II. 10 Inbreeding depression in barley selection.
S. O. Fejer and G. Fedak, Ottawa Research Station, Ottawa, Ontario, Canada.
In a program of recurrent selection and crossing in a 6 x 6 six-rowed feed barley diallel cross, three different lines were designated, "high" kernel yield from an OB 128-1 x Q.B. 58-14 (sibs of Vanier and Laurier), "low" from a short-strawed Minn. 66-151 x Paragon, and "medium" from a Fort x Trent cross. Crosses were made over the generations within and between lines (two-way and four-way), and resulting F4 material was tested in the field. Highly significant differences were found between lines in kernel yield, ranging from 366.5 g per plant for a "high" x "low" (four-way) to 160.6 g for a "medium" (two-way, sib) cross ("a" and "h" groups in a Duncan's test). By grouping the crosses by origin, the following picture emerged:
"high" x "low" = 325.8 g
"high" x "medium" = 283.6 g
"medium" x "low" = 243.4 g
"high" = 218.4 g
"medium" = 193.3 g
"low" = 203.0 g
It seems that the over-riding factor in this case was not the selection itself, but inbreeding depression, which is perhaps surprising in an advanced generation of self-fertilizing barley.