Chemical and physiological characterization of taxa in theFusarium sambucinum complex

Forty-one isolates ofFusarium sambucinum sensu lato were screened for production of secondary metabolites in agar cultures. Of 16 strains ofF. sambucinum sensu stricto all but two strains produced diacetoxyscirpenol and two unidentified metabolites, TB1 and TB2 respectively. The two remainingF. sambucinum strains produced T-2 toxin, TB1 and TB2.Fusarium venenotum (6 strains) produced diacetoxyscirpenol and an unidentified metabolite BB.Fusarium torulosum (8 strains) produced wortmannin and antibiotic Y. The three species could be differentiated by their pattern of identified and unidentified metabolites detected by agar plug TLC combined with chemical data from HPLC-diode array detection of fungal extracts, and data on growth rates on potato sucrose agar and tannin sucrose agar.     

Production of type A trichothecenes and enniatin B byFusarium sambucinum Fuckel sensu lato

Twenty-nineFusarium isolates, representing three new taxa originated by Nirenberg fromF. sambucinum Fuckel sensu lato, namely:F. sambucinum Fuckel sensu stricto,F. venenotum Nirenb., andF. torulosum (Berk. & Curt.) Nirenb., were tested for in vitro production of toxic secondary metabolites on autoclaved corn kernels.F. sambucinum sensu stricto was able to produce type A trichothecenes and enniatin B (EB). In particular, amongst the 14 isolates tested, 5 produced only diacetoxyscirpenol (DAS) (up to 700 µg/g); 1 produced only neosolaniol (NEOS) (250 µg/g); 2 produced T-2 toxin (T-2) + NEOS (up to 175 and 150 µg/g, respectively); 1 produced NEOS + DAS (300 and 100 µg/g, respectively); and 5 produced DAS + EB (up to 500 and 140 µg/g, respectively). All six isolates ofF. venenotum were able to produce only DAS (up to 100 µg/g).F. torulosum produced no trichothecenes, but four out of nine tested isolates were able to produce EB (up to 140 µg/g). Zearalenones and type B trichothecenes were not found. The toxicity of the culture extracts towardsArtemia salina L. was correlated in general with the occurrence of the above toxins, except for someF. torulosum strains. However, the lack of correlation between the amounts of toxins recovered and toxic activity observed in theGeotrichum candidum Link ex Pers. andA. salina assays suggested the presence of unknown toxic compounds.     

Untersuchungen zur pathogenität und mykotoxinbildung von<Emphasis Type="Italic">Fusarium sambucinum</Emphasis>, dem erreger der trockenfäule an kartoffeln

Investigation into virulence and mycotoxin formation of the dry rot causing pathogen Fusarium sambucinum on potatos 11 strains ofFusarium sambucinum were isolated from tubers with dry rot symptoms from three different depots in the Land Brandenburg and Saxony-Anhalt. All isolates produced diacetoxyscripenol in artificially infected potato tubers. Additionally, two isolates produced T-2 and HT-2 toxins as well. The virulence and mycotoxin formation of the isolates was dependent on the potato varieties ‘Sieglinde’ and ‘Berber’ used in the experiment. The amount of diacetoxyscripenol in diseased tissue was positively correlated with the virulence of theF. sambucinum isolate and the susceptibility of the potato variety as well.     

Mycotoxin production of <Emphasis Type="Italic">Fusarium langsethiae</Emphasis> and <Emphasis Type="Italic">Fusarium sporotrichioides</Emphasis> on cereal-based substrates

The present study investigated and compared the mycotoxin production of two Fusarium species, F. sporotrichioides and F. langsethiae, isolated from grain samples. Fusarium strains were cultivated at 25°C for 7 days on two types of solid media, i.e. rice-flour and cereal-flour agar. Toxins produced were measured after the incubation period with a multi-mycotoxin method based on liquid chromatography–tandem mass spectrometry (LC-MS/MS). Both F. sporotrichioides and F. langsethiae synthesised type-A trichothecenes, i.e. T-2 and HT-2 toxins, diacetoxyscirpenol (DAS) and neosolaniol (NEO). In addition, both species could be verified as beauvericin producers. The toxin production occurred in both cereal-based assays but was more predominant on the carbohydrate-rich rice-flour medium. The two species were potent producers of T-2 toxin, the highest amounts measured being at a level of 20,000 μg/kg after 7 days’ incubation. Differences between the species were observed regarding the quantitative production of the other trichothecenes: F. sporotrichioides was a more prolific producer of HT-2 toxin and beauvericin, whereas F. langsethiae produced higher amounts of DAS and NEO. On rice-flour assay, the toxin production was monitored during the growth period. The production started rapidly at an early growth phase and several toxins could be detected already after the 1st day of incubation, the highest concentrations being at mg/kg level. The results also indicated that the biosynthesis by F. sporotrichioides and F. langsethiae shifted towards the other type-A trichothecenes at the expense of T-2 toxin at the end of the cultivation.     

