ARTÍCULOS
Selection of artichoke plants and analysis of correlation between quantitative traits for fresh consumption
Reolon-Costa, A; M.F. Grando, V.P. Cravero and A. Almeida
A. Reolon-Costa, M.F. Grando and A. Almeida: University of Passo Fundo (Universidade de Passo Fundo), Passo Fundo, Rio Grande do Sul, Brazil. School of Agronomy and Veterinary Medicine (Faculdade de Agronomia e Medicina Veterinário), Graduate Course on Agronomy, University of Passo Fundo (Universidade de Passo Fundo), Passo Fundo, RS, Brazil. V.P. Cravero: Departamento de Mejoramiento Genético y Producción de Semillas, Facultad de Ciencias Agrarias, Universidad Nacional de Rosario, Rosario, Santa Fe, Argentina. Correspondence to: angelreolon@hotmail.com.
SUMMARY
The goals of the present study were to evaluate and select artichoke plants suitable for fresh consumption and to establish correlations between quantitative traits. Clones from 39 accessions were obtained from the germplasm collection of the University of Passo Fundo and evaluated for 17 quantitative and 3 qualitative traits. Data on quantitative traits were subjected to analysis of variance followed by a Tukey test at p<0.05 to compare averages, and correlations were analyzed using the Pearson product moment correlation coefficient. Significant differences were observed for 9 of the 17 quantitative traits analyzed, and 10 of the 39 accessions presented higher values for some of those traits than the remaining tested accessions. Significant correlations were observed between several traits and the capitulum yield, which makes indirect selection easier. For the qualitative traits, nine accessions were selected that presented circular head, violet colored bracts and absence of thorns, which are desirable traits for fresh consumption.
Keywords: Artichoke; Fresh consumption; Quantitative traits.
Seleccion de plantas de alcachofa y análisis de correlación entre caracteres cuantitativos para consumo en fresco.
RESUMEN
Los objetivos del presente estudio fueron evaluar y seleccionar plantas de alcachofa aptas para consumo en fresco y establecer correlaciones entre caracteres cuantitativos. Treinta y nueve accesiones pertenecientes a la colección de germoplasma de la Universidad de Passo Fundo fueron clonadas y luego evaluadas para 17 caracteres cuantitativos y 3 cualitativos. Los datos correspondientes a los caracteres cuantitativos fueron sometidos a análisis de varianza seguido por una prueba comparación de valores medios de Tukey (p<0,05); las correlaciones fueron analizadas utilizando el coeficiente de correlación de Pearson. Se observaron diferencias significativas para 9 de los 17 caracteres cuantitativos analizados y 10 de las 39 accesiones mostraron elevados valores para algunos de esos caracteres. Se observaron valores significativos de correlación entre varios caracteres y el rendimiento, lo que facilita la selección indirecta. Considerando los caracteres cualitativos, se seleccionaron nueve accesiones por presentar capítulo esférico, brácteas violetas y ausencia de espinas, las cuales son características deseables para el consumo en fresco.
Palabras clave: Alcachofa; Consumo en fresco; Caracteres cuatitativos
Fecha de recepción: 03/10/14;
fecha de aceptación: 09/06/15
INTRODUCTION
Artichoke is a crop originating from the
Mediterranean basin. Its immature head is eaten
both fresh and industrially processed. Its high
nutritional and medicinal value (Foti & Mauromicale,
1994) has generated interest in its cultivation in
Brazil. However, in contrast with other vegetable
crops, there are no intensive improvement programs
for artichoke in Brazil. There are also few cultivars
adapted to the state of Rio Grande do Sul (RS), and
the commercially available cultivars do not present
the uniformity of quality parameters demanded by
the market for fresh consumption (Reolon-Costa et
al., 2012).
The establishment of a genetic improvement
program for this crop, with the goal of developing
cultivars adapted to RS and with uniform traits,
especially in terms of shape (circular), head color
(violet) and bract thorns (absence of thorns),
could make new varieties available to the region's
producers and provide incentive for the distribution
of a new and profitable crop. However, producing
new varieties requires genetic variability for these
traits (Cointry et al., 1999).
After the existence of variability is determined,
the next stage is the selection of genotypes and/or individual plants presenting traits desirable for
fresh consumption. These genotypes can be used
as parental lines for hybridization with the goal of,
for example, establishing an initial base population
for phenotypic recurrent selection. An important
factor in this process is the degree of correlation
between the evaluated traits (Carvalho et al., 2003).
