Dan Atsmon

Protein resources in wild barley,Hordeum spontaneum, in Israel: Predictive method by ecology and allozyme markers

Geographic variation in protein content of wild barley,Hordeum spontaneum, and the associations of protein content with ecological and allozyme markers were tested in an attempt to derive predictive guidelines for conservation and utilization in breeding programs. The study involved 195 genotypes of wild barley from 25 populations, 15 central and 10 marginal. These populations had been tested earlier for allozymic variation (Nevo & al. 1979 a, b). The results indicate that protein content varies both within, but particularly between populations. Notably, the 10 marginal populations exhibit high protein content but low kernel weight, as compared with the 15 central populations which displayed lower protein content but high kernel weight. Three variable combinations of climatic factors explain 40% of the variability in protein content among populations. Likewise, 3 variable combinations of allozyme allele frequencies explain a significant degree of spatial variance in protein content (R square = 0.63). — We conclude that natural populations of wild barley in Israel contain large amounts of yet untapped genes for protein content. These could be effectively screened and utilized for producing high protein cultivars of barley by following ecological and allozymic markers as predictive guidelines in screening natural populations of wild barley.

Variation in vegetative parameters related to the nitrogen economy of wild barley, Hordeum spontaneum, in Israel

SummaryHordeum spontaneum, the wild progenitor of cultivated barley, has previously been examined in various studies as a germplasm resource in breeding for grain protein content and related nutritional traits.The nitrogen content and dry weight of leaf and ‘stem’ (stem plus sheath) at anthesis, and the final grain size and grain protein content were measured in 33 H. spontaneum and two H. vulgare genotypes. H. spontaneum was generally higher in nitrogen content of leaves and stems, but lower in dry weight at anthesis. Consistent with previous reports, the H. spontaneum genotypes were considerably higher in grain protein than the cultivars. There was wide variation between and within populations of H. spontaneum suggesting that for breeding purposes lines combining high vegetative nitrogen content, dry weight and grain protein content can be selected.

Vegetative and floral bud abortion in cucumber plants: Hormonal and environmental effects

Abstract The acropetal, zonal pattern of axillary buds along the main shoot of the cucumber plant, which includes bare nodes (no appreciable development), staminate, mixed and, lastly, pistillate (or hermaphrodite) ones, is described in monoecious, gynoecious, andromonoecious and hermaphrodite genotypic lines grown at various seasons and treated with gibberellin (GA 4 + 7 ) or with an ethylene-releasing compound (CEPA, 2-chloroethyl phosphonic acid). Under optimal growing-conditions, GA given to gynoecious and hermaphrodite plants mimicked summer conditions by increasing the number of basal bare nodes and the proportion of abortive female buds and staminate buds. CEPA given to monoecious and andromonoecious plants generally imitated winter conditions by decreasing the proportion of bare and abortive nodes, and increasing female tendency. Bud abortion was also noticed under sub-optimal growing-conditions (low light intensities and relatively low temperatures) during the winter. This seems to be physiologically unrelated to the above mentioned phenomena.

Sex inheritance inRicinus communis L.: Evidence for a genetic change during the ontogeny of female sex reversals

Further evidence has been presented for the finding (Shifriss, 1956, 1960) that there is a higher transmission of femaleness to outcross progeny through female inflorescences of sex reversal castor bean plants, than through reverted (monoecious) inflorescences of the same plant. The change from femaleness to monoecism which occurs during the ontogeny of the plant could be transmitted through the pollen and thus represents a genetic change.

Endosperm protein accumulation in wild and cultivated barley and their cross grown in spike culture.

SummaryThe high protein wild relatives of cultivated cereals have proven difficult to utilize in plant breeding by direct selection for high grain protein percentage, and hence alternative selection criteria are needed. In this study, a spike culture method was used to measure differences in protein accumulation between wild and cultivated barley, and their cross, at different levels of nitrogen supply. Three genotypes, barley cultivar Hordeum vulgare L. cv. Clipper, a wild barley accession H. spontaneum Koch line 363, and a high protein F5 line (38.4) derived from their cross, were grown from 8 to 27 days after flowering in in vitro spike culture. Nitrogen supply in the culture medium was either 0.4 g/l or 2.0 g/l of N supplied as NH4NO3. Spikes were harvested at approximately 3 day intervals during grain development, and salt soluble and hordein protein fractions were measured. Lines 363 and 38.4 differed from ‘Clipper’ in having extremely high initial rates of protein accumulation, even at 0.4 g/l N. In high nitrogen conditions all three genotypes reached similar salt soluble plus hordein protein levels. Hordein-1 and hordein-2 fractions were measured separately; the percent of hordein-1 was higher in lines 363 and 38.4 than in ‘Clipper’ at 0.4 g/l N. For all parameters measured, pot-grown spikes of matching age were harvested and were shown to be similar to the 0.4 g/l N treatment. The possible utilization of spike culture for identification of critical protein accumulation parameters is discussed, in relation to their possible utilization in breeding.

