Morphological characterizations of parsnip (Pastinaca sativa L.) to select superior genotypes

Abstract Parsnip (Pastinaca sativa L.) is an edible root that has long been used in cooking and preparing baby food and livestock. The present study was performed to evaluate the phenotypic diversity of 69 accessions of this species to select superiors in terms of root quality in Paykan village, Isfahan province, Iran, in the year 2022. There were significant differences among the accessions investigated (ANOVA, p < .01). Coefficient of variation (CV) was more than 20.00% in the majority of measured characters (64 out of 66 characters), indicating high diversity among the accessions. Foliage width (crown) ranged from 10 to 55 cm with an average of 32.32 cm. Root shape was tapering (33), obtriangular (10), narrow oblong (5), wide oblong (5), obovate (13), and fusiform (3). Root length ranged from 81.2 to 294 mm with an average of 166.44 mm. Root diameter at its middle point ranged from 15.58 to 125.12 mm with an average of 51.83 mm. Root weight ranged from 15 to 1200 g with an average of 315.36 g. Inner core (xylem) pigmentation/color was cream yellow (11 accessions), light yellow (12), yellow (42), dark yellow (2), and yellow–light orange (2). In the cluster analysis based on Ward's method, the accessions were divided into two main clusters according to morphological traits. This is despite the fact that parsnip is part of the medicinal plant native and valuable in most farms in tropical cities. Compared with carrots, parsnip plants are more adaptable to different environmental conditions. The accessions studied here showed high phenotypic diversity. Based on ideal values of the important and commercial characters of parsnip, such as root length, root weight, inner core (xylem) pigmentation/color, root shape, flesh color intensity, flesh palatability, and total soluble solids, 14 genotypes, including Parsnip‐3, Parsnip‐9, Parsnip‐24, Parsnip‐32, Parsnip‐32, Parsnip‐48, Parsnip‐51, Parsnip‐52, Parsnip‐58, Parsnip‐60, Parsnip‐62, Parsnip‐65, Parsnip‐67, and Parsnip‐69, were promising and are recommended for cultivation.


| INTRODUC TI ON
Parsnip (Pastinaca sativa L.) is an edible root that has long been used in cooking and preparing baby food and livestock (Castro et al., 2012).
It can also have therapeutic applications depending on the dosage and method of cooking (Stannard, 1982). Parsnip root is high in dietary fiber about 4.70-4.90% (Stannard, 1982). Being rich in starch and sugar, the parsnip root is used for human consumption (in soups, cakes, muffins, and puddings), animal feed, and winemaking. Its fresh leaves and buds are also used as vegetables for food and soups.
It has various nutritional and therapeutic applications in different countries. For instance, parsnip is used as an appetizer, digestive, and diuretic in some countries. The seeds of parsnip contain bitter aromatic substances that increase milk in lactating mothers and are also used as food spices; it tastes like dill (Matejić et al., 2014).
Pastinaca sativa has different conventional names in different languages such as Zardak and wild carrot in Persian, parsnip in English, Cujtive and Panipainais in French, Jazar in Arabic, and Kajer in India (Emami et al., 2010). From botanical point of view, there is much controversy about distinguishing the parsnip from carrot. Some historians believe the color and taste of the carrots are gradually changed over time; the wild carrots were pale white or yellow and the native carrots were pale yellow or purple. Pale white and yellow carrots may come from mutations in the colored carrot gene.
In the 18th century, Linnaeus for the first time provided separate scientific names for them, naming the carrot Daucus carota L. and parsnip Pastinaca sativa. Galen was the first who explicitly separated carrot from parsnip in his writings (Bahrami et al., 2018;Grant, 2000;Stolarczyk & Janick, 2011).
Wild parsnip is a tall, stout, herbaceous plant with a long, thick, and deep taproot (Gleason & Cronquist, 1991). Wild parsnip is widely distributed in Europe and temperate Asia, where it originated. Wild parsnip is commonly found in waste areas, old fields, and along roadsides and railroad embankments. It grows best in rich, alkaline, and moist soils, but can survive under poor soil conditions (Gleason & Cronquist, 1991). Under summer drought conditions in Oxfordshire, UK, Sternberg et al. (1999) found that the growth of wild parsnip plants in an old field increased and the growth of perennial grasses decreased. This tolerance to drought by wild parsnip may be due to its deep tap root, which allows access to water and nutrients from deeper soil layers (Tutin, 1980). Wild parsnip plants contain at least seven classes of secondary compounds, including terpenes, flavonoids, polyacetylenes, coumarins, and furanocoumarins (Berenbaum, 1985). Some of the compounds are phenylpropanoids, such as myristicin, which, when combined with xanthotoxin, is synergistically toxic to some insects (Berenbaum, 1985); monoterpenes, which are attractants for pollinators and antimicrobial agents (Harrewijn et al., 1994); sesquiterpenes, which are known to be toxic and deterrents to insects; and fatty acid esters, which are toxic to the larvae of some lepidopterans (Zangerl & Berenbaum, 1993).
Morphological traits are important parameters for the identification and selection of favorable genotypes as plant breeders can use this information for the development of breeding populations (Greene et al., 2004). Both qualitative and quantitative morphological characteristics are useful for germplasm studies. Generally, qualitative parameters are useful for varietal identification, while quantitative parameters are required for the development of new varieties (Luitel et al., 2018). There are no reports about the morphological traits of parsnip. Therefore, a detailed analysis of morphological variability in parsnip core collection is required to understand the diversity in both the qualitative and quantitative parameters.
This characterization of morphological parameters is considered an important step in the description and classification of germplasm.
Thus, the main objective of the present study was to evaluate morphological characteristics of P. sativa in Isfahan province, Iran, to select superiors.

