مقایسه فیلوژنتیک ژنوم A در برخی از گونه‌های جنس Triticum با روش تحلیل کاریوتیپ

نویسندگان

1 گروه زراعت و اصلاح نباتات، دانشکده کشاورزی، دانشگاه صنعتی اصفهان، اصفهان، ایران

2 گروه زیست‌شناسی، دانشکده علوم، دانشگاه اصفهان، اصفهان، ایران

چکیده

کاریوتیپ 48 جمعیت از پنج گونه Triticum aestivum)، T. durum، T. monococcum، T. turgidum و (T. urartu و دو زیرگونه T. boeoticum subsp. boeoticum و T. boeoticum subsp. thaodar دارای ژنوم A از جنس Triticim تحلیل شد. کروموزوم‌ها با نرم‌افزار Micro Measure 3.3 اندازه‌گیری شد. ویژگی‌های کاریوتیپی شامل: تعداد کروموزوم، طول کلی کروموزوم، میانگین طول کروموزوم‌‌ها، درصد شکل کلی کاریوتیپ، اندیس سانترومری، طول بلندترین کروموزوم، طول کوتاه‌ترین کروموزوم، میانگین طول بازو‌های بلند، میانگین طول بازو‌های کوتاه، نسبت بازو‌ها، اندیس عدم تقارن کاریوتیپی، درصد نسبت بین کوتاه‌ترین و بلندترین کروموزوم‌‌ها، تفاوت دامنه طول نسبی کروموزوم‌‌ها، اندیس تقارن درون کروموزومی، اندیس تقارن میان کروموزومی، طول نسبی کروموزوم‌‌ها و فرمول کاریوتیپی اندازه‌گیری و محاسبه گردید. تمام جمعیت‌ها در گروه A1 طبقه‌بندی Stebbines قرار گرفتند. تحلیل خوشه‌ای بر پایه ضرایب A1 و A2 سه گروه کاریوتیپی را در جمعیت‌های مطالعه شده ایجاد کرد: گروه نخست شامل T. aestivum با بیشترین عدم تقارن کاریوتیپی، گروه دوم شامل T. boeoticum subsp. boeoticum، T. boeoticum subsp. thaodar و T. monococcum و با کمترین عدم تقارن کاریوتیپی و گروه سوم شامل T. durum، T. turgidum و T. urartu و با جایگاهی مابین دو گروه قبل. گونه‌های دیپلوئید T. monococcum بر اساس ضرایب A1 و A2 قدیمی‌ترین و ابتدایی‌ترین کاریوتیپ را داشت. با توجه به نتایج به نظر می‌رسد T. durum ابتدایی‌تر از T. turgidum باشد و احتمالاً T. monococcum می‌تواند به عنوان دهنده ژنوم A به T. aestivum و T. durum به حساب آید.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Phylogenetic comparison of the A genome using karyotype analysis in some Triticum species

نویسندگان [English]

  • Mohammad Hosein Ehtemam 1
  • Mohammad Reza Rahiminejad 2
  • Hojatollah Saeidi 2
  • Fatemeh Ebrahim 1
1 Department of Agronomy and Plant Breeding, College of Agriculture, Isfahan University of Technology, Isfahan, Iran
2 Department of Biology, Faculty of Sciences, University of Isfahan, Isfahan, Iran
چکیده [English]

The Karyotype analysis was performed on 46 wheat accessions belonging to five species (Triticum monococcum, T. urartu, T. durum, T. turgidum and T. aestivum) and two subspecies (T. boeoticum subsp. thaodar and T. boeoticum subsp. boeoticum) carrying A genome. All chromosomal sizes were measured with computer-aided program Micro Measure 3.3. Software. RL, TCL, MCL, arm ratio, centromeric index, TF%, mean of long and short arms, AsI%, S%, DRL, A1, A2 and karyotype formula were calculated for each chromosome. All the accessions were placed in 1A category of stebbines asymmetry categories. The scatter diagram based on A1 and A2 constructed three groups of karyotype asymmetry in the accessions studied: 1- T. aestivum with the highest asymmetrical karyotype, 2- T. monococcum, T. boeoticum subsp. thaodar and T. boeoticum subsp. boeoticum with the lowest asymmetrical karyotype and 3- T. urartu, T. turgidum and T. durum being with an intermediate between the two previous groups. T. monococcum based on the A1 and A2 index (asymmetric index) had the oldest and the most primitive karyotype among diploid species. According to the results, it might be suggested that T. durum is more primitive than T. turgidum and T. monococcum could be considered as a donor of A genome to T. durum and T. aestivum.

