Immunocytochemical localization of wheat germ agglutinin in wheat

Immunocytological techniques were developed to localize the plant lectin, wheat germ agglutinin (WGA), in the tissues and cells of wheat plants. In a previous study we demonstrated with a radioimmunoassay that the lectin is present in wheat embryos and adult plants both in the roots and at the base of the stem. We have now found, using rhodamine, peroxidase, and ferritin-labeled secondary antibodies, that WGA is located in cells and tissues that establish direct contact with the soil during germination and growth of the plant In the embryo, WGA is found in the surface layer of the radicle, the first adventitious roots, the coleoptile, and the scutellum. Although found throughout the coleorhiza and epiblast, it is at its highest levels within the cells at the surface of these organs. In adult plants, WGA is located only in the caps and tips of adventitious roots. Reaction product for WGA was not visualized in embryonic or adult leaves or in other tissues of adult plants. At the subcellular level, WGA is located at the periphery of protein bodies, within electron-translucent regions of the cytoplasm, and at the cell wall-protoplast interface. Since WGA is found at potential infection sites and is known to have fungicidal properties, it may function in the defense against fungal pathogens.     

Behavioural responses of wheat stem sawflies to wheat volatiles

1 Adult wheat stem sawflies Cephus cinctus, pests of cultivated cereals that also infests wild grasses, migrate into wheat fields where they oviposit in elongating, succulent stems.
2 Volatiles released by wheat plants at susceptible stages were analyzed to determine potential semiochemical compounds. Seven major compounds were identified and quantified.
3 A Y-tube bioassay was developed to evaluate upwind orientation of adult sawflies in response to an airstream that passed over elongated wheat plants. The bioassay was also conducted with synthetic volatile compounds. The compounds were tested using a range of concentrations spanning those identified in the airstream passing over wheat plants.
4 A significant number of adult females were attracted to wheat plants when given a choice of either purified air or the air passing over plants.
5 A significant number of female C. cinctus were attracted to ( Z )-3-hexenyl acetate, β-ocimene, and ( Z )-3-hexen-1-ol, but were repelled by 6-methyl-5-hepten-2-one. Females did not respond to ( E )-2-hexenal, or ( E )-2-hexenyl acetate. The behavioural responses were concentration dependent; the highest tested concentration of ( Z )-3-hexenyl acetate was repellent to females of this species.
6 Adult males did not discriminate between air passing over wheat plants and air from a purified airstream. Males did not respond to any tested synthetic compound at any concentration.
7 The present study demonstrates for the first time that adult females of wheat stem sawfly display innate behaviours in response to synthetic volatiles. These results provide a basis for the potential development of resistant wheat varieties and for the development of semiochemically-based pest management.     

C-banded wheat chromosomes in wheat and triticale

Summary The C-banding patterns of wheat chromosomes in 7 hexaploid triticale and 7 wheat genotypes are described and compared. All 14 wheat chromosome pairs were individually identified in the triticales and a tetraploid wheat, and all the B and two A genome chromosome pairs in the hexaploid wheat genotypes. Little variation was found between genotypes in the distribution of C-bands but considerable variation was found in their size, total number and total length.     

Distribution of wheat germ agglutinin in young wheat plants

A liquid phase, competition-binding radioimmunoassay for wheat germ agglutinin, with a detection limit of 10 nanograms, was developed in order to determine the distribution of this lectin in young wheat plants. Affinity columns for wheat germ agglutinin removed all antigenically detectable activity from crude extracts of wheat tissue; thus, the antigenic cross-reactivity detected by the assay possesses sugar-binding specificity similar to the wheat germ-derived lectin. The amount of lectin per dry grain is approximately 1 microgram, all associated with the embryo. At 34 days of growth, the level of lectin per plant was reduced by about 50%, with approximately one-third in the roots and two-thirds in the shoot. The data also indicate that actively growing regions of the plant (the bases of the leaves and rapidly growing adventitious roots) contain the highest levels of lectin. Half of the lectin associated with the roots could be solubilized by washing intact roots in buffer containing oligomers of N-acetylglucosamine, whereas the remainder is liberated only upon homogenization of the tissue.     