| Plant material
The present study was performed to evaluate the phenotypic diversity of 69 accessions of parsnip (P. sativa) to select superiors in terms of root quality. The accessions studied were cultivated in Paykan village in Isfahan province, Iran, in the year 2022, under homogeneous conditions in loamy clay soil. Paykan village is located at 32°15′50″ N latitude and 52°10′40″ E longitude. The soil of the researched field was analyzed to determine the amount of elements and check the non-uniformity of the soil. The present experiment was conducted based on a randomized complete block design.

| The characteristics evaluated
The phenotypic diversity of the accessions was investigated using 66 morphological traits ( Table 1). The traits related to dimensions of leaf and root were measured using a digital caliper. A digital scale with an accuracy of 0.01 g was used to measure the weight of root. Total soluble solids (TSS) were determined using a refractometer (pocket PAL-1 ATAGO Corporation, Tokyo, Japan), in Brix. The qualitative traits (

| Statistical analysis
Analysis of variance (ANOVA) was performed to evaluate the variation among accessions based on the traits measured using SAS software (SAS® Procedures., 1990). Simple correlations between traits were determined using Pearson correlation coefficients (SPSS Inc; Norusis, 1998). Principal component analysis (PCA) was used to investigate the relationship between accessions and determine the main traits effective in genotype segregation using SPSS software.
The PCA is the simplest of the true eigenvector-based multivariate analyses. Often, its operation can be thought of as revealing the internal structure of the data in a way that best explains the variance in the data (Iezzoni & Pritts, 1991). Hierarchical cluster analysis (HCA) was performed using Ward's method and Euclidean coefficient with PAST software (Hammer et al., 2001). The first and second principal components (PC1/PC2) were used to create a scatter plot with PAST software.

