A selective and indicative medium for groups of Penicillium viridicatum producing different mycotoxins in cereals

A medium, pentachloronitrobenzene-rose bengal-yeast extract-sucrose agar (PRYES), for the isolation of moulds occurring during storage of cereals has been developed and compared with other selective media. The basal medium is yeast extract agar containing 15% sucrose (w/v). In addition to the sucrose content further selective measures include the addition of antibacterial antibiotics chloramphenicol and chlortetracycline (50 mg/l), the fungicides rose bengal (25 mg/l each), and pentachloronitrobenzene (1 g/l) and a low incubation temperature (20 degrees C). Members of the Mucorales were completely inhibited, and fast-growing species of other moulds were slightly inhibited, allowing important storage moulds to develop. The important ochratoxin A and citrinin-producing Penicillium viridicatum group II was indicated by a typical violet brown reverse on PRYES. Producers of xanthomegnin and viomellein (P. viridicatum group I and P. aurantiogriseum) were indicated on PRYES by their yellow reverse and obverse colours. The medium was used for screening 40 samples of barley, and moulds with the characteristic colours were all identified as the species mentioned above.     

Physiological criteria and mycotoxin production as AIDS in identification of common asymmetric penicillia

The taxonomy of the asymmetric (predominantly terverticillate) penicillia is based on morphological differences that leave identification difficult. The application of physiological criteria facilitated the identification of the common asymmetric penicillia investigated. Changes in the placement of some strains of these penicillia made the connection to mycotoxin-producing ability clearer. The classical criterion of conidium color was deemphasized and replaced by the following criteria: (i) growth on nitrite-sucrose agar and (ii) growth and acid (and subsequent base) production on creatine-sucrose agar (containing bromocresol purple). Other criteria used or developed were: (iii) growth on sorbic acid plus benzoic acid agar (50 + 50 ppm, pH 3.8), (iv) growth on an agar containing 1,000 ppm propionic acid (pH 3.8), (v) growth on an agar containing 0.5% acetic acid, (vi) growth at 37 degrees C, (vii) growth rate on an agar containing 0.1% pentachloronitrobenzene, (viii) production of extracellular tricaproinase, and (ix) fasciculation on a medium containing 10 ppm botran (2,6-dichloro-4-nitroanilin). The pattern of extracellular metabolites after thin-layer chromatography was used as a chemotaxonomic criterion. The species investigated, the number of isolates investigated, and the toxins which some of these isolates produce were: Penicillium roqueforti (18) (patulin), P. citrinum (11) (citrinin), P. patulum (9) (patulin and griseofulvin), P. expansum (patulin and citrinin), P. hirsutum (13), P. brevicompactum (19), and P. chrysogenum (12). Widespread species of the P. cyclopium, P. viridicatum, and P. expansum series of Raper and Thom (A Manual of the Penicillia, 1949) were subdivided into four new groups: "P. crustosum pA" (29) (penitrem A), "P. melanochlorum" (29), "P. cyclopium p" (119) (penicillic acid and infrequently penitrem A), and "P. viridicatum o-c" (43) (ochratoxin A and citrinin). "P. viridicatum o-c" was separated from "P. cyclopium p" due to its ability to grow on nitrite as sole nitrogen source. The species and groups investigated were related to the new taxonomic classification of the genus Penicillium according to Pitt.     

Induction of direct somatic organogenesis in onion (Allium cepa L.) using a two-step flower or ovary culture

A novel method for direct organogenesis in onion (Allium cepa L.) resulting in the formation of multiple shoot structures induced on mature flower buds or ovaries in a two-step culture procedure is described. Flowers were cultured on an induction medium containing 2 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D) and 2 mg/l 6-benzylaminopurine (BAP). After 6 days (superior to 3 or 12 days), flowers or extracted ovaries were transferred to a differentiation medium containing 2 mg/l thidiazuron (TDZ). Medium solidification with gellan gum was superior to agar or agar/gellan gum mixture. A similar regeneration frequency was achieved at high (100 g/l) and lower (50 g/l) sucrose content. Regeneration was obtained from all 12 cultivars or inbred lines examined, although the efficiency and the occurrence of hyperhydricity varied depending on genotype and procedure used. Studies of plant growth regulators revealed that in the induction medium, the auxin 2,4-D was superior to 5 mg/l naphthaleneacetic acid or picloram, which partially or completely inhibited regeneration. Omitting cytokinin in the induction medium or substitution of BAP with 2 mg/l 2iP lowered regeneration, while substitution with 1 mg/l TDZ was equally effective. In the differentiation medium, lower concentrations of TDZ (1 and 0.5 mg/l) or substitution of TDZ with 5 mg/l BAP were equally or less effective. Received: 14 October 1998 / Revision received: 19 November 1998 / Accepted: 30 November 1998     

Establishment of Croton stellatopilosus suspension culture for geranylgeraniol production and diterpenoid biosynthesis

Diterpenoids in higher plants are biosynthesized from isoprene units obtained from two distinct pathways: the mevalonate pathway and the deoxyxylulose phosphate pathway. The metabolic partitioning of both pathways in plant species is dependent upon the type of culture. In order to study the diterpenoid biosynthesis in Croton stellatopilosus cell culture, callus culture was firstly induced from C. stellatopilosus young leaves in Murashige and Skoog (MS) medium in the presence of 1.0 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D), 1.0 mg/l benzyladenine (BA), 3% (w/v) sucrose and 0.8% (w/v) agar. The suspension culture was further induced from its callus in the same medium without gelling agent. Detection of diterpenoid accumulation by gas chromatography-mass spectrometry revealed that a cell culture could accumulate a low amount of geranylgeraniol (GGOH) and a high content of fatty acids and phytosterols. To improve the GGOH production, the culture conditions were optimized by medium manipulation in terms of hormonal factors. The growth rates of cell cultures were similar in all kinds of media. The GGOH production curve indicated that GGOH plays an important role as a primary metabolite in the cell culture. The optimum medium for GGOH production was MS medium supplemented with 2.0 mg/l 2,4-D and 2 mg/l BA that could produce GGOH with a yield of 1.14 mg/g FW.     