کلیدواژه‌ها [English]

  • A genome
  • Karyotype analysis
  • Phylogeny
  • Triticum

Introduction

Plant nuclear genomes are enormously variable. Chromosome number, the degree of gene clustering, and chromosome size can all differ considerably, even between closely related species (Kellogg and Bennetzen, 2004).

The earliest work on wheat chromosomes relied on reconstructions made from microtomal serial sectioning of root tips. The development of squash technique reduced the possibilities of misinterpretations. Studies of the morphology of chromosomes in Triticum species have been made by many workers, including Schulz-Schaeffer and Haun (1961), Khan (1963), Kimber (1971), Johnson and Dhaliwal (1978), Kerby and Kuspira (1987), Miller (1987) and Khan (2005).

Because of different workers had to do without standardization of techniques in different laboratories, their reports showed inconsistencies in the standard karyotype analysis based on chromosome length and arm ratio still holds its merit (Jahan and Vahidy, 1989). The analysis of plant genomes has provided insight into how these evolutionary events have occurred and the rate at which evolution could have taken place. Wheat has played a major role in the development of the world civilization. The domestication of wheat was a major event in the world civilization because it allowed humans to change from nomadic hunter gathers to permanent residents of specific locations. Many useful genes from wild species are available to be used in breeding Programmers as source of genes for disease resistance applying different chromosomal engineering techniques involving backcrosses, "bridges" crosses and selection of cytological as well as desired agronomic characteristics (Stalker, 1980; Dhalival et al., 1986; Gale and Miller, 1987). By 1951, the work of Lilienfeld and colleagues had established many of the genomic relationships of the diploid and polyploid Triticum L. and Aegilops L. species on the basis of chromosome pairing in hybrids (Lilienfeld and Kihara, 1951). These studies have continued to the present and have accurately classified chromosome translocations (Naranjo, 1995; Naranjo et al., 1988; Maestra and Naranjo, 1999; Jauhar et al., 1991). Archaeological evidence has shown that Triticum turgidum L. (AABB) has been grown in both Mesopotamia (Tigris and Euphrates River Valley) and in the Nile River Valley 10,000 years ago. Because wild T. tauschii (Coss.) Schmalh. is found only in the mountain region of south Russia, west Iran and north Iraq, it is thought that the hybridization that produced T. aestivum L. have occurred in these regions. It has been suggested that this occurred as recently as 8,000 years ago which coincides with the development of collective settlements by man (Wazuddin and Driscollt, 1986).

The goal of the present study was to find relationships between Triticum species using karyotype analysis and molecular markers.

 

Materials and Methods

Plant materials

A total of 46 wheat accessions were collected for this study. The materials were taxonomically identified based on Rahiminejad and Kharrazyan (2005). The Karyotype analysis was performed on the accessions belonging to five species and two subspecies carrying A genome (Triticum monococcum L., T. boeoticum Boiss. subsp. thaodar (Reut.) Schiemann, T. boeoticum subsp. boeoticum, T. urartu Tumanian ex Gandilyan, T. durum Desf., T. turgidum and T. aestivum) (Table 1).