Mycotoxin production by Fusarium species isolated from New Zealand maize fields

Forty Fusarium isolates obtained from maize fields were screened for moniliformin production on maize kernels. Twelve isolates, including seven of F. subglutinans, were found to produce moniliformin at levels ranging from 0.4 to 64 ppm. Twenty six isolates were also screened for production of deoxynivalenol, diacetoxyscirpenol, T-2 toxin and zearalenone. Of these, 22, including all 11 isolates of F. graminearum, produced zearalenone at levels ranging from 0.1 to 96.0 ppm, while 13 produced T-2 toxin at low levels, (<1.1 ppm). Deoxynivalenol and diacetoxyscirpenol were each produced by six isolates, also at low levels (<1.0 ppm). Three isolates of F. graminearum and one of F. sambucinum produced four toxins simultaneously.     

Toxicity ofFusarium sambucinum Fuckel sensu lato to brine shrimp

In a screening test sevenFusarium strains out of 17 proved to be toxic towards brine shrimp. Among these, fourF. sambucinum strains as well as threeF. venenatum isolates caused toxic effects. The chemical screening by TLC analysis revealed the presence of sambucinol and diacetoxyscirpenol in the extracts of the toxic isolates ofF. venenatum 64537.     

Diversity of the <Emphasis Type="Italic">Fusarium</Emphasis> species associated with head and seedling blight on wheat in Slovakia

Species associated with Fusarium head blight are depending on the production and edaphic conditions. The differences are found in the representation of various Fusarium spp. in the diseases, which sporadically occur all over the territory of Slovakia, in all agricultural production types. We identified fifteen Fusarium species during ten years of investigation. Most of the mentioned species F. culmorum (W.G. Smith) Sacc., F. graminearum Schwabe, recently F. cerealis (Cooke) Sacc. (crookwellense Burgess, Nelson & Tousson) and F. sambucinum Fuckel in diseased caryopsis are seed transmitted. The significant differences among species and intra species in cultural and pathogenicity assays in vitro and in vivo were correlated. Some of them are able to produce toxic metabolites — deoxynivalenone, which probably play a role in the aggressiveness of the pathogen and promote disease development and pathogen colonization.     

Production of zearalenone,nivalenol, moniliformin,and wortmannin from toxigenic cultures ofFusarium obtained from pasture soil samples collected in New Zealand

One culture ofF avenaceum, 4 cultures ofF oxysporum, and 11 cultures of Fsambucinum were isolated from soil samples of pasture in New Zealand in 1987. All cultures, when grown on rice media and fed to rats caused a weight loss in rats as well as toxic signs including hemorrhaging and congestion, uterine enlargement, and hematuria. 6 out of 16 cultures caused death in rat feeding tests.F oxysporum #1 killed rats (feeding test) within 5-12hrs. 10 cultures produced zearalenone (19 to 8,849 ppm), 8 cultures produced nivalenol (32 to 117 ppm), 1 culture,F sambucinum #8, produced wortmannin (40 ppm), and 5 cultures produced moniliformin (19 to 9,000ppm). We report for the first time the co-occurrence of zearalenone, nivalenol, and moniliformin produced byF sambucinum #3 in culture.F avenaceum #1 andF oxysporum cultures (nos 1, 2, and 3) produced moniliformin alone.F oxysporum #4 produced zearalenone alone as well.F sambucinum #5 caused erythema in the small intestine of rats and 100% mortality and did not produce any known toxin(s). Nivalenol when administered to the stomach of rats orally at levels 10, 20, and 40mg/kg body weight caused inflammation in the intestines, coma, and death. The mycotoxins T-2 toxin, HT-2 toxin, T-2 tetraol, diacetoxyscirpenol (DAS), monoacetoxyscirpenol (MAS), deoxynivalenol (DON), 3-acetyl-and 15-acetyldeoxynivalenol, depoxynivalenol, fusarenon-X, alpha-and beta-zearalenone, and fusarochromanone (TDP-1) were not detected in the extracts of these cultures.     

