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Chemotaxonomy of Wild Diploid Triticum L. (Poaceae) Species in Iran



Navaz Kharazian and Mohammad Reza Rahiminejad
 
ABSTRACT

This study evaluates the taxonomic status and the variation of wild diploid Triticum L. species using leaf flavonoid compounds in Iran. Two-dimensional maps of these species were provided using polyamide Thin Layer Chromatography. In order to show the taxonomic position of these species, the cluster analysis based on Euclidean Distance Coefficient and Ward Method and Factor analysis were applied (Principle Component Analysis). The flavnoid compounds purification of each accession and species was done. The results of cluster analysis showed that T. boeoticum subsp. boeoticum Boiss. and T. boeoticum subsp. thaoudar Reut. ex Boiss. are completely distinguished from each other. T. boeoticum subsp. thaoudar shows more similarity to T. urartu Tum. ex Gand., but T. boeoticum subsp. boeoticum displays affinity to T. monococcum L. The results of this study showed variability of flavnoid compounds at the diploid levels in Triticum species. Also flavnoid profiles can be mentioned as well marker to show the taxonomic position of these species.

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Navaz Kharazian and Mohammad Reza Rahiminejad, 2008. Chemotaxonomy of Wild Diploid Triticum L. (Poaceae) Species in Iran. International Journal of Botany, 4: 260-268.

DOI: 10.3923/ijb.2008.260.268

URL: https://scialert.net/abstract/?doi=ijb.2008.260.268

INTRODUCTION

Triticum L. genus (Poaceae; Triticeae) has four wild diploid species (2n = 2x = 14; x = 7) growing in Iran (Bor, 1970, Rahiminejad and Kharazian, 2005). These species are as follow; T. boeoticum subsp. boeoticum Boiss., T. boeoticum subsp. thaoudar Reut. ex Boiss., T. monococcum L. and T. urartu Tum. ex Gand. (Bor, 1968, 1970).

There have always been debates concerning the taxonomy of the genus Triticum among the researchers. The complexes occurred among the species were due to the high similarity and the hybridization between the Triticum species which causes a high morphological similarity among these species (Lange and Jochemsen, 1992). These evidences have obscured the morphological limits of the species and caused taxonomic confusions in the number of species and nomenclatural debates in the genus Aegilops (Morrison, 1993). Also, high levels of variations have been observed in this genus (Waines and Barnhart, 1992).

Taxonomically, Dorofeev et al. (1979) reported that T. urartu is in Section Urartu Dorof. and Filatenko, while T. monococcum and T. boeoticum are grouped in Subgenus Boeoticum Migush. and Dorof., Section Monococcon Dum. Furthermore, Van Slageren (1994) showed that Section Monococca Flaksb. includes T. monococcum and T. urartu.

Morphologically, T. urartu is very similar to T. boeoticum (Yamagishi and Tanaka, 1978), while Kharazian et al. (2003) unfolded that T. urartu is different from the two other diploid species. Filatenko et al. (2001) reported that T. boeoticum, T. monococcum and T. urartu are considered as separate species. Controversially, Dhaliwal and Johnson (1976) showed T. monococcum is similar to T. boeoticum. In addition, these species have similar genome; AA, 2n = 2x = 14; x = 7 (Waines, 1995).

