Atmospheric moisture influences on conidia development in Podosphaera xanthii through host-plant morphological responses

This study investigated the effects of atmospheric moisture on conidia development in cucurbit powdery mildew fungus (Podosphaera xanthii) through host-plant responses. Cucumber (Cucumis sativus L.) seedlings were grown under a high vapour pressure deficit (VPD) (3.8 kPa) or a low VPD (0.4 kPa). When the cotyledons had expanded, spores of P. xanthii were inoculated onto the adaxial surface. Inoculated seedlings for both treatments were then placed in a growth chamber maintained at a VPD of 2.1 kPa. The density of visible P. xanthii colonies on the high-VPD-acclimated cotyledons was 0.46 to 0.85 times that of the low-VPD-acclimated cotyledons 7 days after inoculation. It is likely the post-germination behaviour of P. xanthii such as the infection and consequent hyphal development was affected because spore germination did not differ between the treatments. The percentage of adaxial epidermal leaf cells with haustoria was also lower in the seedlings which had acclimated to a higher VPD. The high-VPD-acclimated cotyledons were thicker and had greater dry mass per area. The water potential of cotyledons did not differ between the treatments, although the stomatal conductance of high-VPD-acclimated cotyledons was lower than that of low-VPD-acclimated cotyledons. From these results, we conclude that the inhibition of P. xanthii conidia development on high-VPD-acclimated cotyledons was mainly caused by changes in leaf morphological properties.     

喷施外源激素对棉株棉花黄萎病发病程度的影响

通过温室人工接菌 ,研究了喷施 4种外源激素 3-吲哚乙酸、赤霉素、脱落酸和反 -玉米素对棉苗棉花黄萎病发病程度的影响。结果表明赤霉素在5.0～80.0μg/ml浓度范围内 ,提高了棉苗抗病性 ,但棉苗表现徒长、叶片畸形 ;反 -玉米素25.0～80.0μg/ml明显促进了病情发展 ;3-吲哚乙酸10μg/ml,脱落酸0.5μg/ml,反 -玉米素10 μg/ml的处理对降低棉苗的发病率和发病程度作用较明显。     

Degradation of fluometuron by Rhizoctonia solani

Degradation studies of fluometuron [Cotoran, 1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea] by Rhizoctonia solani have been conducted to elucidate further the pathway of degradation. Analysis by thin-layer chromatography and autoradiography demonstrated that R. solani degraded 88% of fluometuron (¹⁴CF_3^?) into seven nonpolar metabolites after 35 days of incubation. Trace amounts of polar, water-soluble products were detected, but no ¹⁴CO₂ or radioactive volatile products were detected. Two of the major metabolites were identified by thin-layer chromatography and ultraviolet spectroscopy as 1-methyl-3-(α,α,α-trifluorotolyl)urea and (3-trifluoromethylphenyl)urea, which indicated a stepwise demethylation of fluometuron. The remaining five metabolites have not been identified and have not been previously reported in the literature. Time course experiments and metabolite degradative studies indicated that the sequence of degradation involved a multibranched pathway which did not include CO₂ evolution. The proposed pathway does not include the conversion of fluometuron to the aniline derivative as has been reported for other urea herbicides. All of the data from this study indicate the incomplete degradation of fluometuron which suggests a cometabolic degradative pathway.     

Inhibition of photosynthetic pigments in cucumber cotyledons as a principle for a bioassay with fluridone

The response of etiolated cucumber (Cucumis sativus L. cv. National Pickling) cotyledons to fluridone was investigated in terms of inhibition of photosynthetic pigments, and utility as a bioassay. At a light intensity of 35 W/m², chlorophyll levels were higher in the controls, than at either 12.9 W/m², or 75 W/m². Fluridone inhibition was also more pronounced at that intensity. Significant differences between treatments were established as early as 24 h after exposure to light, when at the lowest fluridone concentration of 0.001 μg/ml, chlorophylls and carotenoids were inhibited 25 and 35% respectively. The system's simplicity and sensitivity suggest its use as a bioassay. It is shown that simple monochromatic absorbances of acetone extracts can satisfactorily estimate chlorophylls and carotenoids. Concentrations of fluridone as minute as 10^?9 moles/ litre are easily delected, and the system could feasibly detect even lower levels.     

