Essential oil composition of Hypericum perfoliatum L. and Hypericum tomentosum L. growing wild in Tunisia

The essential oils obtained by hydrodistillation from the aerial parts of Tunisian native Hypericum perfoliatum L. (sect. Drosocarpium Spach.) and Hypericum tomentosum (sect. Adenosepalum Spach.) were analyzed by GC and GC–MS. Thirty-two compounds were identified in the essential oils of H. perfoliatum with α-pinene (13.1%), allo-aromadendrene (11.4%), germacrene-D (10.6%), n-octane (7.3%), α-selinene (6.5%) and β-selinene (5.5%) as main constituents. Sixty-seven components were identified in the oil of H. tomentosum with menthone (17.0%), n-octane (9.9%), β-caryophyllene (5.3%), α-pinene (5.2%), lauric acid (4.1%) and β-pinene (3.7%) as the most abundant components. Both oils were characterized by the presence of many components which could have numerous applications in food, pharmaceutical and perfume industries.     

Chemical composition and anti-fungal properties of the essential oils and crude extracts of Orthosiphon stamineus Benth

The hydrodistilled essential leaves and stems oils of Orthosiphon stamineus Benth were analysed by GC–MS/MS. Sixty nine compounds representing 97.6 and 97.4% of the total leaves and stems oils, respectively were identified, of which β-caryophyllene (24.0 and 35.1%), α-humulene (14.2 and 18.4%), β-elemene (11.1 and 8.5%), 1-octen-3-ol (8.2 and 7.0%), β-bourbonene (3.4 and 3.0%), β-pinene (2.1 and 1.7%), caryophyllene oxide (1.6 and 2.2%), camphene (1.6 and 1.3%) and limonene (1.2 and 1.1%) were the major compounds. Thus, the monoterpenes and sesquiterpenes were the predominant portions of the oils. Essential oils and methanol extract of O. stamineus and the derived fractions of hexane, chloroform, and ethyl acetate were tested for anti-fungal activity, which was determined by disc diffusion and minimum inhibitory concentration (MIC) determination methods. The oils, methanol extract and derived fractions of methanol extract displayed great potential of anti-fungal activity as a mycelial growth inhibitor against the tested phytopathogenic fungi such as Botrytis cinerea, Rhizoctonia solani, Fusarium solani, Colletotricum capsici and Phytophthora capsici, in the range of 49.3–70.3% and minimum inhibitory concentration ranging from 500 to 1000 μg/ml.     

Influence of chemical and biological treatments on volatile oil composition of Artemisia annua Linn.

The relative abundance of isoprenoids and other volatile components in the aerial parts of Artemisia annua Linn. (Asteraceae) after different nutritional treatments was analyzed by GC and GC/MS. Hydro-distillation of untreated (control) plants yielded 0.28 ± 0.04% essential oil on fresh weight basis. Monoterpenes were predominant in the essential oil of which cis-limonene-1,2-epoxide (22.1%), artemisia ketone (11.5%), iso-pinocamphone (11.4%), thujyl alcohol (9.9%) and camphor (8.4%) were the major components. The essential oil distilled from A. annua treated with Azospirillum (2 ml/plant) amounted to 0.30 ± 0.03% of fresh weight and consisted mainly of neral (31.1%), β-caryophyllene (25.1%), artemisia ketone (10.0%), thujyl alcohol (9.4%), trans-bergamotene (8.5%) and spathulenol (4.8%). The essential oil from plants treated with basal N, P, K and S application (in the form of urea P₂O₅, K₂O and gypsum at a rate of 120, 50, 100 and 50 kg/ha, respectively) amounted to 0.32 ± 0.03% of fresh weight and consisted mainly of thujyl alcohol (33.3%), β-caryophyllene (15.5%), cis-undec-5-ene (14.4%), artemisia ketone (6.0%), trans-nerolidol (5.8%) and undec-4-ene (4.6%). The hydrodistillation of A. annua treated with Glomus (Mycorrhizal soil 50 g/plant) yielded 0.50 ± 0.02% essential oil on fresh weight basis. The sesquiterpenes were predominant in this essential oil and consisted of β-caryophyllene (51.2%), trans-bergamotene (15.4%), α-gurjunene (14.3%), germacrene D (5.1%) and ledol (4.5%) as major components. The only monoterpenes in the essential oil were neral, nerol and pulegone (each less than 1%). These findings suggest that A. annua treated with Glomus lacks glandular trichomes—the primary sites of synthesis of monoterpenes.     