Chemotaxonomy is one of the important methods that display taxonomic position of taxa (Crowford, 1990). It is now possible to study phenolic profiles of high and low taxonomic levels, even of individual genotypes (Mika et al., 2005). The use of the distribution patterns of natural plant products-alkaloids, terpenes, phenolics, glucosinolites, terpenoids and carbohydrates is well-established as a major tool for investigating population structures, species, taxonomical problems and phyletic relationships of genera. Taxonomically, the most important phenolics are the flavnoids, which have a relatively common nucleus with great variety of types and patterns of side-groups that characterize the individual compounds. There is usually a considerable diversity of flavnoids in species (Nakipoklu, 2002). Also, extensive chemotaxonomic flavnoid research on the Poaceae detected the presence of flavone C-glycosides and tricin 5-glucoside (Bouaziz et al., 2001). Using thin layer chromatographic patterns, Dedio et al. (1969) presented the original taxonomic relationships in the genus Secale L. Thin-layer chromatography in these genus supported the general taxonomic relationships based on the morphological and cytological studies. The differences in chromatographic patterns were sufficient to determine the position of the Section of Secale genus. In addition, Bouaziz et al. (2001) showed the flavnoids of Hyparrhenia hirta Stapf (Poaceae) which grows in Tunisia. The most important compounds are 7-o-glucoside and vitexin. Also, Frey (1996) showed different phenolic profiles among Trisetum Pers.

Moreover, since Iran is one of the secondary centers of genetic diversity for diploid Triticum species, there is a need of using this genetic resource effectively in wheat improvement in this country. So far, the survey of flavnoid compounds in Triticum genus in Iran has not been studied, therefore the aims of this study are as follow:

Detect the flavnoid compounds among the accessions
Determine the taxonomic position via flavnoids
Identify variability in accessions of wild diploid Triticum species in Iran

MATERIALS AND METHODS

Extraction, isolation and identification of flavnoids were based on the protocol of Markham (1982). Using leaf flavnoid chemistry from 14 accessions (Table 1) of wild Triticum species, the taxonomic status and the phytochemical variations of these species were studied. Two-dimensional maps (2DM) of these species were provided using methanol extracts on polyamide (MN-Polyamid-DC6) Thin Layer Chromatography (TLC). Moreover, Spots` detection in NP identifiers (Diphenylboric acid 2-Aminoethyle Ester) was performed under UV-254 nm and the presence/absence of spots was taken as a character state and it was applied in each accession of these species. In addition, Rf values (migration distance of the bands/distance of solvent front) in each accession were studied (Apaydin and Bilgener, 2000; Gulen and Eris, 2004). In order to show the taxonomic position of these species the Cluster analysis based on Euclidean Distance Coefficient, Ward Method as well as Factor analysis (Principle Component Analysis) via SPSS. V. 14 were applied; besides, the descriptive analysis was studied to estimate the Coefficient Variation (CV). The flavnoid compounds purification of each accession and species was carried out through a sephadex (LH20) column and one-dimensional maps (1 DM) on polyamide TLC plates. Identification of the purified compounds was performed based on their UV spectra (200-500 nm) and shift reagent, such as AlCl3, AlCl3/HCl, NaOAC, NaOAC/H3BO3 and Methanol (Markham, 1982).

Table 1: Locality of wild diploid Triticum species in natural habitat of Iran

RESULTS

The two-dimensional flavnoid patterns of crude extracts of the taxa under study displayed the variability for each accession. Total number of spots were obtained in each species are presented as: (1) in T. boeoticum subsp. boeoticum 6-7 spots, (2) in T. boeoticum subsp. thaoudar 1-6 spots, (3) in T. monococcum 2-14 spots and (4) in T. urartu 2-4 spots. Dark yellow spots were common in T. urartu, T. boeoticum subsp. boeoticum and T. monococcum, blue spots were in T. boeoticum subsp. boeoticum and T. monococcum, orange spots were in T. boeoticum subsp. thaoudar, boeoticum and T. monococcum but violet spots were in T. urartu. Also, the presence and absence of flavnoid spots were surveyed in each accession (Table 2, Fig. 1, 2). Based on the color of each profile, the kind of flavnoid type is partially detected; T. urartu accessions have 3-OH flavonol, 5-OH flavonol or flavone, 4`-OH chalcone (Table 3, 4). In T. boeoticum subsp. boeoticum accessions observed Hydroflavone, flavonol, 5-o-glycosides, 3-o-flavonol, 5-OH flavone, dihydroflavonol, biflavonyl, 2`-OH chalcone, 6`-OH chalcone. T. boeoticum subsp. thaoudar have 2,4-OH chalcone. T. monococcum have flavone, flavonol, 3-OH flavonol, 5-OH falvonol, 2`-OH chalcone, 6`-OH chalcone.

