Cowpea data for six environments in the Guinea ecologies of Northern Ghana for 2016 and 2017 drought evaluation
The research hypothesis was that F2-derived F8 Recombinant inbred could perform better than the parental checks under contrasting soil moisture conditions in the Guinea Savanna ecologies of Northern Ghana. Seeds of the parental lines were planted in plastic buckets measuring 32cm in diametre, filled with black, loamy top soil in a screen house facility at SARI. At flowering, the male parent was crossed with the female parent to generate F1 seeds. Series of plantings of the parents were carried out between the period of June and December 2010 to synchronize flowering and several crosses were done to generate enough F1 seeds. In the following season, in July 2011, the F1 seeds were individually planted at a spacing of 60cm x 60cm. The F2 population was obtained by harvesting seeds from each F1 plant separately. The F2 seeds were planted in a field at a spacing of 60cm x 60cm in July 2012 and allowed to self-polinate. Seeds from each plant were harvested and kept separately to obtain an F3 population. In July 2013, the F3 seeds were planted in the field in progeny rows to obtain an F4 population. Single plants harvested from each line in each of the F4 and F5 populations led to the development of an F6 population of recombinant inbred lines. Seedling drought screening was done in wooden boxes in two sessions using augmented design. Moisture stress was applied for 4 weeks during which various physiological indices for drought was taken. Proportion of survived seedlings, relative water content among others were used to select potentially drought lines which were subsequently evaluated in 2016 and 2017 at Golinga and Libga irrigation sites respectively in the Guinea Savanna ecology. Split plot design was used for the field experiment. The watering regimes at two levels were the main plots and the 22 recombinant inbred lines plus two parental checks were the subplot factor The genotypes were completely randomized with three replicates. An experimental unit consisted of five row plots of two-meter-long, and 10 plants per row giving a plot stand of 50 plants per plot. Spacing between and within plants were 60 cm x 20 cm. The inner three ridges were used for sampling and data collection. Blocks and plots in both experiments were separated by a spacing of 2 m. Moisture stress was imposed 10 days after planting and watering resumed at 40 days after planting. Physiological and agronomic data were collected during moisture stress at vegetative, flowering and at harvest. The use of two contrasting parents; drought tolerant and drought susceptible advance breeding lines in generating the inbred lines for the study revealed classes of maturity groups for drought tolerance. This resulted in identifying the inbred lines based on the performance of the parental lines and thus enabling the test of superiority for the inbred lines in relation to the parental performance across the environments used for the study.