Influence of aFusarium culmorum inoculation of wheat onin sacco dry matter degradation of wheat straw and wheat chaff

The aim of this study was to investigate the effect of aFusarium culmorum inoculation of wheat on thein sacco dry matter degradation (DG) of wheat straw and wheat chaff in dairy cows. The ruminal disappearance of dry matter was measured with thein situ nylon bag technique. Samples of wheat straw and wheat chaff from non-inoculated andFusarium-inoculated wheat were used to examine the ruminal dry matter degradability. Samples were subjected to ruminal incubation in two dairy cous fitted with a permanent rumen fistula and incubated for 4, 8, 16, 24, 48, 72, 96 and 120 h. To describe the degradation kinetics, the equation by Ørskov and McDonald (1979) was used. DG rates obtained for contaminates straw and chaff were higher compared to the corresponding rates of the non-contaminated samples, which is assumed to be due to the activity of fungal enzymes. It can be concluded that an infection of wheat withF. culmorum may have an influence on the dry matter degradation of straw and chaff.     

Sweet wheat

The major components of storage starch are amylose and amylopectin, and in wheat, both an amylose-free mutant lacking granule-bound starch synthase I and a high-amylose mutant lacking starch synthase IIa have been produced recently. Here, we report the production of an amylose-free/ high-amylose double mutant. This double mutant has kernel and carbohydrate characteristics that are remarkably different than those of either single mutant, including a dramatically shrunken seed shape. Surprisingly, the double mutant has maltose and sucrose levels that are high enough to make it worthy of being called "sweet wheat".     

Microsatellite-based molecular diversity of bread wheat germplasm and association mapping of wheat resistance to the Russian wheat aphid

Genetic diversity of a set of 71 wheat accessions, including 53 biotype 2 Russian wheat aphid (RWA2)-resistant landraces and 18 RWA2 susceptible accessions, was assessed by examining molecular variation at multiple microsatellite (SSR) loci. Fifty-one wheat SSR primer pairs were used, 81 SSR loci were determined, and 545 SSR alleles were detected. These SSR loci covered all the three genomes, 21 chromosomes, and at least 41 of the 42 chromosome arms. Diversity values averaged over SSR loci were high with mean number of SSR alleles/locus = 6.7, mean Shannon’s index (H) = 1.291, and mean Nei’s gene diversity (He) = 0.609. The three wheat genomes ranked as A > D > B and the homoeologous groups ranked as 7 > 3  > 1 > 2 > 6 > 5 > 4 based on the number of alleles per locus. Xgwm136 on chromosome arm 1AS is the most polymorphic SSR locus with the largest number of observed and effective alleles and the highest H and He. Among all 2485 pairs of wheat accessions, genetic distance (GD) ranged from 0.054 to 1.933 and averaged 0.9832. A dendrogram based on GD matrix showed that all the wheat accessions could be grouped into distinct clusters. Most of the susceptible cultivars (13/18) were clustered into groups that contains all or mostly susceptible accessions. Most of the U.S. cultivars belong to a group that is distinguishable from all the different RWA2 resistant groups. Diversity analysis was also conducted separately for subgroups containing 53 RWA2-resistant accessions and 18 RWA2-susceptible accessions. Association mapping revealed 28 SSR loci significantly associated with leaf chlorosis, and 8 with leaf rolling. New chromosome regions associated with RWA2 resistance were detected, and indicated existence of new RWA resistance genes located on chromosomes of all other homoeologous groups in addition to the groups 1 and 7 in bread wheat. This information is helpful for development of mapping populations for RWA2 resistance genes from different phylogenetic groups, and for wise utilization of the RWA-resistant germplasm in wheat breeding programs.     

