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Mark J. Bassett and Phillip N. Miklas

Bassett (2007) wrote a comprehensive review of the genetics of seed-coat color and pattern in common bean ( Phaseolus vulgaris ). The gene loci T , P , and V have multiple alleles, which express pleiotropic effects on color and pattern in

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J. E. Wyatt

Abstract

Differences in water absorption by intact seeds and in osmotic properties of excised seed coats were measured in 4 near-isogenic breeding lines of snap bean, Phaseolus vulgaris L. White seeds absorbed water more rapidly than colored seeds. Excised white seed coats were more permeable to water than colored seed coats in response to an osmotic gradient. Seed coat thickness and seed coat dry weight were negatively correlated with rate of osmosis through the seed coats. Colored seeds had greater seed coat dry weight and thickness than white-seeded isolines.

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Rodney O. Jones and Robert L. Geneve

Seed coat anatomy in the hilar region was examined in dry, imbibed and germinating seeds of Eastern redbud. A discontinuous area was observed between macrosclereid cells in the palisade layer of the seed coat which formed a hilar slit. A symmetrical cap was formed during germination as the seed coat separated along the hilar slit and was hinged by the macrosclereids in the area of the seed coat opposite to the hilar slit. The discontinuity observed in the palisade layer was the remnant of the area traversed by the vascular trace between the funiculus and the seed coat of the developing ovule. There were no apparent anatomical differences in the hilar region of the seed coat between dormant and non-dormant imbibed seeds. However, the thickened layer of mesophyll cells of the seed coat in this region and the capacity of the endospetm to stretch along with the elongating radicle may contribute to maintaining dormancy in redbud seeds.

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S. L. Kitto and Jules Janick

Abstract

An assay using in vivo-produced embryos, with and without tegmen, of monoembryonic ‘Temple’ tangor [Citrus sinensis (L.) Osbeck x C. reticulata Blanco) and polyembryonic ‘Troyer’ citrange (C. sinensis x Poncirus trifoliata Raf.) was developed to screen compounds as synthetic seed coats for in vitro-produced, asexual embryos. Of 8 compounds evaluated, Polyox WSR-N 750 proved to be the most suitable as a synthetic seed coat based on its film-forming ability, its ability to redissolve in water, and its nondeleterious effects on citrus embryos.

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Safi S. Korban, Dermot P. Coyne, and John L. Weihing

Abstract

A Hunter Color Difference meter and a white-paint color chart were used to determine the degree of whiteness among 8 white-seeded Great Northern (GN) cultivars of Phaseolus vulgaris. A correlation coefficient of +0.84 was found between the 2 methods. The former method provided better separation of cultivars for degrees of whiteness than the latter method. Two genetic studies were conducted, with seed-coat whiteness determined by use of the white-paint color strip. ‘GN Emerson’ had the whitest seed-coat. The inheritance of seed-coat whiteness was investigated in 1978 using parents, F2s of the crosses Plant Introduction (PI) 165078 (bright white) with ‘GN Emerson’ (moderately bright white), ‘GN Valley’ (dull white) and ‘GN UI 59’ (dull white) and in the reciprocal cross ‘Bulgarian White’ (brightest white) × ‘GN UI 59’ (dull white). A quantitative pattern of inheritance was observed. Broad sense heritability estimates for this trait ranged from 46 to 57%. The Gardner and Eberhart model, Analysis II, was used in 1979 to estimate genetic effects for the trait in a 6 parent diallel cross involving ‘GN Emerson’, ‘GN UI 59’, ‘Bulgarian White’, ‘GN Star’ (dull white), ‘GN 1140’ (dull white) and ‘GN D-88’ (dull white). Additive genetic effects were predominant; but heterosis effects were also important, including significant effects for specific combining ability, and reciprocal crosses. ‘Bulgarian White’ showed high combining ability for brighter whiteness. The genetic data indicate that improvement of seed-coat whiteness in dry beans should be relatively easy to accomplish.

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Clifford W. Beninger, George L. Hosfield, and Muraleedharan Nair

Dry bean (Phaseolus vulgaris L.) seed coat color is determined by the presence and relative amounts of phenolics, flavonoids, and anthocyanins present in the lumen of epidermal cells. Some of these chemicals may interact with proteins of the cotyledon to form complexes that render beans hard to cook and digest. Eight genetic loci control seed pigment chemistry. When all eight loci are dominant, a shiny black seed coat results, but recessive substitutions at one or more loci yield colors ranging from white, yellow, and brown to dark violet. In order to relate Mendelian genes for seed coat color to the pigments formed, we studied eight genetic stocks that had recessive substitutions at one or more color-determining loci in an otherwise all-dominant genetic background. Seed coat from each genotype was extracted exhaustively with hexane, EtOAc, MeOH, MeOH:H2O 1:1, and H2O 100%. Silica gel thin-layer chromatography (TLC) (solvent system CHCl3:MeOH 4:1) analysis of the MeOH fraction showed that one genotype had no phenolic compounds and two had only simple phenols. Once flavonol glycoside was present in relatively large amounts in four of the genotypes, but absent in genotypes with anthocyanins. Cellulose TLC (2-dimensional, Butanol:Acetic Acid:H2O 4:1:5 first dimension, 1% HCl second dimension) of the anthocyanin-containing genotypes showed that the presence of one flavonol and three anthocyanidin-3-glycosides (UV spot color and color shift with NH3). The relative importance of the seed coat chemicals in digestibility and their antioxidant will also be discussed.

