Evaluation of Hybrid Maize Varieties in Three Agro- Ecological Zones in Ghana
ABSTRACT
Maize (Zea mays L.) is an important food crop in Ghana, but its productivity in farmers‟ fields throughout the country is generally low. The low grain yields can be attributed partly to the use of traditional low-yielding maize varieties. Farmers‟ adoption of hybrid varieties would reduce deficit of demand and supply of maize in the country. A study was undertaken to assess the relative yielding abilities and stability of 20 hybrids selected from the breeding programme of the West Africa Centre for Crop Improvement maize breeding program together with three locally released varieties. The trial was conducted in the coastal, savannah and transitional forest zones over major and minor seasons in 2012 and 2013. A randomized complete block design with three replications was used in each experiment. The relationship between yield and its components were also determined. Significant differences (p<0.05) were observed among the genotypes for days to anthesis, days to silking, ear height, plant height, field weight and grain yield. Highly significant (P<0.01) differences were observed among the three trial locations for all the traits studied. Grain yield showed highly significant differences (p<0.01) among the genotypes across the three locations. Significant differences among locations were observed for the 23 genotypes for grain yield, days to tasseling, days to silking, plant height, field weight, ear height. For genotypes, variations were highly significant for grain yield, field weight, plant height, days to anthesis and silking. However, there were no significant differences among the genotypes for ear height, ear harvest and plant stand. Apart from grain yield and field weight, differences due to the interaction (genotype x location) were not significant for all the other traits studied. The magnitude and nature of genotype by environment (GE) effect was significant using additive main effects and multiplicative interaction (AMMI) analysis of variance for grain yield. The main effects also were highly significant. Further analysis showed that the genotypes
significantly contributed more than the environments in these effects. The significant genotype – environment interaction revealed by AMMI suggests that the relative performance of the genotypes changed for grain yield across all environments. The study also identified Wenchi as the location for the best grain yield performance and Tamale as an environment yielded low grain yield in both seasons. GGE biplot analysis revealed that varieties “wacci-m-1212”, “wacci- m-1204”, “wacci-m-1208”, “wacci-m-1209”, “wacci-m-1206”, “wacci-m-1220”cc, i-“mw-a
1205” and “wacci-m-1207” were the high yielding and very stable hybrids. This supports the general opinion held by many stakeholders that use of hybrids holds the future of maize production in Ghana‟s agriculture and that serious efforts must be made to encourage the adoption and use of superior hybrid maize varieties in Ghana as a means of increasing maize productivity and production in the country.
CHAPTER ONE
1.0. INTRODUCTION
Maize (Zea mays L.) is the second most important food crop after cassava on the African continent (De Vries and Toenniessen, 2001). It is the most important grain crop in West Africa in terms of quantity produced and consumed (Tweneboah, 2000). According to FAO (2009), the area in West Africa countries planted to maize increased from 3.2 million ha in 1961 to 8.9 million ha in 2005. Between 1987 and 2007, this area increased from 7,958,927 ha to 11,752,136 ha (FAO 2010). This phenomenal expansion of the land area devoted to maize resulted in increased production from 2.4 million tonnes in 1961 to 10.6 million tonnes in 2005. However, although the average yield in the developed countries is up to 8.6 t/ha, production in several areas of West Africa is still very low 1.3 t/ha (FAO, 2010). Maize currently covers 25 million hectares in Sub-Saharan Africa, largely in smallholder systems that produced 38 million metric tons in 2005-2008 primarily for food (Melinda et al., 2011).
Maize is used as human food, livestock feed, and as raw material for industry (FAO, 1992). Average annual per capita human consumption of maize is 20 kg in developing countries, but in Latin America and the Caribbean, it approaches 80 kg and, in Sub-Saharan Africa, it is estimated 60 kg (CGIAR, 2002).