Hook opening in cucumber seedlings by narrow-band red and far-red light

Abstract Intermittent red (R, 660 nm, 3.9 Wm−2) and far-red (FR, 728 nm, 7.0 Wm−2) light treatments caused hook opening in etiolated cucumber (Cucumis sativus L.) seedlings, by cell elongation at the concave side only, but had no significant effect on hypocotyl elongation. The relative positive effect of FR on the hook increased with age of the seedling. FR counteracted the hook opening effect of R only if given simultaneously with R in young seedlings, whereas FR by itself had no effect or a slightly negative one. Results are not readily explained in terms of high energy response (HER); alternative mechanisms are discussed.

Characterization of drought resistance in a wild relative of wheat, Triticum kotschyi

Wild relatives of wheat have served as a genetic source for economically useful traits. A better understanding of the mechanisms underlying such traits may be useful in the genetic transfer and selection processes. Research was undertaken to compare the effects of controlled water stress on photosynthetic parameters in Triticum kotschyi, a drought resistant wild wheat and Triticum aestivum cv. Lakhish, a drought sensitive wheat cultivar. During stress development, the leaf water potential decreased at a slower rate, and the quantum yield of oxygen evolution, measured photoacoustically in vivo, decreased to a smaller extent in the drought resistant wild wheat than in the wheat cultivar. The decrease in quantum yield at water potentials from −0.9 Mpa down to −2.3 Mpa was not accompanied by damage to PS II reaction centers as there was no change in variable fluorescence. Below −2.3 Mpa the fluorescence yield of both species decreased indicating loss of intrinsic efficiency of PS II. The osmotic potential of cell sap was found to decrease at the same rate in both species at high hydration states. Proline accumulated to a much greater extent in the wild wheat as compared to the cultivated wheat as a result of water stress. Drought resistance was also examined in relation to thylakoid membrane fluidity measured by fluorescence polarization. Thylakoid membrane fluidity was fully maintained in the wild wheat, but decreased substantially in the wheat cultivar, at equal tissue water potentials below −1.9 Mpa. One mechanism for maintaining the higher quantum yield of oxygen evolution during severe stress (at water potentials below −1.9 Mpa), may involve the greater stability of thylakoid membrane fluidity in the wild wheat.

WILD BARLEY ( HORDEUM SPONTANEUM KOCH) AND ITS POTENTIAL UTILIZATION IN BARLEY PROTEIN IMPROVEMENT

ABSTRACT The aim of this review is to summarize existing knowledge about the biology of Hordeum spontane um Koch and then to discuss some ideas about its potential and limitations as a gene resource for breeding cultivated barley (Hordeum vulgare L.) with improved protein production.

Extraction and immunochemical assays of a tubulin-like factor in cotton seedlings

Antibodies to tubulin were prepared in rabbits by immunization with reduced-carboxymethylated calf-brain tubulin. In immunodiffusion tests the antibodies showed full cross reactivity with the immunogen as well as with native calf-brain tubulin. The same antibodies showed cross reactivity with a factor in extract of cotton (Gossypium hirsutum L.) cotyledons but there was no full immunological identity between calf-brain tubulin and this factor. A solid-phase radioimmunoassay for quantitative estimation of this plant tubulin-like factor was developed. It measured the binding of antibodies to immobilized calf-native tubulin. Competition between the unknown soluble tubulin-like factor, and immobilized tubulin was assayed at serum dilution of 1:50. Extraction conditions which preserved the antigenic properties of the tubulin-like factor from cotton cotyledons were defined. The radioimmunoassay measured quantities of the tubulin-like factor in the range of 0.1–10 μg-equivalents of calf-brain tubulin. Immediately after homogenization of the tissue only 25% of the total amount of tubulin-like activity was present in soluble form, while most of it remained in the insoluble fraction. Apparent maximal solubilization was achieved spontaneously 10 h after homogenization or by treatment with guanidine hydrochloride. These results indicate that in this material, tubulin is not released immediately by homogenization but remains assembled in microtubules and-or in a bound or sequestered form.

Measurements of Water Potentials and Hormone Transport Associated with the Growth of Cucumber Hypocotyls

Rapid growth responses in non-dividing cells are essentially brought about by water uptake. This increased water uptake (Jv) may result from an increased driving force (Δψ) or a change in membrane permeability (Lp), thus: