1992. Embryogenic suspension culture of rice and NaCl selection from suspension culture derived somaclones

1992. Embryogenic suspension culture of rice and NaCl selection from suspension culture derived somaclones

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ABSTRACT

Embryogenic suspension cultures of rice (Oryza sativa L. cv. Basmati-370 and Taipei-309) were established. Various explants, types, and different concentrations of growth regulators, different concentrations of sucrose, and transfer techniques were investigated to identify parameters which control the initiation of and plant regeneration from rice callus.

The types of calli induced in various media also were tested for ability to initiate suspensions which could regenerate plants. Friable embryogenic calli from caryopses on LS medium supplemented with 1 or 2 mg-L'1 2,4-D and 1 or 2 g-L'1 sucrose proved to be the most suitable starting material.

Histological studies demonstrated embryogenesis in somatic cell suspensions. Friable calli developed embryoids after two to three months in suspensions. "Proembryogenic masses" formed at the peripheries of the inoculated callus clumps. Fragmentation of the proembryogenic masses gave rise to embryoids in the cell cultures. Embryogenic masses also arose from the development of cell aggregates into organized structures. Plant regeneration occurred from embryoids transferred to solid LS medium with or without NAA and BAP. Plants could be obtained from long term suspensions of Basmati-370 (up to 9.5 months old) by adding GA3 or NaCl to the medium. Two embryogenic cell lines were cultured in 200 mM NaCl for two months with increased regenerability. Greenspots and formation of leafy structures were obtained from forty-four months and one week old suspension cultures by adding sorbitol, ABA, and NaCl.

Somaclonal variations were observed in suspension culture-derived somaclones of rice cv. Taipei-309. Variants expressed inferior and superior agricultural traits, such as height, maturity, and yield. Most somaclones were shorter, later in maturity, and low yielding compared to the check.

Seedling screens and whole plant testings were conducted over four generations to select somaclones for NaCl tolerance. Heritable tolerance was obtained. X-ray microanalyses and ion analyses revealed that tolerant lines accumulated fewer Na+ ions in the plant tissues compared to susceptible lines. Tolerant plants also secreted less salt through their leaves compared to the susceptible ones.

This study indicated that somaclones derived from rice embryogenic suspension cultures may be a potential source for NaCl selection and that the acquired traits also are heritable  .