Larvicidal property of essential oils against Culex quinquefasciatus Say (Diptera: Culicidae)

Essential oils from 22 aromatic plant species were tested for mortality of the mosquito larvae Culex quinquefasciatus. Lethal concentrations were determined for individual essential oils. Essential oils obtained from Thymus vulgaris, Satureja hortensis and Thymus satureioides plants showed the highest effect, with LC₅₀ found lower than 50 μg/ml (33, 36 and 44 μg/ml, respectively). Analyses showed that majority substances for T. vulgaris were thymol and p-cymene (60.3 and 10.1%, respectively); carvacrol and γ-terpinene for S. hortensis (48.1 and 36.7%, respectively), and borneol and thymol for T. satureioides (30.3 and 32.5%, respectively).The selected essential oils also showed very good effectiveness with respect to mortality and percentage of adult emergence upon short-term exposure in water contaminated with lethal doses of individual oils. While there was 77% adult emergence from the larvae in the control, in T. vulgaris, T. satureoides and S. hortensis there was only 12.3, 15.3 and 16.0% adult emergence, respectively. High antioviposition effectiveness was found in all selected oils. Almost 100% deterrence of female oviposition was determined for all oils in concentrations of 0.02%. Significant differences were seen with tested concentrations of 0.01 and 0.005%, where the oil of T. vulgaris proved most effective (repellency about 99.8 and 62.3%, respectively).     

Molecular characterization and comparative analysis of four new genes from Sec2 locus encoding 75K γ-secalins of rye species

Using a PCR-based strategy, four new 75K γ-secalin genes were isolated from Secale cereale, Secale vavilovii, Secale sylvestre, and Secale strictum in genus Secale (rye). Based on amino acid sequences, the primary structure of the 75K γ-secalin subunits was demonstrated, which was composed of four main structural regions: (a) a conservative 19 amino acids signal peptide, (b) a steady short N-terminal region of 12 amino acids containing a cysteine residue, (c) a repetitive domain, which began with the conservative tetrapeptides PQ₃ and was rich in glutamine and proline. PFPQ₁₋₂(PQQ)₁₋₂ was the core repeat motif in the repetitive region. Besides amino acid substitutions, this region showed variations in length due to the insertion and deletion events. In the repetitive region of EF432549 (Secale strictum), there were two octapeptides (PFPQQPQQ and PVPQQSQQ) insertions. On the contrary, deletion events of two residues (QT) took place in EF432546 (Secale sylvestre). Accounting for the amino acid replacement, an extra cysteine residue appeared in the repetitive region of EF432546, which did not exist in other genes, and (d) a conserved 143 amino acids C-terminal domain including eight cysteine residues. The implications of the results for quality improvement are discussed.     

Chemical Composition,Antifeedant, Repellent,and Toxicity Activities of the Rhizomes of Galangal,Alpinia galanga Against Asian Subterranean Termites,Coptotermes gestroi and Coptotermes curvignathus (Isoptera: Rhinotermitidae)