Differential influence of herbicide treatments on activity and kinetic parameters of C4 photosynthetic enzymes from Zea mays

The recommended field dose of rimsulfuron, imazethapyr, alachlor, atrazine or fluometuron differentially reduced shoot fresh and dry weight of 10-day-old maize seedlings as well as leaf protein content during the following 12 days. These reductions seemed consistent during the whole period with fluometuron, atrazine and alachlor but appeared to be nullified by the 5th day of treatment with rimsulfuron and imazethapyr. On the other hand, all herbicides mostly provoked significant inhibitions in specific activities of phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31), malate dehydrogenase (MDH, EC 1.1.1.82), pyruvate phosphate dikinase (PPDK, EC 2.7.9.1) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) in leaves during the first 2 days. Thereafter, the inhibition was recovered in samples treated with rimsulfuron and imazethapyr, leveled off with alachlor but consistently augmented with atrazine and fluometuron. The kinetic characterization showed that rimsulfuron or imazethapyr unchanged V_max of all enzymes in vitro, however, V_max of PEPC, PPDK and Rubisco were decreased in vivo. Nevertheless, atrazine or fluometuron substantially reduced V_max of all enzymes while alachlor showed a reduction in this value of PEPC, MDH and Rubisco. Thus atrazine, fluometuron and, to a lower extent, alachlor reduced concentrations of all enzymes as well as rimsulfuron and imazethapyr for only Rubisco. On the contrary, K_m values of all enzymes were progressively increased by all herbicides indicating that the different herbicides altered the structural integrity of all enzymes. These findings conclude that rimsulfuron or imazethapyr competitively inhibited MDH but revealed mixed inhibition to PEPC, PPDK and Rubisco. Atrazine or fluometuron revealed mixed inhibitions to all enzymes whereas alachlor seemed to be either a competitive inhibitor to PPDK or a mixed inhibitor to PEPC, MDH and Rubisco.     

Effects of propanil on growth and cell constituents of Nostoc calcicola

The rice field herbicide, propanil, was toxic to the nitrogen-fixing cyanobacterium Nostoc calcicola. A decrease in growth was observed with the increasing concentrations of propanil, 30 μg/ml being lethal. Since toxicity of the herbicide could be reversed by exogeneous supplementation of assimilable organic carbon glucose, it is suggested that carbon fixation was sensitive to the herbicide. The herbicide inhibited heterocyst differentiation and nitrogen fixation. There was a rapid decrease in total protein, nucleic acids (DNA, RNA), and carbohydrate content accompanied by a loss of photosynthetic pigments. The phycocyanin: chlorophyll a ratio showed positive correlation with increased dosages of the herbicide, suggesting the inhibition of chlorophyll a.     

Effect of Margosan-O on the development of the leafhopperasymmetrasca decedens

The effect of Margosan-O, a formulation of a natural insecticide obtained from the neem (Azadirachta indica A. Juss) tree, on the development of the leafhopperAsymmetrasca decedens (Paoli), was investigated by testing insect performance (i) on cotyledons ofGossypium hirsutum cotton seedlings treated with different concentrations; (ii) on cotton seedlings stood with their petioles in different aqueous dilutions of Margosan-O and recording mortality until the adult stage; and (iii) determining the repellent effect on adults by recording their location on treatedvs untreated cotyledons in choice and no-choice situations. In foliar and in systemic treatments with 2% Margosan-O, practically none of the leafhoppers reached the adult stage. As the concentrations were lowered there was a gradual rise in the percentage of adults emerging; on untreated cotyledons 60-80% of the adults emerged. Feeding was zero or very low at high Margosan-O concentrations. Adult leafhoppers settled in significantly higher numbers on untreated than on treated cotyledons in both choice and no-choice experiments.     

