Inheritance of Spike Nodding Angle in Spring Barley 1

The objective of this study was to evaluate the inheritance and gene action of spike nodding angle in spring barley ( Hordeum vulgare L.). Spike nodding angle measurements were made on the basis of both individual plants and 1.5‐m rows of plants as the units of measurement. Individual plant measurements were made at Madison, Wis. in 1979 on F 1 , F 2 , and F 3 plants from a diallel cross without reciprocals among six parents that had spike nodding angles ranging from erect to nodded during much of the postheading period of growth. Spike nodding angles were measured 30 d after heading. One analysis indicated that both additive and dominance gene effects were important, while another hadicated that general combining ability (additive gene effects) was more important than specific combining ability (nonadditive gene effects). Narrow‐sense heritabillty estimates on individual plant basis were low, ranging from 0.15 to 0.27. Because there was concern about the reliability of measuring spike nodding angles on an individual plant as the unit of measurement, parentoffspring regression analyses were conducted on 1.5‐m rows of plants as the unit of measurement. The row‐plot measurements were made at Madison and Arlington, Wis. in 1980 and at Madison in 1981. The F 3 –F 4 generations were evaluated in 1980 and the F 4 –F 5 generations were evaluated in 1981. In general, heritability estimates calculated by three methods were medium to high, ranging from 0.35 to 0.99. Although these heritability estimates may have been inflated by dominance gene effects, they are considered to be more meaningful than heritability estimates obtained on the basis of an individual plant. The nodded spike characteristic should be transferrable in barley breeding programs without unusual difficulty.