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Hybrid Wheat seed Production Methods for North Dakota¹

A North Dakota male fertility restorer, R5 (Triticum zhukovskyi Men. & Er./3* T. aestivum L. em ThelL ‘Justin’), and several male-sterile wheat lines (T. aestivum with T. timopheevi (Zhuk.) Zhuk. cytoplasm) were planted in a systematic arrangement of alternate drill strips to evaluate hybrid wheat seed production. Approximate ratios of 1:1, 2:1, and 3:1 of male sterile to restorer were tested over several environments from 1972-1974. Drillstrip widths of the male sterile ranged from 3.1 to 11.0 m. Overall mean yields of hybrid seed were 13.7, 10.0, and 8.4 quintals/ha for the 1:1, 2:1, and 3:1 ratios, respectively. A production unit concept was used to compare the efficiencies of the three different ratios from a commercial perspective. Actual yields of hybrid seed from a production ha were 6.9, 6.7, and 6.3 quintals for the 1:I, 2:1, and 3:I ratios, respectively.

Narrowing the drill.strip width of male-sterile and restorer parents within the 1:1 or 2:1 ratios from 3.1:3.1 m to 1.5:1.5 m or from 6.1:3.1 m to 3.1:1.5 m did not increase yields of hybrid seed. Therefore, adequate hybrid seed production can be accomplished with machinery (2.1 to 3.7 m/drill section) currently used on North Dakota farms.

The growing degree day technique was used to determine timing of planting dates between a male sterile and its maintainer for proper synchronization of maximum pollination of the male line and optimal floret opening of the female line. In 2 years of study, higher yields were obtained with the projected 44 C growing degree day difference than with 0, 22, or 66 growing degree day differences.

Hybrid seed production yields were highly correlated with restorer yields over several environments indicating that hybrid seed production would be most successful in high yielding production regions. Decreases in hybrid seed yields at low yielding environments were due to environmental factors affecting yield and pollination potential of both parents. The low yields of the restorer, especially in adverse environments, were attributed to its low vigor and poor adaptability. Consequently, successful hybrid seed production is dependent on availability of high yield environments and on stable, high yielding, adapted parents.

Key Words: Seed production • Cross-pollination • Cytopalsmic male sterility • Growing degree days • Triticum aestivum L em. Thell.

² Instructor and professor of agronomy, N.D. State Univ., Fargo, N.D. 58102.

Received for publication May 8, 1975.