DIGITALNA ARHIVA ŠUMARSKOG LISTA
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| ŠUMARSKI LIST 5-6/2013 str. 28 <-- 28 --> PDF |
Gene diversity of conifer species in the Mediterranean Basin decreases along east-west gradient (Fady and Conord 2010). The eastern Mediterranean Basin, especially Greece and Turkey, has high species and gene diversity than other parts of Mediterranean Basin due to heterogeneous features such as biogeography, microclimates, biotic and abiotic factors (Grivet et al. 2009, Medail and Diadema 2009). Turkey is a biologically diverse region and has great variability in topography and climate due to its geographical location joining two continents (Ciplak 2003). Thus, this variability has given Turkey a diverse range of ecosystems. Turkey, surrounded by seas of different ecological properties on 3 sides, with altitudes ranging from sea level to above 5000 m resulting in a variety of climatic conditions through the country, has a biological wealth incomparable to any of the neighboring countries. It has several distinct biogeographic regions, each having its own endemic species (totally over 30%) and natural ecosystems providing major flyways for millions of migratory birds with about 21 million ha of forested land which constitutes 27.2% of total land area of the country (Anonymous 2006, Ture and Bocuk 2010). In Turkey, P. brutia and P. halepensis forests cover approximately 5.5 million ha and total conifer forests have about 10 million ha area (Anonymous 2006). However, forest lands both in Turkey and in all over the world are under threat of climate change, tourism and urban development, population growth, human activity, grazing, pollution, fire and habitat loss (Kaya and Raynal 2001, Isik 2011). Conserving genetic diversity is essential for a sound forest ecology and management practices. Genetic diversity within species plays important role in resistance and adaptability of forests. Today’s forests as well as their genetic diversity would probably be maladapted to future climate. According to The Intergovernmental Panel on Climate Change (IPCC) held in 2007, global average surface temperatures will rise about 1.8 to 4.0 °C during the 21st century, and up to 30% of the world’s species will be at increased risk of extinction (Maciver and Wheaton 2005, StClair and Howe 2011). Changes in climatic events such as annual rainfall patterns, decrease in precipitation, reduction in soil moisture and decrease in water availability have strong effects on forest ecology and managements (De Dios et al. 2007, Ravindranath 2007, D’Amato et al. 2011). Productivity of pine forests is related to climatic, geological and topographic parameters, and also successional stage (Vila et al. 2003). When the rates of change of the future climate exceed the historical rates, rate of forest losses from fires, insects, diseases, population and urbanization are expected to change significantly. Forest management strategies will need to be prepared in a proactive adaptive manner with taking consideration of threats of climate change for tomorrow’s forests (Maciver and Wheaton 2005, D’Amato et al. 2011). Seed orchards have important role in afforestation and reforestation strategies. They are established with the aim of obtaining high genetic quality seeds and seedlings compared to phenotypically or genotypically selected stands (Buiteveld et al. 2001, Zhuowen 2002, Gomory et al. 2003, Hansen 2008). In other words, seed orchards, containing genetically superior trees, are expected to provide genetically and physiologically high value seeds frequently and also they are isolated from undesirable pollen sources (El-Kassaby et al. 1989, Di-Giovanni and Kevan 1991, Kang et al. 2004). The establishment of seed orchards requires time, money, expertise, investment and collaboration of concerned organizations (Di-Giovanni and Kevan 1991). The composition and breeding values of parent genotypes, pollen contamination rate, mating system components and the distribution of maternal and paternal gametes in orchard are main factors that affect the genetic quality of seeds produced (Stoehr et al. 1998, Kang et al. 2001a, Gomory et al. 2003). Thus, seed orchards are kept to produce genetically improved forest tree plantations. The basic objectives of forest tree breeding activities are establishment of new forest by taking advantage of the genetically superior features of natural forest, raising quality and quantity of wood raw material per unit area and providing resistance to pests such as insects and fungi. Forest tree breeders want to get maximum breeding progress and high genetic diversity from establishment new seed orchards (Hosius et al. 2000). Panmictic reproduction is required for production of genetically superior seeds in the seed orchard and obtaining maximum gene diversity based on a given number of clones (Harju and Muona 1989, Stoehr et al. 1998, Kang et al. 2001a, Funda et al. 2009, Alizoti et al. 2010). If seed orchards do not reproduce panmictically, some reduction in expected genetic gains will be observed (Harju and Muona 1989, Funda et al. 2009). Gene diversity is important for the sustainability of forest ecosystems and the adaptability of seeds to some environmental factors such as climate change and diseases. Fertility variation and pollen flow from outside stands have various undesirable effects on gene diversity of seed orchard crops (Kaya et al. 2006, Bilir et al. 2008). The number of clones used in establishment of seed orchards has an important role in ensuring gene diversity, maximizing roguing possibility and minimizing inbreeding (Lindgren and Prescher 2005). Using equal number of ramets per clones is an important approach in orchard establishment. Unequal production of female flowers, male flowers and gametes might occur due to variation in the number of ramets per clones. It is often preferred to use an equal number of ramets per clone but unintentional variation in the number of ramets occurs during establishment. Graft availability, graft incompatibility, dying of grafts due to unfavorable growing conditions, biotic and abiotic factors, and mislabeling of grafts are main |