Volume 12, No. 2, 1988

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(pp. 107-113)
Seed Maturation in Cuphea
I. Kaliangile and D.F. Grabe
Cuphea is a potential source of medium-chain triglycerides for manufacture of soaps,  pharmaceuticals, and nutritional products. Indeterminate flowering and seed shattering are wild-type characteristics that cause difficulty in determining the proper time to harvest for maximum yields of seed and oil. This study was undertaken to determine when seeds reach maturity in two Cuphea species with potential for domestication.

Seed maturity is defined as that stage of development when maximum dry weight and oil content are first attained. Seed development of C. lutea Rose and C. wrightii Gray was studied from flowering to maturity in two greenhouse and one field experiment by harvesting seeds from tagged flowers at frequent intervals and measuring dry weight, oil, and moisture  content. Maximum seed dry weight was attained by 19 d after anthesis in the 1986  greenhouse studies. At this time, dry weight was 2.62 mg seed, moisture content was 420 g H2O kg- fw (42%), and oil content was 240 g oil kg dw (24%) in C. lutea. Measurements for  C. wrightii were 1.89 mg seed dw, 320 g H20 kg fw (32%) moisture, and 310 g oil kg-l (31%)  oil content. Simple correlation coefficients for oil and dry weight were 0.97 and 0.96 for C. wrightii and C. Iutea, respectively. Similar relationships between seed quality components were evident in the 1985 greenhouse and field experiments. Seeds of C. lutea were mature at the time of emergence from the calyx tube in the field. Waiting beyond this time for green seeds to turn yellow or brown before harvesting will not increase seed dry matter or oil content, and would lead to increased shattering and seed loss.
Additional index words: Cuphea lutea Rose, Cupea wrightii Gray
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Determining Viability of Green Needlegrass (Stipa viridula Trin.)1
A.L. Rubida and T.J. Gutormson2
Germination of green needlegrass (Stipa viridula Trin.) seed was increased 24% by acid scarification with 95% sulfuric acid for 6 to 12 mins. Additions of 0.055% gibberellic acid (GA3) and 0.46% tetramethylthiuram disulfide (Thiram) as the blotter moistening solution produced germination equal to tetrazolium viability (86%). This treatment improved germination by removing seed dormancy and controlling saprophytic fungi.

The average germination response of 10 seed lots treated in this manner was 86% after only 14 d in dark conditions at 15-30o C. compared to 42% following a 14 d prechill (5o C.) and 21 d germination (15-30o C. ) as recommended by the Association of Official Seed Analysts Rules for Testing Seeds. Acid scarification, GA3, and Thiram fungicide treatment is an accurate method for obtaining green needlegrass seed germination which is equal to tetrazolium viability.
Additional Index Words: Acid Scarification, Gibberellic Acid, Prechilling, Sulfuric Acid, Dormancy
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(pp. 120-126)
Electrophoresis of Esterases to Identify Bentgrass Cultivars1
G.W. Freeman and F.A. Yoder, JI.2
Bentgrasses (Agrostis spp.) are economically important turfgrasses in the Northeastern United States and, consequently, new and rapid methods of bentgrass cultivar identification need to be developed. Protein extracts obtained from unimbibed seeds of 10 bentgrass cultivars were characterized using 7% polyacrylamide gel electrophoresis to isolate esterase isoenzyrnes.