Furthermore, Rf values of each accession were studied in aqueous and organic solvent system. Both maximum and minimum Rf in aqueous system were observed in T. boeoticum subsp. boeoticum (1.76, 0.09, respectively), T. monococcum (1.72, 0.09, respectively). Also, maximum and minimum Rf in organic system were in T. monococcum (2.11, 0.14, respectively) (Table 5). In aqueous solvent systems, most of the stains have Hydroxyl groups with high polarity, but in organic solvent systems they have little polarity. In order to determine the flavnoid compounds, the fractions of each accession were surveyed. Absorption of UV spectrum via shift reagent such as AlCl3, AlCl3/HCl, NaOAc and NaOAC/H3BO3 were examined. Among T. urartu accessions, increased intensity (bathochromic shift) of Band I displays Hydroxylation at 2` and 4-positions and variability in B-ring o-Dihydroxylation. That is when Band II shows Oxygenation at 6 or 8-position. In T. boeoticum subsp. boeoticum, Band I shows Hydroxylation at 5 and 4-position and variability in B-ring o-Dihydroxylation and A-ring o-Dihydroxylation while Band II shows Hydroxylation at 7-position and Oxygenation at 6 or 8-position. In T. boeoticum subsp. thaoudar increased intensity demonstrates Hydroxylation at 7 and 2`-position and Oxygenation at 3`-position. Increased intensity of Band I in T. monococcum accessions indicates the variability of B-ring-o-Dihydroxylation and Hydroxylation at 4-position (Table 4).

Table 2: Presence and absence of each spot in each accession of Triticum accessions
+: Presence of especial spot, -: Absence of especial spot

Similar flavnoid compounds between T. urartu and T. monococcum are flavone, 4`-Hydroxychalcone, Pseudobaptisin, T. boeoticum subsp. boeoticum and T. monococcum are flavone, 4`-Hydroxychalcone, 3`,4`,7` Trihydroxyflavone, between T. urartu and T. boeoticum subsp. boeoticum are flavone, 4`-Hydroxychalcone, between T. boeoticum subsp. thaoudar and boeoticum are 2-Hydroxychalcone, 4`-Hydroxychalcone, 2`-Hydroxy4`-Methoxychalcone, 2`,4- Dihydroxychalcone, between T. monococcum and T. boeoticum subsp. thaoudar are 2`-Hydroxychalcone, 2`-Hydroxy4`-Methoxychalcone, 4`-Hydroxychalcone and between T. urartu and T. boeoticum subsp. thaoudar is 4`-Hydroxychalcone. Therefore 4`-Hydroxychalcone one of the flavnoid compounds which is common among these species (Table 3).

Fig. 1: Chromatogram of spots in Triticum species; b.b: T. boeoticum subsp. boeoticum, b.th: T. boeoticum subsp. thaoudar

Fig. 2: Chromatogram of spots in Triticum species; m: T. monococcum, ur: T. urartu

Table 3: Flavnoid compounds among Triticum accessions in Iran
+: Presence of especial flavnoid compound, -: Absence of especial flavnoid compound

Table 4: Summary of the main flavnoid variation features among diploid Triticum species
+: Presence of flavnoid variation features, -: Absence of flavnoid variation features

Fig. 3:
Cluster and Factor analysis among Triticum accessions in aqueous and organic system; A and C in aqueous system, B and D in organic system, b.b: T. boeoticum subsp. boeoticum, b.th: T. boeoticum subsp. thaoudar, mn: T. monococcum and ur: T. urartu

