Yield responses of Nepalese spring wheat (Triticum aestivum L.) cultivars to inoculation with Azospirillum spp. of Nepalese origin

Azosprilla were collected in wheat fields from subtropical and temperate soils of central Nepal at various elevations. Different wheat cultivars responded positively and significantly in grain yield, grain N-yield, and total N-yield in plant shoots to the inoculation with Nepalese isolate Azospirillum 10SW. Nepalese wheat cv. Seto responded significantly better with Azospirillum 10SW than with the Brasilian isolate A. lipoferum Sp 108 st, a strain which was found highly efficient in earlier experiments with German wheat cultivars, especially cv. Turbo. Yield of Turbo was increased by inoculations of both Azospirillum strains too, but it showed no significant differences depending from the inoculum used. The higher efficacy of combining Azospirillum 10SW and Seto, both collected from the same locality, indicates the possibility of improved associations using traditional cultivars and local bacteria. ei]{gnR O D}{fnDixon}     

Treatment of potato tubers with a growth promotingPseudomonas sp.: Plant growth responses and bacterium distribution in the rhizosphere

Rifampicin-nalidixic acid resistant mutants of a plant growth promotingPseudomonas sp., strain PsJN, were evaluated for their ability to stimulate in vitro growth of potato. Two mutant strains, MFE (a consistent growth promoter), and IIM15 (an inconsistent growth promoter), were selected for root colonization study. Root colonization of potato plants was consistently greater with MFE than with IIM15. The population density of indigenous bacteria on the root surface of potato plants inoculated with strain MFE was significantly lower as compared to non-bacterized controls and to the plants bacterized with strain IIM15. Soil sterilization did not affect plant growth in any of the treatments. Bacterization of seed tubers with strain MFE stimulated plant emergence and root development in the field, during the first two weeks after planting. Bacterized plants also formed stolons and tubers earlier and had increased yields of commercial size tubers (55 mm) as compared to non-bacterized controls. Root colonization by strain MFE was positively correlated with plant growth stimulation.     

玉米幼苗根际土壤微生物活性对芘污染的响应

用根际袋法土培试验研究了玉米幼苗根际与非根际土壤微生物量碳、微生物熵、代谢熵和土壤酶活性对不同芘污染水平(50、200、800mg·kg-1,记为T1、T2、T3)的响应差异。结果表明,较低浓度芘可适当的刺激玉米幼苗的生长,而较高浓度芘则抑制幼苗生长,其抑制作用随芘处理浓度的提高而增强;芘对玉米根系的影响要大于对茎叶的影响。玉米幼苗能够明显促进土壤中芘的去除。根际和非根际土壤中芘的去除率分别为56.67%-76.18%和32.64%-70.44%,根际土壤中芘的平均去除率比非根际土壤高16.06%。同处理中根际土壤芘含量显著低于非根际土壤,随着芘处理浓度的提高其差异更加显著。根际土壤微生物量碳、微生物熵、多酚氧化酶活性、脱氢酶活性和磷酸酶活性均高于非根际土壤,代谢熵低于非根际土壤,且其差异随芘处理浓度的提高而增大。在不同芘污染水平下,微生物量碳、微生物熵和脱氢酶活性根际和非根际土壤为T1T2T3,代谢熵为T3T2T1;多酚氧化酶活性根际土壤为T2T1T3,非根际土壤为T1T2T3;磷酸酶活性根际土壤为T3T1T2,非根际土壤为T1T2T3。土壤中残余芘含量与土壤微生物量碳、微生物熵、多酚氧化酶、脱氢酶和磷酸酶活性呈显著负相关,与代谢熵呈显著正相关。     

Specific binding of a hypersensitive lignification elicitor from Puccinia graminis f. sp. tritici to the plasma membrane from wheat (Triticum aestivum L.)

