CYTOGENETICS OF SOLID STEM IN COMMON WHEAT: I. MONOSOMICF2ANALYSIS OF THE VARIETY S-615

Abstract

The F₂lines of monosomics of Chinese Spring by S-615 were compared with normal F₂lines for stem solidness. The solid stem index of each plant was determined by totalling index numbers (ranging from 1 for thin-walled, hollow, to 5 for completely solid) assigned to cross sections of the culm at seven designated points. As both the normal and monosomic lines showed a continuous distribution of this index, the factorial analysis was not too reliable. The normal F₂gave an estimated difference between the parents of at least four genes; the monosomic XIII F₂, which was more solid than the normal, gave a difference of three genes.Quantitative differences between monosomic F₂lines and the normal indicated that chromosomes II, XIII, and XX, comprising homoeologous group 2, tend to make the culm hollow. Chromosomes XIX and XXI also inhibit pith development. Of these five chromosomes, XIII has a gene for hollow culm in Chinese Spring only; XIX, XX, and XXI, which are in the D genome, are effective in both S-615 and Chinese Spring, and II is inconclusive. Chromosome VIII in Chinese Spring promotes pith production. The chromosomes of S-615 bearing genes for solid stem were not identified by this method, as a monosomic F₂analysis does not reveal recessives present only in the variety being tested.