Lipid metabolism in tomato and bean as a sensitive monitor for biocontrol of wilt diseases

The lipids metabolism of tomato and bean plants during biological control of wilt pathogens (Fusarium oxysporum f.sp.lycopersici andF. oxysporum f.sp.phaseoli, respectively) byBacillus subtilis was investigated. The interaction of wilt pathogens with both tomato and bean caused an imbalance and drastic reduction in total lipids, triacylglycerol, sterol and all phospholipd fractions except phosphatidic acid. The application of a formulated biocontrol agent,B. subtilis, eliminated the detrimental effect of both wilt pathogens and consequently prevented catabolism of lipid fractions in both tomato and bean. Moreover, the changes in the lipid fractions as a sensitive monitor for biocontrol of wilt diseases suggest a positive correlation between the application ofB. subtilis and improvement in the host metabolism towards anabolism. http://www.phytoparasitica.org posting Sept. 20, 2006.     

Effect ofCuscuta infection on chloroplast lipid composition ofBrassica leaves

Brassica campestris was infected with the angiosperm parasite,Cuscuta reflexa, on 24 DAS (days after sowing). A significant reduction (43%) in carbon dioxide assimilation in leaves was found compared to normal plant, when both were assayed on 38 DAS. At this stage, the chloroplast lipid in infected leaves had decreased by 34%, with a reduction of 13, 38 and 55%, respectively, in neutral, glyco- and phospholipids. Among the glycolipids, the decrease in the content of MGDG, DGDG and SQDG was 21, 67 and 44%, respectively, with 2.4-fold increase in the MGDG/DGDG ratio. The chlorophyll content was reduced by 24%, while the carotenoid level increased by 44%. The free fatty acid content was enhanced by 47% which may be attributed to an increase in lipase activity. The contents of saturated fatty acids (capric, lauric, myristic, palmitic and stearic) increased while the contents of unsaturated fatty acids (palmitoleic, oleic, linoleic and linolenic) decreased. The ratio of unsaturated to saturated fatty acids decreased over 50%. These findings may suggest chloroplasts as reactive sites of the host-parasite interaction in case of the angiosperm parasite.Abbreviations DAS day after sowing - DGDG digalactosyl diglyceride - FAME fatty acid methyl esters - FFA free fatty acids - MGDG monogalactosyl diglyceride - SQDG sulfoquinovosyl diglyceride     

Phytotoxic activity of middle-chain fatty acids I: effects on cell constituents

Phytotoxic activity of several middle-chain fatty acids, especially pelargonic acid (C9 acid) was investigated. C9–C11 acids caused strong non-selective damage to plants such as crabgrass, cucumber, velvetleaf, and tobacco, while C6 and C14 fatty acids had almost no activity. Middle-chain fatty acids caused a strong and rapid electrolyte leakage. They reached highest conductivity in 3 h in the case of cucumber cotyledons. Middle-chain fatty acids caused a decrease of the amount of polar lipids, particularly MGDG and PG, and chlorophylls. They also caused an increase of free fatty acids in 24 h after treatment. These results suggested that middle-chain fatty acids caused severe damage to cell membranes and thylakoid membranes of treated leaves. C6 volatile compounds such as cis-3-hexenal, trans-2-hexenal, and cis-3-hexenol were generated in less than 1 h after spraying pelargonic acid to tobacco leaves. The application of pelargonic acid was thought to be the trigger for linolenic acid degradation in the thylakoid membranes.     

Effect of seed treatment of<Emphasis Type="Italic">Arachis hypogaea</Emphasis> with<Emphasis Type="Italic">Bacillus subtilis</Emphasis> on nodulation in biocontrol of southern blight (<Emphasis Type="Italic">Sclerotium rolfsii</Emphasis>) disease

The employment of formulatedBacillus subtilis for peanut seeds (Arachis hypogaea cv. ‘Shulamit’) counteracted the destructive effects of the seedborne pathogenSclerotium (Athelia)rolfsii on the nodulation, leghemoglobin and nitrogenase activity of peanuts. Moreover, the changes in crop vigor index, total nitrogen content and survivability of bothRhizobium spp. andB. subtilis have been related to compatibility and even an occasional synergism between them. http://www.phytoparasitica.org posting Nov. 12, 2006.     

