Diversity Assessment of Algerian Wild and Cultivated Olives (Olea europeae L.) by Molecular, Morphological, and Chemical Traits

Abstract

Algeria has several genetic resources on olive trees, mainly made up of small indigenous cultivars, and a very important wild heritage. Twenty olive samples including eight cultivars and twelve wild trees from the province of Bejaia (Algeria) are characterized, by combining molecular data (13 SSRs), fruit and pit morphological traits, fatty acids composition, and phenolic compounds of the extra virgin olive oils (EVOOs). The genetic results based on PCoA, UPGMA, and AMOVA analyses demonstrate that olive cultivars and wild trees are mixed, suggesting kinship relationships between cultivated and wild olive trees and even cases of synonymy between some cultivars. PCA analysis on morphological traits shows a good separation of the two olive botanical varieties, the wild olive trees producing smaller fruits than those of the cultivated ones. Significant differences are also found in terms of fatty acids and phenol compounds composition of the EVOOs. Wild olive oils show the highest contents on phenolic compounds, mainly oleocanthal, as well as a considerable richness on oleic acid. The comparison of pairwise distances between olive trees obtained by genetic, morphological, fatty acids and phenolic compounds contents data using Mantel's test indicates a significant correlation among morphological characteristics, DNA polymorphism, and phenolic compounds. The results obtained in the present work contribute to reveal the diversity existing in the cultivated and wild olive trees of the region of Bejaia, shedding some light on the importance of Algerian olives germplasm. Practical Applications: Cultivated and wild olive diversity are assessed by genetic, morphological, fatty acids and phenolic composition. SSR marker analysis demonstrates the presence of a high genetic variation between the analyzed samples. A significant correlation of morphological characteristics with DNA polymorphism and phenolic compounds is found. A significant diversity in the wild and cultivated olive trees is observed. Kinship relationships between wild and cultivated Algerian olive trees are demonstrated using SSR markers, while the morphological parameters allow a good distinction between the two taxa. Significant differences are found for fatty acids and phenol compounds composition for the EVOOs; the wild olive oils present an interesting composition compared to the cultivated form.

The newly developed genomic-SSR markers uncover the genetic characteristics and relationships of olive accessions

“…2 and 3), thereby confirming the effectiveness of the 21 SSR markers. The separation of olive accessions is consistent with their geographical origins and genetic background to some extent (Boucheffa et al, 2019). The olive is originally present in the eastern Mediterranean coast and then gradually expands to the central and west Mediterranean basin (Vossen, 2007;Díez et al, 2015).…”

“…The average Ho for the 21 SSR markers was 0.52 and represented a high degree of genetic variability among the 53 accessions. In several previous reports, the average Ho was higher than 0.5 based on around ten SSR markers in the olive (Lazović et al, 2016;Mousavi et al, 2017;Dridi et al, 2018;Boucheffa et al, 2019). This phenomenon indicates that the average value of Ho is influenced by the number of SSR markers to some extent.…”

“…Several studies revealed that SSR markers are more suitable for the identification and genetic variation analysis of olive cultivars than SNP markers because the former has higher mutation rate than the latter (Biton et al, 2015;Belaj et al, 2018).The SSR markers of olive were originally developed by Sefc et al (2000), Carriero et al (2002) and Cipriani et al (2002), and they distinguished 12-47 olive accessions using 15-30 pairs of polymorphic SSR primers based on dinucleotide repeats. These dinucleotide genomic-SSR markers were then extensively used for the identification of more olive accessions in later researches (Beghè et al, 2015;Lazović et al, 2016;Dridi et al, 2018;Boucheffa et al, 2019). However, dinucleotide SSR markers produce less easily detected differences in the length of alleles, thereby increasing allele miscalling compared with a longer core of repeats such as trinucleotide SSR markers (Diwan & Cregan, 1997;Song, Fickus & Cregan, 2002).…”

Recovery, Assessment, and Molecular Characterization of Minor Olive Genotypes in Tunisia

“…Today, there is a strong interest in the recovery and preservation of agro-biodiversity, and several projects are in place to avoid the loss of this patrimony, setting up recovery collections [32][33][34][35]. In Tunisia, although there are institutions, such as the Olive Institute, that hold a large number of olive genotypes, it is still necessary to enlarge the existing collection and develop new conservation management strategies [36][37][38]. At the same time, it is crucial to improve the plant material certification circuit to be more competitive in the global market, offering plant material with high quality standards [39].…”

Marginal Grapevine Germplasm from Apulia (Southern Italy) Represents an Unexplored Source of Genetic Diversity

“…Simple sequence repeats (SSRs/microsatellites) are informative molecular markers used for the genotyping and traceability of many Mediterranean crops [21][22][23][24][25][26][27]. Sometimes, their discriminating power is limited; therefore, they are combined with SNP markers to further improve genotyping [28].…”