Genotypic response of brachiaria grass (Brachiaria spp.) accessions to drought stress.

Background and Objective: Brachiaria, a warm season C4 grass, is rapidly gaining popularity as fodder crop in Africa where it is also used as a component of a habitat management strategy for maize stem borers. However, increasing drought limits productivity of this grass species. The aim of this study was to evaluate and select high yielding brachiaria genotypes under simulated drought conditions. Materials and Methods: The morphological and physiological performance of 18 apomictic accessions of brachiaria in simulated drought conditions in a screen house were evaluated. Plants were exposed to different watering regimes. Well-watered (control) plants were watered every 48 h to 100% field capacity while drought was simulated by suspending watering for 14 and 28 days, representing moderate and severe drought conditions, respectively. Shoot length, leaf length and width, number of tillers, leaf relative water content, chlorophyll content and above ground biomass were studied. Result: Water stress had negative effects on the morphological and physiological traits, with the effects being more pronounced under severe drought stress. Based on the drought stress index (DSI) values for the measured parameters and Principal Component of Analysis (PCA) biplots, the following accessions were least affected under severe drought stress: ʻXaraesʼ, ʻPiataʼ, ʻMaranduʼ, ʻCIAT 679ʼ, ʻMulato IIʼ and ʻMulato Iʼ. Conclusion: Under increasing drought conditions, biomass yield was an accurate predictor of drought tolerance of the genotypes. ʻPiataʼ and ʻXaraesʼ combined both drought tolerance and biomass yield. These two accessions were proposed as of value in improvement of the sustainability of cereal-livestock farming systems under conditions of increasing aridification.