The cultivars from the following species were studied: Agrostis palustris Huds. (creeping bentgrass) 'National', 'Penncross', 'Seaside', 'Penneagle', 'Pennlinks', 'Emerald'; Agrostis canina L. (velvet bentgrass) 'Kingstown'; Agrostis tenuis Sibth. (colonial bentgrass) 'Dutchess', 'Exeter', 'Highland'. The results revealed that esterase banding profiles separated creeping, colonial and velvet bentgrasses. Prominent bands at Rf 0.55-0.59 were unique to the colonial bentgrass cultivars. Creeping bentgrass cultivars were charcterized by bands at Rf 0.50-0.60 but these lacked the intensity of the colonial cultivars. Velvet bentgrass was distinguished from the creeping and colonial bentgrasses by bands which were prominent at Rf 0.57-0.66. Minor banding pattern variations characterized the individual cultivars within each of these species groups. This study demonstrated that esterase isoenzyme analysis using polyacrylamide electrophoresis can be an effective tool in screening bentgrass species or identifying various cultivars within each species. These tests can be used to supplement visual seed analysis or traditional field and growth chamber tests.
Additional Index Words: Agrostis palustris L., Agrostis canina L., Agrostis tenuis Sibth., Cultivar identification, Isoenzymes.
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(pp. 127-132)
Germination of Intact and Naked Seed of Indian Ricegrass1
Jones, T.A., R. Hill, and D.C. Nielson2
Indian ricegrass (Oryzopsis hymenoides (Roern. & Schult.) Ricker) exhibits two types of seed dormancy: mechanical, which persists as long as the seed coat is not ruptured, and physiological, believed to be a result of low levels of endogenous giberellins in freshly harvested seed. Six accessions were tested for germination with lemma and palea present (intact seed) and absent (naked seed).

Seeds were planted on blotter paper and prechilled for 4 wk at 5o C.  before the 3-wk 15o C. (9 h)/5o C. (15 h) test. Seeds were less than six mo old when evaluated and exhibited more physiological dormancy than mechanical dormancy. Differences among the accessions were observed for germination of intact and naked seed. Germination of intact and naked seed from the same accession was positively correlated. Mechanical dormancy and physiological dormancy were negatively correlated across accessions.
Additional index words: Oryzopsis hymenoides (Roem. 81 Schult.) Ricker, Seed dormancy.
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(pp. 133-142)
Transmission of Phaeoisariopsis griseola by Bean Seed1
A.W. Saettler and F.J. Corea2
Outbreaks of angular leaf spot, caused by Phaeoisariopsis griseola, occurred in a number of Michigan seed fields of the 'Montcalm' red kidney bean cultivar. Seed assays revealed low amounts of P. griseola in 8 of 20 (40%) and 6 of 59 (10%) seed lots from 1982 and 1983, respectively.

Infestation sites in seeds of cultivars 'Charlevoix' and 'Montcalm' red kidney bean were primarily in the hilum, whereas in seeds of cultivar 'Laker' navy bean they were in both the hilum and seed coat. Greenhouse and field studies established that seedborne P. griseola is transmitted to the developing seedlings and thus may serve as a source of inoculum in Michigan. Viability of P. griseola in seeds decreased over time.
Additional Index Words: Angular leaf spot, Phaseolus vulgaris L. Primary inoculum.
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(pp. 143-148)
Osmoconditioning and Hormonal Influences on Soybean Emergence at Optimal and Suboptimal Temperatures
E.J. Lorenz1, J.T. Cothren1, and D.E. Longer2
Osmoconditioning (OC) seed treatments were evaluated for effect on emergence of two soybean cultivars [Glycine max (L.) Merrill], 'Lee 74' and 'Forrest', under a simulated soil crust at 15 and 20o C. Weighted pistons (60 g) were placed over planted seed 24 h after planting to simulate a soil crust. A specially designed apparatus featuring tubes containing seed planted in sand and the weighted piston was placed inside a controlled climate chamber. Data were collected for total and cumulative percent emergence, seedling and root development, and emergence force. The ability of a seedling to displace weight was an indicator of emergence force.

For both cultivars, osmoconditioning seed with polyethylene glycol (PEG) plus GA3  showed positive effects in cumulative percentage emergence and emergence force. At 20o C., mean percentage emergence (daily percentage emergence averaged over time) from seed treated in PEG plus GA3 was significantly (=0.05) greater than from untreated seed for Forrest and numerically greater for Lee 74. At 15o C., seed treated in PEG plus GA3 showed significantly (=0.05) greater mean displacement (emergence force) versus untreated seed for both cultivars. At 20o C., seed treated in PEG plus GA3 failed to show a significantly greater displacement mean than untreated seed for either cultivar. These results suggest that osmoconditioning plus GA3 may be beneficial for improved emergence of soybean under suboptimal temperature and simulated soil crust.
Additional Words: Glycine max, Soil crust, Emergence force
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