Discriminating characters of diploid wheat species

A. 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


Introduction

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)
Anthers,length: 3-4 mm
G
L
U
M
E
Keel tooth, length: 1,3-3,0 mm
Lateral tooth, length: 0,2-0,5 (1) mm
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
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
B
A
S
A
L

L
E
A
F
Basal node:
Shape: slight convex till cylindrical

(DC 11)
Apex shape: oblong sharp
Edge leaf blade ciliate: absent
Hairs, length: 0,07-0,3 mm
Hairiness, dense: strong
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

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
Anthers,length: 5-6 mm
G
L
U
M
E
Keel tooth, length: 1,0-1,3 mm
Lateral tooth, length: 0,2-0,5 (1) mm
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
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
B
A
S
A
L

L
E
A
F
Basal node:
Shape: spherical

(DC 11)
Apex shape: blunt
Edge leaf blade ciliate: absent
Hairs, length : 0,03-0,06 mm
Hairiness, dense: absent or weak
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

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)
Anthers,length: 6-7 mm
G
L
U
M
E
Keel tooth, length: 1,0-2,5 mm
Lateral tooth, length: 0,3-1,0 (1,5) mm
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
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
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
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
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

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)