We have recently reported the isolation and characterization of a glycoprotein (M_r 67 000) from germ-tube walls of Puccinia graminis f. sp. tritici which elicits the cellular hypersensitive lignification response in wheat (G. Kogel et al., 1988, Physiol. Mol. Plant Pathol. 33, 173–185). The present study uses this glycoprotein, referred to as Pgt elicitor, to identify putative elicitor targets in wheat cell membranes. In enzyme-linked immunosorbent assays using anti-Pgt elicitor antibodies, specific binding sites for Pgt elicitor were detected in highly purified plasma-membrane vesicles of wheat (Triticum aestivum L.) primary leaf cells. Binding proved to be independent of the presence or absence in wheat of the Sr5 gene for rust resistance, and also occurred on barley (Hordeum vulgare L.) plasma membrane. The binding sites have an Mr of 30 000 and 33 000, respectively, and binding activity was not lost in the presence of sodium dodecyl sulfate. [¹⁴C]imido-Pgt elicitor was used to determine the apparent K _d value for specific binding, found to be 2.0 M, and the maximum content of binding sites, found to be 250 pmol per mg of plasma-membrane protein. The relevance of the elicitor binding for the outcome of the interaction of P. graminis and wheat is discussed.Abbreviations BSA bovine serum albumin - ELISA enzyme linked immunosorbent assay - IDPase inosine 5-diphosphatase - MPLC medium-pressure liquid chromatography - MF microsomal fraction - Pgt elicitor elicitor of Puccinia graminis f. sp. tritici - SDS sodium dodecyl sulfate - Pre U₃, Pre U₁ pure plasma membrane from wheat cultivar Prelude and plasma membrane contaminated by intracellular membrane, respectively This work was supported by the Deutsche Forschungsgemeinschaft. We wish to thank C. Larsson, Lund, Sweden for his kind support in the preparation of plasma membrane.     

Inheritance of cell size in wheat (Triticum aestivum L.) and its relationship to the vernalization loci

Reduced cell size is an important adaptive feature in plant response to environmental stresses. The objectives of the present study were to determine the inheritance and location of genes controlling cell size and to establish the relationship between cell size, low-temperature (LT) tolerance, and growth habit as determined by the Vrn loci in wheat. Guard cell length was measured in F₁, F₂, andF₂-derived F₃ populations from parents ranging widely in cell size and in the Chinese Spring/ Cheyenne (CS/CNN) chromosome substitution series. The cell size of F₁ hybrids was similar to the parental midpoint and the F₂ frequency distribution was symmetrical about the mean indicating that cell size was determined by additive gene action with little or no dominance. It appears that there are several genes involved since none of the F₂ progeny had a cell size as large or as small as the parental mean range. The cell size of the homozygous spring and winter lines from F₂-derived F₃ populations fell into two distinct groups that were related to plant growth habit. Large cell size was associated with the spring-habit alleles (Vrn-A1) and small cell size was associated with the winter-habit alleles (vrn-A1) on chromosome 5A. Analyses of the CS/CNN chromosome substitution series showed that CNN chromosomes 5A and 5B both reduced cell size without changing the growth habit, indicating that growth habit per se does not determine cell size. The group-5 chromosomes therefore appear to carry homoeologous alleles with major effects on cell size in wheat. This places cell-size control and many other low-temperature (LT) tolerance associated characters in close proximity to the vrn region of the group-5 chromosomes. Received: 17 August 2000 / Accepted: 20 November 2000     

Mapping QTLs for nitrogen uptake in relation to the early growth of wheat (Triticum aestivum L.)