Correlation coefficients can therefore be used as selection criteria, associating a trait that is easy to
evaluate with another that is more difficult or time-consuming to assess.
The goals of the present study were to evaluate
and select plants suitable for fresh consumption
from a collection of artichokes from the University of
Passo Fundo and to establish correlations between
the major quantitative traits.
MATERIALS AND METHODS
This study consisted of the evaluation of 39
accessions pre-selected from the artichoke
germplasm collection from the University of Passo
Fundo based on the presence of desirable traits
for fresh consumption such as circular shape,
violet color and absence of thorns at the external
bracts. These accessions originated from varieties
GG - Green globe (11 plants), GGI - Green Globe
improved (19 plants), RM - Romanesco (5 plants),
VS - Violet the Sicilia (1 plant), RO - Roxa Romana
(1 plant) and RE - Roxa Redonda (2 plants).
The assay was conducted at Passo Fundo,
Planalto Médio region of Rio Grande do Sul
state, at 687 m altitude. The climate of the region
is characterized as fundamentally humid and
subtropical (Kuinchtner & Burial, 2001).
The pre-selected accessions were cloned:
axillary buds of each plant were collected at the
end of the harvest (January 2010) and considered
replicates of each mother plant evaluated.
Seedlings collected in the feld were established
in flower box-type recipients containing 3 kg
commercial substrate, and they were kept in a greenhouse until being transferred into the field.
Seedlings were established in the field in April
2010, with a completely randomized experimental
design, with 4 to 6 replicates (buds) per mother
plant.
Evaluations were performed when the primary
capitulum reached the commercial stage, or Stage
4 (Baggio et al., 2012), in terms of the following
quantitative traits: length, width and thickness of
the bract base (mm), length, diameter (cm) and
fresh mass of the primary head (g), diameter,
thickness (mm) and fresh mass of the bottom (g)
of the primary head, harvest duration, period from
planting until harvest, number of secondary heads
(head massing more than 100 g), height, diameter
(cm) and fresh mass of secondary head (g), total
head per plant at the end of the harvest, and yield
(total number of head x head fresh mass).
The following qualitative traits were evaluated:
(1) shape of primary head: circular, elliptical,
oval, triangular or large transverse elliptical; (2)
external bract color: green, violet-striped green,
green-striped violet, mostly violet, or completely
violet; and (3) presence or absence of thorns at the
external bracts.
Quantitative data were subjected to analysis
of variance (ANOVA) followed by a Tukey test,
with p<0.05 considered significant. Correlations
between quantitative traits were tested by
calculating the Pearson product-moment
correlation coefficient. Quantitative traits were
visually assessed, and the percentage of plants in
each category was recorded.
RESULTS AND DISCUSSION
Significant differences among the 39 studied accessions were observed for 9 of the 17 traits evaluated (p<0.05): length and width of the bract base of the primary head, harvest duration, number, height, diameter and fresh mass of secondary head, total head per plant and yield (Table 1).
Table 1: Analysis of variance for 17 quantitative characters
evaluated in 39 plants of artichoke, Passo Fundo -2014
Analysis of variance (p<0.05*) length of the bract base (LBB), width
of the bract base (WBB), thickness of the bract base (TBB), length
of the primary head (LPH), width of the primary head (WPH), fresh
mass of the primary head (FPH), diameter of the bottom (DB),
thickness of the bottom (TB), fresh mass of the bottom (FMB),
harvest duration (HD), period from planting until harvest (PPH),
number of secondary heads (NSH), height of secondary heads
(HSH), diameter of the secondary heads (DSH), fresh mass of the
secondary heads (FSH), total heads per plant at the end of the
harvest (TPH) and yield (Y).
The observed variations in the evaluated traits
between accessions may be due to genetic
differences because the mother plants of the
germplasm collection were mostly established from
seed (and thus each plant has a different genotype),
to environmental differences, and sometimes to
interactions between genotype and environment.
However, variability between replicates (clones)
of a given mother plant are due to environmental
effects because the replicates possess the same
genetic makeup.
