Antifungal proteins and grain mold resistance in sorghum with nonpigmented testa.

Levels of four antifungal proteins (AFPs) were determined in mature caryopses (40-45 days after anthesis) of eight grain mold resistant (GMR) and eight susceptible (GMS) sorghum lines using the immunoblot technique. These 16 lines came from the same cross and were selected for high and low grain mold resistance. The 16 lines were grown in eight environments over three years. In the environments with grain mold incidence, levels of sormatin, chitinases, and ribosomal inactivating proteins (RIP) in the GMR group were higher than those in the GMS group. In a grain mold-free environment, the GMR group had higher RIP and lower beta-1,3-glucanase levels than the GMS group. Unlike the GMS group, chitinase, sormatin, and RIP levels in the GMR group were higher in the environments with grain mold than in the mold-free environment. AFPs correlated among themselves and with grain mold resistance. Grain mold infection pressure caused GMR lines to induce and/or retain more AFPs compared to GMS lines. The coexpression of these four AFPs may be a necessary prerequisite for resistance to grain mold in sorghums without a pigmented testa.     

Antifungal proteins and other mechanisms in the control of sorghum stalk rot and grain mold

Research on antifungal proteins and other mechanisms that provide the biochemical basis for host-plant resistance to stalk rot and grain molds is reviewed in this paper. Stalk rot caused by Fusarium species leads to substantial yield loss due to poor grain filling and/or lodging. A transgenic sorghum expressing high levels of chitinase exhibited less stalk rot development when exposed to conidia of F. thapsinum. Grain mold of sorghum is associated with warm humid environments and results from colonization by several fungi (F. thapsinum, Curvularia lunata, and Alternaria alternata) of the developing caryopsis. The roles of several biochemical mechanisms (tannins, phenolic compounds, red pericarp, proteins, hard endosperm, and antifungal proteins) on grain mold resistance are discussed. Resistance mechanisms related to these compounds appear to be additive, and pyramiding of genes is a feasible approach to limit grain deterioration. Several experimental approaches are proposed to extend current findings.     

Role of chitinase and sormatin accumulation in the resistance of sorghum cultivars to grain mold

Experiments were conducted to determine the association between resistance to grain mold and the accumulations of chitinase and sormatin. Eight sorghum lines were treated at 50% bloom with Fusarium thapsinum, Curvularia lunata, a mixture of the two fungi, and a water-sprayed control. At maturity, percent disease severity, seed germination rates, and kernel weight were recorded. Chitinase and sormatin content (mg/g of dry weight) were measured in seed samples taken at 30 and 50 days after treatment (DAT). Seed chitinase content was moderately affected by sorghum line (P = 0.10) and significantly affected by the developmental stage of the kernels (P = 0.05). Cultivars Sureno, 98LB650, and 98LB723 exhibited larger negative changes in chitinase content at 50 DAT over water-sprayed control treatment at 30 DAT than the susceptible cultivars Dorado, RTx2536, and RTx430. In 2000, significant negative correlations were observed for percent disease severity and chitinase content at 30 DAT, seed germination and sormatin content at 50 DAT, and between seed germination and kernel weight. There also was a significant positive correlation between germination and chitinase content at 30 DAT. No association between disease severity and changes in chitinase content at 50 DAT was observed. Sormatin content also was significantly affected by the stage of kernel development. Sorghum cultivars inoculated with fungal pathogens responded differently as indicated by the significant sorghum line x treatment interaction for sormatin content in 2000. In both years, larger increases in sormatin content over the water-sprayed control treatments were observed on moderately susceptible to susceptible cultivars such as 98LB650, 98LB723, 98LB789, RTx430, and RTx2536 than on Sureno. Except for percent disease severity and germination, there was no significant association among all of the other parameters measured in 2001. The results of this study did not clearly demonstrate a strong association between resistance to grain mold and the accumulation of sormatin and chitinase. Thus, there is the possibility that certain moderately resistant to resistant sorghum cultivars, such as Sureno, may employ other strategies to eschew or restrict fungal invasion either before or after physiological maturity.     

