1. Introduction
Goji berry plants have been used in Chinese medicine and cuisine for thousands of years [
1] and presently, the berries are acknowledged as one of the most recognized 'superfruits' of the 21st century [
2,
3,
4], being considered a functional food [
1,
5]. The goji berry has attracted significant attention in Western countries due to its nutritional profile, especially for its abundant vitamins and antioxidants. Its ORAC (Oxygen Radical Absorbance Capacity) values, which lie between 25,000 and 30,000, surpass those of other nutritionally beneficial fruits like pomegranates and blueberries, indicating its superior antioxidant capacity [
6]. Its medicinal uses go from improving visual acuity [
5,
7,
8], infertility [
5], abdominal pain [
5], dry cough, fatigue, and headache [
5], immune system support, cancer prevention [
7,
8], antidiabetic activity [
7,
8] to increased longevity [
8,
9,
10] and enhanced fertility [
10,
11,
12,
13].
In China, out of the existing nine
Lycium taxa [
14], only four are traditionally utilized, with
L. barbarum and
L. chinense being the main species traded worldwide [
14,
15]. For over two millennia, various pharmacological substances have been collectively referred to as "
gou qi" [
4,
5,
16], although it is likely that a diverse range of genetic materials is hidden behind this generalized term. The genus
Lycium, distributed in temperate and subtropical regions worldwide [
17,
18,
19], actually comprises 436 species names [
20]. Out of these, only 92 are acknowledged as accepted species. 241 of these names are considered synonyms, while the remaining 103 names are categorized as unplaced [
20]. Yao and al. (2018), cites 97
Lycium species, out of which 35 species and 2 varieties with recorded uses of food and/or medicine worldwide [
14]. The Plants of the World Online records 101 officially recognized
Lycium species, indicating their indigenous presence in 71 countries, across 130 regions [
21]. The database also indicate a list of 91 countries and 73 regions where
Lycium species have been newly introduced, including Romania as one of these recent additions [
21].
The flora of Romania recognizes
Lycium halimifolium L. as a native species [
22], however, a manuscript from 1867, referenced by Marian (2008), documents the traditional usage of
Lycium vulgare Dun. in Romania, also mentioning its identification as
L. barbarum in the Transylvania region [
23]. Although it is scientifically acknowledged that
L. halimifolium is typically considered a synonym of
L. barbarum [
24,
25,
26], widespread public belief, likely shaped by online media and local traditions, treats
L. halimifolium and
L. barbarum as separate species, attributing different culinary and toxicological properties to them [
27,
28]. In fact, both
L. halimifolium and
L. vulgare are today synonym names of
L. barbarum [
25,
29]. Evidence of the long-standing presence of wild goji berry species in Romanian regions is found in the variety of local names used historically. These include names like ‘licie’, ‘lician’, ‘lițian’, ‘răchișoară’, ‘răchițică’, and ‘zaharică’ in Bucovina, ‘licină’ in Transylvania, and ‘cătină’ and ‘cătină de garduri’ in Moldova region [
23]. The plant is characterized as a shrub with red berries, which not only serves as a natural fence in the countryside, but it is also recognized for its medicinal properties. Traditionally, it has been used to treat conditions related to fear and anxiety, demonstrating psychological effects, and for epilepsy and spasms, indicating neurological benefits [
30]. In few Romanian regions it is considered an invasive plant, as in Oltenia, Danube riverbanks and Dobrogea [
31,
32].