The highest coefficients of variation were observed for traits that can be influenced by
environmental factors, including bottom fresh
mass, bract base thickness, number of secondary
heads, yield and total head per plant (Table 1). This
was expected because these traits are governed
by many genes with additive effects, and they
present continuous phenotype distribution and low
heritability (Cointry et al., 1999).
Cravero et al. (2004) also observed significant
variations in fresh mass, height, diameter and
number of secondary heads and yield, but with
lower coefficients of variation than the ones found
in the present study. The authors also observed
higher variation for secondary than for primary
head fresh mass. In the present study, however,
no significant variations were observed in primary
head fresh mass or length or in bottom thickness
or fresh mass. This may be because the evaluated
accessions were pre-selected based solely on the
appearance of the primary head.
However, the existence of variability among
the accessions evaluated allows better use of
these genotypes, as well as the identification of
superior plants based on traits useful for selection.
These plants could then be used as progenitors in crossings with the goal of establishing new
segregating populations onto which different
selection models and improvement methods could
be applied, such as recurrent phenotypic selection
(Cointry et al., 1999; Cravero et al., 2004).
The edible parts of the artichoke are the bract
base and the bottom (flower receptacle). The
evaluation of these traits is therefore important
because they can be used as parameters of head
quality for fresh consumption (Reolon-Costa et al.,
2012). Accessions GGI16 and GGI76 presented
greater bract base length than accessions
RM6, RM2, GG15, GG19 and GGI57 and were
not significantly different from the remaining
accessions evaluated. For the bract base width,
accessions GG40 and GG31 were superior to 20
of the remaining accessions evaluated, and they
were not significantly different from accessions
GGI67, GGI70, GGI72, GGI76, GGI13, GGI9,
GGI16, GGI38, GGI65, GGI64, GGI58, GGI29,
GG39, GG29, VS5, RM1 and RE21 (Figure 1a).
The deviation for this trait varied between 0.52 and
12.22 mm. Variation was also observed between
replicates (clones); this variation was environmental
in origin and not genotypic because the replicates
are genetically identical.
Figure 1. Comparison of averages by Tukey test at 5% of probability de error for characters: length of the bract base (a), duration harvest
(b), height of the secondary heads (c), diameter of the secondary heads (d), between 39 plants of artichoke. Letters comparing the
averages between treatments, Passo Fundo - 2014.
Harvest duration is correlated with the time
over which the plants remain productive and
corresponds to the period between the harvest
of the primary head and the harvest of the last
secondary head with acceptable market traits (in
this case, head with fresh mass greater than 100
grams). This trait influences total plant productivity
and depends on environmental conditions and plant
vegetative vigor. GGI64 presented longer duration
of the harvest period than accessions RO26, RM4,
GG19, GGI29, GGI65 and was not significantly
different from the remaining accessions evaluated.
This trait varied between 9 and 16 days (Figure 1b).
Accession GGI38 presented high average
height for secondary head, significantly different
from accessions GGI71 and GGI13. For the
secondary head diameter, accessions RO26
and GG9 were larger than GGI72 but were not
significantly different from the remaining evaluated
accessions (Figures 1c, d).
Among the traits related to productivity, the fresh
masses of the primary and secondary head are
highlighted. Accession GG39 presented higher
averages for these two traits than accessions RM4,
GG29, GGI58, GGI19, GGI16 and GGI72 (Figure
2a). A wide range of variation was also observed
for this trait, between 0.82 g and 163.2 g, indicating
the possibility of its selection. The production of
head with higher fresh mass is important for both consumption fresh and production of hearts and
bottoms for the canning industry.
Figure 2. Comparison of averages by Tukey test at 5% of error probability for characters: fresh mass of the primary heads (a), number
of the secondary heads (b), total heads per plant (c) and yield (d) between 39 plants of artichoke. Letters comparing the averages
between treatments, Passo Fundo - 2014
Accession GGI19 presented higher numbers
of secondary heads than 10 of the remaining
accessions evaluated (Figure 2b). GGI19 was also
superior to the majority of the tested accessions in
the total head per plant (Figure 2c). The number of
head per plant is a varietal trait (Foti & Mauromicale,
1994; Miccolis et al., 1999) and the main yield
component in artichoke (Cravero et al., 2004).
Accessions GGI19 and GGI70 presented higher
yield per plant than accessions RM4 and GGI71
(Figure 2d). The large observed range of variation
for the yield (220.73 to 719.21 g) was because this
trait is determined by several genes with minor
effects and low heritability and is influenced by
environmental factors (Borém & Miranda, 2009).
