Studies on Restoration and Substitution of Nucleus in Aegilotricum

Abstract

Nuclear exchange by successive backcrosses to both parents was accomplished with Tschermak''s amphidiploid hybrid [female] Aegelops ovata x [male] Triticum durum, known as Aegilotricum. The process of restoring A. ovata genomes to A. ovata took three successive backcrosses. The final offspring were morphologically similar to A. ovata with 14 bivalents at the first metaphase and anthers containing functional pollen. Three substitution backcrosses of Aegilotricum to T. durum resulted in T. durum plants with A. ovata plasma. There were 14 completely paired bivalents at the first metaphase. Tetrad formation was normal, but only degenerate pollen was present in small dry anthers. The female organs were functional and seed formation after pollination with durum or dicoccum was normal. Male sterility was transmitted to the next generations by the mother. Durum plants with ovata plasma having extra chromosomes of A. ovata as univalents in addition to the 14 durum bivalents were only partially male-sterile. A 29-chromosome plant of this type showed a high pollen fertility of 92%.