Dual choice bioassays were used to evaluate the antifeedant property of essential oil and methanolic extract of Alpinia galanga (L.) (locally known as lengkuas) against two species of termites, Coptotermes gestroi (Wasmann) and Coptotermes curvignathus (Holmgren) (Isoptera: Rhinotermitidae). A 4-cm-diameter paper disc treated with A. galanga essential oil and another treated with either methanol or hexane as control were placed in a petri dish with 10 termites. Mean consumption of paper discs (miligram) treated with 2,000 ppm of essential oil by C. gestroi was 3.30 ± 0.24 mg and by C. curvignathus was 3.32 ± 0.24 mg. A. galanga essential oil showed significant difference in antifeedant effect, 2,000 ppm of A. galanga essential oil was considered to be the optimum concentration that gave maximum antifeedant effect. The essential oil composition was determined using gas chromatography-mass spectrometry. The major component of the essential oil was 1,8-cineol (61.9%). Antifeedant bioassay using 500 ppm of 1,8-cineol showed significant reduction in paper consumption by both termite species. Thus, the bioactive agent in A. galangal essential oil causing antifeeding activity was identified as 1,8-cineol. Repellent activity shows that 250 ppm of 1,8-cineol caused 50.00 ± 4.47% repellency for C. gestroi, whereas for C. curvignathus 750 ppm of 1,8-cineol was needed to cause similar repellent activity (56.67 ± 3.33%). C. curvignathus is more susceptible compare to C. gestroi in Contact Toxicity study, the lethal dose (LD₅₀) of C. curvignathus was 945 mg/kg, whereas LD₅₀ value for C. gestroi was 1,102 mg/kg. Hence 1,8-cineol may be developed as an alternative control against termite in sustainable agriculture practices.     

Variability in essential oil and bioactive chiral monoterpenoid compositions of Indian oregano (Origanum vulgare L.) populations from northwestern Himalaya and their chemotaxonomy

The chemical composition of essential oils isolated from aerial parts of native populations of Origanum vulgare L. from northwestern Himalaya was investigated by enantioselective gas chromatography (enantio-GC), capillary-gas chromatography (capillary-GC) and GC–MS. Seventy compounds, which accounted for 84.9–97% of the oil composition, have been identified. The oils were allotted to two main groups; the first group had a high percentage of components belonging to the thymol/carvacrol biosynthetic pathway and the second was characterized by a different sesquiterpene composition and a high linalool and bornyl acetate percentage. Essential oils of O. vulgare populations from Rilkot and Dhanachuli areas in northwestern Himalaya were characterized by high monoterpenoids proportions as compared to Nainital and Bhowali populations, which were dominated by sesquiterpenoids. High proportions of thymol (29.2–82%) were found only in two populations. Composition of the samples collected from Dhanachuli area differed from Nainital and Bhowali collections by a unique presence of carvacrol. Notably, there were significant differences in the concentration of rest of the terpenes in all the collections. On enantio-GC, enantiomeric excess for (3R) (−)- and (3S) (+)-linalool, (S) (+)- and (R) (−)-terpinen-4-ol, (S) (−)- and (R) (+)-α-terpineol, (1S) (−)-bornyl acetate and (1S) (−)-borneol were established in populations from Bhowali and Dhanachuli area. Moreover, linalool type oregano may be useful in promoting wider commercial utilization of the biodiversity of this species.     

Genetic variability in yellow pigment components in cultivated and wild tetraploid wheats

Yellow pigment concentration (YPC) in durum wheat is an important criterion in the assessment of semolina quality, particularly in determining the commercial and nutritional quality of end-products. Genetic variability of YPC and carotenoid components was analysed in 102 wild and cultivated tetraploid wheat accessions in two trials. Overall, modern cultivars showed significantly higher values of YPC compared to old cultivars and wild ssp. dicoccum and ssp. dicoccoides accessions. Total carotenoid concentration varied between 1.178 and 4.416 μg/g with an average of 2.460 μg/g. The portion of carotenoids amounted to 33.2% of the YPC in 80 wheat accessions examined in the 2006 trial. Lutein was the main component of carotenoids, followed by zeaxanthin and β-carotene. α-carotene and β-cryptoxanthin were minor components. Pigment concentration was negatively correlated with kernel weight and grain protein concentration. Significant positive correlations were found between b* index and YPC. Knowledge of the carotenoid composition and concentration is useful for wheat breeders in the development of cultivars with high yellow colour and enhanced phytochemical concentrations, and provides valuable information for evaluating contributions to health benefits from the consumption of durum wheat end-products.     

