Utilization of Sorghum (Sorghum bicolor L. Moench. hybrids in Kenya: A review
Hybrid seeds are known to increase productivity of many crops including sorghum (Sorghum bicolor L. Moench) This review was conducted to reveal the extent of sorghum hybrid seed utilization in Kenya and how nonutilization constrains sorghum production. Hybridization is one of the major discoveries that contributed to the green revolution which saved countries that were at the brink of famine. Although this is generally known, utilization of sorghum hybrid seeds is uncommon in Kenya. Even though low productivity is associated with climatic, edaphic, economic and agronomic factors, the contribution of the genotype cannot be ignored. The use of sorghum hybrid seeds has the potential to increase sorghum production for food, malting, brewing, baking, ethanol and fodder. Sorghum has both industrial and domestic utility making it an excellent crop for improving livelihood of rural communities living in agriculturally low potential areas in Kenya. Being a C4 crop, it has the ability to grow well in a wide range of climatic conditions making it an important crop for a country like Kenya. The use of hybrid seeds can be justified for almost all crops. However, for a multipurpose crop like sorghum, utilization of hybrid seeds cannot be ignored. Suggestions on how to improve the utilization of sorghum hybrid seeds have also been made. Corresponding Author: Moses Oyier oyierkilli2@yahoo.com International Journal of Agronomy and Agricultural Research (IJAAR) ISSN: 2223 7054 (Print) 2225 3610 (Online) http:/www.innspub.net Vol. 9, No. 6, p. 65 76, 2016 Int. J. Agron. Agri. R. Oyier et al. Page 66 Introduction Sorghum (Sorghum bicolor L. Moench. is the fifth most important cereal crop in the world after rice (Oryza sativa) barley (Hordeum vulgare L. wheat (Triticum aestivum) and maize (Zea mays) (Taylor, 2009) Being a C4 crop, it is highly adapted to a wide range of climatic conditions including marginal lands hence can be grown without competition with the other weather sensitive crops (Khawanja et al. 2014) It can grow at an altitude range of 900m to 2500m, temperatures of 12 to 37oC and an optimum rainfall of 550 to 800 mm (Srinivasa, Rao and Kumar, 2013) Sorghum does well in a wide range of soils such as alvisols and vertisols and can tolerate pH of 5.5 to 8.5 (Du Plessis, 2008) Kenya has a wide range of climatic and edaphic factors that can favor sorghum growing. Although Kenya has high production potential of the crop, it has remained under utilized (Muui et al. 2013).The aim of this paper is to assess the utilization of sorghum hybrids in Kenya. Kenya's agricultural productivity rests on the quality of improved seeds (Denning et al. 2009) Correct selection of seeds also come with incentives for better management practices. Use of improved varieties makes the subsistence farmers grow to commercial production due to increased productivity (Altieri et al. 2012) Studies indicate that 78% of total seeds for the top 7 grains grown in Kenya is from the informal sector and not the seed industries (Tegemeo Institute, 2004) The seed industries in Kenya have been known to be slow in the production of seeds that target the rural poor for fear of failing to get returns on their investment (Nyoro and Ariga, 2004) The rural poor farmers are known to depend on their saved seeds and have low capacity to purchase the improved seeds (Lipton and Longhurst, 2010) This makes the seed companies unwilling to produce seeds of crops such as sorghum. Even though researches conducted by various scholars around the world have revealed that sorghum hybrids can be better performing in various environmental conditions including drought, soil infertility, acidity and aluminum toxicity, production of the sorghum hybrid seeds has not been done by the seed companies (Chapman et al.,2000) This is likely because of the fear that the companies would not realize the return on their investment due to low purchase of the products. This vicious situation has led to continuous low productivity of sorghum in Kenya. However, the realization of sorghum as an industrial crop has created a new increased demand for sorghum making it an important crop that will demand improved seeds to meet its market requirement (Vermeris et al, 2007) Hybridization has the potential of increasing sorghum productivity by more than twice the potential under the same conditions as the non hybrids (Rooney et al. 2007) House et al. (1997) reported that utilization of hybrid sorghum seeds can significantly increase yields. Bantilan et al. (2004) quantified the increase potential of hybrid utilization between 20 to 60% (House et al. 1997; Bantilan et al. 2004) Hybridization has the potential of increasing both the grain and the plant biomass accumulation in sorghum Zeng et al. 2011) For Kenya to realize high productivity in sorghum, the challenges facing sorghum hybrid utilization have to be circumvented. Researchers