Variation in Endogenous Gibberellins,Abscisic Acid,and Carbohydrate Content During the Growth Cycle of Colored <Emphasis Type="Italic">Zantedeschia</Emphasis> spp., a Tuberous Geophyte

Phenologic changes and variation in the level of endogenous gibberellins (GAs), abscisic acid (ABA), carbohydrate content, and α-amylase activity were examined in colored Zantedeschia spp. cv. Cala Gold. These changes were examined in the primary bud tissues and in the attached tuber tissue during the growth cycle. Dormant tubers were dry-stored at 20°C for 3 months, planted in a phytotron, and grown under 22/16 ± 1°C. Plant development was monitored under continued irrigation until leaf senescence and tuber dormancy. GAs and ABA were extracted from the primary bud tissues, fractionated by HPLC, and analyzed using GC-SIM. Starch, glucose, soluble protein, and α-amylase activity were monitored in the tuber tissue attached to the primary bud. Endogenous changes in GAs and ABA in the primary bud were correlated with endogenous changes in carbohydrate content and α-amylase activity in the attached tuber tissue. These correlations were observed during the rest and the growth periods and were associated with developmental changes in the plant, that is, bud dormancy relaxation, bud growth, and inflorescence differentiation. ABA content decreased and a transient pulse of GA was measured in the primary bud concomitantly with the onset of shoot elongation in dry tubers during storage, before planting. The sharp increase of GAs in the bud preceded inflorescence differentiation as observed in dissected apices by about 15 days, as well as the increase in α-amylase activity in the attached tuber tissue. A steep decrease in starch level was measured in the tuber after planting, concomitantly with massive plant growth. These findings suggest a possible involvement of gibberellin in the initiation of α-amylase activity during dormancy relaxation in colored Zantedeschia and in the autonomous induction of flowering.     

Propagation and tuberization of potato bud clusters from bioreactor culture

Summary Single node stem segments fromin vitro potato shoots cultured in liquid medium in the presence of ancymidol (23.4 μM) developed into bud clusters in either shaken flasks or bioreactor cultures. Buds on the clusters developed tubers after subculture to a tuber induction medium with 23.2 μM kinetin, 19.5 μM ancymidol, and 6-8% sucrose. The number of tubers per cluster and their size were higher in agar induction medium on top of which a second layer of liquid medium was added, than in liquid shake or bioreactor cultures. The highest increase in tuber size (i.e., 720 mg fresh weight after 7 weeks), was obtained in agar cultures flushed twice with liquid tuber induction medium. The potential of bioreactor cultures for potato bud proliferation and enhanced tuber development in double layer agar-liquid cultures is discussed.     

Tuber formation and growth of <Emphasis Type="Italic">Dioscorea cayenensis-D. rotundata</Emphasis> complex: interactions between exogenous and endogenous jasmonic acid and polyamines

Tubers can be initiated and developed in vitro from nodal cuttings of yam (Dioscorea cayenensis-D. rotundata complex). The effect of exogenous jasmonic acid, alone or in combination with putrescine, on these processes was investigated in relationship to endogenous jasmonic acid and polyamine levels. Application of exogenous jasmonic acid at various concentrations positively affected microtuber formation and growth from yam nodal cuttings. In control conditions, 3 weeks were needed to obtain 100% of tuberisation. Jasmonic acid at low level (0.1 μM) accelerated tuber formation (46% after 1 week) as did putrescine (10 μM). But endogenous levels of jasmonic acid were not significantly affected by its exogenous presence in the medium. Jasmonic acid also interacted with other growth regulators as polyamines, but the decrease in time necessary to observe tuber formation could not be correlated with endogenous modifications of PUT content. The presence of jasmonic acid (0.1–1 μM) as PUT (1 μM) induced also an increase of tuber length and weight. The combination of jasmonic acid (0.1 μM) and putrescine (1 μM) had no positive effect on tuber formation (precocity) but had an additive effect on further growth (length and weight). In the future, these results could help the optimising in vitro conditions for mass production of larger yam microtubers.     

