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IntroductionApomixis is a mechanism of seed formation without fertilization and is observed in more than 300 species in 30 out of 460 angiosperm families, but it is not common in crop species (Bashaw, 1980). It was considered as an obstacle for plant breeding. Indeed, the presence of apomixis in the species Hieracium, in which Mendel was asked to prove the genetic principles he had developed in peas, caused him to withdraw from the scientific world due to his failure to do so (Carneiro et al., 2006). In recent years, however, apomixis is seen as a way to maintain superior genotypes as clones of seeds. As such, apomixis has been a major area of investigation in plant genetics.Unlike in animals where it is a hot topic nowadays, cloning is an ordinary process in plants. Many plant species can be propagated using various plant parts. Clonal propagation has some advantages as well as disadvantages. Apomixis combines the advantages of propagation by seed (higher multiplication rate, easier storage and planting, suitability for machine planting, less seed material use, and less bearing of diseases) with those of propagation by clone (maintaining genetic structure and hence fixing superior genotypes after crossing). However, apomixis manifests itself in different mechanisms that have not yet been fully elucidated. Genetic studies reveal that, though complicated, the trait is controlled by a few genes (Barcaccia and Albertini, 2013). In addition, different phases of apomictic reproduction have been achieved artificially (d'Erfurth et al., 2009). Apomictic reproduction of crop species would lead to revolutionary developments in terms of crop improvement. The benefits of apomixis are estimated to surpass those of the green revolution (Grossniklaus et al., 1998).The aim of this review paper is to discuss the use of apomixis in plant breeding. Our main attention is on its benefits in crop improvement rather than its physiological nature or molecular mechanisms. Methods to achieve apomixis in crop species and its economic advantages are also discussed. Mechanisms of apomixisThere are various mechanisms of apomixis, some of which result in unstable chromosome numbers (Naumova, 1993). Here we only discuss the ones with stable chromosome numbers and those that are important for plant breeding purposes without going into much detail.Development of apomictic seed formation takes place in three stages: a) suppression of meiosis (apomeiosis), b) endosperm formation without fertilization (parthenogenesis), and c) seed formation with (pseudo-Abstract: Apomixis is seed formation without fertilization, commonly observed in wild plant species. It has the advantages of clonal reproduction and propagation by seeds. Although it has a complex inheritance, genes controlling apomictic reproduction are being identified. Transfer of apomixis to crop species through wide crosses has not been successful so far, but transgenic technology offers a more powerful way to introgress apomixis into crop species. When crop species acquire this trait, superi...

Turkey is an important tobacco producing country and leading the world in oriental tobacco production. In the present study, effect of heterosis on yield and quality of oriental tobacco was investigated, and development of oriental tobacco hybrids with high yield and quality properties for Black Sea region of Turkey was targeted. Seven oriental tobacco genotypes with considerable acreages in Turkey (Xanthi-2A, Nail, Gümüşhacıköy, Taşova, Katerini, Canik, Erbaa) and 21 hybrids produced by halfdiallel crosses among them were compared. Field trials were conducted in Erbaa and Bafra locations in 2012 and 2013 growing periods. Cured leaf yields, reducing sugar and nicotine contents of leaves and expertise quality were studied. Xanthi-2A × Katerini (1.70 t ha -1 cured leaf yield and 75% quality grade index) and Nail × Katerini (1.64 t ha -1 cured leaf yield and 75% quality grade index) hybrids showed good yield and quality properties in Erbaa conditions, while Nail × Katerini (1.88 t ha -1 cured leaf yield and 75% quality grade index) and Katerini × Erbaa (1.65 t ha -1 cured leaf yield and 78% quality grade index) had good yield and quality properties in Bafra conditions. It has been concluded that hybrid cultivars that can meet the demands of tobacco sector could be developed from some currently grown oriental tobacco cultivars in Turkey. Based on average of locations, an average of 16.20% and 6.85% heterosis were found as the average of all hybrids for cured leaf yield and expertise quality. Yield effects due to heterosis could be increased in future by adopting growing techniques adjusted for hybrids.