Genetic Diversity of Potato for Nitrogen Use Efficiency Under Low Input Conditions in Ethiopia

Genetic Diversity of Potato for Nitrogen Use Efficiency under Low Input Conditions in Ethiopia Baye Berihun Getahun Thesis committee Promotor Prof. Dr Richard G.F. Visser Professor of Plant Breeding Wageningen University & Research Co-promotor Dr C.G. van der Linden Group leader, Plant Breeding Wageningen University & Research Other members Prof. Dr Paul C. Struik, Wageningen University & Research Prof. Dr Anton J. Haverkort, Wageningen University & Research and Nigde University, Turkey Dr Frits K. van Evert, Wageningen University & Research Dr Peter G. Vos, HZPC Holland BV, Metselawier This research was conducted under the auspices of the Graduate School of Experimental Plant Sciences. ii Genetic Diversity of Potato for Nitrogen Use Efficiency under Low Input Conditions in Ethiopia Baye Berihun Getahun Thesis submitted in fulfillment of the requirements for the degree of doctor at Wageningen University by the authority of the Rector Magnificus, Prof. Dr A.P.J. Mol, in the presence of the Thesis Committee appointed by the Academic Board to be defended in public on Monday 18 September 2017 at 1.30 p.m. in the Aula. iii Baye Berihun Getahun Genetic Diversity of Potato for Nitrogen Use Efficiency under Low Input Conditions in Ethiopia, 219 pages. PhD thesis, Wageningen University, Wageningen, the Netherlands (2017) With references, with summaries in Dutch and English ISBN: 978-94-6343-659-5 DOI: https://doi.org/10.18174/420903 iv Contents Chapter 1 General Introduction .................................................................................................. 1 Chapter 2 Genetic diversity of potato cultivars for nitrogen use efficiency under contrasting nitrogen regimes ....................................................................................................................... 16 Chapter 3 Identification of QTLs associated with nitrogen use efficiency and related traits in a diploid backcross potato population ...................................................................................... 44 Chapter 4 Genome-wide association mapping of nitrogen use efficiency and related traits in potato under contrasting nitrogen regimes ............................................................................... 71 Chpater 5 Genotype-by-Environment interaction for nitrogen use efficiency of potato (Solanum tuberosum L.) under different growing conditions in North western Ethiopia. ...... 95 Chapter 6 General Discussion .............................................................................................. 117 References .............................................................................................................................. 142 Supplementary data ................................................................................................................ 168 Summary ................................................................................................................................ 204 Acknowledgments .................................................................................................................. 211 About the author ..................................................................................................................... 214 Education Certificate .............................................................................................................. 217 v vi Chapter 1 General Introduction 1 The potato: Origin, expansion and production trends Potato (Solanum tuberosum L) is the 3rd most important food crop in the world after wheat and rice in terms of human consumption. The crop originated in the Andes Mountains of South America, where it has served as a staple in the diet of native people for a long time. It was domesticated 7,000 years ago near Lake Titicaca, (on the border between Bolivia and Peru), where the greatest diversity of wild species is currently found (Simmonds, 1995; Spooner et al., 2005). The successful journey of potato around the globe started in the 16th century, when the Spanish brought it to Europe from the South American Andes. From Europe, the crop found its way to Asia and Africa in the 17th and in the 19th century, respectively (Hawkes, 1994). In modern agriculture the crop is by far the most widely cultivated tuber-bearing species, with a production of 365 million tonnes fresh weight of tubers produced in 2012 from 21 million hectares of land (FAOSTAT, 2012). Globally, more than a billion people utilize potato, making it a critical crop in terms of food security in the face of population growth and increased hunger. In many developing countries the poorest and most undernourished farm households depend on potatoes as a primary and secondary food and nutrition source (FAOSTAT, 2008). The overall trend in potato production from 1991 to 2012 shows a 27% increase, from 268 million tons (Mt) to 365 million tons (FAOSTAT, 2012). Globally, in developing countries, the production of potato has increased from 28 million metric tons in 1963 to 149 million metric tons in 2005, which more than offsets the drop in production in industrialized countries (FAOSTAT, 2011). Several governments are appreciating the economic and nutritional importance of potato and are developing appropriate policies to encourage its production and consumption with medium and long-term strategies for sustainable potato development. According to the International Potato Center CIP, as much as 50% of the increased food production that will be necessary to produce to meet the demands in the next 20 years will come from potatoes in China, the world’s biggest producer of potatoes (2012). Generally remarkable progress has been made in potato production and productivity levels in certain countries of the world, whereas in other countries the progress is limited. The opportunities for further development of the potato industry appear to be considerable, however at the same time the production constraints to be addressed are huge. 2 Production constraints of potato In the past, potato breeding programs focused primarily on developing varieties with maximum yield and quality, good storage properties, low incidence of physiological disorders and improved genetic resistance to major pests and pathogens that adversely affect the potato industry. Production constraints related to nutrient use efficiency were not considered as a priority research agenda for potato. Nowadays, problems related to nitrogen fertilization and use have become more critical, economically as well as environmentally. According to Hirel et al. (2011), nitrogen availability has become the second priority production constraint after drought to be addressed in the crop’s abiotic stress improvement program. A dramatic increase has occurred in crop yield through global utilization of synthetic nitrogen (N), increasing from 11.6 million tons in 1961 to 104 million tons in 2006 (Hoang et al., 2010). Consequently, high crop productivity is heavily dependent on nitrogen fertilization. However, the increase in crop yield and synthetic N consumption has resulted in increased air pollution, alteration of the quality of surface and ground water resources through runoff and leaching, increased greenhouse gas emission and coastal eutrophication (Billen et al., 2013). Moreover, N fertilizer prices are currently very high, which is a direct result of the cumulative world demand for the limited fossil fuel reserves. The high costs and low returns of fertilizer use particularly burdens smallholder farmers in developing countries, forcing them to grow their crops under suboptimal N supply (Lafitte and Edmeades, 1994; Dethier et al., 2012). Potato is one of the major contributors to the leaching of nitrogen into the groundwater. Different research results indicate that adequate nitrogen application in the growing season is required to realize high potato yield and quality (Stark et al., 2004). However, effective management of nitrogenous fertilizers is a challenging task in potato production. Elevated ground water nitrate concentrations have been attributed to commercial potato production (Hill 1986; Richards et al., 1990) and significant emissions of nitrous oxide (a greenhouse gas) have been measured from potato fields (Flessa et al., 2002; Burton et al., 2008). Moreover, because of the high cost of N fertilizer, potato is one of the crops that suffer from being cultivated at N limiting conditions in tropical and sub-tropical regions of developing countries like Ethiopia. Potato was introduced in Ethiopia in 1858 by the German Botanist Schimper (Pankhurst 1964), and used to be an important garden crop in many parts of the country. Currently it is one of the major food crops produced in large farm lands, especially in the highland parts of the country. The production area has increased more than fivefold from 30,000 ha from the 3 1970s (Kidane Mariam, 1979) to more than 179,000 ha today (CSA, 2014). Potato can potentially be cultivated on 70% of the 10 million hectares of arable land in the country (FAOSTAT, 2008). However, the average productivity in Ethiopia is below 10 tons/ha, which is far below the country’s potential. Poor soil fertility is one of the major production constraints that contribute to this low productivity. The Ethiopian potato breeding program has developed a number of improved potato varieties under high input conditions, while most farmers are producing in low input farming systems. According to Mulat (1999), the amount of fertilizer applied by most Ethiopian farmers to crops is below

Load more