植物内生枯草芽孢杆菌Em7菌株对葡萄灰霉病菌的抑菌活性

通过室内皿内对峙抑菌试验、分生孢子萌发抑制试验、离体果实接种试验以及电镜技术,研究测定了分离自小麦根部的植物内生枯草芽孢杆菌Em7菌液对葡萄灰霉病菌Botrytiscinerea Pers.的抑制作用及抑菌机理。结果表明:用Em7菌液处理葡萄灰霉病菌后,在PDA培养基上形成了明显的抑菌圈,直径达2.81 cm;菌液对分生孢子萌发的抑制率达到88.65%;经Em7菌液处理后,离体果实病情指数明显低于空白对照,相对防治效果达到78.92%。电镜观察发现,处理组菌丝生长异常,体表凹凸不平,局部膨大成结或缢缩,分枝变多,菌丝体内液泡增多,细胞壁增厚,细胞膜透性发生变化。表明植物内生枯草芽孢杆菌Em7菌株对葡萄灰霉病菌有良好的抑制作用,并且可以有效控制葡萄灰霉病的发生。     

Biological control ofBotrytis cinerea in residues and flowers of Rose (Rosa hybrida)

Microbial isolates from living petals, petal residues and leaf residues of rose, and from laboratory collections, were evaluated for control ofBotrytis cinerea in rose. In leaf residues artificially infested withB. cinerea, isolates of the filamentous fungiGliocladium roseum, FR136 (unidentified) andTrichoderma inhamatum reduced sporulation of the pathogen by >90%, other filamentous fungi were 25–90% effective, and those of yeasts and bacteria were <50% effective. In artificially inoculated petal residues, no microbe reduced sporulation ofB. cinerea by >75%, but isolates ofCladosporium oxysporum and four yeasts were 51–75% effective, and three filamentous fungi, eight yeasts andBacillus subtilis isolates were 26–50% effective. Isolates ofT. inhamatum, C. oxysporum andG. roseum performed best againstB. cinerea among isolates evaluated in leaf residues naturally infested with the pathogen and indigenous microorganisms. Totals of ten isolates of filamentous fungi (includingC. oxysporum andC. cladosporioides), two of yeasts and five ofBacillus subtilis completely prevented lesion production byB. cinerea in detached petals, and a further six isolates of filamentous fungi (includingG. roseum) and six yeasts were 90–99% effective. Isolates ofC. oxysporum, C. cladosporioides andB. subtilis, the most effective microorganisms againstB. cinerea in flower buds, reduced number of lesions in the range of 42–65% compared with 59–89% for à standard fungicide (vinclozolin). It is suggested that application of leading antagonists Jo living rose leaves and flowers should optimize control of inoculum production byB. cinerea when the tissues die. Optimal biocontrol of lesion production in flower buds requires a better understanding of the microenvironment of petals.     

枯草芽胞杆菌与氟环唑联用对禾谷镰孢霉的增效作用机制

为验证枯草芽胞杆菌与氟环唑联用对禾谷镰孢霉的增效作用,用平板倒扣法和固体平板扩散法—打孔法测定菌药联用后枯草芽胞杆菌挥发性物质、抗真菌蛋白对禾谷镰孢霉的抑菌活性,观察抗真菌蛋白对禾谷镰孢霉菌丝形态的影响,并用刚果红染色法测定菌药联用后枯草芽胞杆菌纤维素酶活性。结果表明:菌药联用对禾谷镰孢霉的最高抑菌活性可达74.44%,表现增效和持效作用;枯草芽胞杆菌挥发性物质和抗真菌蛋白分别与氟环唑联用均可增强禾谷镰孢霉抑菌活性;菌药联用后枯草芽胞杆菌纤维素酶活性提高。研究表明枯草芽胞杆菌与氟环唑联用的增效机制是增强枯草芽胞杆菌挥发性物质对禾谷镰孢霉的抑菌活性,抗真菌蛋白活性的提高加强了禾谷镰孢霉菌丝溶解的程度,纤维素酶活性的增强提高了禾谷镰孢霉空间竞争作用和生物防治潜能。     

