| The Triticum x Agropyron hybridization
project at Montana State University1) J. SCHULZ-SCHAEFFER Department of Plant and Soil Science, Montana State University, Bozeman, Montana U.S.A. The possible value of derivatives from Triticum x Agropyron hybridization has been recognized since the first successful crosses were reported by TSITSIN in 1933. Many such projects have explored the possibilities of wheat improvement, but the project reported here is oriented towards improvement of intermediate wheatgrass, Agropyron intermedium (HOST.) BEAUV., as a forage crop. During the period from 1923 to 1935, SANDO established hybrids between species of Triticum and Agropyron (VINALL and HEIN 1937, USDA, 1958). Two of the hybrid combinations were T. durum DESF. (2n=28) xA. intermedium (2n=42) and T. durum (2n=28) x A. trichophorum (LINK) RICHT. (2n =42). Derivatives of these two crosses were distributed to several agricultural experiment stations, and were observed for possible usage in both wheat and forage grass breeding programs. In 1953. F4 and F5 seed of several of these hybrids was received for testing at the Montana Agricultural Experiment Station by Mr. R. F. ESLICK. Chromosome counts of this material in 1958 revealed 2n numbers from 58 to 74 with an average number of 2n=65, demonstrating that the material was amphidiploid (AD). The theoretical chromosome number of the amphidiploid is 2n=70. The author assumes that the missing bivalents were from the Agropyron parent since they were foreign to the cytoplasm of the female Triticum parent and may have been eliminated as laggards in meiotic divisions. Induced chromosome doubling has not been reported for this material and amphidiploidy must have arisen by the fortuitous union of unreduced compatible gametes. LOVE and SUNESON in 1945 described the progeny of 2 hybrid seeds of T. durum x A. trichophorum which had been sent to them by Mr. W. J. SANDO in 1938. Both F1 plants had the expected 2n number of 35 chromosomes. From the 35 F1 seeds harvested only 11 F2 plants were established. Cytological investigations of 4 of these F2 plants revealed 2n=35 in one, 2n =56 in another and 2n=70 chromosomes in 2 plants. It appears clear therefore, that amphidiploid formation occurs naturally in this material through the union of partially reduced or unreduced gametes. Chromosome pairing of Triticum x Agropyron in the very early generations was not as expected. However, LARTER and ELLIOTT (1956) reported regular chromosome pairing of 2n=56 derivatives of Triticum x Agropyron hybrids in the F6 and F7 generations. They consistantly observed 28 bivalents at metaphase I. The SANDO amphidiploid Agrotricum material had meiotic instability as shown by the number of micronuclei in the microspores (Table 1). On the average, 50% of the microspores contained micronuclei in 28 plants. Micronuclei result from lagging chromosomes which were not included in the daughter nuclei and thus are lost to the gametes. Such chromosome loss may have caused chromosome numbers with less than 2n=70 in this amphidiploid material. |
| 1) Contribution of the Montana Agricultural Experiment Station, Bozeman, Montana, U.S.A. Paper No. 125, Journal Series, Montana Agr. Exp. Sta., published with approval of Director. |
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