Effect of chitosan for the control of potato diseases caused by Fusarium species

The antifungal activity of chitosan against Fusarium spp. was investigated based on in vitro and in vivo assays, and its possible modes of action were also explored. Chitosan applied at 4.0 g/L of acetic acid-distilled water solution significantly decreased the mycelial growth of Fusarium oxysporum, Fusarium sambucinum and Fusarium graminearum by 88.4%, 89.0% and 89.8%, respectively. Tuber treatment by chitosan (4.0 g/L) of acetic acid-distilled water solution, prior to inoculation, reduced dry rot severity induced by F. oxysporum and F. sambucinum by 60.0% and 48.2%, respectively. When tested as plant treatment, potato plants inoculated with Fusarium species, exhibited 33.5%–45.3% less wilting severity as compared to the control. This abiotic treatment improved the phenolic compounds activities and defence-related enzymes such as peroxidase and polyphenoloxidase in potato tubers inoculated with Fusarium spp. Results clearly demonstrated that chitosan could be explored as an alternative agent to chemical fungicides for the control of tuber dry rot and Fusarium wilt through induction of the plant defence system.     

Effects of<Emphasis Type="Italic">Fomitopsis pinicola</Emphasis> extracts on antioxidant and antitumor activities

We investigated the effects ofFomitopsis pinicola extract on biological activity by examining the antioxidant and antitumor activityin vitro andin vivo. When theF. pinicola extract concentration was raised from 60 to 120 μg/mL, the DPPH scavenging rate increased from 50.3 to 88.2% and the superoxide anion radical scavenging rate increased from 45.2 to 85.3% when theF. pinicola extract concentration was raised from 500 to 700 μg/mL. After incubatingF. pinicola extract for 12 h, the linoleic acid scavenging rate increased from 35.5 to 90.5%. A similar finding was observed for butylated hydroxytoluene. The total phenolic content of theF. pinicola extracts were approximately 10- to 16-fold higher than what was observed in theP. nebrodensis andA. camphorate extracts. The glutathione production, using decoctions prepared fromF. pinicola, was 20.0 μM/g of liver, which corresponded to approximately 4.0-fold higher than the control. The glutathione peroxidase activity was 8.3 U/mg of protein, which was approximately 2.8-fold higher than the activity level observed in the control rat livers. The cell viability rates of all the human cancer cells, when 100 μg/mL of ethanol extract was used for the different types of cancer cells, decreased with increasing extract concentrations in comparison to the hot water extract. In particular, when HeLa and Hep3B cells were incubated with 1.000 μg/mL of methanol extract, the cell viability rates were 20 and 25%, respectively, which was approximately 3.0-fold higher than what was observed for the hot water extract. The first two authors contributed equally to this work.     

Soil Patches of Inorganic Nitrogen in Subtropical Brazilian Plant Communities with Araucaria angustifolia

One-year old tubers of two hybrid calla lily (calla) cultivars (Zantedeschia ‘Pot of Gold’ and ‘Majestic Red’) were inoculated with the arbuscular mycorrhizal fungus (AMF), Glomus intraradices, or not, and grown at three different rates of phosphorus (P) supply to asses the effects of AMF-inoculation on plant development (time of shoot emergence and flowering), flowering (number, length and rate of flowering), and tuber biomass and composition over two growing cycles (2002, 2003). Tubers and flowers of calla responded differently to AMF inoculation. Differences in mycorrhizal responsiveness between cultivars was related to differences in P requirements for flower and tuber production, and the influence of P supply on resource allocation to different reproductive strategies. Inoculation increased shoot production and promoted early flowering, particularly in 2003. Inoculated plants also produced larger tubers than non-inoculated plants, but only increased the number of flowers per plant in 2003. High P supply also increased tuber biomass, but decreased the number of flowers per plant in 2002. Plants grown at a moderate P-rate, produced the most flowers in 2003. For ‘Majestic Red’, benefits from AMF were primarily in terms of tuber yield and composition, and AMF effects on marketable flower production could potentially have negative impact on production strategies for growers. Inoculation of ‘Pot of Gold’ primarily influenced flower production and aspects of tuber quality that caused detectable enhancement of tuber yield and flowering in the second growing cycle following inoculation (2003). The results of this study show that the responses of calla to AMF are partially a function of how nutrient supply alters resource allocation to sexual and vegetative reproduction. Whether AMF-induced changes in resource allocation to flowering and tubers significantly alters commercial productivity and quality of calla depends on the crop production goals (e.g. tubers, cut flowers or potted plants). The U.S. Government’s right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged.     