Biochemical changes in sunflower plants due to seed treatment/spray application with biocontrol agents

The application ofTrichoderma harzianum andPseudomonas fluorescens led to increases in dry matter content, starch, total soluble sugars (TSS) and reducing sugar contents in leaves of sunflower (Helianthus annuus) when done as seed treatment or coupled with spray. There was a significant increase in TSS and reducing sugars in stem tissue after treatment with biocontrol agents. The content of total phenols in leaves increased after treatment at 30 and 60 days after sowing (DAS) and at 30 DAS in stem tissues. Biocontrol agents increased the activities of phenylalanine ammonia lyase (PAL) in leaves and stem tissue after 30 DAS and significantly reduced total phenolic content and PAL activity in the stem at 60 DAS. Following treatment with biocontrol agents, seed lipid content increased, the proportion of linoleic acid increased and that of oleic acid decreased. Application of biocontrol agents to sunflower plants initiated certain biochemical changes, which can be considered to be part of the plant’s defense response. http://www.phytoparasitica.org posting August 6, 2008.     

Effect of soil amendments and biological control agents (BCAs) on soil-borne root diseases caused by <Emphasis Type="Italic">Pyrenochaeta lycopersici</Emphasis> and <Emphasis Type="Italic">Verticillium albo-atrum</Emphasis> in organic greenhouse tomato production systems

The effect of different soil amendments and biological control agents on soil-borne root diseases that cause significant economic losses in organic and other soil-based tomato production systems (Pyrenochaeta lycopersici and Verticillium albo-atrum) was compared. Organic matter inputs (fresh Brassica tissue, household waste compost and composted cow manure) significantly reduced soil-borne disease severity (measured as increased root fresh weight) and/or increased tomato fruit yield, with some treatments also increasing fruit number and/or size. Soil biological activity also increased with increasing organic matter input levels and there were significant positive correlations between soil biological activity, root fresh weight and fruit yield. This indicates that one mechanism of soil-borne disease control by organic matter input may be increased competition by the soil biota. Chitin/chitosan products also significantly reduced soil-borne disease incidence and increased tomato fruit yield, number and/or size, but had no effect on soil biological activity. Biological control products based on Bacillus subtilis and Pythium oligandrum and commercial seaweed extract (Marinure) and fish emulsion (Nugro)-based liquid fertilisers had no positive effect on soil-borne disease incidence and fruit yield, number and size. The use of ‘suppressive’ organic matter inputs alone or in combination with chitin/chitosan soil amendments can therefore be recommended as methods to control soil-borne diseases in organic and other soil-based production systems.     

Influence of soil type and pH on the colonisation of sugar beet seedlings by antagonistic Pseudomonas and Bacillus strains,and on their control of Pythium damping-off