Effect of residual distillation water of 15 plants and three plant hormones on Scotch spearmint (Mentha × gracilis Sole)

Distillation waste water is a byproduct from steam distillation of aromatic crops, and is currently discharged into streams and rivers. We evaluated distillation waste water (extract) from 15 essential oil crops plus three plant hormones (methyl jasmonate, MJ; gibberellic acid, GA3; and salicylic acid, SA) as foliar spray for Scotch spearmint (Mentha × gracilis Sole). GA3 and Achillea millefolium extract decreased essential oil content. Hypericum perforatum extract increased α-pinene, whereas SA decreased it. H. perforatum extract increased β-pinene and sabinene concentrations relative to hormones but was not different from the control. H. perforatum also increased l-limonene, while SA and GA3 decreased myrcene and MJ and SA decreased l-limonene. Application of MJ and SA increased l-carvone concentration relative to the control and most other treatments. The sulfur concentration in plant extracts was positively correlated to β-caryophyllene. None of the residual distillation waters showed significant antimicrobial or antimalarial activity. The distillation waste water from essential oil crops may serve as a modifier for Scotch spearmint essential oil.     

Nutrient composition of the leaves and flowers ofColocasia esculenta and the fruits ofSolanum melongena

The nutrient composition, ofColocasia esculenta flowers (CF) and leaves (CL), and the green fruits ofSolanum melongena (SM) were carried out as a means to determine their nutritional potential. Results showed that these food materials had high moisture and fiber levels which ranged between 888 and 906 g·kg^–1; and 204 and 303 g·kg^–1 dry weight (dw) for moisture and fiber respectively. The calorific values were between 3889 and 4001 kcals·kg^–1 dw, while the total lipids ranged from 53 in CF to 71 g·kg^–1 dw in SM. The leaves ofColocasia esculenta had the highest crude protein value of 307 g·kg^–1 dw. The flowers had 149 g·kg^–1 dw while SM had 138 g·kg^–1 dw. The amino acid profile in the flowers and leaves ofColocasia esculenta in contrast to SM were balanced comparable to the reference FAO pattern. Ash values were high (ranging from 76 in SM to 98 g·kg^–1 in CL) with potassium being the principal element. Iron and Zinc levels were also high especially in CF (with 303 and 82 mg·kg^–1 dw respectively). These foods also contained moderate quantities of calcium, phosphorus and magnesium but were poor in manganese and copper.     

Toxicity of essential oils isolated from three Artemisia species and some of their major components to granary weevil,Sitophilus granarius (L.) (Coleoptera: Curculionidae)

The essential oils of aerial parts of three Artemisia species (A. absinthium, A. santonicum and A. spicigera) were isolated by hydrodistillation method and tested for their toxicity against to granary weevil, Sitophilus granarius (L.) (Coleoptera: Curculionidae). All of the essential oils tested were found to be toxic to adults of S. granarius. The oils showed about 80–90% mortality of granary weevil, S. granarius at a dose of 9 μl/l air after 48 h of exposure. The constituents of these oils isolated from Artemisia spp. were also analyzed by GC–MS method. Camphor, 1,8-cineole, chamazulene, nuciferol propionate, nuciferol butanoate, caryophyllene oxide, terpinen-4-ol, borneol and α-terpineol were the predominant components of the oils. Some pure compounds (camphor, 1,8-cineole, terpinen-4-ol, borneol, bornyl acetate and α-terpineol) identified as major component in the oils, at 0.5, 0.75 and 1 μl/l air doses were also tested for their toxicity against S. granarius. While all pure compounds were found to be toxic against S. granarius, 1,8-cineole and terpinen-4-ol were more toxic among the tested pure compounds. 1,8-Cineole and terpinen-4-ol showed 100% mortality at all doses after 12 h of exposure. It can be concluded that essential oils of three Artemisia species and their major components, 1,8-cineole and terpinen-4-ol are potential control agents against S. granarius.     