Effects of Methyl jasmonate with indole-3-acetic acid and 6-benzylaminopurine on the secondary metabolism of cultured <Emphasis Type="Italic">Onosma paniculatum</Emphasis> cells

Summary Methyl jasmonate (MeJA) interacted significantly with both indole-3-acetic acid (IAA) and 6-benzylaminopurine (BA) to influence cell growth of cultured Onosma paniculatum cells. Cell growth decreased with increasing concentrations of MeJA from 0.004–4.45 μM with or without IAA and BA. The same concentrations of MeJA (0–4.45 μM) increased the cell growth with IAA and BA, when administered to the cultured cells in M₉ medium. This was found to enhance the production of shikonin. The optimum time for MeJA addition for enhanced shikonin formation was 4 d after cell inoculation in M₉ medium. Furthermore, shikonin formation was affected significantly by both MeJA/IAA and MeJA/BA combinations. Shikonin content was enhanced by increasing MeJA concentrations with IAA concentrations in the range of 0–28 μM and with BA concentrations in the range of 0–44.38 μM in MeJA/BA experiments, respectively. The optimal combination of MeJA and IAA was 4.45 μM and 0.28 μM, while MeJA and BA concentrations of 4.45 μM and 2.22 μM were optimal for shikonin formation. The result also showed that MeJA increased phenylalanine ammonia-lyase (PAL) and p-hydroxybenzoic acid-geranyltransferase (PHB-geranyltransferase) activites during the course of shikonin formation, but decreased the activity of PHB-O-glucosyltransferase within 9 d after inoculation. These results suggest that enhanced shikonin formation in cultured Onosma paniculatum cells induced by MeJA involves regulation of the key enzyme activities.     

<Emphasis Type="Italic">Strboh A</Emphasis> homologue of NADPH oxidase regulates wound-induced oxidative burst and facilitates wound-healing in potato tubers

During 30-months of storage at 4°C, potato (Solanum tuberosum L.) tubers progressively lose the ability to produce superoxide in response to wounding, resist microbial infection, and develop a suberized wound periderm. Using differentially aged tubers, we demonstrate that Strboh A is responsible for the wound-induced oxidative burst in potato and aging attenuates its expression. In vivo superoxide production and NADPH oxidase (NOX) activity from 1-month-old tubers increased to a maximum 18–24 h after wounding and then decreased to barely detectable levels by 72 h. Wounding also induced a 68% increase in microsomal protein within 18 h. These wound-induced responses were lost over a 25- to 30-month storage period. Superoxide production and NOX activity were inhibited by diphenylene iodonium chloride, a specific inhibitor of NOX, which in turn effectively inhibited wound-healing and increased susceptibility to microbial infection and decay in 1-month-old tubers. Wound-induced superoxide production was also inhibited by EGTA-mediated destabilization of membranes. The ability to restore superoxide production to EGTA-treated tissue with Ca⁺² declined with advancing tuber age, likely a consequence of age-related changes in membrane architecture. Of the five homologues of NOX (Strboh A-D and F), wounding induced the expression of Strboh A in 6-month-old tubers but this response was absent in tubers stored for 25–30 months. Strboh A thus mediates the initial burst of superoxide in response to wounding of potato tubers; loss of its expression increases the susceptibility to microbial infection and contributes to the age-induced loss of wound-healing ability.     

Gibberellic acid regulation of adventitious shoot formation from tuber discs of potato

Summary The formation of adventitious shoots from potato tuber discs explanted onto a modified Murashige and Skoog (MS) medium containingN ⁶-benzylaminopurine (BAP) (3.0 mg/l), and α-naphthaleneacetic, acid (NAA) (0.01 mg/l), was affected by gibberellic acid (GA). The presence of GA in the explant medium was required for shoot formation and 3×10⁻¹⁰ M GA appeared optimum. However, microscopic examination of the tissue protuberances on the surface of the tuber discs from which shoots arose revealed that GA inhibited the formation of shoot meristems. Tuber discs cultured for 6 wk on MS medium containing BAP and NAA without GA did not initiate adventitious shoots that could be determined visually, but microscopic examination of the tissue protuberances revealed the presence of numerous shoot meristems. Subsequent transfer of these tuber discs to medium with GA but without BAP or NAA resulted in the formation of shoots from 100% of the recultrued dises. Thus it appears that although GA inhibits shoot meristem initiation from potato tuber discs, it is required for shoot development once meristems are initiated. This is Journal Paper 8297 of the Purdue University Agricultural Experiment Station. The research was supported by Purdue University Agricultural Experiment Station Program Improvement Funds. Potato tubers were supplied by Wm. Gehring Farms, Inc., Rensselaer, Indiana.     

