Growth responses of cassava (Manihot esculenta Crantz) genotypes to increasing drought stress at early vegetative stage
2003
Bolatete, D.M. Jr | Bergatin, R.V. | Belmonte, D.V. Jr | Esquibel, C.B. | Pardales, A.D. | Pardales, J.R. Jr | Mariscal, A.M. (Leyte State Univ., Visca, Baybay, Leyte (Philippines). Philippine Root Crop Research and Training Center) Sebidos, R.F. | Banoc, D.M. | Subere, J.Q. | Yamauchi, A.
The growth performance of three cassava genotypes under progressing drought was studied at their early establishment phase. The plants were grown in plastic pots (24.5 cm wide and 26.5 cm high) filled with sandy loam soil and place under a plastic-covered rain shelter to regulate the moisture content of the soil in the pots. All plants were established under well-watered condition (25% soil moisture content (SMC)) for 1 month. Afterwards, half of the total number of plants were subjected to drought condition by witholding water until a desired level of 15% SMC was reached and was maintained regularly. Control plants remained well-watered. Staggered harvesting was done at 10, 20 and 30 days after drought imposition. With reference to the well-watered plants, the length of stem, petiole and leaf, number of leaves, number of second order lateral roots, total root length and total plant biomass were significantly reduced by drought, and their respective reduction increased as drought stress progressed. The value of these traits varied significantly among the genotypes. Likewise, transpiration rate and water use also decreased significantly. In contrast, drought stress significantly increased root to shoot ratio and stomatal resistance. Genotype effect was also noted in root to shoot ratio, transpiration rate and stomatal resistance but not in water use. Psb cv-19 stood out to be the most drought resistant genotype with the highest biomass production under drought. This variety had high total root length which resulted in high water use, and had an ability to sharply close stomates and maintain high leaf water potential at midday, which led to an increased water use efficiency and high production of biomass under drought
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