In five different soils originating from Scotland (Craibstone and Cruden Bay), Germany (Magdeburg and Uelzen) and Greece (Tymbaki), Pseudomonas fluorescens B5 reached higher population sizes (4.7–5.7logCFU/plant) on 12-day-old sugar beet seedlings than Bacillus subtilis MBI 600 (4.1–4.8logCFU/plant). Total population size per plant was not affected by soil type. In all five soils, the antagonists reached highest population densities in the hypocotyl and the upper 2cm root section (P. fluorescensB5: 5.2–6.8log₁₀CFU/g plant fresh weight, Bacillus subtilisMBI 600: 5.2–6.1log₁₀CFU/g plant fresh weight) and declined to 0–3log₁₀CFU below 4cm root depth. Colonisation by P. fluorescens B5 down the root was slightly increased in the soils from Craibstone, Magdeburg, and Uelzen compared to the sandy clay loam from Tymbaki. In lux-marked P. fluorescens B5, population density was positively correlated with light emission in all soils; the light emission indicated physiological activity of the strains. However, P. fluorescens B5 reduced Pythium damping-off (measurement after 14 days plant growth) only in three of the five soils (Craibstone, Cruden Bay and Magdeburg). Co-inoculation of B. subtilis MBI 600 increased downward colonisation of the root by P. fluorescens B5, but not the total population ofP. fluorescens B5 per plant. Bacillus subtilisMBI 600 did not reduce Pythium damping-off in any of the soils nor did it influence the efficiency of co-inoculated P. fluorescens B5; its population consisted mainly of physiologically inactive spores. In Craibstone soil, pH did not affect population density, distribution along the root or biocontrol activity against P. ultimum of P. fluorescens B5 or B. subtilis MBI 600.     

Bacillus subtilis as an alternative biologically based strategy for controlling Fusarium wilt disease in tomato: A histological study

The employment of formulateBacillus subtilis as a biocontrol agent successfully controlledFusarium oxysporum f.sp.lycopersici within tomato seedlings (in vivo). B. subtilis was able to proted cortex and vascular tissues of tomato against progression of the wilt pathogen. No changes were observed in tomato tissues due to application ofB. subtilis except for hypertrophy and elongation of cortex tissues, which indicates the production of plant growth hormones byB. subtilis.     

Chemical and Biological Treatments for Control of Gummy Stem Blight of Greenhouse Cucumbers

Experiments were conducted to determine the effects of chemical and biological treatments on gummy stem blight of cucumber caused by Didymella bryoniae in vitro and under greenhouse conditions. Eleven strains of Bacillus subtilis, strain AGB10 of B. cereus, and strain B8Fr of Enterobacter agglomerans produced antagonistic zone against D. bryoniae in vitro. Of four experiments conducted, the chemical treatments Nova,¹ kresoxim-methyl, and azoxystrobin controlled the disease in three experiments and the biological treatments E. agglomerans (B8Fr), B. subtilis (AGS-4), and lysozyme in one experiment when applied as sprays on lesions caused by D. bryoniae on cucumber plants under greenhouse conditions. Fruit rot of cucumber was significantly reduced when the fruit was treated with Nova or kresoxim-methyl. These results suggest the potential of azoxystrobin, kresoxim-methyl, E. agglomerans (B8Fr), and B. subtilis (AGS-4) applied post-inoculation to control gummy stem blight on greenhouse cucumbers.     

枯草芽胞杆菌HMB-20428与化学杀菌剂互作对葡萄霜霉病菌抑制作用和替代部分化学药剂减量用药应用

为明确生防菌剂枯草芽胞杆菌Bacillus subtilis HMB-20428与化学杀菌剂互作对葡萄霜霉病菌Plasmopara viticola的抑制作用,采用生物测定与田间药效试验研究其最佳用药时期,筛选最佳生化互作组合,结合空间竞争能力和诱导抗病性生理测定试验了解互作增效机制,并建立葡萄霜霉病的综合防控技术。结果显示,枯草芽胞杆菌HMB-20428预防葡萄霜霉病最佳时期为发病前1个月,连续喷雾用药3~4次,间隔期10~15 d。研发出协同增效生化互作组合生防菌剂HMB-20428+嘧菌酯,及其与硅氧烷化合物增效组合,防效分别为91.06%~98.92%和87.78%~92.04%。枯草芽胞杆菌HMB-20428与嘧菌酯互作可增强枯草芽胞杆菌HMB-20428定殖能力和植株抗病作用,且定殖能力和抗病机制作用的增强时间基本一致。以生防菌剂HMB-20428替代部分化学药剂减量用药流程的防效为91.40%。表明枯草芽胞杆菌HMB-20428与嘧菌酯互作可达到减少化学药剂用量的目的。     

