EARLY GENERATION SELECTION FOR DROUGHT RELATED TRAITS IN GROUNDNUT (Arachis hypogaea L.) IN MALI
Groundnut, an important food, feed and cash crop in the Sahel, is mostly rain-fed and most of the time, the growing phase terminates under a period of drought. This exposes the crop to end-of season drought, causing high yield losses. The main objective of this study was to develop drought tolerant groundnut lines following early generation selection. The specific objectives were to (i) assess farmers’ understanding of drought and identify their preferences for groundnut varietal traits in Mali, (ii) estimate the combining ability for yield and drought related traits and the mode of gene action, (iii) estimate the heritability and genetic advance of early generations for drought and yield traits under well-watered and water-stressed conditions, (iv) identify promising F2:3 high yielding and drought tolerant lines, and (v) assess the performance of selected F2:4 drought tolerant lines across environments. The results indicated that farmers considered drought particularly end-of-season drought and non-availability of seed for planting as the top two major constraints limiting groundnut production in the Sahel area of Mali. Farmers’ varietal preferences among other traits included high yield potential, drought tolerance, early maturity, high storability, large seed, good pod filling and resistance to termites and rosette disease. Additive gene effects were predominant over non-additive effects for most of the measured traits under both water regimes (full irrigation and drought stress) and environments (pots and field). Two females ICGV 91317 and ICIAR 19BT and two males ICGV 97182 and ICGS 44 were identified as good general combiners. The crosses ICIAR 19BT/ ICGS 44 and ICGV 91317/ ICGV 87378 were selected as best progenies with high yield under both well-watered and water-stressed environments. Quantitative genetic analyses (broad and narrow-sense heritability, genetic advance) were carried out for two crosses at early generation of F2 and F2:3
progenies under well-watered and water-stressed conditions. In most cases, the regression and correlation coefficients were low to moderate and sometimes negative for several traits (Specific Leaf Area (SLA) and SPAD Chlorophyll Meter Reading (SCMR) at 60 and 80 DAS) irrespective of the generation and watering conditions. Similarly, moderate to low genetic advance was detected. However, high estimates of broad sense heritability under well-watered and water-stressed conditions were detected for SLA, SCMR at 60 DAS and 80 DAS and pod yield. Environmental factors have important effect on these traits which could hinder progress during selection for progeny for both populations. Due to the limited number of individuals at F1, F2 and F3 generations, the precision of estimating the quantitative traits was low. Using selection indices with 10% selection intensity, genotypes ICGX-IS 13012F2-B1-297, ICGX-IS 13012F2-B1-40, ICGX-IS 13005F2-B1-46, ICGX-IS 13005F2-B1-252, ICGX-IS 13012F2-B1-29, ICGX-IS 13005F2-B1-205, ICGX-IS 13005F2-B1-287, ICGX-IS 13012F2-B1-525, ICGX-IS 13012F2-B1-576 and ICGX-IS 13005F2-B1-91 were identified as the top 10 drought tolerant F2:3 progenies with high yield stability in both water regimes. Overall, the top six drought tolerant genotypes showed increases of up to 20% in grain yield over means of parental checks and landraces. Of these, three genotypes ICGX-IS 13005F2-B1-287-1, ICGX-IS 13005F2-B1-205-1 and ICGX-IS 13012F2-B1-29-1 were found to be stable across environments. The best performing genotypes for each specific environment were ICGX-IS 13005F2-B1-287-1 for Tioribougou and ICGX-IS 13005F2-B1-252-1 for Samanko. Before recommendation of new drought tolerant varieties to farmers, it is recommended that the superiority of the newly developed genotypes should be confirmed in at least one more season since drought is a natural phenomenon that is random.