Characterization of polymeric proteins from vitreous and floury sorghum endosperm

Differences in protein content and composition between vitreous and floury endosperm were investigated using a number of different techniques. Differences in protein cross-linking between vitreous and floury endosperm were investigated using differential solubility, size exclusion chromatography (SEC), and analysis of sulfhydryl content and composition. Vitreous endosperm was found to have higher levels of total protein and kafirins, but floury endosperm had a higher proportion of gamma-kafirins than the vitreous. Floury endosperm was found to have higher levels of SDS-soluble proteins than SDS-insoluble proteins extracted using sonication than vitreous endosperm. Conversely, vitreous endosperm had a greater proportion of the insoluble proteins. SEC analysis of the polymeric proteins revealed that the insoluble proteins had more polymeric proteins than did the soluble proteins, indicating greater cross-linking and a larger Mw distribution. Vitreous endosperm was also found to have a greater percentage (i.e., a higher ratio of disulfide to total sulfhydryls) of disulfide bonds than floury endosperm. These results show that the proteins in vitreous endosperm have a higher degree of cross-linking and a greater Mw distribution than those found in floury endosperm.     

Biochemical traits associated with growing sorghum genotypes with saline water in the field

Abstract

This study was aimed to determine biochemical traits related to higher phytomass production in sorghum genotypes irrigated with saline water. It was also attempted to consider whether or not forage yield production under non-saline conditions could be used as an index for for the selection of high yielding genotypes of sorghum under saline conditions. Forty-five sorghum genotypes were grown under field conditions using saline water or normal irrigation water in two growing seasons in Yazd, Iran. It appeared that salinity tolerance in sorghum genotypes, in addition to local adaption, was highly related to forage yield as well as some biochemical traits as carotenoid concentration, catalase activity, and K⁺/Na⁺ ratio. The screening method based on biochemical traits appeared to be applicable for identification of the salt-tolerant genotypes.     

Impact of mashing on sorghum proteins and its relationship to ethanol fermentation

Nine grain sorghum cultivars with a broad range of ethanol fermentation efficiencies were selected to characterize the changes in sorghum protein in digestibility, solubility, and microstructure during mashing and to relate those changes to ethanol fermentation quality of sorghum. Mashing reduced in vitro protein digestibility considerably, and a large amount of polymers cross-linked by disulfide bonds were developed during mashing. As a marker of cross-linking, protein digestibility of the original samples was highly related to conversion efficiency. gamma-Kafirin (%) neither correlated to ethanol yield nor conversion efficiency significantly. Solubility of proteins in an alkaline borate buffer in conjunction with SDS decreased substantially after mashing. Solubility and the SE-HPLC area of proteins extracted from mashed samples were highly correlated with ethanol fermentation. Ethanol yield increased and conversion efficiency improved notably with the increase of extracted proteins from mashed samples. SE-HPLC total area could be used as an indicator to predict ethanol fermentation. CFLSM images proved that sorghum proteins tended to form highly extended, strong web-like microstructures during mashing. The degree of protein cross-linking differed among samples, and more open microstructures were observed in samples with higher conversion efficiencies. The web-like protein matrix was found to hold not only starch granules but also some oligosaccharides or polysaccharides inside. The formation of web-like microstructures because of cross-linking reduced conversion efficiency.     

In vivo antifungal activity of the essential oil of Bupleurum gibraltarium against Plasmopara halstedii in sunflower

The antifungal activity of the essential oil of the aerial parts of Bupleurum gibraltarium was evaluated against Plasmopara halstedii. Fungus spores were inoculated in sunflower seedlings, previously treated with several essential oil solutions, and the sporulation percentage was measured after an 11-day treatment. The oil at a concentration of 5.0 mL/L clearly inhibited the fungus sporulation. The contact between fungus sporangia and essential oil was minimized, so it seems that the oil pretreatment could activate the defense response of the sunflower seedlings against the pathogen invasion. The main compounds in the oil were sabinene (31.1%), alpha-pinene (15.6%), and 2,3,4-trimethylbenzaldehyde (10.9%), among a total of 65 components identified.     

