STUDIES ON THE HYPOANEUPLOIDS OF COMMON WHEAT. II. QUADRUPLE MONOSOMICS AND QUINTUPLE MONOSOMICS

Abstract

1. Four kinds of quadruple monosomics and one kind of quintuple monosomics were produced by a systematic procedure in a variety Chinese Spring of common wheat, Triticum aestivum ssp. vulgare.
2. Quadruple monosomics (17_II+4_I) were selected in the progeny of the cross between triple monosomics (18_II+3_I) and a nullisomic, which lacks the fourth pair of chromosomes. The quadruple monosomics were pollinated with pollen grains of a nullisomic, which lacks the fifth pair of chromosomes, and in their F₁'s quintuple monosomics (16_II+5_I) were selected.
3. Quadruple monosomics were more or less smaller in size, and reduced in vigor with somewhat later maturity, but they were fertile in both sexes. Quintuple monosomics were still inferior to the quadruple monosomics in their various characters, though they retained reproductive ability.
4. Crosses between quadruple monosomics (_??_) and normal plants (_??_) were made to maintain the quadruple monosomic strains; F₁'s obtained had 38 to 42 chromosomes. The 38-chromosome plants appeared at a frequency of 21.2 per cent, and showed the 17_II+4_I chromosome configuration at meiotic metaphase I, which indicated that they were quadruple monosomics.
5. The present results indicated that the female gametes with the least chromosome number in expectation participate at a high frequency in fertilization in every kind of hypoaneuploids, so far produced in hexaploid wheat.