Cytological observations of the F1 and two backcross generations of Triticum vulgare X Agropyron trichophorum

1. Although exhibiting low cross-fertility, A. trichophorum was successfully crossed with T. vulgare. Individual Agropyron plants differed in their ability to cross with wheat. Two backcross generations were obtained using T. vulgare as the recurrent parent. 2. All F1 plants were self-sterile. Only those plants having A. trichophorum #4 in their parentage were backcross fertile with the wheat. Individual F1 plants in this group also differed in their backcross fertility. 3. A pollen study to determine the percentage of normal pollen was conducted on F1 plants grouped according to their Agropyron parent. The F1 plant having A. trichophorum #4 in their parentage had the highest average percentage of normal pollen of all groups. 4. All first backcross plants examined were triploids (3n chromosome number), evidently produced by the fertilization of an unreduced F1 egg when the backcross was made. By this assumption they are composed of two complements of T. vulgare chromosomes and one complement of A. trichophorum chromosomes. 5. The second backcross generation was composed of the same chromosome complements as the first backcross generation, with the exception that fewer univalents, presumably A. trichophorum chromosomes, were present. 6. The 2n chromosome number and pairing relationship of the parents and the succeeding generations were determined. 7. Abnormalities observed in three generations (F1, first backcross, and second backcross) were noted to have the following trends: The average percentage of normal pollen increased in each generation; the number of micronuclei per quartet increased in the first backcross but decreased in the second backcross; and the number of lagging chromosomes at metaphase I and anaphase I decreased significantly only in the second backcross generation. 8. Phenotypically, the F1 was generally intermediate to the Agropyron and the wheat parent with many characters dominantly Agropyron. After two backcrosses to wheat, the pubescence and perennial habit of the Agropyron parent were still present. In spike type, awn type, and kernel size and shape, the plants resembled the recurrent wheat parent. Self and cross-fertility increased with each generation. Variable reaction to leaf rust was noted with some F1 and backcross plants being highly resistant.