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Inheritance and Interrelationships of Grain Yield and Selected Yield-Related Traits in a Hard Red Winter Wheat Cross¹

The parents, F₁, F₂, and backcrosses derived from two hard red winter wheat (Triticum aestivum L. em Thell.) cultivars were studied in a field experiment grown on the Agronomy Research Station at Stillwater, Okla., during the 1971-1972 crop season. Data were taken on individual plants to estimate gene action, heritability, and interrelationships of grain yield and selected yield-related traits. Characters studied were 1) grain yield, 2) tiller number, 3) kernel weight, 4) kernels/spike, 5) spikelets/spike, and 6) kernels/spikelet. The direct and indirect effects of characters 2, 3, and 4 on grain yield were also studied.

Additive and dominance variances were much smaller than the environmental variance for each character except kernel weight. Kernel weight, tiller number, and spikelets/spike displayed rather high broadsense herRabilities while kernel weight was the only character to display a high narrow-sense estimate. Other heritability estimates ranged from intermediate to low. On the basis of gene action and heritability estimates, direct selection to improve a trait, should be more effective for kernel weight than for any of the other traits.

Tiller number had a high positive phenotypic correlation and an intermediate genetic correlation with grain yield. Phenotypic correlations of kernel weight and kernels/spike with grain yield were intermediate and low, while their genetic correlations were low and intermediate, respectively. Negative associations observed between kernel weight and tiller number and between kernel weight and kernels/spike suggests that simultaneous improvement of these characters will be difficult. Large positive phenotypic and genetic correlations were observed between kernels/spike and spikelets/spike and between seeds/spike and kernels/spikelet.

Path coefficient analyses at the phenotypic level indicated that the direct effect of tiller number on grain yield was large while the direct effects of kernel weight and kernels/spike were intermediate and low, respectively. At the genetic level, the direct effect of each component was intermediate and about equal in magnitude. This implies that the large direct effect of tiller number at the phenotypic level was due largely to nonadditive genetic or environmental effects or both.

The results of this study indicated that selection for kernel weight in early generations is the most important factor in a breeding program for increasing grain yield. Tiller number makes a greater contribution toward grain yield but is much more difficult to improve by selection in early generations.

Key Words: Triticum aestivum L. em Thell. • Heritability • Phenotypic correlation • Genetic correlation • Path coefficients • Yield components

² Former graduate research assistant (now plant breeder, Northrup King and Co., Box 2625, Lubbock, TX 79408) and Professor, Dep. of Agronomy, and associate professor, Dep. of Statistics, Oklahoma State Univ., Stillwater, OK 74074.

Received for publication August 8, 1975.

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