Phenotypical characterization of Portulaca umbraticola : A non-conventional edible ornamental crop

. Purslanes are frequently used in Brazil as potted plants and for landscaping because of their beautiful colored flowers. Despite their commercial importance, the genetic diversity within ornamental purslane remains largely unknown. Thus, a complete characterization of ornamental purslane resources is essential for its utilization since genetic variability is indispensable for the efficient development of new cultivars. This study aimed to evaluate genetic variability and recommend accessions to start a genetic breeding program for purslane ( Portulaca umbraticola) . Twenty purslane accessions were collected in public places in Areia City and Santa Rita City, Paraiba State, Brazil. The experiment was conducted in a greenhouse. An entirely randomized experimental design with 20 accessions and 5 replicates was utilized. Plants were evaluated for quantitative and qualitative traits. Data were submitted to analysis of variance and grouped by Scott –Knott’s criteria (p ≤ 0.05). The accessions were grouped using Tocher’s method based on the generalized Mahalanobis distance. Principal component analysis was also used to analyze the genetic divergence. There were significant differences (p ≤ 0.05) for all evaluated traits except for internode distance, plant height, and leaf length. The Scott – Knott criteria clustered the accessions into two groups for all traits except days to flowering (five groups). Tocher’s grouping based on Mahalano bis distance allowed the accessions to be separated into eight clusters. The genetic diversity observed in this study was supported by the consonance between the Tocher cluster method and the PC analyses. The traits that most contributed to genetic divergence among accessions were days to flowering (70.37%), flower length (6.10%), leaf width (3.89%), branch number (3.57%), and stem length (3.36%). Considering the criteria for use in outdoor spaces, wider plants with several large colored flowers, thicker stems, greener leaves, and earliness were interesting. Accessions 5, 7, 13, 14, 16, 18, and 20 should be selected as parents for further breeding programs. However, if the objective is to produce potted plants, dwarf plants with bigger leaves are desired, and accession 1 should be selected. This will create greater variability in segregating populations, which will increase the overall quality of ornamental use of this species. For those accessions with no reproductive verticils but with other excellent attributes, for example, high chlorophyll content breeding strategies, such as induced mutations or protoplast fusion, can be used.


Introduction
Portulaca umbraticola Kunth belongs to the Portulacaceae family, which includes 10 genera and 258 species (The Plant List, 2020).They are mainly distributed in the west of North America, South America and Africa, with a smaller number of representatives in Europe and Asia (Coelho, Giulietti, Harley, & Yesilyurt, 2010).
Most Portulaca species have no major commercial importance, except Portulaca oleraceae (common purslane), Portulaca grandiflora (nine o'clock) and P. umbraticola (moss rose purslane or large-flowered purslane) (Ocampo & Columbus, 2012).Most literature involving ornamental Portulaca is about P. oleraceae or P. grandiflora; however, some authors have affirmed that P. umbraticola is taking the floriculture industry by storm.Portulaca umbraticola is planted as a bedding plant or as a container plant for landscaping with morphological characteristics that resemble those of common purslane (P.oleracea L.) (Elias, 2018;Jia et al., 2017).
Purslane has flowers with diverse colors, such as yellow, white, red, orange, pink, purple and violet (Coelho et al., 2010;UPOV, 2019).Flower color variation and small plant size potentialize ornamental use for this species (Datta, 2021;Franca & Maia, 2008).Purslane can also be used as a food source because it has essential nutrients, phenolic compounds, flavonoids, carotenoids and antioxidants and has been considered medicinal (Alam et al., 2014a;2014b;2014c).
Brazil has eight thousand ornamental plant producers.Most of them are small-and medium-sized producers that produce in an area of more than 15.6 thousand hectares (Ibraflor, 2022).In Brazil, small farmers produce purslane, making it difficult to quantify the commercialized amount.Other species occupy the place in the big chains, such as the roses, orchids, cacti, succulents, ornamental pepper, violets and lisianthus (Ibraflor, 2021).
In Ibraflor's assessment, there is a tendency for home office work and some consumption habits acquired during the pandemic to persist, which makes the sector invest in increased production for the coming years, especially the production of potted plants.This market grew during the pandemic to the detriment of ornamental plants for cutting, such as flowers and foliage (Globo Notícia, 2020;Pereira, Aguiar, & Pires, 2022).
The Ornamental plant's global market is expanding (Ibraflor, 2021), and it is extremely dynamic and demands the constant release of new cultivars.Safdari and Kazemitabar (2009) reported that millions of micropropagated plants of Portulaca are being afforded to the commercial ornamental market and the agricultural, clonally propagated crop market large-scale through many mircopropagation laboratories.Thus, to meet this market, ornamental plant breeding programs need to accelerate the production of new cultivars synchronized with the market's demands (Filliettaz, 2007).
Thus, this study aimed to evaluate genetic diversity and recommend accessions to start a breeding program for moss rose purslane (Portulaca umbraticola).

