THE EFFECT OF TELOMERIC HETEROCHROMATIN FROM SECALE CEREALE ON TRITICALE (X TRITICOSECALE). II. THE PRESENCE OR ABSENCE OF BLOCKS OF HETEROCHROMATIN IN ISOGENIC BACKGROUNDS

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Abstract
The influence of telomeric heterochromatin blocks on early embryo and endosperm development, and on various agronomic parameters seen at maturity, was investigated using triticales (.times. Triticosecale Wittmack) isogenic for the presence or absence of the heterochromatin blocks on rye (S. cereale L.) chromosomes 6R and 7R/4R. Absence of the telomeric heterochromatin blocks from the long arm of rye chromosome pair 7R/4R in DRIRA, and from the short arm of rye chromosome pair 6R in ''Rosner'' was significantly related with a lower production of aberrant endosperm nuclei and an increased kernel weight. The loss of the heterochromatin block on rye chromosome pair 7R/4R in ''DRIRA'' resulted in a significant yield increase, while there was no increase in yield when the heterochromatin block was missing from rye chromosome pair 6R in ''Rosner''. The lack of yield increase in ''Rosner'' was apparently due to a significant decrease in fertility when the heterochromatin block on 6R was lost. The loss of the heterochromatin block on the short arm of rye chromosome 6R appears to have the same effect on aberrant endosperm nuclei production and kernel weight in two different genetic backgrounds. The rate of embryo and endosperm development showed a small but significant increase when the heterochromatin blocks were lost from both 6R and 7R/4R.