Degree Type


Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Kenneth J. Frey


Three S[subscript]1-recurrent selection programs to increase protein yield of oat (Avena sativa L.) were conducted for five cycles of selection. The selection criteria in each program (line of descent) emphasized different components of protein yield; high grain yield in HG, high grain yield and high groat-protein concentration in HP, and protein yield per se in HGP. The objectives of this study were to evaluate the effectiveness of S[subscript]1-recurrent selection and to compare indirect responses in yield components and agronomic traits. Thirty to sixty random S[subscript]0-derived lines from each cycle and ten check lines were grown in hill plot experiments at two locations in 1989 to measure the various responses to selection. The results indicate that S[subscript]1-recurrent selection is an effective breeding method which is capable of producing rapid gains in protein yield of oat. Groat-protein yield increased in all three lines of descent, with HG showing slightly greater average gains per cycle than HP or HGP (4.4 vs 3.4 and 2.2% per cycle, respectively). Groat yield increased in all three lines of descent, but HG showed the greatest rate of gain at 7% per cycle, followed by HGP (3% per cycle) and HP (about 1% per cycle). Groat-protein concentration increased by 1.6% per cycle in HP, but showed significant declines in HGP (-0.9% per cycle) and HG (-1.8% per cycle). The large increases in groat yield in HG were the result of a combination of increased biomass and groat index (groat index is analogous to harvest index, but on a groat yield basis), while the simultaneous gains in groat yield and groat-protein concentration in HP were the result of increased biomass at a relatively constant groat index. Seed number increased in all three lines of descent (by 3.1, 5.6, and 2.1% in HGP, HG, and HP, respectively). Groat weight remained relatively constant across all cycles of selection. The only unfavorable correlated responses in agronomic traits detected in these populations were decreases in test weight in HGP and HP, and a decline in groat percent in HP. HG and HGP are the most agronomically acceptable lines of descent, while HP is slightly later in maturity and lacks in seed quality traits such as test weight, groat percent, and seed weight. This selection protocol is an efficient breeding method that can improve source populations rapidly.



Digital Repository @ Iowa State University,

Copyright Owner

Hal Stuart Moser



Proquest ID


File Format


File Size

171 pages