Discriminating characters of diploid wheat speciesA. Filatenko1, M. Grau2, H. Knüpffer2, K. Hammer3 1N.I. Vavilov Institute for Plant Industry (VIR), St. Petersburg, Russia 2Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Germany 3University of Kassel, Faculty of Agriculture, International Rural Development and Environmental Protection, Witzenhausen, Germany |
By the data of IPGRI (http://www.ipgri.cgiar.org/)
collections of Genebanks of the Globe hold more than 710.000 samples of wheats,
7.800 of them belonging to diploid species of the genus Triticum L.
Comprehension of this diversity of forms is possible only with classifications,
elaborated in detail and based on investigation of variability of each species,
over all its range and by as many characters as possible, that allows to reveal
the structure of the each species, determine its limits and the optimum volume.
The diploid wheat species Triticum boeoticum Boiss.,T. urartu Thum.
ex Gandil., and T. monococcum L. remain imperfectly studied as to
botanical-geographical principles of their variability, for this reason there
is no agreement upon the rank of these taxa.
Materials and Methods
Drawn in the study were all the samples of diploid wheat species from the collection of IPK-Genbank and, partly,
Vavilov Institute (VIR) (88 of Triticum boeoticum, 53 of T. urartu, 146 of T. monococcum). Since in these collections
wild species from the West Asia are insufficient as to their geographical range, over 120 samples of the diploid
wheats were loaned from the collection USDA (principally, collections of B.Johnson). Selecting samples for the
study was made on the base of GRIN Passport data: http://www. ars-grin.gov/npgs/searchgrin.html).
The Vavilov’s botanical-differential method (1923) in systematics was used.
Results and Discussion
The investigation of the diploid wheat species has allowed to specify diagnostic characters and increase their
number. Before, distinctions between wild species of the diploid wheats were determined according to an extent of
development of the keel and lateral teeth, length of anthers and pattern of pubescence of the leaf blade. It was
obviously insufficient, especially when working with a collection material. The examination of variability of these
species by a large number of characters has allowed to reveal complexes of constant characters, typical of all the
plants belonging to a certain species throughout its geographical range. Used as diagnostic characters at different
stages of plant development can be those of leaf (type of pubescence, ciliation of the blade margin, color and
ciliation of auricles, shape of the leaf tip), stem nodes, spike, spikelets, glumes. A morphological similarity of
characters of the first leaf (color and ciliation of auricles, short or lacking pubescence) suggest a common
ancestor of all the diploid species. However, the wild species at this stage of development already demonstrate
characters of leaf xerophyty: smaller leaf blade and more corrugated as compared to the cultivated species
T. monococcum. Dorofeev and Gradchaninova (1971) indicate also their small epidermal and guard cells. At the
booting stage, the further differentiation of the species by patterns of their pubescence takes place:
T. boeoticum, in addition to the shortly hamate-velvety pubescence observed in T. urartu, develops
long hairs (1,2–1,6 mm) on the leaf blade, mainly at veins. The leaf of T. monococcum is peculiar for the
lacking pubescence or covered with short spinules and very sparse short papillae. Each species retains its own
pattern of pubescence up to the development of the flag leaf, where a certain decrease of its density is observed.
As a whole, the species are distributed by types of their organization as follows: T. monococcum possesses
the characters of the mesomorphic type, mare ancient in the system of grasses (spike medium- or scarcely fragile,
spikelet bearing one thin awn, rachis segments glabrous or very slightly pubescent, keel less distinct, glumes
weakly tuberculate up to completely glabrous, leaf blades soft, long); T. boeoticum and T. urartu are
xerophytes of dry foothills, the fact explaining the strong sclerification of strengthening elements of stem and
leaves, rigid structure of glumes etc. However, xerophily of spike characters in T. urartu is somewhat less
distinct as compared to T. boeoticum. Softer and longer leaves of T. urartu, covered with velvety
pubescence, are as well elements of the mesophilous organization. This probably explains the features of the
species arrangement in the dendrogram (Fig.), which reflects a genetic diversity of the diploid species by 25 wheat
microsatellites (V. Korzun et al., 1998). The microsatellite analysis made for a small number of samples gives an
evidence, that at the molecular level the boundaries between these species are also clearly distinct (1 species – 1 claster).
Conclusions
Each of the diploid wheat species (Triticum urartu Thum. ex Gandil., T. boeoticum Boiss.,
T. monococcum L.) has its own series of variability of the characters, that gives an evidence, along with
archaeological data, of their ancient separation. Such natural groups deserve their own specific names; furthermore,
use of them will facilitate a work with plant collections and any other scientific research.
Acknowledgements
Ms. B. Fouquet has given help with translation of botanical terms. Ms. Grau has designed the poster. We express our cordial gratitude to them. Dr. A. Filatenko carried out works under the auspices of the joint research program of Russia and Germany in the field of the agricultural science.
References
S P I K E |
Triticum urartu Length: 6-12 cm Spikelet number per spike: 16-29 Rachis, brittleness: strong through the spike Spike rachis segment, length: 3,5-4 (5) mm Spike rachis segment, hairiness: very strong, strong Awns per spikelet, their divergence: 2 (preading) |
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Anthers,length: 3-4 mm | |||
G L U M E |
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Keel tooth, length: 1,3-3,0 mm Lateral tooth, length: 0,2-0,5 (1) mm |
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F L A G L E A F |
Flag-leaf blade: Length: (6)12-18 cm; (short) intermediate, long Width: 6-11 mm; narrow, intermediate Pubescence, type: velvet-like Hairiness, dense: intermediate Hairs, length: 0,05-0,1; 0,3 mm Auricle, coloration: ligth-green Edge leaf blade ciliate: absent |
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N O D E |
Uppermost node of stem: Shape: cylindrical, slight convex Length: 1-3 mm Hairiness, dense: medium or strong Hair, length: uniform very short till uniform medium Node, coloration: green Ring below the nodes, expression: weak expressed Ring below the nodes, coloration: absent or light brown |
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B A S A L L E A F |
Basal node: Shape: slight convex till cylindrical (DC 11) Apex shape: oblong sharp |
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Edge leaf blade ciliate: absent Hairs, length: 0,07-0,3 mm Hairiness, dense: strong |
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G R O W T H H A B I T |
At maturity (DC 50-59): prostrate, semi-prostrate, medium, semi-erect At the end of tillering stage (DC 25): prostrate, semi-prostrate, medium, semi-erect, erect |
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S P I K E |
Triticum monococcum Length: 6-12 cm Spikelet number per spike: 25-28 Rachis, brittleness: weak till intermediate Spike rachis segment, length : 2-3 mm, Spike rachis segment, hairiness: absent, very weak, weak Awns per spikelet, their divergence : 1 |
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Anthers,length: 5-6 mm | |||
G L U M E |
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Keel tooth, length: 1,0-1,3 mm Lateral tooth, length: 0,2-0,5 (1) mm |
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F L A G L E A F |
Flag-leaf blade: Length: 18 cm; short, long Width: 7-14 mm; narrow till wide Pubescence, type: short-toothed Hairiness, dense: (absent) very weak Hairs, length: 0,03-0,06 mm Auricle, coloration: ligth-green Edge leaf blade ciliate: absent or long |
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N O D E |
Uppermost node of stem: Shape: spherical Length: 1,5- 4,0 mm Hairiness, dense: weak till medium Hair, length: uniform very short till uniform short Node, coloration: green, brown Ring below the nodes, expression: weak or good expressed Ring below the nodes, coloration: brown |
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B A S A L L E A F |
Basal node: Shape: spherical (DC 11) Apex shape: blunt |
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Edge leaf blade ciliate: absent Hairs, length : 0,03-0,06 mm Hairiness, dense: absent or weak |
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G R O W T H H A B I T |
At maturity (DC 50-59): erect At the end of tillering stage (DC 25): semi-erect, medium |
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S P I K E |
Triticum boeoticum Length: 6-12 cm Spikelet number per spike: 16-30 Rachis, brittleness: strong through the spike Spike rachis segment, length:(3) 4-5 mm Spike rachis segment, hairiness: Very strong, strong Awns per spikelet, their divergence:1-2 (parallel) |
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Anthers,length: 6-7 mm | |||
G L U M E |
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Keel tooth, length: 1,0-2,5 mm Lateral tooth, length: 0,3-1,0 (1,5) mm |
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F L A G L E A F |
Flag-leaf blade: Length: 5-13 cm; very short till intermediate Width: 4-9 mm; very narrow till intermediate Pubescence, type: 2 Hair types: velvet-like short and against this background – long hairs Hairiness, dense: weak, intermediate, strong Hairs, length: (0,01) 0,03-1,0 (1,6) mm Auricle, coloration: ligth-green, greenish-violet, violet Edge leaf blade ciliate: intermediate and very long |
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N O D E |
Uppermost node of stem: Shape: cylindrical till slight convex Length: 2,0 bis 6,0 (8,0) mm Hairiness, dense: weak till strong Hair, length: long, upper longer than from below Node, coloration: green, brown, violet Ring below the nodes, expression: expressed Ring below the nodes, coloration: violet, brown |
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B A S A L L E A F |
Basal node: Shape: slight convex till spherical (DC 11) Apex shape: oblong sharp till sharp-pointed |
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Edge leaf blade ciliate: absent, rarely or long on all length Hairs, length: 0,02-0,8 (1,8) mm Hairiness, dense: intermediate till strong |
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G R O W T H H A B I T |
At maturity (DC 50-59): prostrate, semi-prostrate, genuflexuous, rare medium, semi-erect, erect At the end of tillering stage (DC 25): prostrate, semi-prostrate, semi-erect, erect |
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Fig.1. Dendrogram summarising the genetic diversity revealed by 25 wheat microsatellites in a group of 76 accessions of diploid wheat. (nach Korzun et al. 1998) |