Morpho-physiological and Yield Responses of Sweet Potato (Ipomoea batatas (L.) Lam.) Genotypes to Frequency of Irrigation under Greenhouse Condition

Abstract

Introduction: The sweet potato (Ipomoea batatas Lam.), is one of the root and tuber crops grown from low land to high land region of Ethiopia. However, its productivity depends on adaptability and tolerance to different environmental stresses and the capacity of the crop to enhance water use efficiency under moisture stress conditions. The objective of this study was to evaluate impact of irrigation interval on morpho-physiological characteristics of sweet potato varieties. Methodology: The trial was a 3 x 2 factorial arrangement in CRD design consisting: three irrigation intervals (daily-control), four days and seven days interval) combined with two sweet potato genotypes (Hawassa-83 and Kulfo) with three replications. Results: The morpho-physiological indicators, morphological traits, water use efficiency (WUE), Relative leaf water content (RLWC), leaf gas exchange, stomata density, and tuber yield were evaluated. The result indicated that morphological traits were significantly (P≤0.05) responded to genotype and irrigation frequencies. As compared to daily irrigation, an extended watering interval to seven days irrigation interval significantly reduced leaf number, vine length, branch number and internode length by 55.42, 19.83 cm, 2.17 and 0.35 cm, respectively. Stomata density was strongly responded to genotypes than effect of irrigation frequency. Genotype Hawassa-83 had approximately 2.0 more stomata per mm2 than genotype Kulfo regardless to irrigation frequency. The interaction effect between genotype and irrigation frequency revealed significant influence on photosynthesis and transpiration rate. The rate of assimilate accumulation was significantly reduced (by 9.97μmol m-2s-1) in Hawassa-83 irrigated due to extended irrigation interval to seven days than variety irrigated daily. Delay irrigation for four and seven days reduced transpiration rate in genotype Hawassa-83 by 0.74 mmol m-2s-1and 0.84 mmol m-2s-1, respectively. Result on WUE indicated that Kulfo was found better in efficiently utilizing water under extended irrigation interval than Hawassa-83. The leaf water content was significantly (P ≤ 0.001) responded to irrigation frequency than genotypes. The higher leaf relative water content was obtained from daily irrigation than extended irrigation interval. Conclusion: Finally it was observed that tuber yield under daily and four days irrigation interval was not statistically different in both varieties, This is therefore, the four days irrigation interval is recommended for sweet potato production from farmers economic point of view.