| Scope and method of study. Hard red winter (HRW) wheat cultivars of the southern Great Plains are traditionally bred in a grain-only (GO) management system, but are commonly grown for the dual purpose (DP) of forage and grain from the same crop. Our objectives were to determine whether genetic progress in grain yield and related agronomic and quality traits is equally expressed in DP and GO systems, and whether the DP system has any detrimental effect on wheat grain quality. A historical set of 12 widely adopted HRW wheat cultivars (released from 1919 to 1997) was evaluated in each system for 3 years near Marshall, OK. The DP experiments were planted 4 to 6 weeks earlier than the GO system, and were grazed by cattle from early November to late February (first-hollow-stem stage). Genetic variances, heritabilities, and genetic correlations were estimated in another study involving 37 HRW wheat lines to suggest an optimum selection strategy for simultaneous genetic improvement in both systems.; Findings and conclusions. The correlations between management systems for all traits were significantly high (r = 0.74 to 0.99, P < 0.01), with no significant differences between the DP and GO systems for grain yield, yield components, and quality traits. Cultivar by system interactions were not significant for any trait, indicating consistent performance of cultivars in both systems. However, genetic progress in grain yield, estimated from linear regression of cultivar means on year of release, differed significantly between systems. The rate of genetic progress for grain yield was 18.8 kg ha−1 yr−1 (1.3% of the mean of Turkey) in the GO system vs. 11.3 kg ha−1 yr−1 (0.9% of the mean of Turkey) in the DP system. While significant and similar genetic progress was observed for kernel weight per spike, 1000-kernel weight, and large kernel fraction in both systems, improvements in spike density, kernels per spike, test weight, grain protein, flour yield, and other quality traits were not evident under either system. No detrimental influence of the DP system was observed on extrinsic or intrinsic characteristics of bread wheat quality. We conclude that breeding materials should be simultaneously evaluated both in the DP (one that features grazing instead of clipping) and GO systems if future progress is to be maximized in both systems. |