优化高压电场处理提高高粱种子活力

为了探讨高压电场处理对高粱种子萌发活力的影响,以晋杂122#高粱种子为试材,采用种子发芽试验、生物化学分析及二次通用旋转组合设计相结合的方法,研究电场强度和处理时间对高粱种子的活力指数和内源赤霉素(gibberellin,GA)含量的影响,通过建模分析,寻求高压电场处理条件的优化方案。结果表明:不同高压电场(high voltage electric field,HVEF)处理对高粱种子活力指数和内源GA含量影响均达到显著水平(P0.05);二因素对高粱种子的活力指数和内源GA含量影响效应顺序为电场强度处理时间;电场强度和处理时间对高粱种子活力指数和内源GA含量影响有阈值效应;二因素耦合效应对高粱种子的活力指数的影响呈现负交互效应,对内源GA含量的影响表现出正交互效应,且交互效应显著(P0.05),二因素交互作用对内源GA含量影响大于对种子活力的影响;经模型寻优,同时满足活力指数≥14.25、内源GA质量分数≥11.55 ng/g的优化方案为:电场强度485.53~605.38 k V/m,处理时间31.41~48.99 min,在此基础上,进一步确定优化条件为:电场强度500 k V/m,处理时间36 min,经试验验证,高粱种子活力指数和内源GA质量分数理论值15.50、14.92 ng/g,与实测值(15.38±0.18)、(14.85±0.13)ng/g基本一致,进一步验证了方案的可靠性。研究结果为高压电场技术处理种子在农业生产中的应用提供理论依据。     

Potent in vivo antifungal activity against powdery mildews of pregnane glycosides from the roots of Cynanchum wilfordii

Two new pregnane glycosides, kidjoranine 3-O-β-D-glucopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 4)-α-L-cymaropyranosyl-(1 → 4)-β-D-cymaropyranosyl-(1→4)-α-L-diginopyranosyl-(1 → 4)-β-D-cymaropyranoside (5) and caudatin 3-O-β-D-glucopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 4)-α-L-cymaropyranosyl-(1 → 4)-β-D-cymaropyranosyl-(1 → 4)-α-L-diginopyranosyl-(1 → 4)-β-D-cymaropyranoside (6), were isolated from the roots of Cynanchum wilfordii along with four known compounds (1-4). The antifungal activities of the six compounds against barley powdery mildew caused by Blumeria graminis f. sp. hordei were compared to the antifungal activity of polyoxin B. The caudatin glycosides (1, 4, and 6) showed stronger antifungal activities than polyoxin B, whereas kidjoranine glycosides (2, 3, and 5) had weaker activities than polyoxin B. A wettable powder-type formulation (C. wilfordii-WP20) of the ethyl acetate extract from C. wilfordii roots prohibited the development of barley powdery mildew much more effectively than the commercial fungicide polyoxin B-WP10. In addition, C. wilfordii-WP20 effectively controlled strawberry powdery mildew caused by Sphaerotheca humuli under greenhouse conditions. Thus, the crude extract containing the pregnane glycosides can be used as a botanical fungicide for the environmentally benign control of powdery mildews.     

Characterization of volatile constituents of Haplopappus greenei and studies on the antifungal activity against phytopathogens

Essential oil of Haplopappus greenei A. Gray was obtained by hydrodistillation of aerial parts, which were subsequently analyzed by gas chromatography and gas chromatography-mass spectrometry. Major components were identified as carvacrol (8.7%), beta-pinene (7.6%), trans-pinocarveol (6.2%), and caryophyllene oxide (5.8%), respectively. In total, 104 components representing 84.9% of the investigated essential oil were characterized. Furthermore, the essential oil was evaluated for antimalarial, antimicrobial, and antifungal activities. However, only antifungal activity was observed against the strawberry anthracnose-causing fungal plant pathogens Colletotrichum acutatum, Colletotrichum fragariae, and Colletotrichum gloeosporioides using the direct overlay bioautography assay. Major essential oil components were also evaluated for antifungal activity; the carvacrol standard demonstrated nonselective activity against the three Colletotrichum species and the other compounds were inactive.     

连作对高粱生长及根区土壤环境的影响

以玉米－高粱轮作为对照,研究连作对高粱生长、产量的影响及根区土壤中酶活性和微生物的变化。结果表明：高粱连作3年对产量的抑制开始显现。与轮作相比,连作3年高粱的株高、茎粗、叶面积、生物量显著降低,连作4年更为明显;连作4年高粱根系生长也明显受到影响,0~40 cm深度范围内根系的生物量、根表面积和根体积分别仅为轮作的61.5％、84.4％、73.8％。连作4年增加了土壤中可培养真菌数量,在拔节期和灌浆期分别是轮作的1.9、1.3倍,而对细菌和放线菌的影响没有明显规律;连作显著增加土壤中过氧化氢酶、蔗糖酶的活性,分别比轮作增加了14.7％、17.2％。由此可见,连作不仅抑制高粱植株的生长,并对土壤中微生物区系组成和酶活性产生显著影响。     