Relationships between these species based on the Rf data are shown graphically in Fig. 1 and 2. Maximum CV in aqueous solvent system is related to subsp. thaoudar (75.3) and boeoticum (64.6) and in organic solvent system it is in T. boeoticum subsp. thaoudar (64.2) and T. monococcum (67.8), while minimum C.V. in both systems were in T. urartu (34.7 aqueous, 15.27 organic) (Table 6). The statistical analyses such as Cluster analysis were investigated in both aqueous and organic solvent systems. In aqueous system, two groups were comprised. (1) T. monococcum, T. boeoticum subsp. boeoticum, T. boeoticum subsp. thaoudar; T. boeoticum subsp. thaoudar, T. urartu, T. monococcum; T. urartu, T. boeoticum subsp. thaoudar, (2) T. monococcum, T. boeoticum subsp. boeoticum. In most of the clusters T. urartu and T. boeoticum subsp. thaoudar grouped together, also T. monococcum and T. boeoticum subsp. boeoticum were close together. Two subspecies of T. boeoticum were discrete from each other and T. monococcum clustered with two subspecies of boeoticum (Fig. 3). Using Factor analysis for aqueous system, it was observed that two groups in two components were comprised; (1) T. urartu, T. boeoticum subsp. thaoudar, T. monococcum (2) T. monococcum, T. boeoticum subsp. boeoticum, T. boeoticum subsp. thaoudar. In this analysis, two subspecies are exactly separated (Fig. 3). The results of clustering in organic solvent system proved three distinct groups, (1) T. urartu, T. boeoticum subsp. thaoudar, T. monococcum, T. monococcum, T. boeoticum subsp. boeoticum, T. urartu, T. boeoticum subsp. thaoudar (2) T. monococcum, T. boeoticum subsp. boeoticum. In this system, two subspecies of T. boeoticum were distincted. Using Factor analysis for organic data presented two comprised groups and therefore, affirmed the Factor analysis performed for aqueous solvent system (Fig. 3). Based on these results, aqueous solvent system is more appropriate for determining taxonomic position than organic system.

DISCUSSION

Little information is available about the variation extension among the wild progenitors of Triticum species (Hedge et al., 2000). There are conflicting reports on the amount of diversity in diploid wheat populations, specifically in chemotaxonomy. Based on the results of this study, T. urartu accessions with B-ring o-Dihydroxylation, Oxygenation at positions 6 and 8 and 4-Hydroxylation are common in T. monococcum and T. boeoticum subsp. boeoticum (Table 5), which is in accordance with Hammer et al. (2000) using micro satellites. Van Slageren (1994) and Dubcovsky and Dvorak (1995) reported that T. monococcum and T. urartu were related in phylogenetic trees. Using flavnoid chemistry, it was observed that T. monococcum and T. urartu were related, noticeably T. urartu having 2`- Hydroxylation is similar to T. boeoticum subsp. thaoudar (Table 5). In this study two subspecies of T. boeoticum were distincted in flavnoid variation, whereas these are exclusively similar in 7-Hydroxylation.

In cluster and Factor analysis T. urartu and T. boeoticum subsp. thaoudar were approximately grouped together. Morphologically, T. urartu is very similar to T. boeoticum (Yamagishi and Tanaka, 1978). T. monococcum and T. boeoticum subsp. boeoticum also grouped together and displayed affinity between them, which in accordance with Dorofeev et al. (1979) and Jaaska (1993, 1997). In addition, Dhaliwal and Johnson (1976) and Waines and Barnhart (1992) proved that T. monococcum is similar to T. boeoticum. Furthermore, using meiotic paring behavior and analysis of the polymorphisms of repeated nucleotide sequences T. urartu was found to be as a donor of A and B genome in polyploid wheat (Dhaliwal and Johnson, 1976, Dvorak et al., 1993; Hammer et al., 2000). Controversially, Filatenko et al. (2001) reported that T. boeoticum, T. monococcum and T. urartu are considered as separate species. Also, Dorofeev et al. (1979) and Kharazian et al. (2003) evolved that T. urartu is different from the two other diploid species. Using isoenzyme markers, Jaaska (1993) reported that T. boeoticum and T. urartu were found to differ with regard to acid phosphatase, esterase and superoxide dismutase, showing distinctly different gene pools.

