The B chromosome system of Inner Mongolian Agropyron Gaertn. 2. Effects of Bs on homologous and homoeologous meiotic chromosome pairing

SUMMARYB chromosomes in diploid Agropyron species alter the level of meiotic homologous pairing. The decrease of pairing was gradual and appeared significant when the number of Bs was higher than 2. A significant drop in homoeologous chromosome associations was also observed in B-containing intergeneric hybrids between wheat and diploid or tetraploid Agropyron. B chromosomes of Agropyron in which A chromosomes can interact with the pairing regulatory gene Ph1 of wheat have comparable effects on homologous and homoeologous pairing as those found in other genera in Triticeae: Secale and Aegilops. Evidence of similarities with the activity of the Ph system of wheat is presented.