CYTOGENETICS OF SOLID STEM IN COMMON WHEAT: II. STEM SOLIDNESS OF MONOSOMIC LINES OF THE VARIETY S-615
Lines of a variety of common wheat, S-615, monosomic for chromosomes III and XVI of homoeologous group 3 had culms less solid in the top internode than normal S-615. Monosomics of homoeologous group 5, namely, V, IX, and XVIII, were less solid in the bottom four internodes than S-615. These five chromosomes carry genes for solid stem in this variety. Monosomics XIX, XX, and XXI, the D-genome chromosomes of homoeologous groups 6, 2, and 7 respectively, were more solid than the normal check in both top and lower internodes, indicating that the missing chromosomes carry genes for hollow stem. Chromosome XIII, a homoeologue of XX, which in Chinese Spring has a gene for hollow stem, does not affect the amount of pith in the culm of S-615.The concept of the culm phenotype in a given environment resulting from an interaction of genes promoting pith development and those opposing it makes it possible to reconcile results of genetic experiments on solid stem in wheat that previously appeared contradictory.