An evaluation of the factors influencing seed oil production in Camellia reticulata L. plants
Introduction
Camellia is known worldwide for the production of tea, however, there is a growing industry utilizing the oil derived from Camellia seeds. Camellia oil, extracted from a number of different species, including Camellia reticulata, Camellia sinensis, Camellia oleifera, and Camellia japonica, has long been processed as an industrial oil, used in the production of cosmetics, soaps, hair oil, medicines and now it is generating interest as a biofuel source (Rajaei et al., 2008, Lin and Fan, 2011). With the very high production of tea worldwide, totalling 3.6 million tonnes annually, there is enormous potential for the Camellia oil industry (Wang et al., 2011, Chen et al., 2012). China alone harvests 650,000 tonnes of Camellia seeds each year, producing around 165,000 tonnes of seed oil, and this figure is predicted to rise to as much as 2.5 million tonnes by 2015 (McDowell and Owuor, 1992, Cao et al., 2005).
Camellia seeds are known to have a high oil content, on average ∼30% oil per seed, however, the seed oil content varies according to species, cultivar and environmental conditions, ranging between 24% and 50% (Ravichandran and Dhandapani, 1992, Xia et al., 1993, Yazicioglu et al., 1997, Sahari et al., 2004, Wang et al., 2011, Huang et al., 2010). The high seed oil variability is likely the result of a number of factors, but environmental variables such as soil, altitude, light, rainfall, humidity and temperature are likely to play a key role as they have been shown to influence the oil content of seeds for a variety of plants (Kang et al., 1993, Linder, 2000, Debin and Yangzhu, 2002, Junang et al., 2010). Furthermore, fruit traits such as seed size, fruit number, fruit size and dry weight have been linked to the oil production in seed oil plants (Li et al., 1992, Abdelgadir et al., 2010, Yanru and Zhangju, 2010). Thus, by understanding the impact of fruiting behaviour and fruit characteristics, and at a larger scale that of environmental conditions, seed oil production can, to a certain extent, be predicted and/or manipulated.
Seed oil from a variety of plants, including Camellia, can consequently be influenced by a variety of mechanisms. Given the growing demand for Camellia oil, it is important to understand exactly what is causing the variability in oil production, and what factors result in optimum seed oil production. The forecast increase in demand for Camellia oil will almost certainly entail an increase in Camellia cultivation and land use, and knowledge regarding the impact of environmental factors on oil production can help to enhanced productivity. Thus, we aim to determine which fruit traits are associated with high seed oil production as well as which environmental factors most strongly influence oil production in C. reticulata, a species indigenous to Yunnan Province, China. Based on these findings, a map depicting the optimal growing areas for Camellia oil production in southwestern China will be produced.
Section snippets
Sites, sampling, and environmental data
Plantation grown C. reticulata, cultivated from seed, with a minimum population size of 10 ha, were used for sampling of fruit and seed oil, during the period of March 2008 and August 2009. Sample populations were located at 8 different sites (Fig. 1), spread over in 3 districts: Tengchong, Changning, and Gaoligong Shan, all in western Yunnan Province, China. The elevation of the sites ranged between 1715 and 2290 m.a.s.l., and slope between 5° and 30°. For more detailed information regarding the
Fruit traits
The various fruit traits are shown in Table 2. Of the factors tested, percentage seed oil was positively influenced by the kernel ratio per fruit, the seed fresh weight to fruit weight ratio and, to a smaller extent, by fruit weight. Once these effects were accounted for the seed number had a negative effect on seed oil percentage. The final model took the form of seed oil percentage ∼−20.59 + 0.75 kernel ratio per fruit + 0.41 seed weight percentage of total fruit weight + 0.02 fruit weight (g) –
Discussion
The results of this study have shown that Camellia seed oil is influenced by a number of factors, both at the fruiting level and at the environmental level. At the level of individual plants, a high kernel ratio per fruit and seed weight percentage of fruit weight as well as fruit weight (positively correlated with fruit size) positively influenced Camellia seed oil production. The number of seeds decreased seed oil percentage once the above variables were accounted for a given seed weight
Acknowledgments
We would like to thank the CGIAR Research Program 6: Forests, Trees and Agroforestry, for partially funding this research. In addition, we would also like to thank MISEREOR (335-031-1030Z) for partially funding the field work.
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