Due to goji berry increased fame, the market demand grew exponentially in the last two decades [
33,
34]. China dominates goji berry production, particularly in the Northwest regions, like Ningxia and Xinjiang, two main exporting regions [
9,
35,
36]. In contrast, production in North America and Europe is limited due to a lack of traditional use and the challenge of adapting Chinese varieties to these regions [
37,
38,
39,
40]. Ideal U.S. cultivation spots include Northern California and parts of the Northwest, while in Europe, Italy and Romania are leading in production [
41,
42]. Italy boasted the largest European goji farm in 2013, with 35 hectares and 60,000 plants [
6]. Romania has emerged as a significant producer of goji berries [
41], focusing also on plant material for cultivation [
43], with a market that is showing a rising trend [
42]. Especially in the difficult context of climate change constraints, goji berry planting material adapted to local conditions is required by European farmers. Therefore, initiatives on identifying new cultivars and crop production processes were launched, together with breeding programs that considered
Lycium as an important target [
44]. In Romania, by 2023, seven varieties of
Lycium spp. were registered on the Official catalogue of cultivated plant varieties: 'Erma’, ‘Transilvania’, ‘Kirubi', '‘Kronstadt‘, ‘Bucur’, ‘Sara’ and ‘Anto’, belonging to both
L. barbarum and
L. chinense [
45].
Genetic diversity is the cornerstone of biodiversity, offering significant value in numerous areas, both scientific and practical [
46]. It plays a crucial role in comprehending the origins and evolutionary processes of species, conserving genetic resources, investigating valuable germplasm resources and use the genetic materials displaying valuable traits [
47,
48]. Having a deeper understanding of native goji berry genetic resources is important both for preserving local biodiversity and for the breeding sector [
36,
47,
49]. Since the rise of goji berry market demand, extensive molecular studies have been undertaken, to determine valuable genes in both cultivated and native or spontaneous plants, as a resource for valuable traits in the future breeds [
1,
18,
36,
49,
50,
51].
The process of crop plant breeding focuses on identifying and cultivating new plant varieties that exhibit beneficial characteristics like higher yields, better disease resistance, and enhanced nutritional value [
52]. The high-throughput technologies, including genomics, transcriptomics, and metabolomics, have opened a new phase in crop breeding, enhancing the efficiency and precision of this process [
52,
53]. The last two decades have seen a significant growth in both the volume and quality of publicly available plant genomes [
53]. This progress is largely due to advancements in sequencing technologies such as PacBio Sequel, Illumina HiSeq, Oxford Nanopore PromethION, and Illumina NovaSeq, alongside bioinformatic tools like the chromosome conformation capture technique (Hi-C) and BioNano optical maps. These developments have greatly enhanced the efficiency of genome sequencing, assembly, and annotation [
53,
54,
55].
In the Solanaceae family, which includes around 90 genera and 3,000 species, 170 full genomes of 46 species have been reported [
54]. These genomic studies primarily targeted horticultural crops and their wild relatives, such as the cultivated tomato (
Solanum lycopersicum) and its wild counterpart (
Solanum pimpinellifolium), potato (
Solanum tuberosum), hot pepper (
Capsicum annuum), and eggplant (
Solanum melongena). They also extend to tobacco (
Nicotiana tabacum), decorative flowers like
Petunia inflata and
Petunia axillaris, and herbs with medicinal properties, including
Datura stramonium and
Lycium barbarum [
52,
56], or its invasive relative,
L. ferocissimum [
57].
L. barbarum genome contains 12 chromosomes [
34] (2n = 2x = 24) and is 1.8 Gb in size, with a level of heterozygosity of approximately 1% [
56]. The sequenced and annotated genome ASM1917538v2 [
58] was obtained by sequencing a haploid plant developed from pollen culture, using PacBio Sequel technology [
56]. The annotation allowed identification of 47,740 genes and 34,339 protein-coding sequences. The availability of another annotated genome, of
L. ferocissimum, of 1.2 Gb size, 40,291 genes and 30,549 protein-coding genes [
57] will ease even more the characterization of the future goji berry sequenced genomes, allowing identification of new genes of interest.
Exploring the genetic diversity in Romanian wild and cultivated genotypes of
Lycium species could bring the breeding sector one step closer to rapidly developing new varieties, adapted for specific ecopedological conditions and market requirement, indicating potential genetic markers for required traits. Generally, the goji berry in Romania has three major biotic threats, the powdery mildew, the goji berry gall mite and the stink bugs [
59,
60], being much more suitable for organic production than in China [
40,
61]. The escalating threat of extreme weather events caused by climate change is set to pose an increasingly serious challenge to goji berry production, major threats being extreme drought and insolation [
62,
63]. The Romanian homologated varieties were developed based on Chinese varieties germplasm, due to their high fruit quality traits [
64,
65], without using the local germplasm.