have to tailor their studies to the market needs of the sorghum crop (Pingali and Traxler, 2002) There is need for the government to motivate the farmers by seed subsidies through active involvement in hybrid seed development. Importance of sorghum Grain sorghum is food for millions of people living in the arid and semi arid tropics (Sing and Sing, 1992; Sharma and Ortiz, 2000) In Kenya, it is grown for subsistence in Western, Nyanza and Eastern provinces. It is a food security crop with good storage properties. Various communities have diversified the use ranging from ugali, porridge, githeri and even as a beverage (Leder, 2004) Sorghum is rich in carbohydrates and proteins but lacks preference due to the presence of phenolic compounds resulting to high tannin concentration in the seed coat (Jansman, 1993) It is believed that the tannins are an adaptive mechanism to protect the grains from birds as many bird resistant varieties have high tannin content (Husle et al. 1990) Int. J. Agron. Agri. R. Oyier et al. Page 67 Sorghum forms a good alternative to farmers living in the arid and semi arid lands giving them an opportunity to harvest from the otherwise non productive land with minimal input. It is therefore a source of livelihood for the rural communities who would otherwise not get anything from farming. In USA, sorghum is one of the most preferred fodder crops with quick biomass accumulation and high value calories (Almodares et al. 2011) Forage sorghum can therefore be a major contributor in the development of livestock industry (McDermott et al. 2011) It is easily made into silage with high protein content if harvested at the correct time. Sorghum has not been utilized for forage in developing countries (Rooney et al. 2007) This is particularly because the most common variety is the grain sorghum which does not have good forage properties. In Kenya for example, there is no production of forage sorghum yet there is high demand for fodder. Sweet sorghum has been known to have high sugar content in the stem and has both ethanol and forage production potential (Rooney, 2007) With the efforts to reduce consumption of fossil fuels to reduce global warming, sweet sorghum has the potentials of playing the double role through food and energy provision (Yuan, 2008) The growing of sweet sorghum has not been adopted by the Kenyan farmers. Production of sorghum hybrids Hybridization refers to the act of mating organisms of different varieties or species resulting to a hybrid offspring. Studies have indicated that the new offspring may have improved performance due to heterosis. Heterosis has been used in crop improvement for several decades (Duvick, 2005) It is believed to be caused by dominance and or over dominance gene actions (Birchler et al. 2010; Kaeppler, 2012) Sorghum is a self pollinated crop except for isolated instances of cross pollination. Studies have established that the crop is about 6% cross pollinated (Sing, 1995) Self pollination makes hybrid seed production challenging due to complex procedures in emasculation. However, with the discovery of male sterility among some varieties of sorghum, hybrid production has been made highly feasible. Application of male sterility in hybrid production involves identification of the male sterile line (A line) male fertile line (B line) and the restorer line (R line) The use of male sterile line enables mass production of seeds since emasculation occurs naturally due to the non production of viable pollen. Cytoplasmic Male Sterility (CMS) is caused by a gene present in the cytoplasm. This kind can be transferred to a given strain using it as a pollinator. It has been utilized in hybrid production in several crops (Sing, 1995) In maize, Texas male sterile cytoplasm was used to make hybrids (Deway et al. 1996) in Petunia (Young and Hanson 1987) in sunflower (Helianthus annus) (Monenger et al. 1994) and in beans (Phaseulus vulgaris (Abad et al. 1995) several hybrids have been produced. In sorghum, this has been reported in many varieties originating in India, Africa and America (Sane et al. 1996) It is currently used in many breeding centers to produce sorghum hybrids. The technology is also used by seed companies for production of hybrid seeds which have contributed to significant increase in sorghum production especially in the USA. Globally, USA is leading in sorghum production for the animal feeds (Stewart et al. 2005) while India is leading in grain sorghum production (Fig. 4) (Almoderas and Hadi, 2009) There has been a declining trend in the production of sorghum in Kenya (Connelly, 1994; Thornton, 2010) Many sorghum hybrids have been developed to meet various needs (Edgerton, 2009) There are those which have been improved specifically for fodder, ethanol and grains. Several seed producing companies have released various sorghum hybrids for use in other countries (Tripp and Rohrbach, 2001) Utilization of hybrid seeds is highest in the USA which also happens to be l