The production of haploid wheat plants from wheat x maize crosses

Summary Hybrid embryos from hexaploid wheat x maize crosses rapidly lose the maize chromosomes to produce haploid wheat embryos. Such embryos almost always aborted when left to develop on the plant, and only 1 was recovered from 2440 florets (0.17% of the expected number). Embryos had greater viability in spikelet culture, 47 (26.5% of the expected number) being recovered from 706 ovaries. Thirty-two of these embryos germinated to give green plants, 31 of which were haploid (21 wheat chromosomes) and 1 of which was euploid (42 wheat chromosomes). Spikelet culture enabled 17.1% of the expected number of embryos to be recovered as haploid plants, a 100-fold improvement on allowing embryos to develop in vivo. Ten haploid plants of Chinese Spring (kr1, kr2), 13 plants of Chinese Spring (Hope 5A) (kr1, Kr2), and 8 of Hope (Kr1, Kr2) were recovered. The potential of wheat x maize crosses for wheat haploid production and for gene transfer from maize to wheat is discussed.     

小麦叶片气孔性状与产量和抗旱性的关系

以小麦旱选10号/鲁麦14 DH群体为试材,对干旱胁迫和正常灌溉条件下花后10 d和20d旗叶中部气孔密度、气孔大小、气孔导度、光合速率、蒸腾速率与产量和抗旱系数的关系进行相关和通径分析.结果表明:在两种水分条件下,花后10 d气孔密度、气孔大小、气孔导度、光合速率、蒸腾速率与产量和抗旱系数的相关性大多不显著;但花后20 d与千粒重呈极显著正相关,与穗粒数、单株产量和抗旱系数的相关性仍大多不显著.气孔导度、光合速率和蒸腾速率是影响单株产量和抗旱系数的主要因素,不仅对单株产量和抗旱系数的直接作用较大,间接作用也较大;气孔密度与气孔大小对单株产量和抗旱系数的直接作用和间接作用均较小.在两种水分条件下,花后10 d和20 d,气孔密度与气孔长度之间,气孔长度与气孔宽度、气孔导度、光合速率和蒸腾速率之间的相关性均显著或极显著,但气孔密度、气孔长度与气孔导度、光合速率和蒸腾速率间的相关性在不同水分条件和不同生育阶段存在差异,表明水分条件、生长发育阶段对这些性状之间的相关性影响较大.通过育种手段以叶片气孔密度和气孔大小为选择目标,来改善小麦气孔导度、光合速率和蒸腾速率,进而提高产量并不总是一种有效手段.     

Fractionated extracts of Russian wheat aphid eliciting defense responses in wheat

It is hypothesized that the interaction between aphids and plants follows a gene-for-gene model. The recent appearance of several new Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Homoptera: Aphididae), biotypes in the United States and the differential response of wheat, Triticum aestivum L., genotypes containing different resistance genes also suggest a gene-for-gene interaction. However, aphid elicitors remain unknown. This study was conducted to identify fractionated Russian wheat aphid extracts capable of eliciting differential responses between resistant and susceptible wheat genotypes. We extracted whole soluble compounds and separated proteins and metabolites from two Russian wheat aphid biotypes (1 and 2), injected these extracts into seedlings of susceptible wheat Gamtoos (dn7) and resistant 94M370 (Dn7), and determined phenotypic and biochemical plant responses. Injections of whole extract or protein extract from both biotypes induced the typical susceptible symptom, leaf rolling, in the susceptible cultivar, but not in the resistant cultivar. Furthermore, multiple injections with protein extract from biotype 2 induced the development of chlorosis, head trapping, and stunting in susceptible wheat. Injection with metabolite, buffer, or chitin, did not produce any susceptible symptoms in either genotype. The protein extract from the two biotypes also induced significantly higher activities of three defense-response enzymes (catalase, peroxidase, and beta-glucanase) in 94M370 than in Gamtoos. These results indicate that a protein elicitor from the Russian wheat aphid is recognized by a plant receptor, and the recognition is mediated by the Dn7-gene product. The increased activities of defense-response enzymes in resistant plants after injection with the protein fraction suggest that defense response genes are induced after recognition of aphid elicitors by the plant.     

A diploid wheat TILLING resource for wheat functional genomics

Background

Cultivated peanut (Arachis hypogaea L.) is an important crop worldwide, valued for its edible oil and digestible protein. It has a very narrow genetic base that may well derive from a relatively recent single polyploidization event. Accordingly molecular markers have low levels of polymorphism and the number of polymorphic molecular markers available for cultivated peanut is still limiting.

