Local and Systemic Activity of BABA (DL-3-aminobutyric Acid) Against Plasmopara viticola in Grapevines

The non-protein amino acid BABA (DL-3-amino-n-butanoic acid, -aminobutyric acid) is reported here to induce local and systemic resistance against downy mildew in grape leaves. Leaf discs of susceptible cultivars placed on BABA solutions and inoculated with Plasmopara viticola on the counter surface produced brownish restricted lesions below the inoculation site (Hypersensitive-like response, HR) which failed to support fungal sporulation. Histochemical analyses of such HR lesions revealed the accumulation of lignin-like deposits in the host cells. In contrast, water-treated inoculated discs produced expanded chlorotic lesions with profuse sporulation in which no lignin accumulation was observed. Mock-inoculated BABA-treated leaf discs showed no HR or lignin accumulation. Concentrations as low as 25µg/ml (0.25mM) of BABA sufficed to prevent tissue colonization with the fungus. Five other isomers of aminobutyric acid, namely L-2 aminobutyric acid, 2-amino isobutyric acid, DL-2-aminobutyric acid (AABA), DL-3-amino isobutyric acid, and 4-aminobutyric acid (GABA) gave no protection against the downy mildew fungus. Of the two (R and S) enantiomers of BABA only the R form was active in producing HR, suggesting a specific stereostructure requirement for activity. BABA could stop fungal colonization even when applied post-infectionally to leaf discs. Resistance of BABA-pulse-loaded leaf discs persisted for more than 14 days. BABA provided systemic protection against the disease when applied via the root system or via the lower leaves of grape plants. Application of ¹⁴C-BABA to a single leaf of intact plants showed the accumulation of the ¹⁴C label in upper leaves (and root tips), suggesting sink-oriented transport.     

De invloed van kaligebrek op de vatbaarheid van bloemkool voor peronospora parasitica

Summary Peronospora parasitica was found to attack cauliflower plants which suffered from potash deficiency, very heavily, while plants with a sufficient quantity of potash were only slizhtly attacked. Aphids (Brevicoryne brassicae L.) occurred more abundantly on potash deficient plants.     

Development and physiology of infection by the downy mildew fungus Peronospora parasitica (Pers. ex Fr.) Fr. in susceptible and resistant Brassica species

The growth of two isolates of the downy mildew fungus Peronospora parasitica , one obtained from cauliflower ( Brassica oleracea ) and the other from oilseed rape ( B. napus ) was assessed in their respective hosts of origin, and also in the alternative combination. Both isolates were capable of infecting either host, but there were marked contrasts in the time course and extent of mycelial development, the amounts of associated host-cell necrosis, and eventual intensity of sporulation. Oilseed rape, which was partially resistant to the isolate from cauliflower, exhibited extensive necrosis of mesophyll cells, in conjunction with reduced mycelial development, and delayed and reduced sporulation by the pathogen. The isolate from oilseed rape was virulent on both host species. Pathogenesis in the susceptible combinations was accompanied by large increases in electrolyte leakage, and increased activity of the enzymes β-glucosidase, ribonuclease, and peroxidase. Effects on chlorophyll content were variable and activities of acid phosphatase and acid phosphodiesterase were unaffected. Electrophoretic analyses of extracts from fungal sporangia and infected seedlings indicated that the large increases in β-glucosidase were of pathogen origin, while evidence from inhibitor studies suggested that enhanced ribonuclease activity was due to a new post-infectional form of the enzyme. The significance of these findings is discussed in relation to pathogenesis and host resistance mechanisms.     

