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

Abstract

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.

Previous Grazing or Clipping Affects Seed of Indian Ricegrass

“…3A). This strongly suggested that seed size is an inheritable characteristic in Indian ricegrass, as noted by Zemetra and Cuany (1984). These findings supported work by Bohmont and Lang (1957) and Zemetra et al (1983) who found ecotypic differences in seed weight of Indian ricegrass.…”

“…Seed germination for Nezpar was not different from seed germination of native strains. Zemetra and Cuany (1984) found that seed weight of Indian Ricegrass was not highly correlated with germination percentage, as was found in the present study. Mechanical scarification of seed caused a significant increase in seed germination of most entries of Indian ricegrass, except for grazed and ungrazed hillside populations.…”

“…Strains of Indian ricegrass have been shown to differ in composition of their polymorphic forms and germination characteristics (Young and Evans 1984). Zemetra and Cuany (1984) recommended that lemma thickness be utilized to determine proper acid scarification procedures to minimize seed damage and maximize germination.…”

“…High dormancy of Indian ricegrass seed has caused concern for many years and a number of studies have been conducted to investigate dormancy mechanisms and methods for breaking dormancy to improve seed germination of this species (Stoddart and Wilkinson 1938, Toole 1940, Clark and Bass 1970, McDonald and Khan 1977, Zemetra et al 1983, Zemetra and Cuany 1984, Young and Evans 1984, Young et al 1985, Jones and Nielson 1992. Seed dormancy is a mechanism to optimize the distribution of germination over time, and its importance is best illustrated in an ecological context (Bewley and Black 1982).…”

Seed Dormancy and Aging in Atra Paspalum

“…and Schult.) is affected by lemma thickness, a genetically controlled trait (Zemetra and Cuany, 1984) In kleingrass ( Panicum coloratum L.), genotypes differed in the degree, and possibly the mechanism, of dormancy (Tischler and Young, 1983) Germination of fresh kleingrass seed from 107 plants selected for reduced postharvest dormancy ranged from 20 to 90% (Tischler and Young, 1987)…”