Growth, physiological and yield responses of yam landraces (Dioscorea cayenensis-rotundata complex) evaluated under different water regimes in southern Ethiopia

Abstract

Drought stress is one of the most critical abiotic factors limiting sustainable agricultural production globally. It significantly affects plant growth, physiological processes, and crop yields. This study evaluated the drought tolerance of seven yam landraces under varying soil moisture regimes in a greenhouse during the 2024 growing season. A completely randomized design (CRD) with four replications was implemented, utilizing four soil moisture treatments: T1 = 100% FC (control), T2 = 60% FC, T3 = 30% FC, and T4 = 0% FC (halted after saturation at the experiment's commencement). Growth parameters (plant height [PH], leaf number [LN], branch number [BN], internode length [IL], leaf area [LA], biomass), physiological traits (photosynthetic rate [A], transpiration [E], water use efficiency [WUE], intercellular CO 2 concentration [Ci], stomal conductance [gs], stomatal density [SD], relative water content [RWC], chlorophyll content [CC], electrolyte leakage [EL], and drought tolerance indices (drought susceptibility index [DSI], drought tolerance index [DTI], and yield index [YI]) were evaluated. Data were analyzed using two-way ANOVA at a 5% significance level. Drought stress significantly reduced growth, physiological performance, and yield across all landraces compared to the control (T1). However, landraces Aha, Ayno, and Duurundufa maintained higher plant height, yield, and biomass under drought stress (T2–T4). Notably, Afri, Gandifa, and Gebsh did not survive under the most severe stress (T4) after three months, showing no measurable height, yield and biomass. Significant differences (p < 0.05) in aboveground biomass (AGB), belowground biomass (BGB), LN, LA, IL, and SD were observed among landraces and treatments. Most physiological traits (i.e A, E, WUE, Ci, RWC, and CC) were markedly reduced with increasing drought (T2-T4) in most landraces, though Aha, Ayno, Duurundufa, and Qekila performed relatively better. Tuber yield declined sharply under T3 and T4 treatments and was positively associated with physiological and growth traits, and negatively with electrolyte leakage. Electrolyte leakage increased under drought stress in most landraces, especially Afri, Gandifa, and Gebsh, while remain lower in Aha, Ayno, and Duurundufa. Based on drought tolerance indices and physiological resilience, Aha, Ayno, Duurundufa, and Qekila were identified as drought-tolerant landraces. These varieties exhibited stable photosynthesis and efficient water use under stress. Their selection could support breeding programs, germ-plasm conservation, and climate-resilient agriculture, particularly in drought-prone areas like Ethiopia.