Studies on the mechanism of action of cymoxanil in Phytophthora infestans

Colony growth and germ tube emergence of sporangia and encysted zoospores of Phytophthora infestans were highly sensitive to cymoxanil (ED₅₀ 0.5–1.5 μg/ml), whereas differentiation of sporangia and zoospore release were insensitive at concentrations up to 100 μg/ml. Treated sporangia did not show distorted germ tubes. Oxygen consumption for glucose oxidation by germinating sporangia and zoospore motility were not inhibited at concentrations up to 100 μg/ml. Cymoxanil hardly affected the uptake of radiolabeled precursors of DNA, RNA, and protein at concentrations up to 100 μg/ml. Incorporation of [¹⁴C]phenylalanine into protein was completely insensitive. RNA synthesis as measured by [³H]uridine incorporation was differentially inhibited in the various developmental stages of the fungus. Inhibition did not occur at differentiation of sporangia, whereas at cyst and sporangial germination and mycelial growth this process was inhibited 20–45% at a concentration of 100 μg cymoxanil/ml. Endogenous RNA polymerase activity of isolated nuclei was not inhibited by cymoxanil. DNA synthesis as measured by [methyl-³H]thymidine incorporation was inhibited 20–80% at the various stages of development at cymoxanil concentrations higher than 10 μg/ml. Metalaxyl, a specific inhibitor of ribosomal RNA synthesis, inhibited [³H]uridine incorporation 40–60% at all developmental stages. The data suggest that although DNA synthesis is affected more than RNA synthesis, inhibition of both biosynthetic processes is a secondary effect. The primary mode of action of cymoxanil thus remains unknown.     

Characterization of a dicarboximide-fungicide-resistant laboratory isolate ofMonilinia laxa

Monilinia laxa, the incitant of blossom blight in stone fruits in Israel, is sensitive to 5μg/ml of the dicarboximide fungicides vinclozolin and iprodione in the growth medium. When a large number of spores, from an isolate never exposed to these fungicides, was seeded on a medium containing 15 μg/ml iprodione, spontaneous resistant mutants appeared at 10^-5 frequency. These mutants showed cross resistance to the dicarboximide fungicides vinclozolin, procymidone, l-(3,5-dichloro-phenyl)-3-propen(2)-pyrrolidin-2,5-dion (Co 4462), l-(3,5-dichlorophenyl)-3-methoxymethyl-pyrrolidin-2,5-dion (Co 6054), and to dicloran. Growth rate on fungicide-free medium was similar to that of the parental sensitive strain but sporulation was much reduced. Growth rate on media supplemented with dicarboximide fungicides decreased gradually with increasing fungicide concentrations. The resistance has been stable for more than one year in the absence of fungicides. Artificial inoculation of cherry, apricot and plum fruits previously treated with 500 μg/ml vinclozolin, iprodione, procymidone or Co 6054, with a resistant strain, resulted in brown rot; similar treatments provided full protection of the fruits against the sensitive strain.     

Photosynthetic activity of MSMA-resistant and -susceptible common cocklebur

MSMA-resistant (R) and -susceptible (S) biotypes of common cocklebur (Xanthium strumarium L.) were used to study PSI and PSII activities, and chlorophyll and carotenoid content of MSMA-treated and -untreated R and S biotypes. MSMA at 1, 10, and 100 mg/L did not inhibit either PSI or PSII activities. The R biotype had higher PSI and PSII activity than the S biotype with and without MSMA treatments. R biotype leaf discs had higher chlorophyll and carotenoid content than the S biotype after treatment with MSMA; the S biotype cotyldeons had higher levels of both pigments as compared to the R biotype cotyledons. MSMA induced a reduction in both pigments in S biotype cotyledons, and in young and mature leaf discs. Results indicate that photosynthetic capability might indirectly be involved in the resistance mechanism and carotenoids may protect against MSMA toxicity, possibly caused by an induced free radical mechanism.     

Effect of pentachloronitrobenzene,pentachloroaniline, and albinism on epidermal penetration by appressoria of Pyricularia

Pentachloroaniline or pentachloronitrobenzene at concentrations between 0.5 and 5 μg/ml blocked appressorial melanization and appressorial penetration of onion epidermal cell walls by Pyricularia oryzae, strain P-2, without affecting conidial germination or appressorial formation. Among polyphenol oxidase inhibitors, salicylhydroxamic acid, and phenylthiourea at 100 μg/ml inhibited appressorial penetration of onion epidermis without affecting appressorial melanization, whereas sodium diethyldithiocarbamate and 2,3-naphthalenediol did not affect either process at 1.0 μg/ml but inhibited conidial germination and appressorial formation at 10 μg/ml. EDTA was without effect on either melanization or penetration at 100 μg/ml. The melanized appressoria of Pyricularia grisea, strain BL-3, penetrated onion epidermal cell walls, whereas nonpigmented appressoria of an albino mutant (AL-3) of this fungus did not. Melanization and penetration ability of AL-3 appressoria were restored by adding melanin biosynthesis intermediates scytalone or 1,8-dihydroxynaphthalene (1,8-DHN). Tricyclazole blocked melanization and epidermal penetration by AL-3 appressoria treated with scytalone but not by those treated with 1,8-DHN. Scytalone (20 μg/ml) increased the effectiveness of tricyclazole in blocking penetration by appressoria of BL-3. Tricyclazole was about 10 times more effective in inhibiting penetration by P-2 appressoria than by BL-3 appressoria.     