Accession GGI19 also presented higher
numbers of secondary heads and head per plant,
along with good yield (1000 g). This is consistent
with Bagget et al. (1982) and Cravero et al. (2004),
who reported that the yield is mainly influenced by
the number of heads and less by their fresh mass.
This also suggests the existence of a correlation
between these traits and poses the following two
questions: Is there a correlation between these
traits? What is the degree of this correlation?
The Pearson product-moment correlation
coefficient tests the correlation between variables
(Falconer & Mackey, 1996) and estimates the joint
influence of genetic and environmental factors on
the expression of a given trait (Ferreira et al., 2003).
The estimation of these associations allows indirect
selection and allows the analysis of a smaller
number of variables in an improvement program.
Bract base length was positively correlated with
bract base thickness and bottom fresh mass, and it
was negatively correlated with harvest duration. A
significant positive correlation was also observed
between the bottom thickness and diameter (Table
2).
Table 2: Significant values of correlation of Pearson between
characters assessed between plants of artichoke of different
cultivars, Passo Fundo - 2013
Significant at 1 and 5% of probability by test t, length of the
bracts base (LBB), width of the bracts base (WBB), thickness of
the bracts base (TBB), length of the primary head (LPH), diameter
of the primary head (DPH), fresh mass of the primary head (FMP),
diameter of the bottom (DB), thickness of the bottom (TB), fresh
mass of the bottom (FB), harvest duration (HD), period from
planting until harvest (PPH), number of the secondary heads
(NSH), height of the secondary heads (HSH), diameter of the
secondary heads (DSH), fresh mass of the secondary heads
(FSH), total of heads per plant (THP) and yield (Y).
Bottom fresh mass is also significantly correlated
with bottom diameter and thickness, primary head
length and diameter, and bract base thickness
and length. This indicates that selecting head with
higher diameter will indirectly select head with
higher bottom fresh mass, diameter and thickness,
eliminating the need for specific evaluations of
these traits, thereby resulting in higher efficacy and
speed of the selection process.
Of the productivity traits, the primary head fresh
mass was significantly positively correlated with
the bottom fresh mass, secondary head average
height, and duration of the harvest period. Another
relevant productive trait with high impact, especially on the marketable yield, is the total head per plant,
which was significantly positively correlated with
the yield and negatively with the secondary head
fresh mass. Through these results, we can infer that, the higher the number of heads per plant, the
lower their individual fresh mass of heads. This is
due to the higher number of sinks competing for
photoassimilates at the plant. Crippa et al. (2011) also observed that plants with more heads produce
higher final yields.
The total number of heads per plant was also
positively correlated with the number of secondary
heads, whereas the number of secondary heads
was significantly negatively correlated with the
secondary head fresh mass, height and diameter,
again showing an inverse correlation between
the head number and fresh mass and size. This
answers the initial questions and confirms the
existence of a correlation between the yield and the number of secondary head and number of heads
per plant (Table 2).
Correlation studies of traits with selection interest
in artichoke have been reported by other authors.
López Anido et al. (1998) evaluated a population
of clones in Argentina and determined the number
of heads at the end of the harvest, fresh mass of
primary and secondary heads, and bottom fresh
mass, to be the traits associated with the yield.
Because the genetic improvement of this crop
must meet the demands of the consumer market,
selection should be applied not only to quantitative
traits such as those mentioned above but also
to qualitative traits of the head (Mauromicale & Copane, 1989). Traits such as color, shape
and absence of thorns at the external bracts,
are therefore of great importance. Accessions
GGI67, GGI20, GGI80, GGI76, GGI12, GGI13,
GGI9, GGI71, GGI65, GGI64, GGI19, GGI58,
GGI29, GG61, GG48, RM1, RM4, RM3, and RM2,
corresponding to 51% of the evaluated accessions,
presented circular primary head (Figure 3a). The
remaining accessions evaluated presented heads
with elliptical, oval and large transverse elliptical
shapes. No triangular head were observed. The
head shape is extremely important for genetic
improvement programs of artichoke because it is
closely related with the head compactness. More
compact heads present a circular shape because
they possess more internal bracts (Reolon-Costa et
al., 2012). Conical heads have lower numbers of
bracts and do not withstand post-harvest handling,
becoming deformed (Foury, 1967). The accessions
listed above, presenting circular heads, could
therefore be selected as progenitors for future
crossings with the goal of improving the capitulum
quality for fresh consumption.
