Response to organic cultivation of heirloom Capsicum peppers: Variation in the level of bioactive compounds and effect of ripening

Abstract

Peppers (Capsicum spp.) are one of the most important vegetables and their double use (vegetable or spice) and two commercial stages (unripe and fully ripe) contributed to their use in many recipes and fast diffusion from America. Nowadays, Spain is a center of diversity for C. annuum, with many landraces, offering a great opportunity for adaptation to organic cultivation. Furthermore, Capsicum peppers contain many bioactive compounds, essential to provide high added-value to these cultivars, especially for organic markets, although knowledge about the effect of organic cultivation on Capsicum fruit quality is still scarce. Here, 37 accessions of Spanish landraces and foreign materials from C. annuum and other species were grown under organic and conventional conditions and evaluated for ascorbic acid (AAC), total phenolics (TP) and total red and yellow/orange carotenoids, considering both ripening stages. A large genotypic variation was found within each ripening stage and growing condition for the studied traits. Also, both stages showed high levels, although fully ripe fruits were the richest. Organic conditions enabled higher levels in fully ripe fruits of AAC and TP on average (135 vs 117 mg·100 g-1 and 232 vs 206 mg·100 g-1) and in most accessions, although the genotype×growing conditions interaction also contributed, but at lower extent, to the observed variation. Significant genotype×ripening stage and growing conditions×ripening stage interactions were also found, suggesting that the magnitude of the increase with ripening depends on the accession and growing conditions. By contrast, there were no differences between growing conditions for carotenoids and differences were mainly due to the genotype factor. Finally, the large genotypic variation and favourable organic conditions allowed identifying several materials from different types and uses with very high levels of bioactive compounds for organic cultivation, in both ripening stages but particularly at fully ripe stage (>500 mg·100 g-1).

Variation in flavonoids in a collection of peppers (Capsicum sp.) under organic and conventional cultivation: effect of the genotype, ripening stage, and growing system

“…). These findings are in agreement with a recent work that detected considerably higher levels of total phenolics through spectrophotometric methods in fully ripe fruits in a collection of 37 accessions …”

“…On the whole, the organic growing system seemed to favor slightly the accumulation of total flavonoids and luteolin during the ripening process because the highest fully ripe/unripe ratios were detected in the organic system on average and in most accessions (Table , Figs and ). This was in agreement with previous works based on total phenolics and a range of Capsicum materials . Finally, according to the ANOVA, a significant system × ripening interaction was detected for kaempferol content (Table ), which was due to significant differences between organic and conventional ripening ratios (Fig.…”

“…These findings are in agreement with a recent work that detected considerably higher levels of total phenolics through spectrophotometric methods in fully ripe fruits in a collection of 37 accessions. 34 This average trend was also found considering accessions separately. Thus, most accessions showed higher or similar flavonoid levels at the fully ripe stage compared with their corresponding unripe levels, although the increase in flavonoids with the ripening process differed among accessions (Figs 1-6).…”

“…where X ijkl is the value in one specific ripening stage for fruit sample l of genotype i, growing system j and year k; ⊘ is the general mean; a i is the effect of genotype i; b j is the effect of growing system j; c k is the effect of year k; (⊍ × ⊎) ij is the interaction between genotype i and growing system j and e ijk(l) is the effect of fruit sample l from the combination of genotype i, growing system j and year k. The means were calculated for each set of ten samples and regression analysis was used to study the genotype × growing system interactions. 34 The regression coefficients (⊎) per genotype were calculated from the average contribution of each growing system and the formula Figure 1. Comparative graphs of the average content (mg kg −1 FW, n = 10) of total flavonoids at unripe (green) and fully ripe (red) stages for organic and conventional growing systems on each pepper accession.…”

“…The means were calculated for each set of ten samples and regression analysis was used to study the genotype × growing system interactions . The regression coefficients ( β ) per genotype were calculated from the average contribution of each growing system and the formula where β i is the regression coefficient value for each specific trait and ripening stage for genotype i; μ ij is the mean of genotype i in growing system j; μ ijk is the mean of genotype i for both growing systems j and k, μ j is the mean for all the genotypes in growing system j, μ jk is the mean for all the genotypes in both growing systems j and k. The cases with β values that did not differ significantly from 0 were considered stable genotypes against the growing system effect …”