Material and methods
The experiment was conducted at Laboratório de Biotecnologia e Melhoramento Vegetal of the Centro de Ciências Agrárias, Universidade Federal da Paraíba, Areia, Paraíba State, Brazil.Twenty accessions of P. umbraticola Kunth were used, numbered 1-20 (Figure 1), and collected from public places at Areia and Santa Rita, Paraíba State, Brazil.Accessions were asexually propagated using three cuttings of approximately 15 cm in plastic pots with commercial substrate (Plantmax ® ).They were submitted to the best agronomic practices, including irrigation, fertilization and pesticide application for pest and plant disease control.Fertilizers were supplied monthly in the dosages recommended for vegetables.The plants received a daily water supply until they reached field capacity in the pots through micro-sprinklers installed on the greenhouse benches.They were also in full sunlight for the location 6°58'18.7"S and 35°43'15.0"W.
The evaluated characteristics were flower number, flower length, stem diameter, internode distance, branch number, canopy width, plant height, stem length, chlorophyll b, chlorophyll a, leaf length, leaf width and days to flowering.Data measurements were made with a digital caliper (Leetools ® ) and a graduated rule.Chlorophyll contents were measured with a digital chlorophyll meter (ClorofiLOG -FALKER ® ).The evaluated traits were recorded 83 days after planting.
The qualitatively evaluated traits were corolla type (pentamerous and multi), presence or absence of reproductive verticils, leaf shape, leaf tip shape and leaf base shape.The accessions were also visually evaluated using the color chart from the Royal Horticultural Society for flower color, corolla base color, anther color, style color, stem color, and leaf color.
The experimental design was completely randomized, with 20 treatments (accessions) and five replicates.The data obtained was submitted to analysis of variance and the means were grouped by Scott-Knott's criteria (p ≤ 0.05).Genetic parameters and their estimators were analyzed for each quantitative trait using the following expressions (Cruz, Carneiro, & Regazzi, 2014 where MSt = treatments mean square; k = replicate number; and MSr = residual mean square. Mahalanobis distance was employed to determine the degree of diversity among accessions, and groups were formed following Tocher's method (Rao, 1952).Divergence analysis was also performed using principal component analysis (PCA).The relative importance of the variables was determined using the method described by Singh (1981).Qualitative data were determined by frequency distribution.All quantitative analyses were performed using GENES software (Cruz, 2018).

