CHAPTER I: INTRODUCTION
7. Participatory variety selection of sorghum hybrids using farmers' preferences and
7.4. Discussion
7.4.1. On-station evaluation trial
For grain yield across the two seasons (2015/16 and 2016/17), the main effects of hybrids and seasons (environment) and their interaction were highly significant at (P<0.001). Hybrid TX 631A x MZ 37R had the highest grain yield among hybrids across seasons with a mean of 5.7 t.ha-1 followed by SPL 38A x SDS 6013R with a mean yield of 4.2 t.ha-1. The lowest grain yield was obtained for ICSA 19A x SDS 6013R in the second season with a mean of 1.6 t.ha-1. It was observed that the grain yield was higher in the second season than the first season. One
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of the reasons was the limited amount of rain received in the first season during flowering stage. If the drought occurs during post-flowering, it severely affects the translocation of nutrients to the sink and, premature senescence resulting in drastic reduction in grain filling (Crasta et al., 1999). This suggested that hybrids did not express their grain yield potential in the first season. The environmental conditions affect the yield variability of grain crops during the most sensitive stages of crop development (Wheeler et al., 2000). Borrell et al. (2000) reported that grain yield declined when a deficit of water in hybrids increases. An important element of yield under stress conditions is the water use efficiency of the crops (Blum, 2009).
Therefore, the hybrids in the study exhibited tolerance to drought during the first season and had a higher yield than the commercial/local varieties. This shows that weather conditions were not the limiting factor for the low yields of the adapted varieties like improved varieties and/or local varieties. Similar results were reported in a study that compared exotic genotypes with local adapted genotypes (Calhoun et al., 1994).
The ranking of the hybrids for number of days to 50% flowering changed between the two seasons. The hybrid TX 631A x MZ 37R had the least number of days in the first season and an average number of days in the second season (Table 7-3). A similar trend was observed in the hybrid SPL 38A x SDS 6013R which had the most number of days to 50% flowering.
The hybrids were not consistent in the days to 50% flowering in the two seasons, thus contributing to the hybrid x environment interaction observed This variation might have been due to the drought stress experienced during the flowering stage in the first season (2015/16).
Drought has been reported as an important stress that affects the genetic and physiological mechanism of the plant (Tuinstra et al., 1996). Both pre-flowering and post-flowering drought stress responses have been identified in sorghum (Harris et al., 2006) and these influence the period of flowering and ultimately the grain yield.
Four hybrids had the least number of panicles in the first season, but the panicles were much larger in size. Similarly, plant height showed significant hybrid x environment interaction across the seasons. This indicated that the number of panicles and plant height are strongly influenced by changes in climatic conditions. Graham and Lessman (1966) reported that high yielding sorghum genotypes may be achieved in a combination of plant height and other components. Plant height was reported to be one of the most important yield components (Fernandez et al., 2009) especially for biofuel production in sweet stem sorghum where it contributed to increased biomass.
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The on-farm trials resulted in highly significant main effects for hybrids, environment and their interaction for all the traits. This indicated that the hybrids responded differently under the different agronomic farmer management practices. This shows that the use of unlike farmers was appropriate to capture their variety preferences. Active involvement of farmers in plant breeding has been shown to increase the efficiency of classical breeding (Witcombe et al., 2005; Gyawali et al., 2007). Morris and Bellon (2004) reported different approaches of participatory plant breeding which include inviting farmers to participate in varietal selection and evaluation activities or teaching them formal selection techniques. Additionally, adoption of new improved varieties by farmers requires an understanding of the important environments and production constraints they face and thus involve them from the initial stages of the breeding process (Bänziger and Cooper, 2001). Moreover, Mekbib (2006) suggested that defining or setting goals and objectives especially for breeding multi-purpose varieties should involve final consumers and industrialists. Many years of participatory approaches to identify genotypes with characters preferred by farmers is an approach that leads to the adoption of the new varieties (Nkongolo et al., 2008). Therefore, understanding farmers’ preferences and acceptability of a new variety is essential for the adoption of improved varieties (Horn et al., 2015; Olubunmi, 2015).
Although grain yield was one of the traits that the farmers selected, they had additional characteristics they looked for in a variety. These included adaptability and yield stability. This indicates that farmers were more concerned with their environments which experienced frequent droughts and thus desired a variety that allowed them to harvest something even during the dry seasons. This could be one of the reasons they keep growing the local variety even though it is low yielding. The low adoption rate of high yielding varieties can be explained by the fact that most of the varieties are selected without involving farmers (Asrat et al., 2010).
The best hybrid selected by most farmers was based on good grain yield, early maturity, less bird damage and white grain colour. The majority of men preferred tall plants with sweet stems, while women preferred earliness. This is explained by fact that men are more worried about the use of all the sorghum parts, while women are worried about food for the family. In general, the majority of farmers preferred a sorghum variety with high yield, early maturity, large grain size, white grain colour and tall plants. Moreover, farmers also mentioned that drought tolerance was an important trait for the varieties. These results are in agreement with findings that breeder’s on-station selections produce lines with high grain yields, while farmers’
selections produce varieties with a combination of earliness, plant height, grain size and grain yield (Trouche et al., 2011; Trouche et al., 2012). Other farmers chose earliness as an
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important trait and defined it as the ability of the plants to complete the growing stage up to flowering stage before the rainy season stops so that the grain filing period will not be compromised (Vom Brocke et al., 2010). The white grain colour was mentioned as an important trait as most of the farmers mix sorghum flour with maize flour to cook their staple food, a thick porridge. This characteristic might be an important key for future breeding strategies for farmers’ preferences where it should be used as one of the traits for selection.
Plant height and head size were also important criteria for some of the farmers and it is associated positively with good grain yield. The reasons for selecting plant height were mostly related to the use of the stems for building houses or granaries. The other traits preferred by farmers were post-harvest traits in combination with high yield and variety stability for the short and long rainy season (Lacy et al., 2006). On the other hand, farmers mentioned the importance of having drought tolerant varieties, although the study did not select for drought tolerance among the hybrids due to high amounts of rain during the growing season. Drought resistant crops are essential for food security (Vunyingah and Kaya, 2016).
Farmers, in general, preferred high yielding hybrids combined with other characteristics essential for their environment. Additionally, seed for the improved varieties such as hybrids should be easily accessible and markets for the grain should be available.
7.4.3. Implications for breeding
Farmers’ selections were based on the production constraints in each environment and this resulted in a variety that combined high grain yield, early maturity, large grain size, tall plant height and drought tolerance. This implies that breeders should pay attention to these traits and other traits that confer drought tolerance such as stay green if the varieties have to be adopted. From this study, two groups of varieties should be deployed; one that responds to high yield and early maturity, and the other to high yield with tall plants. The reason is that normally accumulation of plant biomass takes long, thus varieties will not fit in the short and early maturing group. In addition, farmers usually recycle seed, and this might result in yield reduction in a hybrid. Therefore, farmer education on sorghum hybrids is essential.