MEIOSIS AND FERTILITY OF F1 HYBRIDS BETWEEN HEXAPLOID BREAD WHEAT AND DECAPLOID TALL WHEATGRASS (THINOPYRUM-PONTICUM)

As the first step in the transfer of barely yellow dwarf virus resistance and salt tolerance from decaploid tall wheatgrass (Thinopyrum ponticum) into hexaploid bread wheat (Triticum aestivum L.), octoploid intergeneric hybrids (2n = 8x = 56) were synthesized by crossing the tall wheatgrass cultivar 'Alkar' with wheat cvs. 'Fukuhokomugi' ('Fuko') and 'Chinese Spring'. ('Fuko' x 'Alkar') F-1 hybrids were studied in detail. The F-1 hybrids were perennial and generally resembled the male wheatgrass parent with regard to morphological features and gliadin profile. Most hybrids were euploid with 56 chromosomes and showed high chromosome pairing. On an average, in 6 hybrids 83.6% of the complement showed chiasmatic association, some between wheat and wheatgrass chromosomes. Such a high homoeologous pairing would be obtained if Ph1, the major homoeologous pairing suppressor in wheat, was somehow inactivated. Some of the 'Fuko' x 'Alkar' hybrids had high pollen fertility (18.5-42.0% with a mean of 31.5%) and high seed fertility (3-29 seeds wtih a mean of 12.3 seeds per spike), offering excellent opportunities for their direct backcrossing onto the wheat parent.