Modes of antifungal action of (2E)-alkenals against Saccharomyces cerevisiae

A series of aliphatic (2E)-alkenals from C(5) to C(14) were tested for their antifungal activity against Saccharomyces cerevisiae ATCC 7754. (2E)-Undecenal (C(11)) was found to be the most effective with the minimum fungicidal concentration (MFC) of 6.25 microgram/mL, followed by (2E)-decenal (C(10)) with an MFC of 12.5 microgram/mL. The time-kill curve study showed that (2E)-undecenal was fungicidal against S. cerevisiae at any growth stage, and this activity was not influenced by pH values. The (2E)-alkenals inhibited glucose-induced acidification by inhibiting the plasma membrane H(+)-ATPase. The primary antifungal action of medium-chain (C(9)-C(12)) (2E)-alkenals against S. cerevisiae comes from their ability to function as nonionic surface-active agents (surfactants), disrupting the native membrane-associated function nonspecifically. Hence, the antifungal activity of (2E)-alkenals is mediated by biophysical processes, and the maximum activity can be obtained when the balance between the hydrophilic and hydrophobic portions becomes the most appropriate.     

Nitrogen and/or phosphorus fertilization effects on organic carbon and mineral contents in the rhizosphere of field grown sorghum

The effects of nitrogen (N) and/or phosphorus (P) fertilizers on the nutritional status in the rhizosphere were studied by monitoring throughout the growth period the concentrations of organic carbon (C), inorganic N, NaHCO₃ extractable P, exchangeable K, Ca, and Mg in sorghum (Sorghum bicolor L. Moench) down in an Alfisol field, and of all these elements except for extractable P, and exchangeable Ca in a Vertisol field in semi-arid tropical India. These concentrations were compared between the rhizosphere soil and bulk soil of sorghum grown in both fields.

Organic C content of the rhizosphere soil increased with plant age and was significantly higher than that in the bulk soil throughout the growth of sorghum, but it was not affected by the rates of N or P fertilizer. Inorganic N concentration in the rhizosphere soil was significantly higher than that in the bulk soil until maturity in sorghum. The content of available P in the rhizosphere soil was significantly higher than in the bulk soil after the middle of the growth stage. Its average concentration in the rhizosphere soil across growth stages was significantly higher than in the bulk soil, which contradicts the observation in many reports that there is a depletion of P in the rhizosphere soil. The concentration of three exchangeable cations, K, Ca, and Mg, showed different patterns in the rhizosphere and the bulk soils. The concentration of K was almost constantly higher in the rhizosphere soil than in the bulk soil, Ca concentration was not different between the two soils, and Mg concentration was significantly higher in the bulk soil than in the rhizosphere soil. The reasons for these discrepancies cannot be explained at present. The concentrations of these cations were not affected by the rate of N or P fertilizer except for Mg at a later growth stage. The differences between rhizosphere and bulk soils in Alfisol were similar to those in Yertisol with respect to the concentration of organic C, inorganic N, and exchangeable K and Mg.     

Assessment of the reactivity of selected isoflavones against proteins in comparison to quercetin

Selected isoflavones (genistein, daidzein, formononetin, prunetin, biochanin A, and two synthetic isoflavones) were allowed to interact with soy and whey proteins. The reaction products were analyzed in terms of covalent binding at the nucleophilic side chains of proteins. Changes in molecular properties of the proteins derivatives were documented by SDS-PAGE, IEF, and SELDI-TOF-MS. The structural changes induced were studied using circular dichroism. The in vitro digestibility was assessed with trypsin. The results show that the occurrence of the catechol moiety, that is, the two adjacent (ortho) aromatic hydroxyl groups on ring B of the flavonoid structural skeleton appears to be prerequisite condition for covalent binding to proteins. The catechol moiety on ring A was less reactive. Its absence lead to a slight or no significant reaction, although noncovalent interactions may still be possible, even when lacking this structural element. A comparison of the data is also made with quercetin representing the flavonols.     