Figure 3. Relative frequencies for each class of characters: shape (a), color of the primary heads (b), presence/absence of thorns (c),
heads of the artichoke (d) and identification the bracts and bottom (e). Passo Fundo - 2014.
The appearance and color are important
qualitative traits for the majority of vegetables
consumed fresh. Artichoke consumers, in particular,
are very sensitive to the head color, and this is a
marker trait of this crop's quality (Aubert, 1976).
Violet head are preferred in several countries,
including France, Italy, Argentina and Brazil. The
present study included 38% violet-striped green
(GGI76, GGI12, GGI13, GGI9, GGI71, GGI16,
GGI81, GGI56, GGI29, GG41, GG68, GG31,
GG40, GG21, GG15), 15% green-striped violet,
7% mostly violet, and no (0%) completely violet
head. The remaining plants had green head (38%)
(Figure 3b).
This shows the existence of variability for this trait
and thus the possibility of selection of plants with
violet head, which can then be used as progenitors
in crossings with the goal of incorporating genes responsible for the violet color. This variability also
shows the need to develop materials with higher
uniformity of head color and possessing the color
required by the consumer market. Capitulum color
is determined by two allele pairs (P, p and U, u) with
complete dominance on each locus and a recessive
epistatic relationship (Cravero et al., 2005).
Another trait that should be considered in the
selection process is the presence of thorns at the
external bracts, which is not desirable for the market
of fresh consumption. Of the accessions evaluated,
49% did not present thorns at the external bracts (GGI20, GGI70, GGI72, GGI12, GGI13, GGI9,
GGI71, GGI81, GGI65, GGI64, GGI19, GGI58,
GG41, GG68, RM1, RM4, RM3 and RM6) (Figure
3c). Thorn absence is determined by a dominant
gene (Sp), and thorn presence is determined by
its recessive form (sp) (Pecaut and Foury, 1992).
It is therefore very difficult to completely eliminate
this trait from a segregating population because it
remains masked in the heterozygote.
In the present study, heads were observed to
present different sizes, shapes and colors, and
variability for the qualitative traits and nine of the quantitative traits evaluated. Knowledge of
this variability, and of the correlation coefficients
between quantitative traits, will allow better use
of the existing materials and the identification of
progenitors that can be used in crossings with the
goal of establishing a segregating population onto
which various selective models can be applied.
Table 3: Description of 39 plants assessed as three main characters of head quality for fresh consumption, Passo Fundo - 2014
Based on their quantitative traits, eight accessions
(GGI16, GG40, GG31, GG15, GG39, GGI38, RO9
and GGI19) stand out for traits including bract base
length, bract base width, harvest duration, fresh mass, height and diameter of secondary head,
number of secondary head, total heads per plant,
and yield and could therefore be selected. However,
when qualitative traits are considered, accessions
GGI12, GGI13, GGI9, GGI71, GG41, GG68, RM4,
RM3 and RM6 presented all the desirable traits for
fresh consumption: circular shape, violet color, and
absence of thorns (Figure 3d and 3e).
The selection of progenitors for genetic
improvement is directed by the market demand and
the goals of the selection program. Considering the lack of uniformity of the Brazilian varieties for traits
related to head quality and that the main goal of the
improvement program started at the University of
Passo Fundo is to improve head quality.
CONCLUSIONS
(a) Nine accessions were superior for
qualitative traits and can be selected for inclusion
in crossing blocks with the goal of short-term
improvements.
(b) Ten accessions that stood out for the
evaluated quantitative traits can be maintained at
the collection and included in future cross.
ACKNOWLEDGMENTS
The authors thank the Associated Centers for the Support of Brazil-Argentina Graduate Studies Program (Programa Centros Associados para o Fortalecimento da Pós-Graduação Brasil-Argentina - CAFP-BA) of the Brazilian Federal Agency for the Support and Evaluation of Graduate Education (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior- CAPES) for the financial support and sandwich PhD scholarship granted to Angélica Reolon da Costa and to the National Council for Scientific and Technological Development (Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq) for the Scientific Initiation scholarship granted to Ariel Almeida.