Results and discussion
There were significant differences (p ≤ 0.05) for all evaluated traits except internode distance, plant height, and leaf length (Table 1).
The coefficient of genetic variation to the coefficient of the environmental variation ratio (CVg/CVe) was lower than 1 for all traits except days to flowering (Table 1).When the values of the CVg/CVe are higher than 1, this indicates a better chance of genetic gain for this trait.According to Cruz et al. (2014), this parameter should be considered together with the heritability values as an indicator of selection success in breeding programs.Then, it is possible to select for earliness in the evaluated population.The Scott-Knott criteria clustered the accessions into two groups for all traits except days to flowering (five groups) (Table 2).The accessions with a major number of flowers were 13,15,10,18,12,9,20,14,and 6. Genotypes 14,12,20,19,1,6,11,4,18,15,5,and 13 showed larger flowers (Table 2).In an ornamental plant breeding program, it is important to select accessions with larger flowers and an increased number of flowers per plant (Datta, 2021).Thus, accessions 6, 12, 13, 14, 15, 18, and 20 can be selected to improve these characteristics (Table 2).
Regarding stem diameter, accessions 8 and 17 presented minor values of 0.41 and 0.40 cm, respectively (Table 2).Despite all the other accessions presenting thicker stems than these, they had thinner stems than the P. oleraceae genotypes studied by Talei et al. (2020).A higher stem diameter provides better support for the plant and facilitates asexual propagation by cutting.
Accessions 10, 17, 20, 14, 16, 18, 13, 2, and 5 presented higher branch numbers, with mean values varying from seven to eleven (Table 2).The accessions with major canopy widths were 7, 4, 3, 5, 15, 2, 19, and 6, with values varying from 48.2 to 52.8 cm (Table 2).For the variable stem length, accessions 16, 1, 17, 10, and 8 presented the lowest mean values.All other accessions formed a cluster with major stem length means varying from 53.8 to 65 cm (Table 2).The accessions with major values for these three traits should be used as bedding plants since they presented numerous long and wider branches, allowing empty spots to be filled in the garden or outdoor spaces.Talei et al. (2020) reported no differences among genotypes of P. oleraceae for branch number.Despite the lack of significance of plant height, it is important to highlight that the values varying from 15.4 to 36.0 cm (data not shown), showing that the accessions of P. umbraticola were smaller than those of P. oleraceae studied by Talei et al. (2020).
Considering chlorophyll b, accessions 17, 10, 13, 18, 20, 8, and 9 presented higher mean values (Table 2).All accessions showed higher values of chlorophyll a, except accession 20 (Table 2).However, Talei et al. (2020) reported no significant differences in chlorophyll content among the purslane genotypes of P. oleraceae.The accessions with larger leaves were 16,13,11,7,5,19,4,6,17,10,12,18,15,and 20 (Table 2).Traits' mean values are important to help in the decision-making process of plant selection and in choosing accessions with favorable traits in a breeding program.Datta (2021) underlined the importance of pigments as different economic characteristics of ornamental plants.It is important to highlight traits such as canopy width and chlorophyll b leaf width for P. umbraticola species since it can be consumed as a traditional orphan crop (Kumar et al., 2021).According to Alam et al. (2014a) and Alam et al. (2014c), purslane can be consumed and can also be used as medicinal plants for bioactive compounds, such as phenolic compounds, flavonoids, carotenoids, essential minerals and antioxidants.
Accessions 16, 3, 7, 2, 17, and 14 presented earliness.They bloomed from 15 to 16 days after transplanting, while other accessions showed values varying from 17 to 25 days to flowering.According to Datta (2021), earliness is a desired trait for ornamental plants.The faster the plants bloom, the less time will be needed until commercialization.Additionally, the breeding program, based on the hybridization method, can be accelerated.Tocher's grouping based on Mahalanobis distance allowed the accessions to be separated into eight clusters (Table 3).Most of the individuals were included in group I (2, 3, 7, 4, 16, and 15), followed by group II (12, 19, 11, 20, and 13).Accessions 9, 18, 10, and 6 comprised group 3. Accessions 1, 5, 8, 14, and 17 formed clusters IV, V, VI, VII, and VIII, respectively (Table 3).Group I presented the major mean value for branch number and the second major value for canopy width.The second cluster showed the major mean value for internode distance, leaf length, leaf width and days to flowering.Group III exhibited a greater mean flower number.Cluster IV had a major mean leaf width and a minor mean plant height.Group V presented a major mean for canopy width and stem length.Cluster VI showed minor values for canopy width and stem length.Group VII presented bigger flowers, thicker stems and were the most precocious plants.The major means of plant height and chlorophyll a and b were presented by cluster VIII.Alam et al. (2015) grouped 45 purslane accessions into seven clusters using ISSR markers.Thus, we demonstrated that it is possible to discriminate between different accessions based on morphological traits.Several authors opined that the evaluation of genetic diversity within a purslane population is indispensable to germplasm conservation, exploitation and establishment of breeding programs (Alam et al., 2014c;Alam et al., 2015;Talei et al., 2020).The two first canonical variables explained 81.733% of the total variance (Table 4).The genetic diversity results observed in this study were supported by the consonance between cluster and PC analyses, except for accessions 1 and 14, which were grouped together with the accessions of major group I (Table 3; Figure 2).The data support the variability presented among accessions in this study.The lowest values for the two first principal components were presented by Alam et al. (2015) (57.7%) and Talei et al. (2020) (55.5%) in studies with P. oleraceae.Arunachalam (1981) considered joining the distance and principal component analysis a good procedure if the first two components accumulated at least 70% of the total variation.Through Singh's method (1981), it was determined that 5 out of 13 evaluated characteristics contributed to 87.29% of genetic divergence.However, nine traits contributed to only 12.71% of genetic divergence (Table 5).The traits that most contributed to genetic divergence among accessions were days to flowering (70.37%), flower length (6.10%), leaf width (3.89%), branch number (3.57%), and stem length (3.36%) (Table 5).The variables that least contributed to genetic divergence were chlorophyll a, canopy width, stem diameter, plant height, flower number, internode distance, leaf length and chlorophyll b.According to Arunachalam (1981), the variables that contribute a low percentage of the total variability can be discarded in future studies.However, Rêgo et al. (2003) highlighted the importance of choosing the proper method to avoid discarding important variables.Concerning the variable corolla type, 55% of the accessions presented pentamerous flowers and 45% presented multiple petals (Figure 3A).Of the accessions, 55% presented reproductive verticils and 45 did not (Figure 3B).Although accessions 8 and 17 did not present reproductive verticils, they showed minor mean values for canopy width and major mean values for chlorophyll content and belonged to different clusters; they can be selected if the strategy used in the breeding program is induced mutations or protoplast fusion.These strategies can create new variability and increase the attributes of ornamental use of this species.Regarding flower colors, 30% were white, 25% yellow, 20% pink, 10% pink/yellow, 5% red, 5% hot pink and 5% orange (Figures 3C and 5).Each of these flowers had differences in their corolla base color, being 50% yellow, 20% white, 10% pink/yellow, 10% green, 5% pink and 5% orange (Figures 3D and 5).These accessions also have different style colors, presenting 40% yellow, 10% white, and 5% red; the others 45% did not present style (Figures 3E and 5).Datta (2021) emphasized flower color as a desired commercial characteristic of ornamental plants.