Cloning, expression and characterization of novel avenin-like genes in wheat and related species

B-Type avenin-like genes and proteins were characterized in 23 species of Triticeae. Southern blot analysis showed that the avenin-like genes belong to a multigene family. RT-PCR showed expression only in developing endosperms of wheat and related species, between 3 and 22 DPA (days post anthesis) with a peak between 11 and 15 DPA in wheat. The encoded proteins are cysteine-rich, containing 18–19 cysteine residues. An avenin-like protein from wheat was expressed in Escherichia coli, purified and used to raise polyclonal antibodies. These antibodies were used to detect b-type avenin-like proteins in endosperms of wheat and related species by western blotting.     

Cereal β-glucans in diet and health

The native mixed linkage β-glucan of cereals is classified as a soluble dietary fibre, with rheological properties generally similar to guar gum and other random coil polysaccharides. The ability of oat and barley products to attenuate postprandial glycemic and insulinemic response is related to content of (1→3)(1→4)-β-d-glucan (β-glucan) and viscosity. A role of viscosity of β-glucan has not been directly demonstrated for lowering of serum cholesterol levels, and not all studies report a statistically significant lowering. The wide range of effectiveness reported may partially be explained by the properties of the β-glucan in the diets used, as well as the dose.     

Composition and physical properties of cress (Lepidium sativum L.) and field pennycress (Thlaspi arvense L.) oils

The fatty acid profiles and tocopherol and phytosterol contents of crude oils of cress (Lepidium sativum L.) and field pennycress (Thlaspi arvense L.) are reported, along with yields from the corresponding seeds. The physical properties of these oils were also determined, which included oxidative stability, kinematic viscosity, viscosity index, low temperature fluidity, specific gravity, acid value, lubricity, and iodine value. The oil content of dried cress and field pennycress seeds was 22.7 and 29.0 wt%, respectively. The primary fatty acids found in cress oil were oleic (30.6 wt%) and linolenic acids (29.3 wt%), whereas field pennycress oil was principally composed of erucic (32.8 wt%) and linoleic (22.4 wt%) acids. Cress oil contained high concentrations of γ- (1422 ppm) and δ- (356 ppm) tocopherols, whereas α-tocopherol (714 ppm) was the primary tocopherol discovered in field pennycress oil. The overall tocopherol concentrations of cress and field pennycress oils were 1799 and 851 ppm, respectively. The primary phytosterols elucidated in cress and field pennycress oils were sitosterol and campesterol, with avenasterol also present in significant quantity in cress oil. The total phytosterol concentration in cress oil (14.41 mg/g) was greater than that in field pennycress (8.55 mg/g) oil. Field pennycress oil exhibited excellent low temperature fluidity, whereas cress oil was more stable to oxidation and over a range of temperatures displayed lower kinematic viscosities as well as a higher viscosity index. The acid and iodine values of field pennycress oil were lower than those for cress oil, but both oils had excellent lubrication properties.     

Effect of growth stage on the content and composition of the essential oil and phenolic fraction of sweet marjoram (Origanum majorana L.)

The variation in the content and composition of Origanum majorana L. essential oil has been studied. Plant material has been harvested at four phenological stages (early vegetative, late vegetative, budding and full-flowering). Essential oil yield varied from 0.04 to 0.09% reached during the full-flowering stage. Analysis of the essential oils by GC and GC/MS revealed the presence of 38 components represented mainly by oxygenated monoterpenes (64.01–71.4%), monoterpene hydrocarbons (21.73–29.92%) and sesquiterpene hydrocarbons (1.47–4.05%). The main components were terpinen-4-ol (29.13–32.57%), cis-sabinene hydrate (19.9–29.27%), trans-sabinene hydrate (3.5–11.61%), γ-terpinene (2.11–8.20%), bornyl acetate (1.52–2.94%) and linalool (1.05–1.39%). On the other hand, phenolic contents varied from 2.706 to 6.834 mg/g of dry weight obtained during the later vegetative stage. RP-HPLC analysis of the methanolic extract of O. majorana L. dried aerial parts showed the predominance of phenolic acids during the early vegetative stage whereas flavonoids predominate during the other stages of growth. The main phenolic acids identified were trans-2-hydroxycinnamic, rosmarinic, vanillic, chlorogenic, gallic and cinnamic whereas the main flavonoids were amentoflavone, apigenin, quercetin, luteolin, coumarin and rutin. Results obtained showed that later vegetative stage is characterized by the highest contents of bioactive compounds and therefore it could be considered as the best stage for harvesting marjoram plants.     

