Soybean production in southern Africa is complicated by the occurrence of frequent droughts and poor soils, especially those low in phosphorus. During the 2015/2016 season, Malawi, Mozambique, Zambia, and Zimbabwe experienced one of the worst droughts in decades, with very few farmers getting a decent harvest.
Developing soybean varieties with delayed wilting under drought conditions and also early maturing varieties which can escape drought are some of the approaches IITA is taking in its breeding program. In addition, the IITA germplasm which is largely promiscuous nodulating—a trait developed to improve soil fertility in small-scale farms—is apparently showing that nitrogen fixation is the most important trait for delayed wilting, hence it can be used to indirectly develop drought-tolerant cultivars for the region.
To meet farmers’ needs such as developing high-yielding and diseasetolerant varieties, as well as large-seeded ones to meet market needs, IITA’s Soybean Breeding Program is being supported by two soybean projects: the USAID/IITA Genetic Improvement in Soy W3 CGIAR Research Program on Grain Legumes, and the University of Illinois/IITA, Soybean Innovation Laboratory under USAID’s Feed-the-Future initiative. The two projects are complementary; the former focuses on direct variety development, whereas the latter centers on breeding efficiency, capacity building, and integration of USA elite lines into tropical germplasm.
IITA’s work on improving soybean in the Southern African region has recorded significant strides in 2016. Table 1 summarizes these achievements to date.
Yield trials in 2015/2016 season
During the 2015/2016 season, preliminary variety trials and advanced variety trials were planted in Malawi, Mozambique, Nigeria, and Zambia to examine the performance of varieties under different environmental conditions which included drought and low soil phosphorus conditions. Due to the severe drought experienced during the 2015/2016 season, data from several trials could not be used for Malawi. Some of the results of the advanced trials are shown in Table 2 and Figure 1, presenting the reaction of some of the lines under drought conditions at IITA’s Research Station at Chitedze in Malawi.
Exotic germplasm screening and introgression
Infusing germplasm from the University of Illinois’ soybean breeding program into IITA breeding populations is one of the key objectives to increase genetic diversity and also yield potential in African tropical germplasm. A total of 462 genotypes from the Soybean Innovation Lab (SIL), USA (Table 3) were requested and planted at the IITA Research Station in Kabangwe, Zambia, during the 2015/2016 season.
Due to the drought, planting was done late in the season. Twenty-five seeds per genotype were planted in single-row plots in an augmented design, which included six checks from Seedco, SC Samba, SC Sepa, SC Safari, SC Square, and SC Spike. MRI-Syngenta check MRI Dina was also included. Table 3 summarizes the number of genotypes planted.
Observation data collected included days to flowering, plant aspect, and 100-seed weight. Figure 2 summarizes the distribution of the 100-seed weight among the genotypes, a key trait to be introgressed into the IITA germplasm. From the observation nursery a total of 40 genotypes were selected as potential parents to initiate pedigree breeding from IITA genotypes with an emphasis on increasing seed size.
The 100-seed weight of accessions from the genebank ranged from 9 to 33 g with a mean of 17.3 g. The majority of the large-seeded genotypes were of Asian origin, namely, Akiiyoshi and Sudoi No 1, and some USA maturity group 3, Saturn. Mean 100-seed weight for the elite breeding material ranged from 10 to 24 g with a mean of 16.6 g.
Participatory variety selection in Malawi
The soybean breeding technology transfer and scaling up is done through demonstration plots using Participatory Variety Selection (PVS) trials and field days during the growing season. During the 2015/2016 season, three field days were held in Malawi at Chitekwere EPA, Nkhoma, Lilongwe; Kaphuka EPA, Dada District; and Nachisaka EPA, Dowa District. In total, 183 participants attended the field days with 95 males and 88 females. Table 4 summarizes the number of participants for each district.
Partnerships and the Soybean International Trials
In addition to the breeding trials, Soybean International Trials (SIT) were also sent out to collaborating partners on request from various institutes, including the Syngenta Foundation and the Seeds2B program for trials in Mali. Table 5 summarizes the recipients of SIT during the 2015/2016 season. In total, eight countries participated in the 2015/1016 SIT. Results from these trials will be used to identify key lines by collaborating partners for use as direct variety release or parental lines for use in the breeding programs