Effects of various classes of herbicides on four species of algae

Chlorella pyrenoidosa, Chlorococcum sp., Lyngbya sp., and Anabaena variabilis were cultured in Bold's basal medium. They were treated with 0.1, 1.0, and 10 μM concentrations of 2-chloro-2′, 6′-diethyl-N-(methoxymethyl)acetanilide (alachlor), 2-chloro-4-(ethylamino)-6-(tert-butyl-amino)-s-triazine (terbuthylazine), 2-sec-butyl-4,6-dinitrophenol (dinoseb), 1,1-dimethyl-3-(α,α,α-trifluoro-2,6-dinitro-N-propyl-p-toluidine) (profluralin), 2, 4-bis(isopropylamino)-6-(methylthio)-s-triazine (prometryne), and (2,4-dichlorophenoxy)acetic acid (2,4-D). Growth of all algal species tested was markedly reduced by the triazines. Alachlor, dinoseb, and fluometuron inhibited growth of some algae at higher concentrations while 2,4-D and profluralin did not inhibit growth at the concentrations tested. Photosynthesis was greatly inhibited by the triazines, even at the 0.1 μM concentration. Fluometuron was very toxic to the blue-green algae but had less effect on the green algae tested. Lyngbya was most susceptible to photosynthesis reduction by the herbicides. The concentrations of herbicides tested had little effect on respiration of the algae species. It appears that effects on algal growth were due primarily to inhibition of photosynthesis rather than to other metabolic processes.     

红砂优良种源选择及其地理变异规律

收集我国甘肃、宁夏、内蒙古等红砂天然分布区的23个种源的红砂种子,在武威市林业技术服务中心建立红砂种源试验。以23个种源的2 a、3 a生红砂苗木为研究材料,每个种源选取10个单株,测定叶片中可溶性蛋白(SP)、可溶性糖(SS)、脯氨酸(Pro)及叶绿素(Chl)相关指标,每个单株重复测3次。分析红砂苗期不同种源选择效果及其地理变异规律。结果表明:可溶性蛋白、可溶性糖、脯氨酸及叶绿素相关指标在23个红砂种源间存在丰富的变异,为优良种源的选择创造了条件。通过多重比较筛选出XGG(小甘沟)、ZZG1(扎子沟1)、ZZG2(扎子沟2)、JQGZ(酒泉瓜州)4个优良种源,入选率为17.39%。与其他种源相比较,XGG的可溶性糖含量在2 a和3 a生时都是最大,分别为13.13 mg·g~(-1)和15.54 mg·g~(-1);ZZG1的脯氨酸、叶绿素a、叶绿素b以及叶绿素(a+b)含量在3 a生时最大,依次为631.82μg·g~(-1)、595.40μg·g~(-1)、161.85μg·g~(-1)、757.25μg·g~(-1);ZZG2的脯氨酸含量在2 a和3 a生时排第2,为529.99μg·g~(-1)和622.87μg·g~(-1),叶绿素a/b值在3 a生时最大,为3.85;JQGZ的可溶性蛋白含量分别在2 a和3 a生时均最大,为9.63 mg·g~(-1)和7.66 mg·g~(-1)。通过相关性分析,发现红砂种源呈西北-东南抗旱性减弱的变异趋势。     

Combinations of Fungicides with Phylloplane Yeasts for Improved Control of Botrytis cinerea on Geranium Seedlings