Chromosome spread preparation

Triticum seeds were germinated at 25ºC on moist filter paper in Petri dishes. Actively-growing root tips, 1 cm in length, were excised from the germinating seeds and pretreated with α-bromonaphthalene for 4-6 hours at 4ºC in refrigerator and fixed in chromic acid-formaldehyde mixture (1:1 of 1% chromic acid + 10% formaldehyde) at about 4ºC for 24 hours. The root tips were transferred into 70% ethanol solution and kept refrigerated till staining. Subsequently, the root tips were hydrolyzed in 1 N NaOH at 60ºC for 10 minutes, stained for 24 hours in hematoxylin stain at 30ºC, and squashed in 45% glacial acetic acid. Before squashing, the root tips were treated with cellulase-pectinase enzyme solutions at 37ºC for 10-15 minutes. The selected cells were photographed under an Olympus AX-40 light microscope. Karyotypes were obtained from well-spread metaphase plates.

All chromosomal sizes were measured with computer-aided program Micro Measure 3.3. Software (Reeves, 2001). Relative length in proportion to total genome length (RL), total chromosome length (TCL), mean chromosome length (MCL), arm ratio (short arm length/long arm length) with their respective standard errors and centromeric index (length of the short arm/total length of the chromosome X 100) (Arano and Sattio, 1980), total form percentage (TF%) (Huziwara, 1962), centromeric index mean of long and short arms (CI), asymmetry index (AsI%) (Arano and Sattio, 1980), S% (The shortest chromosome length/the longest chromosome length), DRL (difference of range relative length), intrachromosomal asymmetry index (A1) (Romero-Zarko, 1986), interchromosomal asymmetry index (A2) (Romero-Zarko, 1986), Stebbin’s classification (Stebbins, 1971) and karyotype formula (Levan et al., 1964) were calculated (Table 2). The data analyzed with Excel, SAS (version 14) and SPSS (version 16) statistical softwares.

 

Table1. List of scientific name, accessions codes*, ploidy level, kind of genomes and collecting localityies used for comparative cytological study of Iranian Triticum species

Species

Accession

2n

Ploidy level

Genome

Locality and Altitude)m)

T. monococcum

T. mono-30

14

2x

A

Kermanshah: Gardaneh Reno)1480(

T. mono -10

14

2x

A

Kurdistan: 3 km to Saghez (1620)

T. mono -41

14

2x

A

Isfahan: Semirom to Yasouj (2100)

T. mono -39

14

2x

A

Arak toward Malayer (2020)

T. mono -40

14

2x

A

Tehran: Taleghan valley (1850)

T. boeoticum subsp. thaodar

T.b.t.-37

14

2x

A

Kurdistan: 5 km after Jenan to Saqez (1770)

T.b.t.-8

14

2x

A

Chaharmahal va Bakhtiari: Shahr-e- Kord, Shapoorabad to Jooneghan (2090)

T.b.t.-34

14

2x

A

Arak: 15 km to Malayer (1840)

T. boeoticum subsp. boeoticum

T.b.b.-19

14

2x

A

Ilam toward Kermanshah: Gardaneh Reno (1370)

T.b.b.-5

14

2x

A

Lorestan: 35 km to Khorram Abad from Malavi (1100)

T.b.b.-20

14

2x

A

Kermanshah: 10 km to Harsin (1330)

T.b.b.-86

14

2x

A

Kermanshah toward Kamyaran (1340)

T.b.b.-3

14

2x

A

Kohgiluyeh va Boyer-Ahmad near Yasouj

T. urartu

T.ura-156

14

2x

A

West Azarbaijan: Maku (1580)

T.ura-84

14

2x

A

Kermashah: 10 km to Saqez from Asadabad (1320)

T.ura-2

14

2x

A

Ardabil: 10 km to Kaghazkanan (1349)

T.ura-8

14

2x

A

Chaharmahal va Bakhtiari: between Gandoman and Lordegan (2080)

T.ura-59

14

2x

A

Kurdistan: Saqez (1770)

T. durum

T.duru-86

28

4x

AB

Kermanshah: Kamyaran (1440)

T.duru-24

28

4x

AB

Lorestan: Malavi toward Khorram Abad (1200)

T.duru-166

28

4x

AB

Chaharmahal va Bakhtiari: DoAb Samsami (2000)

T.duru-1

28

4x

AB

Kohgiluyeh va Boyer-Ahmad (990)

T.duru-165

28

4x

AB

Chaharmahal va Bakhtiari: near Chaghakhor lake (2190)

T.duru-109

28

4x

AB

West Azarbaijan: Sardasht to Baneh (1050)

T.duru-15

28

4x

AB

Khuzistan: Haftgel to Masjed Soleiman (550)

T.duru-126

28

4x

AB

Kurdistan: 6 Km to Alamoot (1660)

T.duru-7

28

4x

AB

Chaharmahal and Bakhtiari: Borojen to Izeh (2190)

T. turgidum

T.turgi-211

28

4x

AB

West Azarbaijan: Khoy (1110)

T.turgi- 45

28

4x

AB

Chaharmahal va Bakhtiari: Bazoft (2190)

T.turgi- 2

28

4x

AB

Kohgiluyeh va Boyer-Ahmad: Yasouj (2880)

T.turgi- 43

28

4x

AB

Chaharmahal and Bakhtiari: Bazoft Morez valley (2000)

T.turgi- 8

28

4x

AB

Chaharmahal and Bakhtiari: Borojen to Izeh (2190)

T.turgi- 10

28

4x

AB

Khuzistan: Izeh (900)

T.turgi- 194

28

4x

AB

Kurdistan: between Sanandaj and Saghez (1595)

T.turgi- 80

28

4x

AB

Kermanshah: Mahi Dasht (1290)

T.turgi- 25

28

4x

AB

Lorestan: Malavi toward Khorram Abad (1200)

T.turgi-120

28

4x

AB

East Azarbaijan: Ahar (1320)

T. aestivum

T.aest-47

42

6x

ABD

Chaharmahal and Bakhtiari (2000)

T.aest-74

42

6x

ABD

Ilam: Do Rahe (1410)

T.aest-129

42

6x

ABD

Booshehr: Bandargah to Deilam (17)

T.aest-73

42

6x

ABD

Khuzistan: Karkheh (13)

T.aest-97

42

6x

ABD

Malayer 50 km to Arak (2010)

T.aest-96

42

6x

ABD

Tehran: Firooz Kuh (1700)

T.aest-107

42

6x

ABD

West Azarbaijan: Boukan to Mahabad (1290)

T.aest-49

42

6x

ABD

Isfahan: Daran (2190)

T.aest-82

42

6x

ABD

Kermanshah: Mahi Dasht (1290)

Chinese spring

C.S.

42

6x

ABD

Provided by the Institute of Plant Biology, University of Zurich, Switzerland

*All samples are kept in the herbarium of Isfahan University

 

Table 2. The means of karyotypic characters of forty-six mitotic chromosomes in diplo, tetra and hexaploids species of the genus Triticum used in this study (n = Chromosome number, TCL = Total haploid chromatid length, MCL = Mean of chromosomes length, TF% = Total form percent, Cent.Index = Centromeric Index (= S/(L+S)), Lon.Ch. = Longest chromosome length, Sho.Ch. = Shortest chromosome length, ML = Mean of large arms, MS = Mean of short arms, r = Arms ratio, AsI% = Asymmetry index, S% = Ratio between the shortest and longest of the chromosomes percent, DRL = Difference of range relative length, A1 = Intrachromosomal asymmetry, A2 = Interchromosomal asymmetry (C.V.) and RL = Relative length of chromosomes)

Species

2n

TCL

MCL±SE

TF%

Cent.Index

Lon. Ch.

Sho.Ch.