Seed treatment with beta-aminobutyric acid protects Pennisetum glaucum systemically from Sclerospora graminicola

beta-Aminobutyric acid (BABA) treatment of pearl millet [Pennisetum glaucum (L) R Br] seeds influenced seedling vigour and protected the seedlings from downy mildew disease caused by the oomycetous biotropic fungus Sclerospora graminicola (Sacc) Schroet. Of the different concentrations of BABA tested, viz 25, 50, 75 and 100 mM, seeds treated with 50 mM for 6 h resulted in the maximum of 1428 seedling vigour and showed 23% disease incidence in comparison with the control which recorded a seedling vigour of 1260 and 98% disease incidence i.e. 75% protection from disease. Seeds treated with BABA when challenged for downy mildew disease using zoospores of S graminicola required 48 h after inducer treatment to develop maximum resistance. Durability of induced resistance was also tested in plants raised from seeds treated with the inducer and identified as resistant, by second challenge inoculation with the downy mildew pathogen at tillers and inflorescence axes. Reduced disease incidence of only 10 and 12% in these plants, compared with 71 and 76% disease in control plants inoculated at the tillers and inflorescence axes, respectively, suggested that resistance induced in seeds with BABA remained operative through vegetative and reproductive growth of pearl millet plants. Induction of resistance by seed treatment with BABA enhanced vegetative growth, viz height, fresh weight, leaf area and tillering, and reproductive growth, viz early flowering, number of productive ear heads and 1000 seed weight. Studies on induction of resistance in different cultivars of pearl millet with varying resistance reaction to downy mildew indicated that the protection offered by BABA is independent of the nature of cultivars used and not dependent on their constitutive resistance.     

New genes for resistance to downy mildew (Peronospora parasitica) in oilseed rape (Brassica napus ssp. oleifera)

The response of cotyledons of oilseed rape ( Brassica napus ssp. oleifera ) accessions to infection by isolates of Peronospora parasitica under controlled conditions was assessed on a 0–7 scale (disease reaction). In interactions scored 0–3, 4–5 and 6–7, the host was considered resistant, partially resistant and susceptible, respectively. Accession RES-26, selected from the spring oilseed rape cultivar Janetzkis, was partially resistant to isolate R1 and resistant to isolate P003 of P. parasitica , which distinguishes it from three previously described differential response groups ('A', 'B' and 'C') of accessions in B. napus . The resistance of RES-26 to isolate P003 seemed to be conditioned by a single, partially dominant gene and the resistance of RES-02, which belongs to group 'A' (resistant to R1 and P003), by two independent partially dominant genes. The gene for resistance to P003 in RES-26 is either closely linked, allelic or identical to one of the two genes for resistance in RES-02. Resistance of RES-02 to R1 is conditioned by a single, incompletely dominant gene. The genes for resistance to isolates R1 and P003 in RES-02 are either closely linked, allelic or identical. The cotyledonary leaves of each seedling responded independently when inoculated simultaneously each with a different isolate of the pathogen.     

Comparative efficacy of systemic acquired resistance-inducing compounds against rust infection in sunflower plants

ABSTRACT Four inducers of systemic acquired resistance (SAR) were examined for their efficacy in controlling rust infection caused by Puccinia helianthi in sunflower plants. Of the four compounds, DL-3-amino-n-butanoic acid (DL-beta-aminobutyric acid [BABA]) was the most effective and sodium salicylate (NaSA) was the least effective in protecting against rust. In leaf disk assays, full protection was obtained with BABA at 25 mug/ml, benzodiathiazol-S-methyl ester (BTH) at 100 mug/ml, 2,6-di-chloroisonicotinic acid (INA) at 100 mug/ml, and NaSA at >200 mug/ml. L-2-amino-n-butanoic acid (AABA) was partially effective, whereas N-methyl-BABA and 4-aminobutnoic acid (GABA) were ineffective. The R-enantiomer of BABA, but not the S-enantiomer, was more effective than the racemic mixture. In intact plants, BABA applied as a foliar spray or a root dip, before or after (up to 48 h) inoculation, provided significant protection for 8 days. BTH, INA, and NaSA were less protective and more phytotoxic compared with BABA. BABA did not affect urediospore germination, germ tube growth, appressorial formation, or initial ingress of P. helianthi, but strongly suppressed mycelial colonization in the mesophyll and, consequently, pustule and urediospore formation. No accumulation of defense compounds (phenolics, lignin, or callose) was detected in BABA-treated inoculated or noninoculated plants. This is the first report on the activity of BABA against an obligate Basidomycete pathogen in planta.     