Effect of a biocontrol agent (<Emphasis Type="Italic">Bacillus subtilis</Emphasis>) and modified atmosphere packaging on postharvest decay control and quality retention of litchi during storage

The efficacy of biological control and two types of modified atmosphere packaging (MAP) alone and in combinations was evaluated under cold storage as well as simulated market-shelf conditions to control decay and pericarp browning on litchi cv. ‘McLean’s Red’. Fruits were dipped for 2 min at 15°C inBacillus subtilis or prochloraz separately, packed in MAP [low density polyethylene (LDPE) or polypropylene (PP)], heat sealed and stored at 2°C and 90% r.h. for 18 days followed by 2 days at 14°C and 75% r.h. to simulate market-shelf conditions. A commercially adopted sulfur dioxide treatment was included as a comparative control. Fruits treated withB. subtilis + PP or prochloraz + PP and stand-alone PP treatment did not show decay or browning at 2°C. Decay and browning were controlled significantly after 2 days at 14°C inB. subtilis + PP or prochloraz + PP treatments. However, the prochloraz + PP affected the natural pinkish-red color of the pericarp and gave higher h° (hue angle) values. The stand-alone PP treatment (∼14% O₂, ∼5% CO₂) showed 11.3% decay due mainly toAlternaria alternata andCladosporium spp. at 14°C. The effectiveness of the MAP was improved at 14°C whenB. subtilis was combined with PP, controlling decay and pericarp browning and retaining the fruit color and quality.B. subtilis survived in PP at 2° and 14°C, but not in LDPE. Stand-alone LDPE (∼3% O₂, ∼10% CO₂) and combination treatmentsB. subtilis + LDPE or prochloraz + LDPE failed to control decay and pericarp browning. Higher yeast populations were observed in LDPE orB. subtilis + LDPE at both 2° and 14°C.Candida, Cryptococcus andZygosaccharomyces spp. were the predominant yeasts in all LDPE treatments. Reprints ofS. Afr. Litchi Growers’ Assoc. Yearb. references can be obtained from D. Sivakumar.     

<Emphasis Type="Italic">In vitro</Emphasis> Selection of Maize Rhizobacteria to Study Potential Biological Control of <Emphasis Type="Italic">Aspergillus</Emphasis> Section <Emphasis Type="Italic">Flavi</Emphasis> and Aflatoxin Production

The aims of this study were to select bacterial isolates from the non-rhizophere of maize soil and to examine their antagonistic activity against Aspergillus section Flavi strains. The first selection was made through ecophysiological responses of bacterial isolates to water activity (a_w) and temperature stress. Subsequently, an Index of Dominance test (I_D), ecological similarity and inhibition of the lag phase prior to growth, growth rate and aflatoxin B₁ accumulation were used as criteria. From the first assay nine bacterial strains were selected. They grew well at 25 and 30 °C, with growth optima between 0.982 and 0.955 a_W using 48 h of incubation. There was ecological similarity between the bacterial strains Bacillus subtilis (RCB 3, RCB 6), Pseudomonas solanacearum RCB 5, Amphibacillus xylanus RCB 27 and aflatoxigenic Aspergillus section Flavi strains at 0.982 at 25 °C. The predominant interaction between all selected bacteria and fungi in dual culture was mutual intermingling at 0.982. Mutual inhibition on contact and mutual inhibition at a distance was observed at 0.955 a_w, between only four bacteria and some Aspergillus strains. Bacillus subtilis RCB 55 showed antifungal activity against Aspergillus section Flavi strains. Amphibacillus xylanus RCB 27, B.␣subtilis RCB 90 and Sporolactobacillus inulinus RCB 196 increased the lag phase prior to growth and decreased the growth rate of Aspergillus section Flavi strains. Bacillus subtilis strains (RCB 6, RCB 55, RCB 90) and P. solanacearum RCB 110 inhibited aflatoxin accumulation. Bacillus subtilis RCB 90 completely inhibited aflatoxin B₁ accumulation at 0.982 a_W. These results show that the bacterial strains selected have potential for controlling Aspergillus section Flavi over a wide range of relevant environmental conditions in the stored maize ecosystem.     