The objective of this study was to map QTLs for N uptake (NUP) in wheat, and to investigate factors influencing NUP. Two independent field trials with low N (LN) and high N (HN) treatments were conducted in the growing seasons of 2002–2003 (trial 1) and 2003–2004 (trial 2) to measure NUP per plant (N accumulated in the aerial part at maturity stage) of a doubled haploid (DH) population consisting of 120 DH lines derived from winter wheat varieties Hanxuan 10 and Lumai 14. A hydroponic culture with all nutrients supplied sufficiently was conducted to investigate shoot dry weight (SDW), root dry weight (RDW), tiller number (TN) and NUP (total plant N uptake) per plant of this mapping population at seedling stage. SDW, RDW, TN and NUP investigated in the hydroponic culture were significantly and positively correlated with each other, and with NUP under both LN and HN conditions in the field trials. Nine and eight QTLs for NUP were detected under LN and HN conditions in the field trials, respectively. Four to five QTLs for SDW, RDW, TN and NUP were detected in the hydroponic culture. One SDW QTL, three RDW QTLs, two TN QTLs detected in the hydroponic culture were linked with QTLs for NUP under LN or HN condition in the field trials. The positive correlation and genetic linkage for the traits between the field trials and the hydroponic culture demonstrated that greater seedling vigor of root and shoot is an important factor influencing N uptake in wheat. Diaoguo An and Junying Su: These authors contributed equally to this work. Section Editor: H.J. Kronzucker     

An RFLP map of diploid Hordeum bulbosum L. and comparison with maps of barley (H. vulgare L.) and wheat (Triticum aestivum L.)

This paper describes the first extensive genetic map of Hordeum bulbosum, the closest wild relative of cultivated barley. H. bulbosum is valuable for haploid production in barley breeding, and because of desirable agronomic characteristics, it also has potential for trait introgression into barley. A H. bulbosum map will assist introgression and provide a basis for the identification of QTLs for crossability with barley and other potentially useful genes. The present study used a population of 111 individuals from a PB1×PB11 cross to develop a genetic linkage map of diploid H. bulbosum (2n=2x=14) based on barley, wheat and other ”anchor” cereal RFLP markers previously mapped in other species. Because of the cross-pollinating and highly polymorphic nature of H. bulbosum, up to four alleles showed segregation at any one locus, and five different segregation types were found. This enabled maps to be developed for the PB1 and PB11 parents, as well as a combined map. In total, 136 RFLP loci were mapped with a marker coverage of 621 cM. The markers were generally colinear with barley but H. bulbosum had less recombination in the centromeric regions and similar or more in the distal regions. Cytological studies on pollen mother cells at metaphase-I showed marked distal localization of chiasmata and a frequency consistent with the genetic map length. This study showed that H. bulbosum was highly polymorphic, making it suitable for trait analysis and supplementing maps of barley. Received: 20 November 2000 / Accepted: 5 January 2001     

Morphological traits of wheat (Triticum aestivum L.) associated with resistance to shoot fly,Atherigona approximata Malloch

Shoot flies (Atherigona spp.) are the members of muscidae family which have got economic importance as pest of several crops of Gramineae family mostly cereals and millets. One of the most effective management strategies for controlling shoot fly is the use of resistant wheat cultivars carrying specific resistant traits. Among thirty wheat genotypes screened at the University of Agricultural Sciences, Dharwad-Karnataka (India), two advanced germplasms UAS BW-12417 and UAS BW-11110 recorded least oviposition and dead heart due to shoot fly and found to be less preferred by Atherigona approximata Malloch. The morphological traits of different wheat genotypes revealed a significant negative correlation of shoot fly oviposition and dead heart with leaf length, leaf length to breadth ratio, seedling height, average seedling growth rate, seedling vigour, leaf glossiness and trichome density of wheat leaves, which indicated the enhanced shoot fly infestation as decrease in the values of above-mentioned morphological traits. Meanwhile, increase in leaf breadth and leaf area of wheat genotype aggrandised the oviposition and dead heart damage by shoot fly. Under the changing climate where, the minor insect pests attaining major pest status, the present investigation would pave way for breeders to tailor future breeding programmes to evolve shoot fly resistant hybrids with high yielding traits.     