Effect of culture filtrates ofXanthomonas campestris pv.pelargonii and extracts of geranium stems inoculated withX. c. pv.pelargonii on geranium callus and seedlings

Experiments were designed to determine whetherXanthomonas campestris pv.pelargonii produces a toxin which induces symptoms of bacterial blight in geranium, and is active at the cellular level. Culture filtrates ofX. c. pv.pelargonii were prepared by ethyl acetate extraction and ultrafiltration of the aqueous fraction. Culture filtrates adjusted to several pH values induced maximum disease ratings on geranium seedlings in the pH range 7–10. Geranium callus growth was significantly reduced by the filtrate in the same pH range. An active fraction could also be isolated from diseased tissue. A thin-layer chromatography-callus bioassay system detected toxin activity in the culture filtrate and in extracts of geranium stems inoculated withX. c. pv.pelargonii. Callus growth inhibition was located at R_f = 0.2–0.3 for both sources of toxin. These results suggest thatX. c. pv.pelargonii produces a toxin which causes disease symptoms, is present in diseased tissues, and inhibits callus growth. This opens the possibility of developing resistance to this pathogen by selecting cells insensitive to the toxin and regenerating plants from these cells.     

Phosphite uptake and distribution in potato tubers following foliar and postharvest applications of phosphite‐based fungicides for late blight control

Foliar and postharvest applications of phosphite (Phi)‐based fungicides are used to control the oomycete Phytophthora infestans which is responsible for the occurrence of late blight in potatoes. Optimisation of the usage of Phi‐based fungicides for disease control during the growing season and in subsequent storage can lead to improved potato production and processing quality. In order to assess the efficiency of Phi translocation to tubers, following foliar and postharvest treatments of potato crops with the Phi‐based fungicides, the amount of Phi in tubers was determined by a high‐performance ion chromatography method. The quantity of Phi found in tubers increased with the total amount of Phi‐based fungicides applied during the growing season. Foliar applications of Phi resulted in an uneven distribution of Phi in the three tuber regions analysed, with high concentrations being identified in the tuber cortex (32.5–166.4 µg g^?1 fresh tissue) and medulla regions followed by the skin area. Postharvest treatment of tubers led to a different distribution of Phi, with the highest concentrations of Phi found in the skin (411.0–876.6 µg g^?1 fresh tissue) followed by the cortex and medulla regions. As foliar treatments are essential to protect the aerial parts of the plants during the growth season, the best disease management practices of tubers should include the postharvest treatment in addition to foliar applications. The use of both types of treatments ensures that concentrations of Phi in excess of 100 µg g^?1 fresh tissue are present in tuber skin and cortex areas; such concentrations are needed to suppress the growth of P. infestans on tubers during storage.     

Mint essential oil can induce or inhibit potato sprouting by differential alteration of apical meristem

Sprouting of potatoes during storage, due to tuber dormancy release, is associated with weight loss and softening. Sprout-preventing chemicals, such as chlorpropham (CIPC), can negatively impact the environment and human health. Monthly thermal fogging with mint (Mentha spicata L.) essential oil (MEO) inhibited sprouting in eight potato cultivars during large-volume 6-month storage: the tubers remained firm with 38% lower weight loss after 140 days of storage. The sprout-inhibitory action may be nullified: treated tubers washed with water resumed sprouting within days, with reduced apical dominance. MEO application caused local necrosis of the bud meristem, and a few weeks later, axillary bud (AX) growth was induced in the same sprouting eye. MEO components analysis showed that 73% of its content is the monoterpene R-carvone. Tubers treated with synthetic R-carvone in equivalent dose, 4.5 μl l⁻¹, showed an inhibitory effect similar to that of MEO. Surprisingly, 0.5 μl l⁻¹ of MEO or synthetic R-carvone catalyzed AX sprouting in the tuber. To the best of our knowledge, this is the first report of an essential oil vapor inducing early sprouting of potato tubers. R-carvone caused visible damage to the meristem membrane at sprout-inhibiting, but not sprout-inducing doses, suggesting different underlying mechanisms. After 5 days’ exposure to R-carvone, its derivatives transcarveol and neo-dihydrocarveol were found in buds of tubers treated with the inhibitory dose, suggesting biodegradation. These experiments demonstrate the potential of MEO vapor as an environmentally friendly alternative to CIPC in stored potatoes and as a research tool for the control of sprouting in plants.