霜霉属真菌自体荧光现象与萌发活性关系的研究

霜霉属真菌(Peronospora(Corda)Schrdoter)较为重要的种有东北霜霉(Peronospora manshurica(Naoum.)Syd.),散展霜霉(Peronspora effusa(Grev.)Ces.),寄生霜霉(Peronospora parasitica(Pers.)Fr.),烟草霜霉(Peronospora hyoscyami de Bary f.sp.tabacina(Adam)Sklichy)等。本研究对寄生霜霉、散展霜霉和东北霜霉3个种的孢子囊通过物理处理、化学处理和自然死亡等多种致使孢子囊死亡的方法处理后,孢子囊的自体荧光现象和其萌发活性的关系进行了深入研究,并观察了干烟叶上烟草霜霉孢子囊的自体荧光现象和其萌发活性,得出了霜霉属真菌孢子囊的自体荧光现象和孢子囊的萌发活性呈反相关关系的规律性结论,说明检验孢子囊的自体荧光现象可以用于检验霜霉属真菌孢子囊的萌发活性。     

Post infection application of DL-3-amino-butyric acid (BABA) induces multiple forms of resistance against <Emphasis Type="Italic">Bremia lactucae</Emphasis> in lettuce

DL-3-amino-butyric acid (BABA) induces local and systemic resistance against disease in numerous plant species. In a recent study we showed that preventive application of BABA to lettuce (Lactuca sativa) plants induced resistance against downy mildew caused by the oomycete Bremia lactucae by callose encasement of the primary infection structures of the pathogen. Now we show that post-infection application of BABA to the foliage or the roots, even at progressive stages of disease development, is highly protective against B. lactucae. Resistance induced by BABA is manifested in multiple microscopic forms, depending on the time of its application. When applied at 1 day post inoculation (dpi) BABA induced HR in penetrated epidermal cells; at 2 dpi it caused massive encasement with callose of the primary haustoria; and, at 3 or 4 dpi it enhanced the accumulation of H₂O₂ in the developing mycelia runners and altered their colour to red. The pronounced change in the colour of the mycelium was visually apparent to the naked eye. In all cases the pathogen failed to sporulate on the treated plants. This is the first indication that an immunizing compound may be protective at advanced stages of disease development.     

Phytogard® and DL-β-amino Butyric Acid (BABA) Induce Resistance to Downy Mildew (Bremia Lactucae) in Lettuce (Lactuca sativa L)

Downy mildew of lettuce (Bremia lactucae) is a serious disease. An alternative to chemicals is the application of disease resistance inducers. The aim of this study was to test whether DL--amino butyric acid (BABA) and Phytogard® (K₂HPO₃) could induce resistance in downy mildew susceptible plants. Aqueous solutions of BABA (0, 10, 20, 30, 50, 80, 100mM) and Phytogard® (0.0, 5.8, 29.0, 40.6, 58.0 and 87.0ppm) were sprayed on seven-day-old seedlings 0, 3, 7 and 15 days before or 1–3 days after inoculation with B. lactucae. Results obtained showed that Phytogard®- and BABA-induced resistance was dose-dependent. At 40.6ppm for Phytogard® and 10mM for BABA, complete protection was obtained. Both compounds had a curative effect and the induced resistance lasted for at least 15 days. It was also shown that both compounds induced systemic resistance in lettuce against downy mildew. Phytogard® at 40.6ppm completely inhibited spore germination while BABA at 20mM did not. Pathogenesis related (PR) protein analysis showed that BABA induced weak accumulation of PR-2, but not PR-1, PR-5 and PR-9. Phytogard® induced none of these proteins. The use of these two compounds to protect lettuce from B. lactucae is discussed.     