Effects of seed priming with ascorbic acid to mitigate salinity stress on three wheat (Triticum aestivum L.) cultivars.

In this study, the effect of seed priming using ascorbic acid (ASA) on three commercial wheat cultivars i.e., Punjab-2011, Faisalabad-2008, and Ujala-2016 under salinity stress in both homogenous and heterogeneous environments has been investigated. It revealed that different levels of salinity have significantly reduced the growth attributes like percent germination, germination index, radical & plumule length, seed vigor index (In-vitro), seedling length, fresh & dry weight, and total chlorophyll content (In-vivo) with subsequent treatments. Salinity stress was induced by using NaCl in three different concentrations (100, 150, and 200 mM). Seeds of the three cultivars primed with 50, 100, and 150 mg/L ascorbic-acids have not only improved percent germination but also considerably reduced germination time and increased germination index (GI) indicating the potential for tolerating saline conditions. Seedling growth (seedling length, Fresh weight, and dry weight) of seeds primed with 50, 100, and 150 mg/L (ASA) was significantly higher than other non-primed seeds under the prevailing saline conditions. Hormonal priming with different concentrations of ascorbic acid was effective, nevertheless, the best results were obtained with 100 and 150 mg/L (ASA) concentrations. We concluded that the delay in germination and seedling growth was mainly due to excessive Na⁺ accumulation in the seeds of wheat cultivars. On the other hand, seed priming with various concentrations of ascorbic acid has proved to be effective in inducing salt tolerance in terms of germination parameters, seedling characteristics, and chlorophyll retention in the three local commercial wheat cultivars.     

Contribution of the wheat (Triticum aestivum L.) flag leaf to grain yield in response to plant growth regulators

In West-Europe, intensive cereal management uses plant growth regulators (PGRs) especially for wheat. A green-house experiment compared the effects of two PGRs on flag leaf characteristics and yield of winter wheat. Chlormequat chloride + choline chloride (CCC) and chlormequat chloride + choline chloride + imazaquin (CCC+I) were applied to winter wheat at growth stage 5 (Feekes Large scale). CCC and CCC+I significantly increased flag leaf surface area at anthesis. Both treatments also enhanced chlorophyll content of the main stem flag leaf. The grain filling period was extended with PGR application by 2 days. CCC and CCC+I significantly increased net CO₂ assimilation rates during the flag leaf life. No effects of PGR spraying were observed on the pattern of ¹⁴C labelled assimilate distribution. Increased grain yield was due to the increase in average grain weight. The results indicate that PGR treatments increased flag leaf contribution to grain filling. The addition of imazaquin (I) to chlormequat (CCC) improved the effects of CCC.     

Direct effect of colchicine on the microspore embryogenesis to produce dihaploid plants in wheat (Triticum aestivum L.)

Summary In the present experiment, different chromosome reduplication techniques were applied to microspore-originated Triticum aestivum L. (cv Ciano) haploids. In addition to the conventional treatment (whole plant exposure to colchicine solution), spontaneously redoubled haploids were also examined. As an experimental treatment, different concentrations (0.01, 0.02, 0.04%) of colchicine were added directly to the induction media. Colchicine did not affect the anther response or the plant regeneration capacity. The success and stability of genome redoubling was estimated on the basis of the fertility of the regenerated (R₀) plants and their progeny (R₁). Chromosome doubling produced by colchicine before the first microspore mitosis was significantly more efficient than the conventionally used techniques.     