M.L. arm

T. monococcum

14

59.610

8.515 (±1.02)

43.29

0.431

9.775

7.349

4.816

T. urartu

14

48.316

7.606 (±0.36)

42.35

0.423

10.161

7.518

4.433

T. boeoticum subsp. thaodar

14

70.277

8.482 (±0.13)

41.60

0.415

11.457

8.589

5.871

T. boeoticum subsp. boeoticum

14

74.758

10.679 (±1.55)

42.72

0.427

12.233

9.186

6.105

T. turgidum

28

130.133

9.294 (±1.94)

40.66

0.404

13.007

7.81

5.475

T. durum

28

156.210

11.157 (±1.54)

41.437

0.41

13.35

8.151

6.545

T. aestivum

42

241.002

11.475 (±0.88)

40.831

0.406

14.834

7.528

6.777

 

 

 

 

 

 

 

 

 

Species

M.S. arm

r

AsI%

SI%

DRL

A1

A2

RL

T. monococcum

3.698

1.27

56.69

74.55

4.201

0.232

0.114

14.28

T. urartu

3.256

1.36

57.67

74.16

3.767

0.264

0.146

14.28

T. boeoticum subsp. thaodar

4.168

1.41

58.39

75.41

4.002

0.283

0.114

14.28

T. boeoticum subsp. boeoticum

4.554

1.33

57.11

71.25

3.715

0.244

0.102

14.28

T. turgidum

3.819

1.47

59.35

62.425

3.409

0.299

0.147

7.14

T. durum

4.615

1.43

58.63

60.277

3.707

0.276

0.147

7.14

T. aestivum

4.698

1.45

59.085

50.418

3.099

0.305

0.166

4.76

 

Results and Discussion

The results showed that about 33% of diploid accessions had sub-metacentric (sm) chromosomes in their Karyotype formula and other ones had only metacentric chromosomes. Tetraploid accessions had 2-4 sub-metacentrics (sm) and hexaploid accessions possessed 2-5 sub-metacentric (sm) chromosomes in their Karyotype formulae (Table 1).


 

Figure 1. Mitotic methaphase in Triticum speies studied. b.t. T. boeoticum subsp. thaodar; b.b. T. boeoticum subsp.boeoticum; u. T. urartu; m. T. monococcum; d. T. durum; t. T. turgidum; a. T. aestivum. Scale Bar = 20 µm. Arrow shows the satellite chromosome

 

All the accessions without T.duru-1, T.aest-73 and T.aest-47 (2A category), were placed in 1A category of Stebbins (1971) asymmetry categories (not showed in these Tables). Total chromosome length depended on the ploidy levels and chromosome numbers and consequently this parameter was too variable (Table 2).

TCL values varied between genotypes (Table 2). The TCL value ranged from 48.316 µm (T. urartu) with MCL of 7.606 ± 0.63 µm to (T. aestivum) with MCL of 11.475 ± 0.88 µm.

The most variable chromosomes in length SE of MCL were found in T. turgidum (SE of MCL = 1.94 µm) whereas the most similar chromosomes were scored in T. boeoticum subsp. thaodar (SE of MCL = 0.13 µm) (Table 2). The TF% value ranged from 43.29 (T. monococcum) to 40.66 (T. turgidum) (Table 2). The CI ranged between 0.431 (T. monococcum) and 0.404 (T. turgidum). The longest and the shortest chromosome length were found in T. aestivum. The highest mean length arm was in T. aestivum. and the lowest mean was in T. urartu. The arm ratio ranged from 1.27 in T. monococcum to 1.47 in T. turgidum. The ASI% varied from 56.69 (T. monococcum) to 59.35 (T. turgidum). The SI% ranged from 75.41 (T. boeoticum subsp. thaodar) to 50.418 (T. aestivum). DRL in T. monococcum was the highest (4.201) and in T. aestivum was the lowest (3.099). In general, A1 and A2 values showed the high degree of karyotype symmetry in the majority of the genotype studied (Razik Kamel, 2006). A1 ranged from 0.305 (T. aestivum) to 0.232 (T. monococcum) and A2 ranged from 0.102 (T. boeoticum subsp. boeoticum) to 0.166 (T. aestivum) (Table 2). Among the diploid species, the TCL value varied from 74.758 µm (T. boeoticum subsp. boeoticum) to 48.316 µm (T. urartu). Between tetraploid accessions the TCL value ranged between 156.210 µm (T. durum) and 130.133 (T. turgidum). Based on the result of this study, it could be concluded that generally, the chromosomal length in the T. urartu was shorter than other species of the genus Triticum. In this species, minimum value of TF%, CI and A1 belonged to T. boeoticum subsp. thaodar and maximum showed in T. monococcum. Also among this group (diploids) arm ratio (r) and AsI% in T. monococcum were the lowest and in T. boeoticum subsp. thaodar was the highest. Results showed that coefficient of variability for intra-specific chromosome length variation of short and long arms (Table 3) was higher for short arms and that it can be concluded that short arms were more effective in TCL than long arms. Karyotype studies were principally based on the idea that symmetrical karyotypes were more primitive than asymmetrical ones; and this holds true for longer chromosomes compared to shorter ones; median centromeres with arms of equal length are more primitive than chromosomes with arms of unequal length; low basic numbers give rise to higher ones. These features are based on the comparison between karyotypes of known relative antiquity, as determined through classical taxonomy (Sharma, 1990).

