ROOT RESPONSES AND RELATIONSHIP TO POD YIELD IN DIFFERENCE PEANUT GENOTYPES (Arachis hypogaea L.) UNDER MID-SEASON DROUGHT

Large root system and good root distribution reduced yield loss from drought. There is limited detail on genotypic variation for root responses under mid-season drought and more importantly the correlation between root traits and peanut yield. Experiment was conducted in a split plot design with 4 replications at Khon Kaen University in 2011/12 and 2012/13. Sub-plots were assigned as 5 peanut genotypes and main plots were assigned as 2 soil moisture levels. Measurements of root traits and peanut yield were made at drought period and final harvest. Mid-season drought reduced biomass and pod yield. Yield of all peanut genotypes were correlated with percent of root length density (%RLD) and root surface under mid-season drought. The study revealed that genotypes with large root growth and high root distribution maintained high pod yield under mid-season drought. Cultivar KKU 60 maintained high pod yield and also had high %RLD and root surface at lower soil layers under mid-season drought Tainan 9 and KS 2 had low %RLD at the lower soil stratum and did not maintain pod production under mid-season drought. Root traits in peanut genotypes were correlated with biomass and harvest index under water stress. Peanut genotypes have high %RLD and root surface at deeper soil stratum may use more water during drying cycle and had a potential to maintain peanut yield during mid-season drought. %RLD and root surface in the lower soil stratum are the criteria for selecting peanut genotypes for drought tolerance.