Results

Here, we report a large set of BAC-end sequences (BES), use them for developing SSR (BES-SSR) markers, and apply them in genetic linkage mapping. The majority of BESs had no detectable homology to known genes (49.5%) followed by sequences with similarity to known genes (44.3%), and miscellaneous sequences (6.2%) such as transposable element, retroelement, and organelle sequences. A total of 1,424 SSRs were identified from 36,435 BESs. Among these identified SSRs, dinucleotide (47.4%) and trinucleotide (37.1%) SSRs were predominant. The new set of 1,152 SSRs as well as about 4,000 published or unpublished SSRs were screened against two parents of a mapping population, generating 385 polymorphic loci. A genetic linkage map was constructed, consisting of 318 loci onto 21 linkage groups and covering a total of 1,674.4 cM, with an average distance of 5.3 cM between adjacent loci. Two markers related to resistance gene homologs (RGH) were mapped to two different groups, thus anchoring 1 RGH-BAC contig and 1 singleton.

Conclusions

The SSRs mined from BESs will be of use in further molecular analysis of the peanut genome, providing a novel set of markers, genetically anchoring BAC clones, and incorporating gene sequences into a linkage map. This will aid in the identification of markers linked to genes of interest and map-based cloning.     

小麦体内生化物质在抗蚜中的作用

综述了小麦体内生化物质的抗蚜作用 ,主要包括不同抗性品种对麦蚜的影响、小麦体内氨基酸、糖类、酚类物质、生物碱和非蛋白氨基酸等与抗蚜性的关系 ,以及蚜虫对小麦体内抗虫生化物质的诱导作用 ,并提出了深入研究小麦生化物质与抗蚜性关系的前景和意义。     

Inoculationin vitro of wheat seedlings and wheat straw cultures withBacillus azotofixans

Bacillus azotofixans is a recently described species capable of fixing molecular nitrogen efficiently.Ecological studies performed in monoxenic wheat cultures, both in 0.7% agar and in vermiculite-sand mixture, showed that no acetylene reduction occurred and that this bacteria did not grow when supplied only with the wheat plant root exudates. However, after glucose addition to the 0.7% agar cultures, acetylene reduction ability (ARA) was detected. Comparing ARA for media with glucose both with and without plants, it was observed that the plants supply some component leading to the increase of the nitrogenase activity, since the ARA doubled in the samples containing plants.In wheat straw cultures a fast growth of the bacteria was observed in the first 24 hours after inoculation, but no acetylene reduction was detected. After glucose addition to the media with and without straw, nitrogenase activity was detected.     

Light activation of Russian wheat aphid-elicited physiological responses in susceptible wheat

The impact of light and its role in Russian wheat aphid, Diuraphis noxia (Mordvilko), damage symptom formation, and photosynthetic capacity in 'Arapahoe' wheat (Triticum aestivum L.) were examined. After 72 h under continuous dark or continuous light regimes, the number of aphids (nymphs), leaf rolling and chlorosis ratings, fresh leaf weight, and chlorophyll contents were recorded. Photosynthetic rates, chlorophyll a, kinetics and chlorophyll extractions also were determined. Aphid infestation caused significant reductions in plant height, fresh weight, gas exchange, and chlorophyll fluorescence only under continuous light. Under the 72 h continuous dark regime, aphid infestation did not cause either damage symptom formation or reduction in plant growth or metabolism (photosynthesis). Furthermore, significantly more D. noxia nymphs were produced under continuous light condition than continuous dark. Our results demonstrate that the development of D. noxia feeding damage symptoms (i.e., leaf rolling and chlorotic streaks) on susceptible wheat seedlings is a light-activated process, even though the elicitor of the plant damage symptoms is aphid feeding.     