Amino acid metabolism associated with N-mobilization from the flag leaf of wheat (Triticum aestivum L.) during grain development

Field-grown winter wheat (Triticum aestivum L. cv. Castell) was used to study changes in the free amino acid pools of different plant parts and related enzyme activities in the flag leaf throughout the grain-filling period in three consecutive growing seasons. Amino acid analysis data indicated that, during senescence, the nitrogen flow in the flag leaf was directed towards the synthesis of glutamine as a specific nitrogen transport form. Of the enzymes involved, total glutamine synthetase (GS; EC 6.3.1.2) and especially ferredoxin-dependent glutamate synthase (Fd-GOGAT; EC 1.4.7.1) activities declined continuously as senescence progressed. Unlike (chloroplastic) GS₂, (cytosolic) GS₁ was shown to be very persistent suggesting a special role for this isoenzyme in the N-reallocation process. Glutamate-oxaloacetate transaminase (GOT; EC 2.6.1.1), glutamate-pyruvate transaminase (GPT; EC 2.6.1.2) and isocitrate dehydrogenase (IDH; EC 1.1.1.42) showed a characteristic biphasic activity profile after anthesis. It is proposed that these enzymes, for each of which at least two isoenzymes were demonstrated, are involved in glutamate synthesis at the later stages of leaf senescence. Ammonium levels were fairly constant throughout the flag leafs life span, an ultimate rise often following peak values of glutamate dehydrogenase (GDH; EC 1.4.1.4) activity. The enzymology of flag leaf amino acid metabolism during grain development is further discussed in relation to observations of NH₃-volatilization from naturally senescing wheat plants.     

Identification of powdery mildew (Erysiphe graminis sp. tritici) and take-all disease (Gaeumannomyces graminis sp. tritici) in wheat (Triticum aestivum L.) by means of leaf reflectance measurements

The ability to identify diseases in an early infection stage and to accurately quantify the severity of infection is crucial in plant disease assessment and management. A greenhouse study was conducted to assess changes in leaf spectral reflectance of wheat plants during infection by powdery mildew and take-all disease to evaluate leaf reflectance measurements as a tool to identify and quantify disease severity and to discriminate between different diseases. Wheat plants were inoculated under controlled conditions in different intensities either with powdery mildew or take-all. Leaf reflectance was measured with a digital imager (Leica S1 Pro, Leica, Germany) under controlled light conditions in various wavelength ranges covering the visible and the near-infrared spectra (380–1300 nm). Leaf scans were evaluated by means of L*a*b*-color system. Visual estimates of disease severity were made for each of the epidemics daily from the onset of visible symptoms to maximum disease severity. Reflectance within the ranges of 490₇₈₀ nm (r² = 0.69), 510₇₈₀nm (r² = 0.74), 516₁₃₀₀nm (r² = 0.62) and 540₁₃₀₀ nm (r² = 0.60) exhibited the strongest relationship with infection levels of both powdery mildew and take-all disease. Among the evaluated spectra the range of 490₇₈₀nm showed most sensitive response to damage caused by powdery mildew and take-all infestation. The results of this study indicated that disease detection and discrimination by means of reflectance measurements may be realized by the use of specific wavelength ranges. Further studies have to be carried out, to discriminate powdery mildew and take-all infection from other plant stress factors in order to develop suitable decision support systems for site-specific fungicide application.     

Exploring the use of chamomile (Matricaria chamomilla L.) bioactive compounds to control flixweed (Descurainia sophia L.) in bread wheat (Triticum aestivum L.): Implication for reducing chemical herbicide pollution

Intensive chemical herbicide use has resulted in human health and environmental issues. This study evaluated the phytotoxic potential of chamomile extract as a bioherbicide to minimize chemical herbicide use in wheat production. Treatments including four concentrations (0, 50, 100, and 150 mL/L) of three different chamomile plant parts (root, shoot, and root + shoot) extracts were applied to flixweed as a major weed in wheat production. Except for 50 mL/L of root extract, other concentrations of chamomile extracts decreased the germination rate of flixweed. Germnaiton rate of wheat increased with chamomile extracts except at 150 mL/L concentration of shoot extract at which the germination rate of flixweed and wheat reduced by 71.7 and 35.4%, respectively, compared to respective controls. Compared to wheat, malondialdehyde and proline in flixweed were increased fivefold in flixweed and compared to the control, ranged from 84–473 and 240–1422%, respectively. Chamomile extract also declined cell viability much quicker in flixweed than in wheat reflecting on greater inhibitory effect for flixweed control. Chamomile shoot extract reduced seedling weight and vigor index of flixweed by 63.75 and 59.4%, respectively, compared to the respective control. Results of liquid chromatography mass spectrometry of chamomile extract indicated polyphenols, flavonoids, terpenoids, and bioactive phenolic coumarins, glycosylated derivatives, quercetin and its derivatives, herniarin, umbelliferone, P-cymene, chamazulene, farnesol, amitrole, 1,8-cineole, and limonene were effective in inhibiting the germination and growth of flixweed. We concluded that 150 mg/L of chamomile shoot extract could be used as a bioherbicide to sustainably suppress flixweed in wheat production.     

