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Variation in Lemma Thickness in Indian Ricegrass: Implications for Dormancy, Scarification, and Breeding¹

Indian ricegrass [Oryzopsis hymenoides (Roem. & Schult.) Ricker] has been of interest for revegetation of western mine lands, however, high seed dormancy restricts stand establishment. Breeding to improve Indian ricegrass is hampered by this inherent dormancy, often as high as 98%. Scarification to break dormancy using sulfuric acid has been successful but reduction of viability has occurred. This study examined whether the number of seeds damaged by scarification was related to the thickness of the indurate lemma possessed by Indian ricegrass. Twelve strains and cultivars of Indian ricegrass were examined with a range in lemma thickness of 42 to 76 µm. They differed significantly for this trait, which was not affected by environment. Acid scarification treatments of 20, 30, and 40 rain were followed by water rinses. Viability before and after scarification was determined by tetrazolium tests. Lemma thickness had a significant protectiveffect on seed viability after scarification for all three scarification durations. Coefficients of determination (R²) values were 0.56, 0.75, and 0.79 for 20, 30, and 40 min time, respectively. These results indicate that lemma thickness can be utilized to determine proper scarification duration to minimize seed damage while maximizing germination, resulting in uniform stand establishment and evaluation of Indian ricegrass germplasm.

Key Words: Oryzopsis hymenoides • Revegatation • Dormancy • Germination • Scarification

² Graduate research assistant and associate professor, Dep. of Agronomy, Colorado State Univ., Fort Collins, CO 80523.

Received for publication October 3, 1983.