Seeds from three phenotypes of Yucca glauca were germinated using two pre-germination treatments for each phenotype. Treatments were: a 10% NaOCl (10 NaOCl) soak for 15 minutes and a 50% NaOCl (50 NaOCl) soak for 24 hours. Seeds were then placed on Linsmaier-Skoog (LS) medium in darkness for two weeks at 27-28 C. All radicles were emerging through the seed coats at the end of 50 NaOCl as compared to no visual difference in the seed appearance after 10 NaOCl. At the end of the two incubation periods, seeds from 50 NaOCl exhibited shoot development and elongation while seeds from 10 NaOCl exhibited little or no shoot development or elongation. Seeds from 10 NaOCl exhibited contamination and/or “bleeding” (phenolic exudates) within 4 weeks. All seedlings were transferred to fresh LS medium and cultured for 6, 12 and 18 weeks. Seedlings that received the 50 NaOCl developed fibrous roots at 8-10 weeks and the beginnings of a tap root at 16-20 weeks. Ten seedlings from 50 NaOCl were transplanted 9 months after germination.
Fruits of four cucurbit crops, cucumber, melon, watermelon. and squash, were harvested 25, 35 and 45 days past anthesis (dpa) and their seeds were extracted immediately or after 10 or 20 days of pre-extraction storage. Upon extinction, the seeds were subjected or not subjected to fermentation, washing and drying, The effects of these procedures on terminability was examined immediately after extraction or after up to 48 months of storage. Cucumber, melon and watermelon reached full germinability by 35 dpa, but squash required a longer period. Fermentation and drying were important for improving terminability of immature seeds of cucumber, melon and watermelon. Fermentation had a deleterious effect on immature squash seeds, but drying and washing improved terminability of squash seeds. Washing of cucumber, melon and watermelon seeds increased the rate of germination but not the percentage. Pre-extraction storage had a positive effect on terminability but was less effective than leaving the fruit on the vine for a comparable period of time. The seed coat completed its growth earlier than did the embryo.
Seeds of two shrunken-2 (sh2) sweet corn (Zea mays L.) cultivars, Crisp N' Sweet 711 and How Sweet It Is were used to analyze seed quality factor differences between the cultivars. Negative correlations occurred among germination percentage and imbibition, electric conductivity, potassium concentration and total soluble sugars of the seed leachate. Imbibition and total soluble sugar in the leachate significantly increased as imbibition temperature increased from 5°C to 25°C in both cultivars. A significant increase in conductivity of the leachate also occurred in `Crisp N' Sweet 711' when temperature increased. Cracks in the seed coat were more frequent in `How Sweet It Is' than `Crisp N' Sweet 711'. The higher concentrations of soluble sugars in the seed, greater imbibition rate, leakage conductivity, potassium and sugar concentration in the leachate may have been directly related to the poorer seed quality of `How Sweet It Is'. The alteration in cell membrane structure caused by a rapid water uptake in `How Sweet It Is' may have led to the high concentration of electrolytes in the seed leachate. This, in turn, might provide a greater nutritive subtrate for fungi development.
Advanced, two-species CBC individuals were used to create the first-ever, three-species hybrids between P. acutifolius, P. coccineus and P. vulgaris. M6 (2 species) × H15 (3 species) is the only three-species hybrid to date that segregates for diagnostic traits. Three generations of M6 (F2, F3, F4,) were used to create the series. Hybrid breakdown was most severe with M6 F2 × H15, producing 100% cripples that died before anthesis. In M6 F3 × H15 hybrids, segregation for stigma position, flower color, germination type, growth habit, leaf length/width ratios, and seed morphology commenced in the F1 hybrid generation. F, phenotypes, with P. coccineus flowers & seeds and P. acutifolius leaves & growth habit, had severe hybrid breakdown with weak self compatibility; purple seed coats, with or without black circundatus markings, and new flower colors were also produced. F1's with P. vulgaris growth habits were self-fertile and ceased segregating after the F2.
Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] is a diverse crop, with much variability for fruit and seed traits. This study measured the inheritance of scarlet red flesh color, egusi seed type, yellow belly (ground spot) rind pattern, and intermittent stripes on the rind. Scarlet red is a dark red flesh color found in `Dixielee' and `Red-N-Sweet'. Egusi seed is an unusual mutant having a fleshy pericarp adherent to the seed coat found in PI 490383 and PI 560006. Yellow belly is found in `Black Diamond, Yellow Belly'. Intermittent stripes are found in `Navajo Sweet', which has narrow dark stripes that are irregular or nearly absent across the fruit. In order to study the inheritance of these traits, six generations, including parents, crosses, and backcrosses (Pa, Pb, F1, F2, BC1Pa, BC1Pb), were produced in each of seven crosses. Phenotypic data were recorded in the field, and analyzed with the Chi-square method for the segregation of Mendelian genes. Scarlet red color in `Dixielee' was allelic to scarlet red color in `Red-N-Sweet'. Four new genes were identified and named, in conformance with gene nomenclature rules for Cucurbitaceae: Scr for scarlet red, eg for egusi seed, Yb for yellow belly, and ins for intermittent stripes. Thus, we have added four new genes to the 52 morphological and disease resistance genes already published.
Germination inhibitors found in parsley (Pertroselium hortense) seed have serious effects on field establishment. Studies have been conducted on chemical and physical attributes in relation to cultivar, age of seed and location of the seed on the seed stalk. Results indicate that the inhibitor is highly soluble in H2O and can be removed with as little as a half-hour aqueous wash. Soaking 30 g (∼500 seeds/g) of seed in an aerated graduated cylinder containing 100 ml distilled H2O for 24 hours then applied to radish, lettuce, and parsley seeds revealed complete germination inhibition of these seeds. Decreasing the soaking time did not reduce the inhibitory effects of the solution. Location of the inhibitor within the seed was found to be specific to the seed coat. The amount of inhibitor present varied with the cultivar and seed lot within that cultivar. Size and age of the seed had little effect on the amount and strength of the inhibitor. Location of the developing seed on the seed stalk effected the amount of inhibitor present. Primary umbels contained the least amount of inhibitor when compared to the secondary and tertiary umbels.
Abstract
The inheritance of 8 monogenically controlled plant, fruit, and seed characters in Carica species is reported. The gene for red stem is dominant to that for green stem and the gene for red petiole is dominant to that for green stem and the gene for red petiole is dominant to that for green petiole. Genes for white and purple-blush flower colors are dominant to those for pale yellow; while the gene for red skin color of ripe fruit is dominant to that for yellow. However, the gene for red skin color is not dominant to that for orange skin color; the heterozygote has pink-skinned fruits. The gene for ridging on the fruit (carpel fusion lines) is dominant to that for wide groove, which in turn is dominant to that for narrow groove. Spiny vs. non-spiny seed coat produces an intermediate F1, indicating no dominance. The gene for succulent fruit pulp is dominant to that for dry pulp. The gene for bushy branching is dominant to that for sparse branching.
Native turfgrasses have received greater attention in recent years because of their usefulness in growing in areas where many other grasses cannot. Saltgrass (Distichlis spicata) has good salt tolerance, but the natural germination rate for the seed is low. This is most likely due to the thickness of the seed coat inhibiting normal imbibition of water. Previous research in our laboratory has demonstrated increased germination with hand-scarification. The purpose of this research was to compare germination rates of machine-scarified, hand-scarified, and nonscarified seed. Scarifying the seeds by hand results in greater uniformity, but the operation is tedious and time-consuming. Machine scarification is quick, but the seeds have reduced uniformity. Two seed lots, one designated “Modoc” and one designated “Granite,” were compared in laboratory and field germination tests. Preliminary observations have shown that “Granite” seed had somewhat higher viability and vigor than the “Modoc” seed. Significantly greater germination occurred with scarification when seeds were germinated at 14 h of light at 30 °C and 10 h of darkness at 20 °C in the laboratory. Although scarification treatments were similar with the “Granite” seeds, near 80% germination, there were significant differences between hand and machine scarification with the”Modoc” seeds; hand scarified seed had greater germination. The field germination experiment had similar results to the laboratory experiments with “Granite” seed. However, scarification did not aid germination of “Modoc” seed. This is thought to be due to low vigor and associated death of seedlings prior to emergence. Preliminary data confirm the low vigor of the “Modoc” seed as compared to “Granite” seed.