干旱胁迫下两种芽胞杆菌对玉米幼苗促生作用研究

供试玉米品种为‘先玉335’（XY335）,供试菌株为NECC11322(Bacillus subtilis)枯草芽胞杆菌、NECC11324(B. megaterium)巨大芽胞杆菌。试验设4组处理：Con（无菌水浸种,干旱胁迫）,C1（无菌水浸种,正常供水）,C2（NECC11322菌液浸种,干旱胁迫）,C3（NECC11324菌液浸种,干旱胁迫）,测定了浸种后盆栽玉米幼苗的生长状况、抗性生理指标及植株的N、P、K含量。结果表明：在干旱胁迫下接种NECC11322、NECC11324后,玉米幼苗叶片及根系SOD、POD、CAT、APX活性较Con均不同程度升高,其中接种NECC11322根系POD活性增长最为显著,较Con增长67.78%;植株叶片及根系可溶性蛋白含量、可溶性糖含量较Con均呈上升趋势,其中接种NECC11322叶片可溶性糖含量增长最为显著,较Con增长152.10%;与Con相比,植株叶片及根系全氮、全磷、全钾养分含量均有所提升,接种NECC11322后叶片全氮含量升高最为显著,较Con增长88.47%;干旱胁迫下接种两种芽胞杆菌后,植株叶片及根系丙二醛含量较Con均显著降低,接种NECC11322[JP2]后根系降幅最为显著,较Con降低51.03%。综上可知,干旱胁迫下接种两种芽胞杆菌均可降低干旱胁迫对玉米幼苗生长的抑制,其中NECC11322菌株更具有抗旱性。通过提高保护酶活性、可溶性蛋白、可溶性糖含量、叶绿素含量以及植株养分含量提高玉米幼苗抗旱性,促进玉米幼苗生长。     

Nitrogen metabolism disorder in watermelon leaf caused by fusaric acid

The effect of fusaric acid (FA) on the activity of leaf nitrogen (N) metabolism enzymes in watermelon seedlings supplied with different N forms was studied. The results showed that FA inhibited nitrogen uptake and caused decreased leaf amide and protein but increased the content of ammonium and amino acids. When treated with FA the activities of enzymes in the pathway for the synthesis of amino acid in leaves (GS, GOGAT, and GDH) were decreased by 15–23%, 13–40%, and 71–86%, respectively. The activity of asparagine synthetase was decreased by 34–57%. The proteinase activity was initially increased by 37–125% at 12 h after treatment of FA but then subsequently decreased. The activity of glutamate-pyruvate aminotransferase was increased by 280–400%, though the activity of glutamate-oxaloacetate aminotransferase was decreased by 30–63%. It was suggested that FA inhibited the uptake of ammonium in seedlings and suppressed the activities of amino acid and amide synthases, while stimulating proteinase activity.A new pathogenic mechanism of watermelon infection by Fusarium spp. was found as FA caused the complete disorder and collapse of the host plant's nitrogen metabolism. This work provides a new insight into the progression of watermelon wilting caused by Fusarium oxysporum f.sp. niveum.     

Evaluation of plant growth-promoting rhizobacteria for biological control of pythium root rot of cucumbers grown in rockwool and effects on yield

