| Callus induction from seedling roots of einkorn wheat (Triticum monococcum,
2n=14), emmer wheat (T. dicoccum, 2n=28), and common wheat (T.
aestivum, 2n=42), and from stem pieces of common wheat were reported
by SHIMADA et al. (1969). They used White's basal medium or a modification
of it (RISSER and WHITE, 1964), both of which were supplemented with 2,4-D
or IAA. They noted that the best callus growth occurred when casein hydrolysate
or coconut milk was added to the media. This study was initiated to determine: (1) conditions suitable for callus initiation and subculturing of wheat, rye, and a wheat-rye hybrid; and (2) the response of such callus lines to various culture media and conditions. Wheat (Triticum aestivum cv. Chinese Spring), rye (Secale cereale cv. Gator), and a wheat-rye hybrid were used in this study. The wheat-rye hybrid was produced by pollinating a Chinese Spring wheat with pollen from the Gator rye plant which also served as a source of rye seed. Culture media were those of Linsmaier and Skoog, modified White's according to SHARP et al. (1972), Gamborg's B-5, and Schenk and Hildebrandt. These media were at times supplemented with 2,4-D or NAA, casamino acids or casein hydrolysate, yeast extract, and sucrose in various combinations and concentrations as described in the results. The basal medium is that of Linsmaier and Skoog containing 4% Sucrose, and supplemented with 1 g/l casamino acids and 4 mg/l of 2,4-D, solidified with 8 g/l of Difco purified agar. All culture tubes and flasks were covered with 0.0015-inch-thick polyetheline film cut into four-inch squares. All cultures were exposed to 16 hours of light followed by 8 hours of darkness unless otherwise noted. Callus Induction Callus induction of wheat, rye, and the hybrid was consistently obtained by the following procedure. Seeds were placed in a mixture consisting of one part bleach (5.25% of sodium hypochlorite) and five parts distilled water and shaken; after 10 minutes the seeds were rinsed three times with sterile, distilled water and placed on a shaker in sterile, 125ml Erlenmeyer flasks containing 25ml of sterile distilled water. After 24 hours, the seeds were removed, treated again with bleach and rinsed as before. The seeds were then individually placed in sterile culture tubes containing the basal medium but lacking 2,4-D. After two to four weeks or when the seeds had sprouted and plants were about four inches tall, they were removed under sterile conditions and the basal part of the stem was cut into thin cross sections about two millimeters thick. Those four or five sections closest to the cotyledon were placed in a one-by-six-inch culture tube containing 20 ml of basal medium. Within a few weeks, abundant callus formed on the upper surface of the stem slices. When IAA at 10 or 50 mg/l was substituted for 2,4-D in the basal medium, little or no callus was formed on wheat sections. No callus was formed when IAA at 10 mg/l or 50 mg/l and NAA at the same concentration were substituted for the 2,4-D. However, good callus was produced when NAA at 10 mg/l was substituted alone for 2,4-D in the basal medium. Among 360 wheat anthers placed on various modifications of the basal medium, callus was produced in 11 cultures, all of which originated from the filament tissue. Four calluses appeared on the basal medium containing 2 mg/l of 2,4-D, six calluses appeared on one-half strength basal medium (except for the iron stock, which was full strength) containing 2 mg/l of 2,4-D, and one callus formed on this same medium but containing 1 mg/l of NAA and no 2,4-D. In this last case, roots rapidly appeared and callus growth cased. |
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