1.1 Background

Common bean Phaseolus vulgaris is a leguminous plant that originated from Mexico in the years 5500-7000 AD (CGIAR, 2007) and is primarily grown for its edible seeds. The plant belongs to the group of grain legumes that are grown worldwide on 12%-15% of the earth’s arable land (Vance, 2002). CGIAR (2015) explains that about 12 million metric tons of common beans are produced annually, with Latin America playing the major role (about 5.5 million metric tons). The crop is also largely produced by Brazil and Mexico. Africa ranks second in terms of production (produce 2.5 million metric tons). Major African producers include Kenya, Burundi, Congo, Uganda, and Rwanda (CGIAR, 2015).

For Malawi, common beans rank second to groundnuts in terms of area planted and quantity produced (Mazuma et al., 2004). In terms of gender, the crop is largely grown by women in Malawi. For the past 11 years, there has been an upward trend of common beans production in Malawi, with central region (Dedza) taking the major role (Birachi 2012). For instance, common beans production increased from 76,964 metric tons in 2004/05 to 182,596 metric tons in 2011/12, though it declined to 128,624 metric tons in 2012/13. The output per hectare also increased i.e. from 376 kilograms per hectare in 2004/05 to 596 kg/ha in 2010/11 (GoM, 2012). Currently, the popular bean varieties available in the markets in Malawi include Nanyati (cream mottled), Khaki/Mulanje (cream), Napilira/Kachinyata (red mottled), Phalombe/ Chimbamba/Thyolo (red kidney), Kaulesi (Purple/greyish), and mixed beans (various colours) (Chirwa & Phiri, 2007). T