Field trials of Metarhizium anisopliae var. acridum (Ascomycota: Hypocreales) against oriental migratory locusts, Locusta migratoria manilensis (Meyen) in Northern China

During 2002–2006, nymph bands of Locusta migratoria manilensis (Meyen) were treated by ground and aerial applications in 6000 ha of grasslands and the nearby beach of Yellow river using a soybean oil miscible suspension ULV formulation of Metarhizium anisopliae var. acridum isolate CQMa102. The formulation was also applied in Tianjin, Henan, Hebei, Shandong and Shanxi provinces of Northern China by ground and aerial applications. During field studies, cage tests were carried out in corresponding field plots in order to estimate the mortality accurately. Doses of 3.3×10¹² and 5.0×10¹² conidia ha⁻¹ were equally effective and caused 90% mortality 9–13 days after treatment. In the ground spray trial, 3.3×10¹² conidia ha⁻¹ killed >90% of L. migratoria manilensis 11–15 days after treatment in a wide variety of vegetation and weather conditions. The decline of locust populations was slower where vegetation was taller and denser. In the aerial spray treatment, the final percent survival of locusts was lowered to 10% at 11 and 14 days in the field cage and open field locusts, respectively. Furthermore, the M. anisopliae oil miscible suspension formulation did not appear to harm natural enemies of locusts in the field.     

Prior weakening of Macrophomina phaseolina and Fusarium propagules for enhancing efficiency of Brassica amendments

In a two year field study, the effect of varying intensities of sub-lethal heating on the efficiency of Brassica amendments in controlling viable populations of Macrophomina phaseolina and Fusarium oxysporum f sp. cumini was determined in an arid region of India. After 30 d of dry summer exposure of pathogen infested soil, incorporation of mustard residues and oil cake (0.18% and 0.04% w/w) and then applying one irrigation caused significant reduction by 75.3–81.3% in viable counts of M. phaseolina that causes dry root rot of legumes and by 93.9% in counts of F.o. f. sp. cumini causing wilt of cumin (Cuminum cyminum L.) at 0–15 and 16–30 cm depths. Increasing duration of summer exposure to 60 d improved the reductions in viable propagules of M. phaseolina by 83.6–90.4% and in F.o. f. sp. cumini by 78.2–94.8% at same soil depths. At certain heat levels, reduction in viable population of Fusarium due to amendments and irrigation was greater than that recorded in Macrophomina. Significantly low levels of reduction in pathogenic propagules of Macrophomina (63.9–71.4%) and Fusarium (48.0–57.2%) under shade compared to unshaded conditions indicated that mild heating did not cause discernible weakening effect. In second season also, 89.2–91.5% and 78.5–95.8% reduction in counts of Macrophomina and Fusarium, respectively was achieved by the application of amendments after 60 d of summer exposure at 0–30 cm soil depth. These results suggested a new approach to improve the control of soil-borne plant pathogens in hot arid regions by combining prolonged sub-lethal heating, effective naturally available on-farm wastes as soil amendments and one summer irrigation.     

