A descriptor list of Silybum marianum (L.) Gaertner – morphological and biological characters

Abstract

Silybum marianum (L.) Gaertn (Milk thistle) is an important medicinal plant which fruits are used for treatment of various liver diseases. In an effort to utilize the genetic potential of cultivated plants in the best way, the breeding of new high-performance cultivars is underway all over the world. Genetic improvement in Silybum can only be, as with all other plants, achieved through a clear understanding of the plant´s behaviour and the amount of variability presented in wild populations. Surprisingly no descriptor list has been compiled up to now, which would permit an objective and easily repeatable description an evaluation of the different Silybum genotypes. The first part of such a descriptor list, which is intended mainly for evaluation of genotypes perspective for fruit production, is presented here and it contains both the morphological and biological characters.

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6th International Symposium Breeding Research on Medicinal and Aromatic Plants, BREEDMAP 6, Quedlinburg, Germany, June 19-23, 2016
Julius-Kühn-Archiv, 453, 2016 107
P 5: A descriptor list of Silybum marianum (L.) Gaertner – morphological and
biological characters
Elena Dušková, Karel Dušek, Kateřina Smékalová
Department of Genetic Resources for Vegetables, Medicinal and Special Plants, Centre of the
Region Haná for Biotechnological and Agricultural Research, Crop Research Institute, Šlechtitelů 29, Olomouc,
78371, Czech Republic, e-mail: Smekalova@genobanka.cz (corresponding author)
DOI 10.5073/jka.2016.453.038
Abstract
Silybum marianum (L.) Gaertn (Milk thistle) is an important medicinal plant which fruits are used for
treatment of various liver diseases. In an effort to utilize the genetic potential of cultivated plants
in the best way, the breeding of new high-performance cultivars is underway all over the world.
Genetic improvement in Silybum can only be, as with all other plants, achieved through a clear
understanding of the plant´s behaviour and the amount of variability presented in wild popula-
tions. Surprisingly no descriptor list has been compiled up to now, which would permit an objec-
tive and easily repeatable description an evaluation of the different Silybum genotypes. The first
part of such a descriptor list, which is intended mainly for evaluation of genotypes perspective for
fruit production, is presented here and it contains both the morphological and biological charac-
ters.
Keywords: Milk thistle, evaluation descriptors, production of fruits
Introduction
Silybum marianum (L.) Gaertn (Milk thistle) is an important medicinal plant of which pharmaceuti-
cal importance rises once again and it is grown commercially almost all over the world. Its fruits
(i.e. achenes), often referred to as seeds, have been valued for their medicinal properties (GAŽÁK et
al., 2004) and currently the most important medicinal application of Silybum is its use as a
hepatoprotectant and as supportive treatment of chronic inflammatory liver disease such as cir-
rhosis, hepatitis, and fatty infiltration due to alcohol and toxic chemicals. It has also been used in
the treatment of liver damage by poisonous mushrooms (KVASNIČKA et al., 2003).
Despite the wide use and considerable volume of Silybum sales - 8,312,867 USD in 2005
(BLUMENTHAL et al., 2006) – there is lack of research efforts on the domestication and improvement
of this plant (RAM et al., 2005) but the breeding of new high-performance cultivars is underway all
over the world. The first step in breeding of wild or native populations is collection and description
of genetic variation of plant populations for desired characters (SHOKRPOUR et al., 2011). Genetic
improvement in Silybum can only be, as with all other plants, achieved through a clear under-
standing of the plant´s behaviour and the amount of variability presented in wild populations,
including genotypes which may represent the maximum expression of adaptation capability to
environmental conditions. The selection of an ideotype with desirable traits will facilitate
agrotechnology and allows to maximal yield (GRESTA et al., 2006).
An objective and easily repeatable evaluation of many important crops is made possible by using
descriptor lists. Surprisingly no descriptor list for different Silybum genotypes has been drawn up
up to now and therefore the first part of such a descriptor list is presented here. It is intended
mainly for evaluation of genotypes perspective for fruit production and it contains both the mor-
phological and biological characters.
Materials and Methods
Presented descriptor list of Silybum marianum was created based on the references for the devel-
opment of crop descriptor lists (BIOVERSITY INTERNATIONAL, 2007) and it comprises results and experi-
ences of 5 years growing and evaluating of milk thistle genetic resources, which were collected in
the Czech gene bank. Own measurements and evaluation, acquired in the period 2007-2009 in