Table 5: Rf values of Triticum accessions in aquatic and organic phase

So far, the researches did not have any supporting evidence which could clearly separate the wild diploid species (Morrison, 1993) and subspecies. In this study two subspecies of T. boeoticum; thaoudar and boeoticum were separated exactly (Fig. 3). Using microsatellites, Hammer et al. (2000) reported that two subspecies of T. boeoticum have different genomes. Based on flavnoid compounds these four species seem to have genomic relationships because of similarity in B-ring o-Dihydroxylation and 4-Hydroxylation, flavone and 4`-Hydroxychalcone which can provide the gene flow among diploid species. This similarity confuses the limits of diploid species. Noticeably, T. monococcum accessions display oxidation patterns of flavones which can be observed in Sciadopitysin, 3`,4`,7`-Trihydroxyflavone 7-o-rhamnoglucoside and 3,3`,4`-Trihydroxyflavone. Both T. uraartu and T. monococcum have Oxidation flavnoids patterns which are related to Pseudobaptisin (Table 4). Therefore, these evidences show that T. urartu can be mentioned as one of the diploid ancestors to other diploid Triticum species. Nevertheless, these four wild diploid species are different from each other (Dhaliwal, 1977).

Little information is available on the extent of genetic variation in the wild Triticum species (Hedge et al., 2000, Moghaddam et al., 2000). Hedge et al. (2000) reported that T. monococcum and T. urartu accessions have polymorphic loci, but the low heterozygosity is indirectly resulting in high hybridization among the accessions. The flavnoid profiles among T. monococcum accessions present high variability in their flavnoid patterns which confirm these results (Fig. 2). Noticeably, they reported that T. urartu has the highest genetic diversity, which is not in accordance with present results (Table 6), T. urartu accessions have the least variability in their profile (Fig. 2). Intraspecific alloenzymic variability was found to be low in this species (Jaaska, 1993). Diversity and polymorphism of flavnoid compounds in accessions of T. monococcum and T. boeoticum subsp. thaoudar and boeoticum are more than T. urartu (Table 5, 6 and Fig. 1, 2) which are in agreement with Hedge et al. (2000) results, therefore maximum CV in aqueous solvent system is related to subsp. thaoudar and boeoticum and in organic solvent system it is in T. boeoticum subsp. thaoudar and T. monococcum, while minimum CV in both systems were in T. urartu (Table 6). Yaghoobi-Saray (1979) and Hedge et al. (2000) reported higher levels of alloenzyme diversity in T. monococcum and T. urartu. Genetic variability which was approximately identical for diploid species may be brought about by similar kinds of evolutionary forces for which all the species might have had identical response. Phenolic profiles specifically demonstrate genetic affinity and significant polymorphism among species (Mika et al., 2005). These polymorphisms of flavnoid profiles have been showed in Fig. 1 and 2.

Table 6: Variability of flavnoid compounds among Triticum accessions in Iran
*Standard Deviation, **Coefficient of Variation

CONCLUSION

The widespread occurrence of flavnoid compounds in Triticum genus makes them useful markers for taxonomy and evolutionary relationships (Mika et al., 2005). To use flavnoid compounds more widely as genetic markers, these would have to be not only universal and abundant, but also environmentally stable and convenient for identifying taxonomic position (Fairbbothers et al., 1975). In addition, such studies should be performed at the population level as well.

ACKNOWLEDGMENTS

Authors are thankful to the University of Isfahan and Shahrekord to grant the research project No. 28. This research was performed at Department of Botany, Faculty of Sciences, University of Isfahan, Isfahan, Iran, on October 2003.

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