Three strains ofPseudomonas fluorescens (63-49, 63-28, and 15), one strain ofPseudomonas corrugata (13) and one strain ofSerratia plymuthica (R1GC4) were tested on rockwool-grown cucumbers for their ability to reduce Pythium root-rot caused byPythium aphanidermatum. These strains were previously selected for biocontrol ability from collections of >4000 bacteria. Strains 63-49 and 63-28 were tested on cucumber plants grown in rockwool in two replicatedPythium-inoculated trials conducted in British Columbia (B.C). Another inoculated, replicated trial was conducted in Quebec with all five strains. Cucumber yields (fruit number and weight) were measured over a ten-week harvest period. Strain 63-49 caused an early promotion of plant growth and increased cucumber yields at early harvests. No measurable effect ofPythium inoculation on disease development was observed in the Quebec trial, due to unfavourable cool weather. However, 63-49 significantly increased the total number of cucumbers (12%) and cucumber weight (18%), compared to the non-treated control. Strains 13, 15 and R1GC4 slightly increased the cumulative cucumber yields, but strain 63-28 had no effect. In the B.C. trial, inoculation withP. aphanidermatum reduced the number and weight of cucumbers by 27%. Treatments ofPythium-inoculated cucumbers with 63-49 significantly increased fruit number and weight by 18%, compared to thePythium-inoculated control. Strain 63-28 increased the cumulative number of cucumbers over time, compared to thePythium-inoculated control, but the increase was less than with 63-49. The use ofPseudomonas spp. in rockwool-grown cucumbers can increase yields, both in the presence and absence of Pythium root rot, and with variable seasonal conditions and disease pressures.     

Impact of malathion stress on lipid metabolism in Limnonectus limnocharis

Despite mounting concerns about amphibian population declines, information on impact of pesticides on physiological changes is meager. The present study deals the influence of an organophosphate pesticide—malathion on the lipid metabolism of Limnonectus limnocharis under laboratory conditions. Changes in the lipid metabolism were analyzed in the liver, muscle, ovary, and testis of frogs exposed to lethal (10.67 mg L⁻¹ for 1, 2, 3, and 4 days) and sub-lethal (2.13 mg L⁻¹ for 1, 5, 10, 15, 20, and 25 days) concentrations of malathion. Upon lethal concentration treatment, against the increase of fatty acids, glycerol, and lipase activities in all tested tissues, there was decrease in the total lipids content over different durations. On the other hand, exposure to sub-lethal concentration, the amount of total lipids content, free fatty acids, glycerol and lipase activity increased. Changes in the lipid metabolism due to lethal concentration of malathion exposure could depict the negative impact on the reproductive success, which would result in decline of amphibian population.     

Fungitoxicity and growth regulation involving aspects of lipid biosynthesis

Triarimol and triforine inhibit ergosterol biosynthesis in fungi and cause accumulation of free fatty acids, 24-methylenedihydrolanosterol, obtusifoliol and 14α-methyl-δ^8,24(28)-ergostadienol. Triparanol also inhibits ergosterol synthesis and causes accumulation of free fatty acids, but not of the latter 3 sterols. Triparanol appears to inhibit prior to lanosterol in the sterol biosynthetic pathway of Ustilago maydis and at unidentified sites subsequent to lanosterol which lead to the accumulation of a sterol which migrates with desmethylsterols on TLC plates. Quantitative abnormalities in sterols and free fatty acids in U. maydis are not produced by the fungicides carbendazim, chloroneb, carboxin and cycloheximide. A deficiency in nitrogen leads to a marked increase in triglycerides, but a normal distribution pattern for other lipids.Inhibition of oxidative demethylation of the sterol 14α-methyl group is probably the prime mechanism of inhibition of ergosterol biosynthesis by triarimol. Rates of formation of obtusifoliol and 14α-methyl-δ^8,24(28)-ergostadienol in triarimol-treated U. maydis cells suggest that C-4 demethylation occurs along an abnormal pathway which operates effectively only at high substrate concentrations. The growth retardant action of triarimol and ancymidol in higher plants most likely results from inhibition of a reaction in the gibberellin biosynthetic pathway analogous to sterol C-14 demethylation.Free fatty acid accumulation in U. maydis cells treated with inhibitors of sterol synthesis are derived mainly from polar lipid degradation and from de novo synthesis as a consequence of the disproportionality between fatty acid synthesis and utilization. The free fatty acids may play a significant role in the lethality of these inhibitors in this organism.