fold higher in stilbenes, 0.5 to 1.5-fold higher in flavonols, and 3.3 to 29.2-fold higher in anthocyanins compared to PSC grapes. Our results contribute to verifying the richness in CFT and CAT in table grape breeding programs, as well as at a specific level, the richness in their main phytochemical compounds, according to the particular characteristics of skin and pulp of the cultivated varieties. In view of the future prospects for research, development, and commercialization of some of the hybrids studied, further investigation should focus on disease resistance, sustainable crop production, genetic analysis, adaptation to new soil and climate types, as well as their potential shelf life under different environmental conditions for marketing and transportation.