Between 2004 and 2006, over 700 million tonnes of maize were annually produced on 145 million ha; of which 380 million tonnes on 100 million ha were in the developing world. By 2020 maize production in industrialized and developing countries will have surpassed that of wheat and rice and will have increased since 1997 by 45% at the global level and by 72% in developing countries (Rosegrant et al., 2001). Within the developing world, the demand for food
maize will be the greatest in sub-Saharan Africa (40 million t), followed by Latin America (30 million t), and then South and Southeast Asia (25 million t).The World maize yield averaged 4.9 t/ha in 2009 (Edgerton, 2009). However, yields in major maize growing areas in the developing world still lag behind the world average, producing only about 2.8 t /ha (Pixley et al., 2009). Yields in the United States for example have increased remarkably from an average of 1.6 t/ha in the early 1930‟s to the current approximately yield of 10 t/ha (Edgerton, 2009) as a result of adoption of hybrid seed maize, whereas yields presently obtainable in Ghana hover around 1.7 t/ha. This large discrepancy in yield has been ascribed partly to the use of unimproved or open pollinated varieties instead of hybrid maize, traditional farming practices, the use of low-yielding varieties, poor soil fertility and limited use of fertilizers, low plant population, inappropriate weed and inadequate disease control. MoFA (2011), reported that achievable yields of about 6 t/ha have been obtained in maize yield evaluation yield. This therefore indicates that the average maize yield of 1.7 t/ha currently obtained in Ghana, is about 70% less than what is usually achieved in maize yield trial by researchers. However, yields as high as 5.0-5.5 t/ha have been realized by farmers using hybrid seeds, under fertilizer, mechanization and irrigation (MiDA, 2010). Maize is grown in all of agro-ecological zones of Ghana. However, the main areas are in the middle parts of Ghana or the transitional forest zone (FAO, 2010). The area includes Brong Ahafo and parts of Ashanti and Eastern regions. In Ghana, maize is mostly grown by peasant farmers and on small scale with low yielding cultivars and therefore leading to low output.
There is low use of improved maize hybrid seed in the country. The rate of adoption of improved maize seeds in Ghana is 1 percent (Langyintuo et al., 2010). Most of the maize varieties used in Ghana are open pollinated varieties (OPVs) with low yields, and degenerate after many years of cultivation without seed renewal. In order to meet the growing needs of farmers in Ghana, nine
- hybrid maize varieties have been released by CSIR – CRI (MoFA, 2011). Maize farmers throughout the country, though yields are still low have adopted these released varieties and small holder farmers continue to meet difficulties in accessing improved hybrid seed maize. At present, there is growing demand for the use of hybrid seed maize and this is thriving the emergency of a number of seed companies in
Farmers and breeders want successful new maize hybrids that show high performance for yield and other essential agronomic traits. Their superiority should be reliable over a wide range of environmental conditions. The basic cause of difference between genotypes in their yield stability is the occurrence of genotype-environment interaction (GEI). Genotype – environment interaction may be expected to be high when environmental differences are high as in Ghana. Hence, it is important to assess the importance of interactions in the selection of genotypes across several environments besides calculating the average performance of the genotypes under evaluation (Fehr, 1991; Gauch and Zobel, 1997).
Various studies have been conducted to analyze effects of GEI on Ghanaian maize varieties and in Sub-Saharan Africa (Badu-Apraku et al., 1995, 2003; Fakorede and Adeyemo, 1986, Abdulai et al., 2007). However, the changing conditions, the introduction of maize to new agro-ecologies as a result of inadequate maize varieties available for the different environments necessitates a rigorous and continuous study of GEI for a dynamic crop improvement program. The West Africa Center for Crop Improvement (WACCI), University of Ghana, maize breeding program has produced a number of high yielding hybrids. These materials are yet to be tested on farmers‟ fields. Hence, the study was conducted of twenty hybrid maize from West Africa Center for Crop improvement, maize breeding program and three locally released hybrid maize to identify
stable and high yielding hybrids with superior agronomic performance for commercial production in Ghana.
The specific objectives of this study were to:
- assess grain yield of hybrid maize varieties in three agro –ecological zones of Ghana
- Determine relationship among grain yield and its components within and across the three agro –ecological
- Assess stability of grain yield of these hybrids
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