Activation of tomato plant defence responses against bacterial wilt caused by Ralstonia solanacearum using DL-3-aminobutyric acid (BABA)

In this study, we investigated the ability of DL-3-aminobutyric acid (BABA) to protect tomato against bacterial wilt caused by Ralstonia solanacearum. This was combined with studies of accumulation of total phenolic compounds, free and total salicylic acid (SA), and activity of enzymes related to plant defence, i.e., polyphenol oxidase (PPO) and catalase (CAT). Under greenhouse conditions, tomato plants pre-treated by soil drenching with BABA profoundly reduced disease severity of bacterial wilt compared to plants receiving a soil drench with water. Thus, BABA reduced leaf wilting index by 75.3 % and vascular browning index by 69.9 %, without any in vitro inhibitory activity on the pathogen. BABA treatment significantly reduced the population of R. solanacearum in stems of tomato plants and additionally also significantly increased both fresh and dry weight of roots and shoots of tomato plants compared with the inoculated control. Application of BABA resulted in a high increase in PPO activity both in plants with and without inoculation. Compared to water-treated plants, treatment with BABA also induced a significant increase of total phenolic compounds as well as of free and total SA in leaves of both inoculated and non-inoculated tomato plants at all sampling times. CAT activity decreased in tomato plants treated with BABA in comparison with the water-treated control plants and the decrease in activity correlated with an increasing total SA accumulation. These findings suggest that BABA treatment resulted in induction of resistance to bacterial wilt in tomato.     

Long‐lasting β‐aminobutyric acid‐induced resistance protects tomato fruit against Botrytis cinerea

Minimizing losses to pests and diseases is essential for producing sufficient food to feed the world's rapidly growing population. The necrotrophic fungus Botrytis cinerea triggers devastating pre‐ and post‐harvest yield losses in tomato (Solanum lycopersicum). Current control methods are based on the pre‐harvest use of fungicides, which are limited by strict legislation. This investigation tested whether induction of resistance by β‐aminobutyric acid (BABA) at different developmental stages provides an alternative strategy to protect post‐harvest tomato fruit against B. cinerea. Soil‐drenching plants with BABA once fruit had already formed had no impact on tomato susceptibility to B. cinerea. However, BABA application to seedlings significantly reduced post‐harvest infection of fruit. This resistance response was not associated with a yield reduction; however, there was a delay in fruit ripening. Untargeted metabolomics revealed differences between fruit from water‐ and BABA‐treated plants, demonstrating that BABA triggered a defence‐associated metabolomics profile that was long lasting. Targeted analysis of defence hormones suggested a role of abscisic acid (ABA) in the resistance phenotype. Post‐harvest application of ABA to the fruit of water‐treated plants induced susceptibility to B. cinerea. This phenotype was absent from the ABA‐exposed fruit of BABA‐treated plants, suggesting a complex role of ABA in BABA‐induced resistance. A final targeted metabolomic analysis detected trace residues of BABA accumulated in the red fruit. Overall, it was demonstrated that BABA induces post‐harvest resistance in tomato fruit against B. cinerea with no penalties in yield.     

Seedling and adult plant resistance to downy mildew (Peronospora parasitica) in cauliflower (Brassica oleracea convar. botrytis var. botrytis)

Seedlings of six cauliflower cultivars ( Brassica oleracea convar. botrytis var. botrytis ) were assessed for resistance to a Danish isolate of Peronospora parasitica , under controlled conditions. Resistance, characterized by restricted sporulation and necrotic dark flecks at the inoculation site on the cotyledons, was expressed in the hybrids 9306 F1, 9311 F1, and the open pollinated cultivar Perfection. Testing of the parent lines and F2 generations of the two resistant hybrids suggested that resistance was a dominantly inherited trait controlled by a single gene. Inoculation of the cultivars with seven isolates, from different geographical origins, showed that the resistance was isolate specific. The two hybrid cultivars expressing cotyledon resistance and two hybrids expressing susceptibility were assessed for adult plant resistance under field conditions. The AUDPC (Area Under the Disease Progress Curve), based on disease incidence and severity, revealed significant differences between the cultivars. At harvest, the cultivars exhibited significantly different levels of defoliation and curd attack. The cultivars 9306 F1 and 9311 F1 showed high levels of resistance in all assessments, whereas the two cultivars exhibiting susceptibility at the seedling stage, 9304 F1 and 9305 F1, also exhibited susceptibility through the adult plant stage. Thus, the resistance exhibited under field conditions resembled that identified at the seedling stage under controlled conditions. The results suggest that cotyledon resistance similar to that described could provide resistance throughout the adult plant stage, including curds.     