 

Table 3. Coefficient of variability for intra-specific chromosome length variation of short and long arms for Triticum species used in this study

Chromosome arms

T. monococcum

T. urartu

T. boeoticum subsp. thaodar

T. boeoticum subsp. boeoticum

T. turgidum

T. durum

T. aestivum

Short arm (in%)

9.88 – 18.64

9.52 – 19.09

13.57 – 16.93

7.85 – 15.75

17.25 – 21.82

9.46 – 24.51

17.38 – 24.77

Long arm (in%)

7.60 – 13.46

8.88 – 15.48

10.70 – 13.01

11.64 – 14.06

11.63 – 16.82

8.19 – 18.32

12.93 – 19.09

 

The scatter diagram based on A1 and A2 (Romero-Zarco, 1986) constructed three groups of karyotype asymmetry in the accessions studied: 1- T. aestivum (a) with the highest asymmetrical karyotype, 2- T. monococcum, T. boeoticum subsp. thaodar and T. boeoticum subsp. boeoticum with the lowest asymmetrical karyotype and 3- T. urartu, T. turgidum and T. durum with an intermediate between two previous groups (Figure 2) (Jalilian and Rahiminejad, 2011).

 

 

Figure 2. Scatter diagram show the relationships between the Triticum species based on the intrachromosomal (A1) and interchromosomal (A2) asymmetry indices. Values of A1 and A2 are summarized in Table 2. (m. T. monococcum; u. T. uratu; b.b. T. boeoticum subsp. boeoticum; b.t. T. boeoticum subsp. thaodar; d. T. durum; t. T. turgidum; a. T. aestivum)

 

In the UPGMA dendrogram (Figure 3), the five Triticum species studied were divided into three groups: (1) A: (T. monococcum and T. urartu), (2) B: (T. boeoticum subsp. thaodar and T. boeoticum subsp. boeoticum), and (3) C: (T. durum, T. turgidum and T. aestivum) (Figure 3) (Akhavan and Saeidi, 2010; Jalilian and Rahiminejad, 2011).

 

 

Figure 3. The UPGMA dendrogram (used Euclidian Distance) shows relationships between Triticum species based on chromosomal characters (see Table 2). T.mono. T. monococcum; T.urar. T. urartu; T.b.t. T. boeoticum subsp. thaodar; T.b.b. T. boeoticum subsp.boeoticum; T.duru T. durum; T.turgi. T. turgidum; T.aest. T. aestivum.

 

According to the results, it might be suggested that T. durum was more primitive than T. turgidum and T. monococcum could be considered as a donor of A genome to T. durum and T. aestivum. This hypothesis verified SSR analysis (Ehtemam et al., 2010; Keshavarzi et al., 2012).

 

Acknowledgments

The authors wish to thank the Office of Graduate Studies and the Department of Biology, of the University of Isfahan for their support.

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