Screening of rainfed rice lines under osmotic stress at seedling stage
2018
Malabanan-Bauan, K.B. | Magnaye, A.M.A. | Lalican, D.J.
Drought is a prevalent occurrence in rainfed rice areas, and developing varieties that can tolerate water deficit condition has been one of the major breeding objectives for rice. This is particularly important for the Philippines, where around 30% of rice lands are rainfed. Screening of breeding materials for drought tolerance as early as seedling stage is important especially for dry-seeded rice that is common in rainfed areas. This study evaluated the germination and seedling growth of UPLB-bred promising rice lines at varying levels of osmotic stress, and identified lines that exhibited water deficit tolerance at early seedling stage. Sixty-six promising rice lines including rainfed purification lines and wide hybridization-derived lines were tested at five water potential levels (control or 0, -0.25, 0-0.50, -0.75, and -1.0 MPa) imposed using varying strengths of polyethylene glycol (PEG 6000 MW) on filter paper. Highly significant differences among treatments were detected for germination percentage, root length and shoot length. Germination percentage was similar from treatment 0 to -0.50 MPa, but it dropped significantly by 30% at -0.75 MPa, while only 27% germinated at -1.0 MPa across rice lines. Shoot and root length were also significantly reduced with decreasing water potential of the growing media. Drastic reduction in shoot length (69%) was observed at -0.50 MPa, while roots were 44.31% shorter at -0.75 MPa relative to control. Out of 66 rice lines, 20 promising lines (19 purification lines and one WH-derived line) were selected to have relative drought tolerance based on seed germination, shoot and root growth.
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