CLASSIFICATION OF GENUS Triticum, SENSU LATO AND SENSU STRICTO, BASED ON SPIKE AND GRAIN MORPHOLOGY

AgroLife Scientific Journal - Volume 4, Number 1, 2015 ISSN 2285-5718; ISSN CD-ROM 2285-5726; ISSN ONLINE 2286-0126; ISSN-L 2285-5718 CLASSIFICATION OF GENUS Triticum, SENSU LATO AND SENSU STRICTO, BASED ON SPIKE AND GRAIN MORPHOLOGY Hristo P. STOYANOV1,2 1 Technical university - Varna, 1, Studentska str., 9000, Varna, Bulgaria, Phone: +359887139789, Email: 2 M-AGRO EOOD, 5, Parvi mai str., 9350, Stozher, Dobrich region, Bulgaria, Phone: +359887139789, Email: Corresponding author email: Abstract The formulation of the present classifications of species of the genus Triticum associates mainly with several plant morphological factors such as fragility of the spikes spindle, grains threshability, grain sphericity, shape and position of glumes, lemmas and paleas and awns, compactness, etc. Special attention is paid to the factor "cultural/wild" form, the ploidy and the genomic constitution of the species, often supported by molecular data which provides considerable comfort in disclosing phylogenetic features in a particular taxonomic unit. Such taxonomic determination is associated with certain disadvantages. It is not sufficiently focused on the spike morphology related to the reproductive apparatus of the plant, and also the causes of phylogenetic differentiation of certain parameters, such as spike branching, multiple spikelets, as well as the ratios of quantitative properties. The existing classifications do not give a precise answer to the taxonomic position of amphidiploids in the genus Triticum, and also for those obtained from hybrid combinations with genera Aegilops, Secale, Haynaldia, Hordeum, Elymus, Leymus, Elytrigia, Agropyron, as transitional and similar forms. Based on studies of spike and grain morphology of a large number of representatives of the genus Triticum and other interspecific and intergeneric amphidiploid forms, a classification of the genus sensu lato and sensu stricto is composed. Sensu stricto, genus Triticum covers all existing wild and cultivated known wheat forms, together with interspecific artificial synthetic forms. Sensu lato, the genus includes intergeneric hybrids, for which a specific generic epithet was coined - ×Triticum, and also a specific epithet, consistent with the originator of the amphidiploid. Special attention was paid to species and amphidiploids with the genus Aegilops. Classification sensu strictissimo was also formulated where the genus Triticum brings together only diploid species, but natural amphidiploids are separated as genus Aegilotriticum, and artificial as genus ×Aegilotriticum, and the remote intergeneric amphidiploids are not subject to the classification. Drawn up in this way, the classifications cover morphological and ecological, evolutionary and phylogenetic features of the representatives of the genus Triticum. Key words: amphidiploids, classification, morphology, taxonomy, Triticum. INTRODUCTION The modern understanding of the systematics of cultivated plants is based on a number of factors, which are mutually complementary. The anatomical and morphological characteristics of the plants both play an important role in this respect, as well as their phylogenetic nature. Essential for the new classification is molecular genetics, which allows following in detail the genetic similarities and differences between individual plant sets (Goncharov et al., 2009). Nevertheless plant species are dynamic, not discrete structures that undergo changes due to the normal processes which involve and are determined by their heredity and variability (Ayala and Kiger, 1984). Therefore the 176 established relationships in a single species are an unsustainable model subjected to the evolutionary factors (Stoyanov, 2014c). Thus the classification of species, regardless of their relative stability, should take into account the dynamic concept of speciation. In essence, the definition of "species" presents versatile information (de Queiroz, 2005). This is due to the many definitions and interpretations that characterize this concept. On the one hand, the classic definition of ‘species’ given by Ernst Meyer - "a group of actually or potentially crossing populations that are reproductively isolated from other such groups" presents difficulties in identifying and classifying some artificially created synthetic species (de Queiroz, 2005), such as a large number of amfphdiploids in Poaceae. This Bowden (1959) proposed to unify the tetraploid and hexaploids forms in common species based on the cytogenetic characteristics of the representatives of the genus, as well as including the species of genus Aegilops in genus Triticum. This classification was later revised by Morris and Sears (1967) and became fundamental to the later classifications of Kimber and Sears (1987). MacKey (1966) reported such classification (without the species of genus Aegilops however), which was later rivized and supplemented (MacKey, 1988). Although it is the most recent classification of the genus Triticum, classification Dorofeev et al. (1979) remains unknown outside Russia. It is considered to be controversial as it gives the ‘species’ status to almost all cultivated and wild forms. Highly significant is the contribution of Gandilyan (1980) in the taxonomy of the genus; his classification and identification key give an extremely simple but effective scheme for grouping the wheat forms on the basis of their spike qualitative morphology. Love (1984) revised the classification of the genus, splitting it into three genera (Chritodium (diploid), Gigachilon (tetraploid), Triticum (hexaploid)). Flora of Turkey (1985) complemented the genus with the extinct species Triticum parvicoccum reported by Kislev (1979), but it gives an overly simplified classification. The classification of Kimber and Sears (1987) gives an idea of the genus Triticum sensu lato, unifying it with the species of the genus Aegilops as a correction to the classification of Kimber and Feldman (1987). Van Slageren (1994) follows the primary classification of MacKey (1988), with slight modifications. Goncharov et al. (2009), based on genetic markers, summarize their classification of the genus Triticum, and include hybrid and amfidiploid forms in a new section, basically following the classification of Dorofeev et al. (1979). All classification of genus Triticum are based on qualittative indices of the current wheat forms with adjustments based on cytogenetic and molecular genetic studies. In any of the wheat classifications, the morphological quantitative characteristics are not considered. Certain indices for species separation, which are confered only of one or several genes become reason for species formation (fragility, view contradicts the idea of artificial interspecific and intergeneric hybridization because it does not allow the different species to cross but defines them as “reproductively isolated”. The ability to create interspecific and intergeneric hybrids in Poaceae (M (...truncated)