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Safi S. Korban, Dermot P. Coyne, John L. Weihing, and Milford A. Hanna

Abstract

Seed-coat cracking injury was determined in Great Northern (GN) dry bean lines in 1977, 1978 (also Pintos in 1978) using 3 methods as follows: Vogel small plot thresher (field), seed dropping, and a controlled rotating impact disk machine. Differences in susceptibility for seed-coat cracking were observed within each testing method. Overall, ‘GN Emerson’, near-isogenic determinate ‘GN Nebraska #1’ and ‘Pinto UI 111’ had the best resistance to seed-coat cracking. A genotype × year interaction for seed injury occurred with the Vogel thresher but not with the other 2 methods. The other 2 methods gave consistent results but the rotating disk machine method was preferred because of ease, rapidity of operation and standardization of the rotation speed. The early and late maturing determinate near-isogenic lines of ‘GN Nebraska #1’ had less seed-coat injury than the early and late indeterminate lines using the Vogel and rotating impact disk method. The early determinate line had the least amount of seed-coat injury for all three methods. ‘Pinto UI 111’, ‘Bulgarian White’, and ‘GN D-88’, which exhibited the best resistance to seed-coat cracking in the 7 parent diallel crossing study, had the most uniform seed-coat thickness as well as having thick seed coats. The cultivars which had thin or thick but non-uniformly thick seed coats were susceptible to seed-coat cracking. Differences in thickness in macrosclerid, os-teosclerid and parenchyma cell layers of the seed coat were observed between cultivars, but no relationship between these cell layers and the seed-coat cracking response was established. Seed-coat cracking was quantitatively inherited. ‘Bulgarian White’, ‘Pinto UI 111’ and ‘GN D-88’ showed high combining ability for resistance to seed-coat cracking. The estimates of the genetic effects indicated that additive effects were mainly involved.

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G. J. Gogue and E. R. Emino

Abstract

Fungal and fire treatments were applied to seeds of Albizia julibrissin to simulate natural mechanisms of seed coat scarification. Seeds in unsterilized soil which contained natural microorganisms resulted in increased germination compared to seeds in sterilized media. Germination in cultures of Rhizoctonia, Fusarium, and Pythium indicated Rhizoctonia was most effective as a seed scarifier. Fire treatment at 1, 3, 5, and 10 seconds indicate that 1 second enhanced seed germination. Scanning electron micrographs of treated seed indicated that fungal hyphae alters the surface of the macrosclereid cells which may allow for imbibition of water. Seeds sub-jected to fire had large cracks in the macrosclereid layer.

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Mark J. Bassett

The effects of gri on seed coat and flower color were investigated in a study using Lamprecht line V0400 (PI 527735) as the known source of gri. Seed and flower color data were taken on observations of F2, BC1-F2, and BC2,-F2 populations from crosses of V0400 with the recurrent parent S-593. Segregation was observed for a unique flower color pattern: wing petals have a very pale tinge of blue (laelia), and the banner petal has two violet dots (≈3- to 4-mm diameter) on a nearly white background. This very pale laelia flower color cosegregates with gray-white seed coats produced by gri. Furthermore, the very pale laelia color depends on the action of V for expression and is extinguished by v, which produces pure white flowers. Thus, it was demonstrated that the very pale laelia flower color, for which Lamprecht tentatively proposed the gene symbol vpal, is not controlled by an allele at V but is a pleiotropic effect of gri. It was also demonstrated that Lamprecht line V0060 (PI 527717) carries vlae, not v, as indicated by the genotypic notes accompanying the Lamprecht seed collection.

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P.C. Lee, A.G. Taylor, and T.G. Min

Sinapine leakage to detect seed germination potential on a single-seed basis in Brassica has been developed as a rapid test. In this test, sinapine leakage predicts that a seed is non-germinable; however, the major source of errors in this method are false-negative (F–)—i.e., the method predicted a seed was germinable because the seed did not leak, and it did not germinate. The sinapine leakage index (SLI) was used to asses the F– for any seed lot by dividing the number of non-germinable seeds that leaked sinapine by the total number of non-germinable seeds. Seed lots including cabbage, cauliflower, and broccoli (B. oleracea L., Captitata, Botrytis, and Italica groups, respectively) were used to examine the F–. The leakage rate as measured by T50, the time for 50% of heat-killed seeds to leak, was linearly correlated to SLI. Cabbage seeds were viewed by scanning electronic microscopy and leaking non-germinable seeds either had cracks or were shrunken. NaOCl pretreatment has been found to increase the rate of sinapine leakage and SLI. The mode of NaOCl was due to high pH altering the seed coat permeability. Chemical analysis was conducted on isolated seed coats for pectin, tannins, hemicellulose, cellulose, phenolic lignin, and cutin. It was found that the higher SLI (more permeable) lots contained lower amounts of cutin, suggesting that cutin may restrict the diffusion of sinapine through the testa.