Little scientific information is available describing morphological development of pawpaw during seed germination. To provide this information, a study was designed to outline important developmental stages and describe seedling characteristics within each stage. Stratified pawpaw seeds were sown in vermiculite and germinated at 25°C in a growth chamber. Ten seedlings were randomly chosen and destructively harvested at 5-day intervals starting at radicle protrusion. Length (mm), fresh and dry weight, and percentage of total dry weight were determined for seedling components. Pawpaw seeds have a small rudimentary embryo with all food reserves stored in a ruminate endosperm. Dry weight measurements showed a dramatic reallocation of reserves from the storage tissue to developing seedling parts. Initial embryo length was less than 3 mm, but within 70 days seedlings exceeded 350 mm. Twelve days after planting, simultaneous radicle and cotyledon growth occurred (3.4 and 3.0 mm, respectively), but neither hypocotyl nor epicotyl was visible. Radicle protrusion was observed at 15 days with radicle, cotyledon and hypocotyl lengths increasing to 4.4, 4.0, and 3.2 mm, respectively. Endosperm comprised 99.1% of total dry weight at this stage. The hypocotyl hook emerged after 30 days and endosperm comprised 76.1% of total dry weight. Cotyledons reached maximum length (29.0 mm) at day 40 and the epicotyl was discernible. At 55 days, the seed coat containing cotyledons and residual endosperm abscised and the average radicle, hypocotyl and epicotyl lengths were 182.0, 61.1, and 7.3 mm, respectively. It is suggested that the cotyledons primary function is absorption of food reserves from the endosperm for transfer to the developing seedling.
Developmental, environmental, and genetic factors affecting seed color were studied in the progeny of a cross between two white-flowered (aa) green cotyledon (ii) field peas (Pisum sativum L.): the pale large-seeded Marrowfat cultivar Primo and the greener small-seeded Prussian Blue OSU442-15. Changes in chlorophyll and carotenoid content during seed development of the parental genotypes were determined by high performance liquid chromatography analysis. Both cultivars accumulated similar pigment quantities per seed, but pigment loss was greater during maturation of `Primo'. Bleached and unbleached mature seed tissues also were compared for pigment composition. Lutein was the predominant pigment in bleached cotyledons of both cultivars. Only trace amounts of pheophytins were detected in unbleached seed. In both genotypes, chlorophyll A : B ratios were ≈1:1 in seed coats compared to 3:1 in cotyledons. Objective measurements of seed color in terms of luminance (lightness) and chrominance (hue and saturation) were made in YUV color space by video image analysis. Inheritance of seed color was studied in an F2 population derived from the `Primo' × `OSU442-15' cross and inbred descendants. Quantitative trait loci (QTL) for seed color were localized by interval mapping using a linkage map of 199 molecular markers spanning most of the genome and by bulked segregant analysis and selective genotyping. Four genomic regions affecting seed color were detected. A major gene accounting for 61% of the phenotypic variance in seed lightness (Y luminance component) was identified on linkage group V linked to r locus. Another major gene, which accounted for 56% of the phenotypic variance in seed hue (U chrominance component), was mapped to a linkage group containing group III and IV markers. A QTL with smaller effect on seed hue (U and V chrominance components) was detected on linkage group VII. Support for overdominant allelic interaction for a QTL on linkage group I, adjacent to the legumin locus Lg-J, was obtained by selective genotyping of the seed lightness distributional extremes.