| RE SULTS AND D ISCUSS I ON
There were significant differences among the accessions investigated (ANOVA, p < .01). Coefficient of variation (CV) was more than 20.00% in the majority of measured characters (64 out of 66 characters), indicating high diversity among the accessions. The range of CV was from 17.02 (in total soluble solids) to 402.61% (in root splitting/cracking tendency) with an average of 64.69 (Table 1).
Foliage width (crown) ranged from 10 to 55 cm with an average of 32.32 ( Table 1) Root shape was tapering (33), obtriangular (10), narrow oblong (5), wide oblong (5), obovate (13), and fusiform (3) (2), and yellow-light orange (2) (Figure 4). The different root color in carrot (D. carota) was conferred by the Y and Y2 loci in chromosomes 5 and 7, respectively, in which Y_Y2_, yyY2_, Y_y2y2, and yyy2y2 genotypes represent white, yellow, pale orange, and orange root color, respectively (Cavagnaro et al., 2011;Ellison et al., 2017). Moreover, the purple root color was due to the deposition of anthocyanin, which was regulated by the genes in the P1 and P3 regions of chromosome 3 (Bannoud et al., 2019(Bannoud et al., , 2021. Color is an important quality parameter of fruits and vegetables evaluated by consumers as it highly affects their marketability (Pathare et al., 2013). In the present study, root color varied greatly among the genetic resources. Most of the accessions showed a differential range of color attributes between the outer and inner parts of the root. This information might be useful for selecting the desired colored carrots because an appropriate color increases consumer acceptance (Nisha et al., 2011).
Significant correlations were observed among some variables (Table 3). The PCA showed 18 independent components that explained 81.98% of the total variance ( Table 4). The PC1 showed positive correlations with number of mature leaves per plant, root length, root diameter at the middle point of the root, root maximum transverse diameter, neck diameter, collar diameter, root diameter at shoulder, root weight, inner core (xylem) diameter at shoulder, inner core (xylem) diameter at root maximum transverse diameter, root diameter of core (xylem) relative to total diameter, outer core (phloem) thickness at shoulder, and outer core (phloem) thickness at root maximum transverse diameter that explained 22.25% of the total variance. Root shape, root tapering, and root tip/end shape were loaded on PC2 and accounted for 7.45% of the total variance. The PC3 was correlated with mature leaf length, length of basal primary leaflet, number of segment tips on lower primary leaflet, and petiole length, accounting for 6.98% of the total variance. Based on the scatter plot generated using PC1 and PC2, the accessions were placed into four groups and most of them were placed in the center of plot ( Figure 5).
PCA has been previously used to investigate the phenotypic di- for future breeding programs as yield is one of the parameters that is considered in commercial breeding programs (Tabor et al., 2016).
However, analysis of seasonal and yearly variations might be useful for gathering information for stable production. The wide variability in both qualitative and quantitative traits found in this study might be useful for identifying genotypes and might be required for the genetic improvement of crops (Hooks et al., 2021;Luitel et al., 2018). It has been reported that differential expression of a number of genes located in chromosomes 1, 2, and 7 is responsible for the differ-

| CON CLUS IONS
The best method of propagation of parsnips is mainly through seed.
Parsnip seeds have a high healing power and do not require any treatment for germination, so it is recommended that the seeds of this plant are collected in the middle of summer and planted directly TA B L E 2 Frequency distribution for the measured qualitative morphological characteristics in the studied P. sativa accessions.  (8) Straight (61) --
F I G U R E 3 Diversity between P. sativa accessions studied in terms of root shape.

TA B L E 4 (Continued)
F I G U R E 6 Ward cluster analysis of the studied P. sativa accessions based on morphological traits using Euclidean distances. seeds per hectare is harvested. The accessions studied here showed high phenotypic diversity and some of them can be selected and cultivated. Therefore, the promotion and development of parsnip plant cultivation, as a native plant adaptable to ecological conditions, is recommended. Based on ideal values of the important and commercial characters of parsnip, such as root length, root weight, inner core (xylem) pigmentation/color, root shape, flesh color intensity, flesh palatability, and total soluble solids, 14 genotypes, including Parsnip-3, Parsnip-9, Parsnip-24, Parsnip-32, Parsnip-32, were promising and are recommended for cultivation.

ACK N OWLED G M ENTS
None.

CO N FLI C T O F I NTER E S T S TATEM ENT
The authors declare no conflict of interest.

DATA AVA I L A B I L I T Y S TAT E M E N T
The data that support the findings of this study are available from the corresponding author upon reasonable request.