Conclusion
There was a high level of genetic diversity among accessions of P. umbraticola in this study, suggesting that morphological traits were effective in the detection of differentiation in this species.Plants belonging to different clusters should be selected as parents and used in the hybridization-breeding program to produce recombinant genotypes of P. umbraticola.This species has big, colored flowers, which has made this plant a unique candidate for ornamental breeding programs for both outdoor environments and potted plants.Considering the criteria for use in outdoor spaces, wider plants with several large colored flowers, thicker stems, greener leaves and earliness are interesting.Accessions 5,7,13,14,16,18, and 20 should be selected as parents for further breeding programs.However, if the objective is to produce potted plants, dwarf plants with bigger leaves are desired, and accession 1 should be selected.This will create greater variability in segregating populations, which will increase the overall quality of ornamental use of this species.For accessions with no reproductive verticils but with other excellent attributes, for example, high chlorophyll content breeding strategies, such as induced mutations or protoplast fusion, can be used.

Figure 2 .
Figure 2. Dispersion of 20 accessions of Portulaca umbraticola based on the first three principal components (PCA).

Table 4 .
Variance estimates (eigenvalues) associated with principal components of the 13 quantitative traits evaluated in Portulaca umbraticola accessions.

Table 5 .
Singh (1981)tribution of quantitative characteristics of major importance to the genetic divergence of Portulaca umbraticola by the method proposed bySingh (1981)based on the generalized distance of Mahalanobis.
*Contribution to the genetic divergence of each variable (S.jʼ).