Seed treatment with growth regulators and crop productivity. I. 2,4-D as an inducer of salinity-tolerance in wheat (Triticum aestivum L.)

The paper investigates how the apoplastic route of ion transfer is affected by the outermost cortex cell layers of a primary root. Staining of hand-made cross sections with aniline blue in combination with berberine sulfate demonstrated the presence of casparian bands in the endo- and exodermis, potentially being responsible for hindering apoplastic ion movement. The use of the apoplastic dye Evan's Blue allowed viewing under a light microscope of potential sites of uncontrolled solute entry into the apoplast of the root cortex which mainly consisted of injured rhizodermis and/or exodermis cells. The distribution of the dye after staining was highly comparable to EDX analyses on freeze-dried cryosectioned roots. Here, we used Rb+ as a tracer for K+ in a short-time application on selected regions of intact roots from intact plants. After subsequent quench-freezing with liquid propane the distribution of K+ and Rb+ in cell walls was detected on freeze-dried cryosections by their specific X-rays resulting from the incident electrons in a SEM. All such attempts led to a single conclusion, namely, that the walls of the two outermost living cell sheaths of the cortex largely restrict passive solute movements into the apoplast. The ring of turgescent living rhizodermis cells in the root tip region forms the first barrier. With increasing distance to the root tip, in the course of their maturation resp. degradation, this particular function of the rhizodermis cells is replaced by the hypodermis resp. exodermis. Furthermore, the restriction of apoplastic ion flow by the outermost cortex cell layers is rather effective but not complete. Thus, the solute transfer into the stele is mainly restricted by the casparian bands of the endodermis. The overall conclusion is that the resistances of the rhizodermis and exodermis are additive to the endodermis in their role of regulating the apoplastic solute movement across roots. This revised version was published online in August 2006 with corrections to the Cover Date.     

Physiological aspects of aluminium tolerance associated with the long arm of chromosome 2D of the wheat (Triticum aestivum L.) genome

Aluminum (Al) uptake in roots of wheat nearisogenic lines having differing tolerances to aluminium toxicity was studied using roots and root segments immersed in a nutrient solution at a controlled pH and temperature. At low Al concentrations a mechanism preventing root tips from accumulating too much Al was observed in an Al-tolerant isoline and a BH1146 euploid. This mechanism was more efficient when divalent cations of calcium or magnesium were present in the nutrient medium. Al accumulation steadily increased in root tips of the Al-sensitive wheat isoline during all 24 h of incubation, and the presence of divalent cations in the medium even increased Al concentration in root tissue. However, at higher Al concentrations in the medium the mechanism preventing the root tips of Al-tolerant genotypes from accumulating too much Al was not observed, and in effect Al concentration in root tips of both Al-tolerant and Al-sensitive isolines increased. It is concluded that genetical factors are located on the long arm of chromosome 2D from the BH1146 euploid that control the mechanism preventing root apical meristems from accumulating too much Al at low Al concentrations in the medium. However, there must be other genetical factors also located on this chromosome segment that control Al detoxication in root tips of Al-tolerant lines at higher external Al concentrations.