Essential oil variation among and within six Achillea species transferred from different ecological regions in Iran to the field conditions

The compositions of essential oils of 19 accessions belonging to six different Achillea species, transferred from the natural habitats in 10 provinces of Iran to the field conditions, were assessed. The relationship between the leaf areas of selected accessions with their essential oil content was also investigated. Essential oil yield of dried plants obtained by hydro-distillation ranged from 0.1 to 2.7% in leaves. Results indicated a significant variation in oil composition among and within species. Total of 94 compounds were identified in 19 accessions belonging to the six species of A. millefolium, A. filipendulina, A. tenuifolia, A. santolina, A. biebersteinii and A. eriophora. The major constituents of the leaves in the tested genotypes were determined as germacrene-D, bicyclogermacrene, camphor, borneol, 1,8-cineole, spathulenol and bornyl acetate. According to the major compounds, four chemotypes were defined as: (I) spathulenol (1.64–34.31%) + camphor (0.2–15.61%) (7 accessions); (II₁) germacrene-D (18.78–23.93%) + borneol (7.93–8.26%) + bornyl acetate (11.56–14.66%) (5 accessions); (II₂) germacrene-D (13.28–36.28%) + bicyclogermacrene (5.93–8.4%) + 1,8-cineole (15.26–19.41%) + camphor (14.95–23.32%) (2 accessions); (III) borneol + camphor (52.04–63.27) (2 accessions); (IV) germacrene-D (45.86–69.64%) (3 accessions). The relationships of chemotypes with soil type and climatic conditions of collected regions were assessed, as probable reasons of high variations in essential oil components, and discussed.     

Development of rice introgression lines with brown planthopper resistance and KDML105 grain quality characteristics through marker-assisted selection

‘Khao Dawk Mali 105’ (KDML105), a Thai aromatic rice cultivar, has been accepted in markets as a prime jasmine rice with premium prices. It has been extensively used as a parental line to develop new cultivars for rainfed lowland areas in Thailand because of its favorable quality and fragrance. However, this cultivar is highly susceptible to brown planthopper (BPH), a phloem sap-feeding insect pest of rice. The main objective of this study was to combine KDML105 essential grain quality traits with BPH resistance from the donor cultivar, ‘Rathu Heenati’. The linkage drag between Bph3 and Wx^a alleles was successfully broken by phenotypic and marker-assisted selections. All introgression lines (ILs) developed in this study showed a broad spectrum resistance against BPH populations in Thailand and had KDML105 grain quality standards. Finally this study was revealed that the ILs can be directly developed into BPH resistant varieties or can be used as genetic resources of BPH resistance to improve rice varieties with the Wx^b allele in rice breeding programs.     

Differences in conformational stability of barley alpha-amylase isozymes 1 and 2. Role of charged groups and isozyme 2 specific salt-bridges

Barley alpha-amylase isozymes 1 (AMY1) and 2 (AMY2) have 80% sequence identity but possess different physico-chemical properties. By incubation in the range 37–85 °C T₅₀ is 75.2 °C of AMY1 and 79.2 °C of AMY2. While AMY2 is also most stable in urea at pH 6.7, [urea]₅₀ being 8.2 M compared to 7.9 M for AMY1, AMY1 has highest stability in urea below pH 6 or in the presence of NaCl. Moreover AMY1 is most stable in guanidinium chloride. Charge screening thus destabilises AMY2 but stabilises AMY1. Isozyme sequence comparison suggests that AMY1 lacks four of the 20 salt-bridges identified in the crystal structure of AMY2. The four residues that differ comprise Lys67_AMY2 and Asp267_AMY2, forming salt-bridges on the surface of the catalytic (β/α)₈-barrel (domain A), and Glu96_AMY2 and His344_AMY2 that participate in charged networks between domain A and the small domain B and the C-terminal domain, respectively. Four corresponding AMY2 mimics A68K; D97E; Q269D; N346H were made in AMY1 by site-directed mutagenesis. While D97E and Q269D have slightly improved stability compared to AMY1 wild-type, N346H and, under certain conditions, A68K are destabilised. The four mutants show 22–176% activity (k_cat/K_m) toward 2-chloro-4-nitrophenol β- -maltoheptaoside and amylose DP17 and 43–117% activity for insoluble starch.