ABSTRACT Control of Botrytis cinerea on geranium seedlings was evaluated in treatments with phylloplane yeasts in combination with 10 fungicides used to manage Botrytis blight of ornamental plants. Rhodotorula glutinis PM4 significantly reduced the development of lesions caused by B. cinerea on geranium cotyledons; however, yeast biocontrol efficacy was highly variable between trials. Treatment with the yeast in combination with azoxystrobin or trifloxystrobin at one tenth the labeled rate (7.5 mug a.i. ml(-1)) or the full labeled rate (7.5 mug a.i. ml(-1)) reduced lesion development, compared to treatment with the yeast or the fungicide alone. Vinclozolin at half the labeled rate or the full labeled rate (250 or 500 mug a.i. ml(-1)), in combination with R. glutinis PM4, significantly reduced the development of lesions caused by an isolate of B. cinerea resistant to vinclozolin. Copper hydroxide and iprodione at one-tenth the labeled rates, with or without yeast, were highly effective in limiting lesion development. Mancozeb did not increase the biocontrol efficacy of the yeast, and thiophanate-methyl negatively affected the yeast efficacy. Improved disease control was observed in treatments with vinclozolin at the labeled rate and R. glutinis PM4 at cell densities of 5 x 10(5) and 1 x 10(6) cells ml(-1), but not 1 x 10(5) cells ml(-1), on seedlings co-inoculated with B. cinerea in a suspension containing 1 x 10(5) conidia ml(-1). Disease control improved in treatments with combinations of vinclozolin and eight other isolates of R. glutinis, two isolates of R. graminis, and two isolates of R. mucilaginosa. Biocontrol was not observed in treatments with two isolates of R. minuta. The combination of yeast and vinclozolin significantly reduced the germination of conidia of B. cinerea and the growth of R. glutinis PM4 in vitro. All combinations of R. glutinis PM4 with azoxystrobin, trifloxystrobin, or vinclozolin provided highly effective and consistent disease control not observed in treatments with the fungicides alone or the yeast alone.     

新型真菌源激活蛋白对豌豆幼苗生理特性影响的初步研究

为探讨真菌源激活蛋白在促进植物生长和增产方面的作用机理,研究了不同浓度激活蛋白处理对豌豆幼苗生理特性的影响。结果表明,经1、2、5μg/mL激活蛋白处理后第7d,豌豆幼苗根系活力比对照分别增加了46.0%、58.5%和21.0%,硝酸还原酶活性比对照分别增加64.38%、140.62%和35.31%;处理后第15d,植物叶片叶绿素含量比对照分别增加了13.69%、18.49%和6.16%,可溶性糖含量比对照分别增加20.68%、32.03%和17.28%,可溶性蛋白含量比对照分别增加18.59%、32.05%和22.10%。不同浓度激活蛋白均能促进与植物生长相关的生理指标的提高,其中以2μg/mL的作用效果最好。     

干旱胁迫对胡杨和灰叶胡杨光合作用及叶绿素荧光特性的影响

采用盆栽试验,研究正常供水(土壤相对含水量70%～80%)、轻度干旱胁迫(50%～60%)和重度干旱胁迫(30%～40%)条件下2年生胡杨(Populus euphratica)和灰叶胡杨(P. pruinosa)的光合作用及叶绿素荧光特性.结果表明:在干旱胁迫进程中,轻度和重度干旱胁迫下胡杨、灰叶胡杨的净光合速率经历了急剧下降--缓慢回升--下降3个阶段.在相同的干旱胁迫处理下,光合作用及叶绿素荧光参数Pn,Gs,Ci,WUE,Fv/Fm,Fv/Fo,qP和NPQ胡杨明显高于灰叶胡杨,表明胡杨比灰叶胡杨对干旱胁迫具有更强的适应性.     