REFERENCES
1. Aubert, S., 1976. Influence de la couleur des aliments et boissons sur acceptabilité: Quelques exemples. Diétét 11:15-30.
2. Bagget, J.R.; H.J. Mack and D. Kean, 1982. Annual culture of globe artichoke from seed. HortScience 7:766-768.
3. Baggio, M.I.; F. Palla, D.S. Boscardin, N. Mantovani, M.F. Grando, L. Augustin, M. Suzin e B. Donida, 2012. Floral biology of artichoke (Cynara scolymus L.) Nobre-UPF brazilian cultivar. Acta Horticulturae 942:297-302.
4. Borém, A e G.V. Miranda, 2009. Melhoramento de Plantas. 2ta. Edição. Editora Universidade Federal de Viçosa, Viçosa, pp. 324-330.
5. Carvalho, C.G.P.; C.M.V.C. Almeida, C.D. Cruz and P.F.R. Machado, 2003. Hybrid cocoa tree adaptability and yield temporal stability in Rondônia State, Brazil. Crop Breeding and Applied Biotechnology 3:237-244.
6. Cointry, E.L.; F.S. López Anido, S.M. García y I.T. Firpo, 1999. Mejoramiento genetico del alcaucil (Cynara scolymus L.). Avances en Horticultura 4:51-60
7. Cravero, V.P.; F.S. Lopez Anido, P.D. Asprelli and E.L. Cointry, 2004. Diallel analysis for traits of economic importance in globe artichoke (Cynara scolymus). New Zealand Journal of Crop and Horticultural Science 32:159-165.
8. Cravero, V. P.; L.A. Picardi and E.L. Cointry, 2005. An approach for understanding the heredity of two quality traits (head color and tightness) in globe artichoke (Cynara scolymus L.). Genetic and Molecular Biology 28:431-434.
9. Crippa, I.; E.A. Martín, M.A. Espósito, V.P. Cravero, F. López Anido and E.L. Cointry, 2011. Correlation and path-coefficient analysis in half sib families of globe artichoke (Cynara cardunculus var. scolymus (L.) Fiori). Electronic Journal of Plant Breeding 2:151-15.
10. Falconer, D.S and T.F.C. Mackay, 1996. Introduction to Quantitative Genetics. 1ta. Edição. Editora Addison Wesley Longman Limited, Londres, pp. 205-240.
11. Ferreira, M.A.J.F.; M. Queiroz, A. Braz e R. Vencovsky, 2003. Correlações genotípicas, fenotípicas e de ambiente entre dez caracteres de melancia e suas implicações para o melhoramento genético. Horticultura Brasileira 21:438-441.
12. Foti, S.E e G. Mauromicale, 1994. Sul miglioramiento del calendario di produzione del carciofo e delle caratteristiche di qualita del prodotto mediante la diffusione di nuove varieta. Semente Elette 40:19-29.
13. Foury, C., 1967. Study floral biology of artichoke (Cynara scolymus L.) Application in the selection. Amélior Plantes 17:357-373.
14. Kuinchtner, A e G.A. Burial, 2001. Clima do estado do Rio Grande do Sul segundo a classificação de Köppen e Thornth waite. Disciplinarum Scientia 2:171-182.
15. López Anido, F.S.; I.T. Firpo, S.M. García and E.L. Cointry, 1998. Estimation of genetic parameters for yield traits in globe artichoke. Euphytica 103:61-66.
16. Mauromicale, G e L. Copane, 1989. Caratteristiche biologiche e produzione di cloni diversi di carciofo isolati in popolazioni siciliane di "Violeto di Silicia". Técnica Agricola 4:1-17.
17. Miccolis, V.; V.V. Bianco, A. Elia, P. Perrino e N. Volpe, 1999. Valutazione della collezione Mediterranea di carciofo allevata nella valle dell' Ofanto. L'Informatore Agrario 45:35-41.
18. Pecaut, P et C. Foury, 1992. L´artichaut. In: GALLAIS, A.; BANNEROT, H. Amelioration des espèces cultivées. 1ta edição. Editora INRA, Londres, pp. 460-470.
19. Reolon-Costa, A.; M.F. Grando, S.M. Scheffer-Basso and V.P. Cravero, 2012. Morphophysiological characterization in artichoke accessions aimed at selecting materials for fresh consumption. Acta Scientiarum Agronomy 43:431-437.