Production and identification of three 4Ag(4D) substitution lines of Triticum aestivum - Agropyron: relative transmission rate of alien chromosomes.

By crossing fertile nullisomics-4D of common wheat (nullisomics 72180 and 'Tianxuan' no. 15) with three octoploid Agrotriticum lines [partial amphiploids (2n=56) 78829 from the offsprings of wheat with Agropyron intermedium (=Thinopyrum intermedium, 2n=42) and 784 and 7631 from those of wheat with Ag. elongatum (Thinopyrum elongatum, 2n=70)], backcrossing the hybrid with 4D nullisomics as recurrent parent for one to two generations, and then selfing the BC individuals, we obtained three different alien substitution lines, 4Ei (4D), 4Ee(4D) blue grain, and 4Fe(4D) hairy leaf. The F1 hybrids of 784×78829 had the basic chromosome pairing configuration of 27″ + 2', indicating that 784 and 78829 differed by only one pair of chromosomes. This means that Ag. intermedium and Ag. elongatum have a genome (or genomes) in common. The formation of 22″ +12' in the F1 of 784×7631 suggested that there was only one pair of homologous chromosomes of Ag. elongatum in 784 and 7631. Because F1 plants of 7631×78829 generally formed 21″ +14' at metaphase I, the Agropyron genomes in the two octoploid Agrotriticums were presumed to differ from each other. Upon intercrossing the three alien substitution lines, we found that all of the pollen mother cells of the F1 plants had 20″ + 2' or more univalents at metaphase I. We concluded that the three Agropyron chromosomes were not homologous but belonged to the same homoeologous group. These results were confirmed by reciprocal crosses of the three octoploids. The relative transmission rates of 4Ee, 4Fe, 4Ei, 4R and 4D were calculated using blue grain and hairy leaf as genetic markers; these were 4D>4Ee>4Ei, 4Fe>4R. The four alien chromosomes could compensate for the 4D of bread wheat, the substitution lines being vigorous and fertile.