T HE genus Bromus has been divided by Hitchcock (5) 3 into the sections Ceratochloa, Eubromus, Bromium, Neobromus, and Bromopsis. This sectional classification has been generally satisfactory from a genetical as well as morphological point of view. Hybridization studies (8,II) have indicated a high degree of reproductive isolation between these sections. Cytologically the sections are further characterized by the presence of euploid series of chromosomes with a basic number of n = 7 for each.The section Bromopsis, as delimited by Hitchcock (5), consists of perennial bromes with terete spikelets. The economic importance of Bromus inermis Leyss. ha9 prompted a survey of fertility relations between this species and others of the section to which it belongs.

No abstract

Progeny from three‐clone combinations of alfalfa (Medicago sativa L.) selected for high or low 6‐hour in vitro matter disappearance (6H‐DMD) had significantly different neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) concentrations. The only significant change in cell wall composition was lower‐calculated hemicellulose (NDF‐ADF) of the cell walls of progeny from clones with high 6H‐DMD. Leaves of two‐clone combinations with high or low 6H‐DMD had similar NDF concentrations, but stems differed significantly in NDF. Histological studies of the stems revealed greater number of xylem cells in progeny with high NDF and low 6H‐DMD.

A 6‐hour in vitro dry matter disappearance (6H‐DMD) procedure was used to evaluate individual progeny of ‘Vernal’ (Medicago sativa L. and Medicago falcata L.) and ‘DuPuits’ (Medicago sativa L.) clones selected for high or low 6H‐DMD values. Progeny derived from clones with high 6H‐DMD values had consistently higher 6H‐DMD values than progeny from low clones. Additional clones of ‘Culver’ MSA‐C4, MSB‐C4, Medicago glutinosa M.B., and Vernal were screened for high or low 6H‐DMD values over two harvests. Selected clones from Vernal and DuPuits progeny and from the five unselected populations were recombined for a second cycle of directional selection.Correlations between yield and 6H‐DMD were negative or near zero. Cell wall analysis of clones selected for a second cycle of improvement indicated a significant positive relationship between total cell wall constituents (NDF) and 6H‐DMD values of the forage.Second cycle clones had significant general and specific combining abilities for yield as well as leaf and NDF content. Progeny from clones with high 6H‐DMD values were higher in leaf content but lower in NDF content than progeny from clones with low 6H‐DMD values. Comparisons of selected two‐clone combinations in the first and second cycles indicated second cycle selection was effective in separating progeny means.