6th International Symposium Breeding Research on Medicinal and Aromatic Plants, BREEDMAP 6, Quedlinburg, Germany, June 19-23, 2016
108 Julius-Kühn-Archiv, 453, 2016
locality Olomouc (CZE) and 2013-2014 in localities Olomouc and Znojmo (CZE), were confronted
and supplemented by many literature references from scientific papers. The presented descriptor
list is intended mainly for the evaluation of genotypes perspective for fruit production. In case of
evaluation in order to other use (fodder plant, production of biomass, ornamental plant, weed
etc.) some additional characters should be added.
Results
The first part of milk thistle descriptor list is presented in Tab. 1 and it contains both the morpho-
logical and biological characters. The economic characters, as the total silymarin and oil content
and the content of its components, are processed.
Tab. 1 Descriptor list of Silybum marianum – Morphological and Biological characters
DescriptorScale Values Note
1.Morphologicalcharacters
1.1PlantAverageof10randomlyselectedplants.
1.1.1Planthabit1erect Recordedinterminalheadfullfloweringstage.
2semi‐erect
1.1.2Plant–height
(cm)
3low <110 Recordedinterminalheadfullfloweringstage;from
groundleveltothetopofterminalhead.
5intermediate 110‐140
7high >140
1.1.3Plant–width
(cm)
3small <70
Recordedinterminalheadfullfloweringstage.
5intermediate 70‐ 90
7great >90
1.1.4Plant‐length
offloweringstem
(cm)
3short <50 Length ofstemfromfirstbranchingpointtothetopof
terminalhead;recordedinterminalheadfullflowering
stage.
5intermediate 50‐ 70
7long >70
1.1.5Plant‐
intensityof
branching
3low <10Numberoffertilebranchesperplant.Recordedatharvest
time.
5intermediate 10‐ 20
7high >20
1.2Lea
f
Averageof10leaves,eachleaffromdifferentrandomlyselectedplant.
1.2.1Rosetteleaf–
length(cm)
3short <50 Fullydevelopedleavesincludingpetiole,inthebeginning
ofstageofgenerativeorgancreation.
5intermediate 50‐ 65
7long >65
1.2.2Rosetteleaf–
width(cm)
3narrow <25 Recordedinthewidestpointoffullydevelopedleaves,in
thebeginningofstageofgenerativeorgancreation.
5intermediate 25‐ 27
7wide >27
1.2.3Rosetteleaf‐
depthofincisions
3pinnatilobed <1/3
Fig.1;Deepofincisionsofblademargintothemainvein.
5pinnatipart 1/3‐ 1/2
7pinnatifid >1/2
1.2.4Rosetteleaf‐
degreeofmarbling
0absent
Fig.2
3low
5medium
7high
1.3Inflorescence
1.3.2Diameterof
primaryhead(cm)
3small <4,5 Averageof20randomlyselectedplants.Recordedin
terminalheadfullfloweringstage.
5intermediate 4,5‐ 5,5
7great >5,5
1.3.3Inflorescence
‐numberofheads
perplant
3small <6Numberofotherflowerheadsperplant(exceptthe
primaryhead).Recordedinterminalheadfullflowering
stage.
5intermediate 6‐ 9
7great >9
1.3.4Flower‐
colour
1white
AspresentorusingRHScolourchart.
2creamy
3pinkish
4lightviolet
5darkviolet
6other

6th International Symposium Breeding Research on Medicinal and Aromatic Plants, BREEDMAP 6, Quedlinburg, Germany, June 19-23, 2016
Julius-Kühn-Archiv, 453, 2016 109
DescriptorScale Values Note
1.4FruitRecordedinfullmaturitystage.
1.4.1Fruit–length
(mm)
3small <7Averageof20randomlyselectedfruits;acheneswithout
crest.
5intermediate 7‐ 8
7great >8
1.4.2Fruit–width
(mm)
3small <3Averageof20randomlyselectedfruits;inthewidestpart
offruit.
5intermediate 3‐ 4
7great >4
1.4.3Fruit‐colour
1darkbrown

Themaincolouroftheseedisthecolourwiththelargest
area.AspresentorusingRHScolourchart.
2brownblack
3other
1.4.4Numberof
fruitsonprimary
flowerhead
3low <80
Averageof10randomterminalflowerheads.
5intermediate 80‐ 120
7high >120
1.4.5Fruit‐Yield
perplant(g)
3low <15 Averageof10randomplants.Yieldofallgradually
harvestedflowerheadsofplant.ExamplevarietySILYB
(CZE,1988).
5intermediate 15‐ 30
7high >30
1.4.6Fruit‐1,000
fruitsweight(g)
3low <20

5intermediate 20‐ 25
7high >25
2.Biologicalcharacters
2.1Vegetationperiod
2.1.1Numberof
daysfromsowing
tobeginningof
generativeorgans
creating(days)
3early<80Beginningofgenerativeorganscreating=flowercentral
headclearlyvisiblebetweenrosetteleaves,verticalbract
tips.ExamplevarietySILYB(CZE,1988).
5intermediate80‐90
7late>90
2.1.2Numberof
daysfromsowing
tobeginningof
terminalhead
flowering(days)
3early<90
Beginningofterminalheadflowering=theflowerbud
bends;firstflowerinblossom.
5intermediate90‐100
7late>100
2.1.3Numberof
daysfromsowing
toterminalhead
maturit
y

(
da
y
s
)

3early<100Terminalheadmaturity=Thebractsaredry.Theheadis
openingandthepappusisvisibleandseeddispersalstart.
5intermediate100‐115
7late>115
2.2Bioticstresssusceptibility
Ineachcase,itisimportanttostatetheoriginoftheinfestationorinfection,i.e.natural,fieldinoculation,
laboratory.Recordsuchinformationindescriptor2.2Notes.Thesearecodedonasusceptibilityscalefrom1
to9
,
viz.:

1verylowornovisiblesignofsusceptibility
3low
5intermediate
7high
9veryhigh
2.2.1Botrytiscinerea ‐Botrytisheadrot
2.2.2Septoriasilyb
i
‐Septorialeafspot
2.2.3
A
lternariasilybi‐ Alternarialeafspot
2.2.4Fusariumoxysporum‐Fusariumwilt
2.2.5Golovinomycescichoracearum‐ Powderymildewofmilkthistle
2.2.others

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110 Julius-Kühn-Archiv, 453, 2016
Fig. 1 Depth of incisions of blade margin to the main vein (scale examples)
Fig. 2 Rosette leaf - degree of marbling (scale examples)
Acknowledgement
The financial support of grant No. LO1204 is gratefully acknowledged. The plant material was
obtained thanks to the National Programme on Conservation and Utilization of Plant, Animal and
Microbial Genetic Resources for Food and Agriculture No. 206553/2011-MZE-17253.
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