外源一氧化氮对Na_2CO_3胁迫下南瓜幼苗碳氮代谢的影响

为探讨外源NO对Na_2CO_3胁迫下南瓜幼苗碳氮代谢过程的影响,以银辉2号南瓜品种为材料,采用盆栽法研究了80μmol·L-1SNP对60 mmol·L-1Na_2CO_3胁迫下南瓜幼苗生长、叶绿体色素含量、碳氮代谢相关酶活性及代谢产物量的变化规律。结果表明:Na_2CO_3胁迫12 d,南瓜幼苗地上和地下部分干重、相对生长量、根冠比、Rubisco羧化活力、光合色素含量和氮代谢相关酶活性均不同程度下降;Rubisco氧化活力、游离氨基酸总量和蛋白水解酶活性显著上升。80μmol·L-1SNP外源处理能明显缓解Na_2CO_3胁迫对南瓜幼苗生长及光合作用的抑制,增加了干物质的积累和光合色素的含量。与Na_2CO_3胁迫处理相比,干物质积累量、相对生长量、叶绿素和类胡萝卜素(caro)含量、硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、Rubisco羧化酶、淀粉酶(AMY)活性和可溶性蛋白含量分别提高了26.72%、30.45%、17.69%、46.15%、46.43%、30.70%、38.75%、70.0%、65.37%;Rubisco加氧酶、蛋白水解酶活性和游离氨基酸总量分别降低了18.29%、31.76%、28.57%。外源NO通过促进淀粉酶和Rubisco羧化活性的提高和氧化活性的下降,维持了可溶性总糖含量的稳定;通过增强NR、GS和谷氨酸合酶(GOGAT)活性、抑制蛋白水解酶和谷氨酸脱氢酶(GDH)活性,降低叶片中游离氨基酸含量,增加了蛋白质的积累。本研究结论:碱性盐胁迫下,80μmol·L-1的SNP通过增强南瓜幼苗的光合碳代谢,促进了酮酸转化为氨基酸。通过提高氮代谢相关酶NR、GS、GOGAT活性,促使碳流由光合碳代谢转向氮代谢,维持了盐害下南瓜幼苗碳氮代谢的正常进行,增强了南瓜幼苗抵御Na_2CO_3胁迫的能力。     

内生真菌紫杉木霉ZJUF0986菌株及其活性代谢产物防治水稻纹枯病的效果

从南方红豆杉分离到的一种新内生真菌紫杉木霉Trichoderma taxi菌株ZJUF0986,与水稻纹枯病菌对峙培养。结果发现,该内生真菌通过菌丝缠绕附着等重寄生方式,导致纹枯病菌菌丝断裂或其内含物降解直至死亡。其产生的活性代谢产物也能强烈抑制纹枯病菌菌丝的生长,显著降低病原菌的菌核萌发率;对病原菌菌丝生长和菌核萌发的有效中浓度EC50分别为1．08和3．59μg／ml。盆栽试验结果表明,菌株ZJUF0986浓度80μg／ml的活性代谢产物对水稻纹枯病的防效达63．82％,与50μg／ml井冈霉素A的防治效果相当。     

Protoporphyrinogen IX-oxidizing activities involved in the mode of action of a new compound N-[4-chloro-2-fluoro-5-{3-(2-fluorophenyl)-5-methyl-4,5-dihydroisoxazol-5-yl-methoxy}-phenyl]-3,4,5,6-tetrahydrophthalimide

N-[4-Chloro-2-fluoro-5-{3-(2-fluorophenyl)-5-methyl-4,5-dihydroisoxazol-5-yl-methoxy}-phenyl]-3,4,5,6-tetrahydrophthalimide (EK-5385) is an experimental substituted bicyclic herbicide. Soil-applied EK-5385 showed good rice selectivity and potent herbicidal activity on barnyardgrass (Echinochloa crus-galli var. oryzicola) at rates of 3.9-250 g a.i./ha. Barnyardgrass was exhibited normal growth under dark condition, however, the growth of shoot and root was severely inhibited under light condition (14/10 h of light/dark, 50 μmol/m²/s of photosynthetically active radiation) when treated with EK-5385, oxadiazon, and oxadiargyl. IC₅₀ of EK-5385 and oxadiargyl to chlorophyll loss in cucumber cotyledons was approximately 0.3 and 0.7 μM, respectively. IC₅₀ of EK-5385 and oxadiargyl to carotenoids loss in cucumber cotyledons was about 0.26 and 0.1 μM, respectively. IC₅₀ concentration of EK-5385 and oxadiargyl on Protox activity was approximately 5.5 and 8 nM, respectively. Cellular leakage occurred without lag period from cucumber leaf squares treated with 1 μM of EK-5385 and oxadiargyl under light exposure.     

Effect of tricyclazole on growth and secondary metabolism in Pyricularia oryzae

Tricyclazole [5-methyl-1,2,4-triazolo (3,4-b)-benzothiazole] controls rice blast disease caused by Pyricularia oryzae at concentrations (5–10 μg/ml) which do not inhibit growth of the pathogen in vitro. However, concentrations of 1 μg/ml or less inhibit melanin formation in the fungus. Production of pyriculol by the pathogen is usually enhanced by 10 μg/ml of tricyclazole, whereas production of 3,4-dihydro-4,8-dihydroxy-1(2H)-naphthalenone is strongly inhibited or markedly reduced and delayed. Evidence suggests that tricyclazole blocks aspects of polyketide metabolism in P. oryzae which may have a role in pathogenicity.