拟南芥霜霉病抗性分子机制研究进展

随着近年分子生物学技术的发展与应用,植物霜霉病抗性的研究有了长足的进展。本文就拟南芥抗霜霉病基因的克隆与结构分析,抗病信号传导,防卫反应和系统获得抗性,以及寄主-寄生菌共进化冲突方面进行了综述,并就今后的研究进行了展望。     

Resistance to Sphaerotheca pannosa in roses induced by 2,6-dichloroisonicotinic acid

The susceptible rose cv. Madelon and the partially resistant cv. Sonia both responded with reduced development of rose powdery mildew when they were treated with the synthetic inducer 2,6-dichloroisonicotinic acid (INA). The EC₅₀ for number of colonies cm⁻² was approximately 0.4 mg L⁻¹ in both cultivars when treated 4 days prior to inoculation. However, conspicuous differences were observed with respect to number of spores per cm². For sporulation, the EC₅₀ was 0.37 mg L⁻¹ in cv. Madelon and only 0.08 mg L⁻¹ in cv. Sonia. A comparison with the pathosystems cucumber/ Sphaerotheca fuliginea and red cabbage/ Peronospora parasitica is made and the importance of the observed phenomenon for the selection of parents in a breeding programme for (partial) resistance is discussed.     

The identification of a gene for race-specific resistance to Peronospora parasitica (downy mildew) in Brassica napus var. oleifera (oilseed rape)

The oilseed rape cultivar Cresor was resistant to 14 isolates of Peronospora parasitica derived from crops of Brassica napus in the UK. Segregation for resistance to one isolate among F₂ plants and F₃ progeny of crosses between Cresor and the susceptible cultivars Victor and Jet Neuf indicated that resistance was controlled by a single gene. There was evidence that genetic background and environment could influence the phenotypic expression of this resistance. Two sexual progeny isolates derived from a homothallic isolate of P. parasitica avirulent on Cresor were completely virulent on this cultivar. This suggested that the parental isolate was heterozygous at a matching locus or loci for avirulence and demonstrated the race-specific nature of the resistance.     

β-Aminobutyric acid-mediated enhancement of resistance in tobacco to tobacco mosaic virus depends on the accumulation of salicylic acid

A number of chemical and biological agents are known as inducers of systemic acquired resistance (SAR) to tobacco mosaic virus (TMV) in tobacco plants. In the present study, a local spray application of the non-protein amino acid DL-β-aminobutyric acid (BABA) was effective in enhancing resistance to TMV in tobacco plants containing the N gene. In contrast, the isomer α-aminobutyric acid (AABA) showed a much lower activity whereas γ-aminobutyric acid (GABA) was completely inactive, indicating a strong isomer specificity of aminobutyric acid in triggering enhanced virus resistance.Rapid cell death was detected in tobacco leaf tissues after foliar application of BABA, subsequently resulting in the development of macroscopically visible, necrotic lesions. BABA-induced cell death was associated with the rapid generation of superoxide and hydrogen peroxide. As further consequences, the occurrence of lipid peroxidation in treated tissues, a local and systemic increase of salicylic acid (SA) levels and the expression of PR-1a, a molecular marker of SAR in tobacco, could be observed. None of these responses was detectable after treatment with GABA.Enhancement of virus resistance by BABA was found to be strictly dependent on SA-mediated signal transduction since it could not be detected in salicylate hydroxylase (nahG) expressing transgenic tobacco plants. These findings suggest that in tobacco, primary processes triggered by foliar application of BABA, resemble those initiated by microbes during a hypersensitive response (HR) that result in SAR activation.     

