Notes on Aegilops cylindrica (Triticeae, Poaceae) in Iran

Introduction

Aegilops cylindrica Host, an annual wild grass and almost close relative to Triticum aestivum L. (bread wheat), occurs throughout Mediterranean, Middle East and Asiatic regions (Linc et al., 1999; Slageren, 1994; Karataglis, 1989). This species with a chromosomal formula of 2n = 4x = 28 (DDCC) has been considered as an allotetraploid species resulted from a natural hybridization between A. caudata L. (2n = 2x = 14, CC) and A. tauschii Coss. (2n = 2x = 14, DD) (Linc et al., 1999; Karataglis, 1989). Jaaska (1978) suggested that this species originated from east parts of Turkey, where the distribution areas of its putative parents might had been overlapped.

In his account Tzvelev (1976) recognized four varieties for A. cylindrica: cylindrica, aristulata (Zhuk.) Tzvel., pauciaristata Eig. and prokhanovii Tzvel. occurring in (the former) Soviet union (USSR); a fifth one, i. e., var. rumelica was added by Velenovsky for Flora Bulgarica (Velenovsky 1891). Bor (1970) recognized this species with no infra-specific subdivisions for the Flora Iranicaareas (Iraq, Afghanistan and NW, W of Iran). Literature review shows that the Iranian materials of this species were the subject of taxonomic (Keshavarzi et al., 2006; Arzani et al., 2006; Kharazian, 2008), molecular cytogenetic and C-banding (Linc et al., 1999; Bordbar et al., 2011), isozyme (Jaaska, 1981), and inter-generic hybridization (Morrison et al., 2002) studies. Aegilops cylindrica is also important from the breeding point of view, due to the gene flow between this species and T. aestivum (Guadagnuolo et al., 2001).

This study aims to review the taxonomic status of A. cylindrica in Iran.

Materials and Methods

A selection of 25 representetives (Table 1) belonging to Aegilops cylindrica from 100 accessions collected during the years 1996-2000 all around Iran were studied. The selected accessions included all distribution areas and main phenotypic variations. In order to provide enough plant materials for the morphological and taxonomic studies, the accessions were grown in the research field of the University of Isfahan. Voucher specimens are deposited in the herbarium of the University of Isfahan (HUI). In addition, all the related materials including the Iranian specimens collected for this study, type specimens of A. cylindrica var. cylindrica (W 2284), A. cylindrica var. pauciaristata (W 1426), A. cylindrica var. rumelica Velen. (W 5377) and two parental species i. e. A. tauschii (W 1973-0008961, W 1970-0016311) and A. caudata (W 0000441) housed in the Natural History Museum Vienna (W) and the Botanic Garden and Botanical Museum Berlin (B) were studied.

Table 1. List of Iranian Aegilops cylindrica accessions studied taxonomically

In addition, to certify the ploidy levels of the studied materials, all the accessions were chromosomally examined from the root tips stained in aceto-orcein by squash method (unpublished data). In order to make a comparison among the materials under study, 20 morphological characters (16 quantitative and 4 qualitative) cited in the relevant literatures were evaluted (Table 2).

Table 2. Quantitative and qualitative characters considered in study of Aegilops cylindrica varieties in Iran (in quantitative characters means have calculated)

Results and discussion

The results of this study showed that the geographical distribution of Aegilops cylindrica in Iran was restricted to an area from northwest (Azarbaijan province) eastwardly along Elburz mountains toward northeast (Khorasan province) and southwardly along Zagros mountains toward southwest of Iran with an elevation ranging from 500-2300 m (Figure 1). In comparison with Bor (1970) our observations expanded the distributional range of this species in Iran. Jaask (1978) considered A. cylindrica as a Mediterranean element, where the two putatively diploid progenitor i. e. A. caudata and A. tauschii underwent the hybridization and allopolyploidy processes to create A. cylindrica in Turky; which then emigrated to Europe and Iran.

In A. cylindrica usually the length of awns gradually increased from lowermost spikelet towards the uppermost one in each spike, so that the uppermost spikelet showed the longest awn. One of the studied accessions collected from NW of Iran showed interesting state in which not only was the awn of the uppermost spikelet the longest but also was longer than the total spike’s length. On the other hand, in this specimen all the spikelets in the middle part of the spike showed awns longer than the accessions collected from the other areas. The majority of accessions studied possessed spikes with an average of eight spikelets per spike, however, the least number of spikelets per spike (five spikelets) was observed in above (Table 2).

Figure1. A distribution map of Aegilops cylindrica varieties in Iran

Also, this study showed that spike shape among the studied materials vary from oblong to cylindrical. All plants having the longest awn and the least spikelets number per spike showed oblong spike shape compared with those having cylindrical spike. These characters were diagnostic features for var. rumelica which we collected from Azarbaijan (Ahar to Kalibar, 35 km to Kalibar, 1716 m) (see Figures 2C, 3, Tables 1, 2).

Figure 2. Aegilops cylindrica varieties. A. cylindrica (HUI 17989); B. prokhanovii (HUI 17985); C. rumelica (HUI 17986); D. Scabrid surface of glume in var. cylindrica and var. rumelica. E: Densly pilose in var. prokhanovii.

Figure 3. A general habit of Aegilops cylindrica Host (var. cylindrica)

The presence of scabrid glumes and rachiswas the normal traits in A. cylindrica; neverthless a collected accession from Yasouj to Babameydan (HUI 17985) showed hairy glumes and rachis which is in accordance with Tzvelev (1976) who took the densely short pilose spikelets and rachis variant to describe his new variety (var. prokhanovii) (see Figures 2B, 2D, 2E). Plants of this accession were characterized by brownish spikes and rachis (Table 2).

According to the results of this study, despite the prevalence of hybridization in Poaceae (even inter-generic); from which natural and artificial hybrids between A. cylindrica and T. aestivum are well known and documented (Morrison et al., 2002 and our unpublished data); taxonomic identity of infra-specific taxa of A. cylindrica could be conserved in the sympatric localities; e.g., var. prokhanovii and var. cylindrica grow side by side but still distinct in Yasouj to Babameydan site.

Based on the results of this study we concluded that A. cylindrica grows in Iran with three varieties: cylindrica, prokhanovii and rumelica. A taxonomic key to these varieties was constructed and presented as below:

Key to the varieties of A. cylindrica in Iran

1- Awns of the uppermost spikelet longer than the total length of spike; spike usually with 3-5 spikelets …………................................................ var. rumelica
- Awns of the uppermost spikelet shorter than the total length of spike; spike with more spikelets ............................................................................................. 2
2- Spikelets and rachis densely and brownish pilose ................. var. prokhanovii
- Spikelets and rachis scabrid, spikes green ….............................. var. cylindrica

Acknowledgments

The authors wish to thank the Office of Graduate Studies of the University of Isfahan for their support. We are also thankful to Dr. Ernst Vitek, Dr. Lia Pignotti, Dr. Robert Vogt and their colleagues in W and B herbaria respectively. Also, we are grateful to Dr. Vello Jaaska, Dr. Bernd R. Frieb and Dr. Van Slageren for their valuable guidance and Ms. Hajian for her precise hand drawing.