抗生素对高粱茎尖再生的影响及再生体系的建立

研究羧苄青霉素、头孢霉素、潮霉素和卡那霉素4种抗生素对高粱茎尖再生的影响及再生体系的建立结果表明,MS培养基中添加甘氨酸、乙二胺四乙酸的铁络合物(Fe-EDTA)和抗坏血酸等有机物有利于高粱茎尖的分化与生长。农杆菌介导的高粱茎尖遗传转化过程中羧苄青霉素为最理想抗生素,最佳浓度为250mg／L。并初步确立了高粱茎尖农杆菌介导的遗传转化过程中抑菌和转化体的筛选策略。     

抗生素对高粱茎尖再生的影响及再生体系的建立

研究羧苄青霉素、头孢霉素、潮霉素和卡那霉素4种抗生素对高粱茎尖再生的影响及再生体系的建立结果表明,MS培养基中添加甘氨酸、乙二胺四乙酸的铁络合物(Fe EDTA)和抗坏血酸等有机物有利于高粱茎尖的分化与生长。农杆菌介导的高粱茎尖遗传转化过程中羧苄青霉素为最理想抗生素,最佳浓度为2 5 0mg/ L。并初步确立了高粱茎尖农杆菌介导的遗传转化过程中抑菌和转化体的筛选策略     

Activity of lycorine analogues against the fish bacterial pathogen Flavobacterium columnare

In a continuing effort to discover natural products and natural product-based compounds for the control of columnaris disease in channel catfish (Ictalurus punctatus), 17 lycorine analogues were synthesized, including new benzoyl analogues 6-16, and evaluated for antibacterial activity against two isolates (ALM-00-173 and BioMed) of Flavobacterium columnare using a rapid bioassay. Two of the lycorine analogues had greater antibacterial activity than 1-O-acetyllycorine, an analogue of lycorine evaluated previously that is highly active against both isolates. Carbamate analogue 18 (1S,2S,3a(1)S,12bS)-2,3a(1),4,5,7,12b-hexahydro-1H-[1,3]dioxolo[4,5-j]pyrrolo[3,2,1-de]phenanthridin-1,2-diylbis(o-tolylcarbamate) had the strongest antibacterial activity toward both F. columnare isolates ALM-00-173 and BioMed, with 24-h IC(50) values of 3.0 ± 1.3 and 3.9 ± 2.2 mg/L, respectively, and a MIC of 5.5 ± 0 mg/L for both isolates. Compound 18 appears to be the most promising lycorine analogue for future efficacy studies to determine its potential for use as an alternative to the currently used compounds to control columnaris disease in channel catfish.     

Nematicidal and antifungal activities of annonaceous acetogenins from Annona squamosa against various plant pathogens

The methanol extract of Annona squamosa seeds was highly active against two phytoparasitic nematodes, Bursaphelenchus xylophilus and Meloidogyne incognita. It efficiently suppressed plant diseases, caused by Phytophthora infestans and Puccinia recondita. Ten annonaceous acetogenins (AAs) were isolated, and their chemical structures were identified by mass and nuclear magnetic resonance spectral data. Out of 10 substances, eight displayed strong in vitro nematicidal activity against B. xylophilus with LD(50) values ranging 0.006 to 0.048 μg/mL. Squamocin-G showed potent nematicidal activity against M. incognita. Squamocin, squamocin-G, and squamostatin-A also displayed potent in vitro and in vivo antifungal activities against P. infestans causing tomato late blight. In addition, squamostatin-A effectively controlled the development of wheat leaf rust caused by P. recondita. Our findings suggested that A. squamosa seeds and its bioactive AAs can be an alternative resource of a promising botanical nematicide and fungicide to control various plant diseases.     

Determination of fungicide residues in field-grown strawberries following different fungicide strategies against gray mold (Botrytis cinerea)

In a 2 year experiment, residues in field-grown strawberries were investigated from the fungicides fenhexamid, pyrimethanil, tolylfluanid, and kresoxim-methyl resulting from different strategies, as regards the dose, number, and time of fungicide applications. Kresoxim-methyl was only used the first year and in full or no dose to control powdery mildew. In the first year, the highest concentrations analyzed were 0.66 mg kg(-1) for pyrimethanil and 0.63 mg kg(-1) for fenhexamid resulting from the use of recommended dose rates and a preharvest interval (PHI) of 10 days, thus not exceeding the Danish maximum residue limit (MRL) of 1 mg kg(-1). Tolylfluanid was used no later than 21 days before harvest, which left residue contents in the berries of 0.48 mg kg(-1), a value well below the MRL of 5 mg kg(-1). In the second year, fungicide residues found in the samples were generally lower, 0.39 and 0.03 mg kg(-1) for pyrimethanil and fenhexamid, respectively. No residues of kresoxim-methyl were found in any of the samples from the field trials, indicating that kresoxim-methyl residues had declined to a level well below the detection limit within the 28 day period between the last application and the harvest.