An analysis of frequencies of chromosome configurations in wheat and wheat hybrids

Presynaptic association of homologous chromosomes is a prerequisite to the sequence of events that lead to chiasma formation. This association of homologous chromosomes, as entire units, occurs with probability a, and chiasma formation occurs independently in opposite chromosome arms with probability c. a and c have been estimated from frequencies of different chromosome configurations at metaphase I of euhexaploid wheat and several derived lines. In the euploid, a is essentially unity and c is of the order of 95%. All changes in the aneuploidy studied involved c rather than a, whereas the change induced by colchicine application primarily involved a.—Observed and expected frequencies of configurations were compared in wheat hybrids in which only homoeologues were present. The expected frequencies of configurations were estimated from the data, based on a being unity for entire groups of homoeologues and c being the probability of chiasma formation between random homoeologous arms. Observed and expected frequences of configurations were in general agreement; however, an excess of observed closed bivalents at the expense of multivalents is interpreted to mean that not all homoeologues are effectively associated in all cells.—In euhexaploid wheat, we suggest that homologues associate with almost certainty, whereas homoeologous pairs of chromosomes associate less efficiently. The aneuploidy examined in this study does not appear to affect the association of chromosomes, but rather the number of chiasmata that eventuate and, in the case of deficiency of chromosome 5B, the distribution of chiasmata within homoelogues, perhaps by way of rendering sites for chiasma formation of homoelogues more similar.     

Characterization of a wheat germ agglutinin-like lectin from adult wheat plants

Radioimmuno-and enzyme-linked immunosorbent assays show that a substantial amount of wheat germ agglutinin(WGA)-like protein is present at the base of the shoot and in the roots of adult wheat (Triticum aestivum L.) plants. The protein can be purified by hapten-and antibody-mediated affinity procedures. It forms an arc of identity with the embryo lectin upon Ouchterlony double-diffusion and is an active lectin that agglutinates trypsinized erythrocytes in an N-acetylglucosamine-and chitin-inhibitable manner. Reduced and carboxyamidated protein comigrates with the 18-kdalton subunits of embryo lectin on sodium dodecyl sulfate-polyacrylamide gels. Invivo labeling of 9-d-old, hydroponically grown plants with ³⁵S-labeled sulfate demonstrates that at least some of the WGA-like protein is synthesized de novo. Immunocytochemistry with rabbit anti-WGA and colloidal-gold-conjugated second antibody shows that cross-reactive protein is present at the tips of new adventitious roots. In reactive cells, the lectin is localized near the inner surface of the vacuole membrane. Wheat plants contain up to 100 ng of WGA-like protein after the first week of growth, but the level fluctuates thereafter. Since most of the lectin is present at the base of the shoot and much less is found in older roots, these fluctuations may be the consequence of changes in the initiation of new advantitious roots.Abbreviations ELISA enzyme-linked immunosorbent assay - GlcNAc N-acetylglucosamine - PBS phosphate-buffered saline - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis - WGA wheat germ agglutinin     

Cuticular wax of wheat

n-Alkanes, esters, aldehydes, free alcohols, -diketones and hydroxy--diketones were found to be the lipid components of the cuticular waxes of common wheat Chinese Spring (Triticum aestivum L.). The ditelosomic lines 7A-L and 7D-S showed a dramatic decrease in the amount of -diketones and hydroxy -diketones which are reduced to traces. The homologue composition within each class of compounds has also been determined for all three of the lines of wheat. The effects of chromosomal deficiencies have been demonstrated. Chromatographic techniques and mass spectrometry have been used for the separation and identification of the substances which compose the waxes. This study has provided further evidence of the role of genes situated on well defined chromosomes in determining the nature of classes of compounds composing wax and governing the homologous composition within each class of substances.     

小麦品种对麦蚜主要生命参数影响的研究

选用经田间鉴定抗蚜性表现不同的１０个小麦品种,在室内外较系统地研究了其对禾谷缢管蚜和麦长管蚜存活、生长发育和生殖的影响,分析了室内外试验结果的相关性．结果表明,小麦品种的抗生性并不能造成若蚜个体的直接死亡,但对若蚜发育历期、成蚜寿命和产仔数影响显著,差异均达极显著水平或显著水平．其中对两种蚜虫若蚜发育历期的影响室内外表现了较好的一致性,可作为小麦品种抗蚜性鉴定的主要指标;其次是对成蚜产仔数的影响,禾谷缢管蚜室内外试验结果比较的吻合性也较好