MORPHOLOGICAL AND PHYSIOLOGICAL RESPONSE OF KENYAN BRACHIARIA ECOTYPES TO DROUGHT STRESS

Abstract

Brachiaria, native to Africa, also known as signal grass, is a plant that uses C4 fixation pathway (C4 ). The grass exhibits advantages that include tolerance to drought, sequestration of carbon, enhancing nitrogen use efficiency and minimizing greenhouse gas emissions. Despite the above advantages, tolerance to extreme drought remains a challenge to some of the re-introduced varieties and ecotypes which reduces herbage yield hence low livestock production. With the onset of climate change, the aim of this study was to use morpho-physiological traits to evaluate the ability of Brachiaria ecotypes (BrK 1 to 25) to tolerate different levels of drought. A total of 23 wild ecotypes and two hybrids (BrK 7 and BrK 10) were evaluated in three treatments: control, moderate and extreme. The study adopted a complete randomized design in a factorial arrangement (3x25). Morpho-physiological parameters evaluated included plant height, leaf length, width, tiller numbers, relative water content, chlorophyll content and biomass. Correlation and Principal Component analysis were also used to determine the relationship between water withdrawal and the ecotypes. Under severe stress, results showed differences (P<0.05) for chlorophyll content, plant height, biomass, tiller number and relative water content. Based on Principal Component analysis, PC1 accounted for 43.2% while PC2 accounted for 17.8% of the variation observed. There was positive correlation (P< 0.05) between biomass and plant height (r=0.2386), internode length (r=0.2367) for the stress experiment. Based on the morpho-physiological traits, BrK 1, BrK 3, BrK 10, BrK 15 and BrK 20 showed tolerance to drought. However, comparative and confirmatory studies based on various drought indices and other physiological and molecular tools should be used to ascertain the results