EFFECTS OF ADDITIONS AND SUBSTITUTIONS OFAGROPYRON ELONGATUMCHROMOSOMES ON QUANTITATIVE CHARACTERS IN WHEAT

Alien disomic and ditelosomic addition lines and disomic substitution lines involving the recipient wheat cultivar Chinese Spring and each of the seven chromosomes of diploid Agropyron elongatum were used to study the distribution of genes affecting date of heading, maturity, tillering, plant height and weight, seed protein content and components of seed yield in the Agropyron genome. Four Agropyron chromosomes, III, IV, V, and VI, affected days to heading and maturity but only chromosome VI conditioned early heading date. Complementary genes on opposite arms of the alien chromosome were responsible for late maturity in disomic addition line V. Tillering was affected by chromosome II which reduced the number of tillers per plant and by chromosome IV which increased the number. Plant height was increased by chromosome II and decreased in the presence of chromosomes III, IV, V and VI. Seed weight was increased in disomic addition lines II, III and VI while it was decreased in dosomic addition line V. Seed shrivelling, which was apparent in the amphiploid, Ag. elongatum × Chinese Spring, is controlled by Agropyron chromosome II. The number of seeds per spike was affected by six and seed yield by seven Agropyron chromosomes. Except for one line, the disomic addition lines and one substitution line showed significantly higher seed protein content than Chinese Spring. However, it was shown that yield depression accounted for a large portion of the increase in protein content. To remove this factor, the actual protein content in each line was compared with the adjusted protein content obtained from the regression of protein content on yield. Then it appeared that five of the seven Agropyron chromosomes are implicated in the control of seed protein. The amino acid compositions of proteins in the Agropyron-wheat derivatives were uniform and did not differ from Chinese Spring. It was shown that genes on Agropyron and wheat homoeologous chromosomes frequently have related effects on the characters studied. Because of genetic similarity among Agropyron and wheat homoeologues, the alien substitution lines tend to be superior to the alien addition lines in which the deleterious characters are largely caused by gene dosage effects. It is suggested that interlocus gene interactions play a significant role in the control of quantitative characters in this Agropyron genotype.