Effect of Daylength Response on Agronomic and Quality Performance of Durum Wheat

Durum wheat (Triticum durum Desf.) varieties grown in the United States are not adapted to the short-day conditions of the middle latitudes (between 28°N and 28°S). Introduction of a gene or genes for daylength insensitivity could broaden the adaptability of these varieties, but the effects of insensitivity on agronomic and quality performance in northern latitudes are not well known. Fifty-two F₃ durum wheat bulks homozygous sensitive to daylength and 52 bulks homozygous insensitive to daylength were selected from 4 crosses between northern varieties and a daylength-insensitive selection (‘Zenati’/‘Bouteille’) introduced from Israel. These 104 F₃ bulks were compared for agronomic and quality performance in North Dakota in 1967 and 1968. Ten pairs of lines, near isogenic except for daylength response, were developed from three of the four crosses by selecting heterozygous plants from F₃ through F₆. The F₃ pairs were compared in a split-plot arrangement in four environments. Insensitive lines tended to be significantly earlier (1 to 3 days) and shorter (3 cm) than the sensitive lines. Genotype ✕ environment interactions were significant for yield. The insensitive near-isogenic F₆ lines yielded slightly more grain than the sensitive lines in two environments, five of the senstive lines yielded as much as 20 to 40% more grain than the insensitive lines in one environment, and the two response types yielded essentially alike in one environment. We conclude that durum wheats for the North Central States can be converted to the insensitive condition without loss in productivity or quality. Insensitive lines must be thoroughly tested over a wide range of temperature and daylength conditions to assure that only the most stable ones are released for commercial production.