CHAPTER ONE
1.0 Introduction
Cultivated sunflower (Helianthus annuus L.) is an annual, herbaceous (2n=34) and a cross pollinated crop, native to North America. It is a member of the Asteraceae family and it is regarded as the fourth most important oilseed crop grown worldwide after soya beans, palm and edible rapeseed (canola) (Moghaddasi, 2011; Sujatha et al., 2012). Sunflower is cultivated on about 18 million hectares worldwide with an annual seed production of 40 million tons (FAOSTAT, 2015). Its seeds are known for their high oil (25 – 48%) and protein (23 – 35%) content and thus used in confectionary and animal feed (Imran et al., 2015). It is used as an ornamental plant due to the attractiveness of its flower (Mayor et al., 2010). Sunflower seeds have abundant health benefits which can be attributed to the high levels of polyunsaturated and monounsaturated fats, phytosterols, tocopherols, protein, copper, folates, iron, zinc, and vitamin B (Nandha et al., 2014; Roche et al., 2010). Its oil is used as raw materials in many industries due to the presence of four commercially important fatty acids namely, palmitic, stearic, oleic, and linoleic acids (Lee et al., 2010).
Gene variability within a species enables the development of new improved varieties with improved characteristics. Therefore, the success of genetic improvement of sunflower depends on the magnitude of genetic variability which enables the selection of desirable genotypes for breeding purpose (Cvejic et al., 2011). In addition, realizing the need for the imperativeness of low-input agriculture being proffered for the 21st century, farmers require a suite of improved crop varieties that are genetically diverse in terms of climate change resilience, input use-efficiency, high yielding potential, resistance to biotic and abiotic stresses, enhanced nutritional and other important quality attributes (Tester and Langridge, 2010; Waines and Ehdaie, 2007). However, the envisaged genetically diverse portfolios of sunflower crop varieties are often unavailable to farmers due to its extreme narrow genetic base (Seiler and Frederick, 2011). This makes its improvement through conventional breeding method alone difficult. In view of this, the induction of genetic variability for sunflower crop, particularly in the era of increasing global food crisis and changing climatic regimes is, therefore, highly desirable.
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