Biocontrol activity and primed systemic resistance by compost water extracts against anthracnoses of pepper and cucumber

We investigated direct and indirect effects of compost water extracts (CWEs) from Iljuk-3, Iljuk-7, Shinong-8, and Shinong-9 for the control of anthracnoses caused by Colletotrichum coccodes on pepper and C. orbiculare on cucumber. All tested CWEs significantly (P < 0.05) inhibited in vitro conidial germination and appressorium formation of the fungal pathogens; however, DL-β-amino-n-butyric acid (BABA) failed to inhibit the conidial development of the pathogens. Direct treatments of the CWEs and BABA on pepper and cucumber leaves at 1 and 3 days before or after inoculation significantly (P < 0.05) reduced anthracnose severities; Iljuk-3, Shinong-9, and BABA for pepper and Iljuk-7 for cucumber had more protective activities than curative activities. In addition, root treatment of CWEs suppressed anthracnoses on the plants by the pathogens; however, CWE treatment on lower leaves failed to reduce the diseases on the upper leaves of the plants. The CWE root treatments enhanced not only the expression of the pathogenesis-related (PR) genes CABPR1, CABGLU, CAChi2, CaPR-4, CAPO1, and CaPR-10 in pepper and PR1-1a, PR-2, PR-3, and APOX in cucumber but also the activity of β-1,3-glucanase, chitinase, and peroxidase and the generation of hydrogen peroxide in pepper and cucumber under pathogen-inoculated conditions. However, the CWE treatments failed to induce the plant responses under pathogen-free conditions. These results indicated that the CWEs had direct effects, reducing anthracnoses by C. coccodes on pepper leaves and C. orbiculare on cucumber leaves through protective and curative effects. In addition, CWE root treatments could induce systemic resistance in the primed state against pathogens on plant leaves that enhanced PR gene expression, defense-related enzyme production, and hydrogen peroxide generation rapidly and effectively immediately after pathogen infection. Thus, the CWEs might suppress anthracnoses on leaves of both pepper and cucumber through primed (priming-mediated) systemic resistance.     

β-aminobutyric acid protects <Emphasis Type="Italic">Brassica napus</Emphasis> plants from infection by <Emphasis Type="Italic">Leptosphaeria maculans.</Emphasis> Resistance induction or a direct antifungal effect?

Resistance to infection in plants can be induced by treatment with various chemicals. One such compound is β-aminobutyric acid (BABA). Its positive effect on disease resistance has been noted in several pathosystems. Here we demonstrate that treatment with BABA protects Brassica napus plants from infection by the fungal pathogen Leptosphaeria maculans. Surprisingly, BABA also displayes in vitro antifungal activity against L. maculans with EC₅₀ similar to the fungicide tebuconazole. Both spore germination and hyphal growth were affected. The toxic effect can be reverted by addition of trypton to the culture medium. We hypothesised that BABA might inhibit inorganic nitrogen assimilation. Suppression of disease progression in plants and antifungal activity in vitro was weaker for α-aminobutyric acid and negligible for γ-aminobutyric acid. In contrast to a resistance inducer benzothiadiazole, the effect of BABA on disease development was nearly independent of the timing of treatment, indicating possible antifungal activity in planta. On the other hand, quantification of multiple hormones and an expression analysis have shown that treatment with BABA induces a synthesis of salicylic acid (SA) and expression of SA marker gene PR-1, but no evidence was observed for priming of SA responses to L. maculans. While we have not conclusively demonstrated how BABA suppresses the disease progression, our results do indicate that antifungal activity is another mechanism by which BABA can protect plants from infection.     

拮抗细菌B8对烟草黑胫病菌的抑制作用及其菌株鉴定

从烟草根际土壤中分离到对烟草黑胫病菌及其它植物病原菌具有抑制作用的菌株B8,平板对峙培养抑菌带内菌丝畸形、原生质凝集或外渗。其发酵原液和发酵液的无菌滤液均能抑制烟草黑胫病菌和蜡状芽孢杆菌;离体叶片接种法测定其发酵液对烟草黑胫病的防效,结果表明预防作用达100%。室内盆栽试验表明B8菌株发酵液对烟草黑胫病的预防作用可达78.1%,优于治疗作用。该菌菌体杆状,芽孢侧生、椭圆形,经形态学、生理生化性状和16S rDNA序列测定,将其鉴定为侧孢短芽孢杆菌。