The current study marks the initial phase of a broader project focused on genes related to resistance to abiotic and biotic stress, focusing here on cuticle thickness. This aspect is critically important due to cuticle significant influence on resistance to drought, insolation, and pests [
66,
67,
68], as the cuticle is essential for plant survival in periods of severe drought [
69] and pests and disease attack [
70].
BODYGUARD genes in plants typically encode for proteins that are directly involved in defending the plant against various stresses, including the biosynthesis of cutin in
Arabidopsis [
69,
71,
72], mainly the α/β hydrolase protein [
69,
71,
73]. Analysing the genetic diversity of cultivated and wild goji plants genes has the final aim of providing information required by the goji berry breeders supporting the development of goji berry production in Romania.
3. Discussion
The sequencing and annotation of the goji berry genome in 2023 [
56] represents a crucial resource for future resequencing projects. The advancements in Next Generation Sequencing/Whole Genome Sequencing (NGS/WGS) [
55] are poised to generate a wealth of data, which will be instrumental in developing new goji berry varieties. The examination of variations in density at the genomic level, particularly for SNPs and InDels, highlights specific genome areas that warrant further investigation, to identify potentially beneficial genes from wild genotypes that could be integrated into new varieties. The observed increased polymorphism near the ends of chromosomes can be attributed to the higher frequency of recombination in these areas [
76].
In Romania, seven new goji berry varieties have already been created and registered, originating from Chinese genomic material, without genetic elements from native plants. Present research is dedicated to enriching the diverse gene pool found in wild germplasm, potentially enhancing the unique characteristics of Romanian goji berries. By examining the morphological and phenological traits of wild goji berries and correlating them with genetic data, characteristics like early or late flowering, high drought tolerance, strong resistance to low temperatures (
Figure 4), as well as features like thicker cuticles and leaves, could become valuable assets in breeding programs.
In earlier research, the morpho-anatomical features of leaves and flowers of both wild and cultivated goji berries in the Bucharest region were analysed. The study aimed to identify key traits of interest to both goji berry breeders and taxonomists [
31]. An other study also involved mapping the spontaneous genetic resources found across Romania [
75]. Notable morphological distinctions were observed in leaf shape, orientation, and width of Romanian
L. barbarum, results that are similar with findings reported in Republic of Moldova, in a similar study between cultivated and wild goji berry [
77]. The leaf anatomical characteristics are particularly significant in relation to biotic and abiotic stress factors, the wild plants having the leaves covered with a thick cuticle, prominently developed vascular bundles, and sheaths surrounding the vascular bundles within the mesophyll. Additionally, the palisade cells in these plants were observed to be considerably larger than in cultivated plants [
31]. These findings motivate further investigation into genes putatively linked to these phenotypic differences. The formation of the plant cuticle involves several proteins that play crucial roles in the biosynthesis and regulation of cutin and waxes, as BDG, CER, KCS, VLCFAs, GPAT, LACS, ABC, SHN/WIN, LTPs, CD1 [
69,
71,
78,
79].
The sequence analyses of the
BDG genes in Romanian goji berry genomes revealed several differences among the three genes. The genes located on chromosomes 4 and 9 are encoding probable lysophospholipase BODYGUARD 3 proteins, whereas the gene located on chromosome 8 encodes a probable lysophospholipase BODYGUARD 4 protein [
56]. The
BDG 4 gene from chromosome 8 is shorter than the
BDG 3 genes, from chromosomes 4 and 9. Although located on different chromosomes, two of the genes presented SNPs affecting the same amino acid, as in 12, 65, 84, 235, 254, 410, 426, 467, and 473 positions. Even if some SNPs are located within conserved regions, many of them are silent (
Figure 5).