STUDIES ON THE HYPOANEUPLOIDS OF COMMON WHEAT. I. DOUBLE MONOSOMICS AND TRIPLE MONOSOMICS

Abstract

1. Eight kinds of double monosomics and five of triple monosomics were obtained by systematic procedures in a variety Chinese Spring of common wheat, Triticum aestivum ssp. vulgare.2. Double monosomics (19II+2I) were obtained by crossing two different nullisomics (20II). Triple monosomics (18II+3I) were produced by crossing these double monosomics to third nullisomics.3. Plants of the double monosomics were hardly distinguishable from normal disomic plants in size, vigor and fertility. The triple monosomics had high fertility necessary for selfing and crossing, though they showed in general reduced size, vigor and fertility.4. In progenies of the crosses, double monosomics (_??_)×nullisomics (_??_), plants with the least chromosome number in expectation, i.e. 2n=39, were obtained at the frequencies between 45 and 54 per cent. In the reciprocal cross, however, their frequency was only 4 per cent.5. Apparently the double monosomics produced three kinds of gametes with 19, 20 or 21 chromosomes. The above results demonstrate that the eggs with 19 chromosomes were more frequently fertilized than those with 20 or 21 chromosomes.6. For the maintenance of triple monosomic strains, crosses between triple monosomics (_??_) and normal plants (_??_) were made; F1's obtained had 39 to 42 chromosomes. The 39-chromosome plants appeared at a frequency of 25.5 per cent and showed the 18II+3I chromosome configuration at meiotic metaphase I, which indicated that they were triple monosomic.7. It was concluded from the results of the present investigation that the 18-chromosome female gametes produced from triple monosomics were functional in fertilization.