Bioassay of Winter Wheat for Gibberellic Acid Sensitivity

Abstract

Increasing winter wheat seedling growth would make it a better winter cover crop. Gibberellic acid (GA 3 ) seed treat ment may accomplish this by stimulating stem growth. A bioassay, mimicking field conditions, could determine the relative sensitivity of conventional and semi-dwarf cultivars. In growth chambers set for cool (10℃/4℃) and warm (21℃/4℃) conditions, wheat seeds were treated with 0 and 125 to 16,000 ppm GA 3 . The cultivars Goodstreak (tall or conventional) and Wesley (semi-dwarf) were compared as standards. Emergence and plant height were measured. “ Goodstreak ” showed a significant growth promotion at 500 ppm GA 3 when seeds were dipped and 2000 ppm when GA 3 was applied in-furrow under both temperature regimes. “ Wesley ” in general required the same or a higher dose of GA 3 . Separately, the seed s of nine other cultivars were treated with GA 3 as the standards. Based on maximum height promotion, the most sensitive cultivars under cool conditions were Goodstreak, Harry, Millenium, and Wahoo; under warm conditions, the most sensitive cultivars were Alliance, Goodstreak, Jagalene, and Millenium. In general, the least GA 3 sensitive cultivars were Arrowsmith, Scout66, and Wesley. “ Buckskin ” and “ InfinityCL ” were intermediate. The rye cultivar Rymin also was tested and showed less sensitivity to GA 3 than “ Goodstreak ” . When 6 benzyladenine (6BA) with GA 3 was applied to “ Goodstreak ” and “ Wesley ” seed, emergence, plant height and weight, and tiller formation were reduced. Wheat cultivars will respond to GA 3 and differ in the amount of GA 3 needed. The results of this growth chamber study will guide subsequent field trials.