Identification of NephrotoxicPenicillium Species from Cereal Grains

A system is described for identifying grain-inhabiting nephrotoxicPenicillium spp. based on their colony characters on Czapek yeast extract agar, yeast extract sucrose agar, and malt extract agar media, and their secondary metabolite profiles on thin layer chromatography plates. Using this system, the identity of 11Penicillium species, or their chemotypes, producing nephrotoxic metabolites could be confirmed. The species areP. verrucosum chemotype I, P.verrucosum chemotype II,P. expansum, P. citrinum, P. aurantiogriseum, P. freii, P. tricolor, P. polonicum, P. viridicatum, P. cyclopium, and P. melanoconldlum. Other non-nephrotoxicPenicillium species present on stored grains were separated from nephrotoxic species by their colony characters and metabolite profiles.     

Isolated microspore derived plant formation via embryogenesis in Triticum aestivum L.

Embryogenesis in isolated microspores of wheat (Triticum aestivum L.) leading to plant regeneration has been established on modified liquid N6 medium (supplemented with 2,4-D, casein hydrolysate and Ficoll). Globular embryoids which were obtained after 6–8 weeks of culture of competent embryogenic microspores produced perfect embryoids when transferred to regeneration medium. Embryoids were differentiated to plants on other modified N6 agar medium (0.75% w/v agar, 20 g/l sucrose, 1 g/l myo-inositol, 8.8 μM 6-benzylaminopurine (BAP), 11.4 μM indoleacetic acid (IAA), 160 mg/l glutamine, 10 mg/l proline). Responses of microspores in regeneration and embryoid differentiation varied depending on the constituents of the media and genotypes used.     

Susceptibility of fungi isolated from clinical materials to voriconazole

The objective of the study was evaluation of the susceptibility of 139 fungal strains isolated from clinical materials to Voriconazole, a new antifungal agent of the triazole group. A dilution method was used. The drug was incorporated into the culture medium at concentrations 0.1-100 mg/l. It was found out that the antifungal effectiveness of the drug varied both between various fungal genera and species, and between strains within the same species. Total inhibition of the growth of 20% of the yeast-like fungi and 23.3% of the moulds was achieved at concentration 0.1 mg/l. It was documented that the species Candida guilliermondii, C. kefyr, Saccharomyces cerevisiae and Aspergillus fumigatus, that as a rule are resistant to triazoles, were highly susceptible to Voriconazole. Dermatophytes, too, were highly susceptible to the drug, particularly Trichophyton mentagrophytes and T. rubrum. The drug at concentration 0.1 mg/l totally inhibited 73.5% of the dermatophytes, and at concentration 1 mg/l--97.0% of them after 7 day incubation. After 14 day incubation, 97.0% of the strains were also inhibited at drug concentration not exceeding 1 mg/l.     

Establishment of a highly efficient transformation system for pepper (Capsicum annuum L.)

Application of modern genetic manipulation has been limited in pepper ( Capsicum annuum L.) due to the lack of an efficient transformation system. Following the development of an efficient protocol for in vitro regeneration of pepper cotyledons, we investigated the key factors affecting transformation and established a highly efficient genetic transformation system using the pepper cotyledon as starting material. In this system, cotyledon explants are preconditioned for 2 days on kanamycin (km)-free DM1 medium [Murashige and Skoog (MS) salts/Gamborg B5 vitamins basal medium supplemented with 20 g/l sucrose, 5,000 mg/l DJ nutrients and a hormone combination of 1.0 mg/l indoleacetic acid (IAA) and 5.0 mg/l 6-benzyladenine (BA) solidified with 0.7% agar, pH 5.8], followed by co-cultivation with Agrobacterium tumefaciens on DM1 for 2 days and delay selection on DM1 with 500 mg/l carbenicillin (carb) for 2 days. The explants are then placed on DM1 containing 10 mg/l AgNO(3), 50 mg/l km-sulfate and 500 mg/l carb. After 4-5 weeks, the explants with buds are transferred to EM1 medium (MS salts/Gamborg B5 vitamins basal medium supplemented with 20 g/l sucrose, 5,000 mg/l DJ nutrients, 10 mg/l AgNO(3) and a hormone combination of 1.0 mg/l IAA, 3.0 mg/l BA and 2.0 mg/l gibberellic acid, solidified with 0.7% agar, pH 5.8) with 50 mg/l kanamycin and 500 mg/l carbenicillin for the elongation of buds. After 3-6 weeks, 1- to 2-cm-long elongated shoots are excised and planted on RM1 medium (MS basal medium supplemented with a hormone combination of 0.2 mg/l NAA and 0.1 mg/l IAA, solidified with 0.8% agar, pH 5.8) with 25 mg/l km and 200 mg/l carb for rooting. We tested four genotypes of pepper, and all presented a high differentiation efficiency (81.3% on average), elongation rate (61.5%) and rooting efficiency (89.5%). Polymerase chain reaction analysis results showed that 40.8% of the regenerated plantlets were transgenic plants.     

陇东地区野生紫花苜蓿植株再生体系的建立

以陇东地区野生紫花苜蓿无菌苗的下胚轴、子叶、叶片和叶柄为外植体,MS为基本培养基,研究划破种皮以及不同生长调节物质种类与配比对愈伤组织诱导和分化影响的结果表明：划破种皮可提高种子发芽率;在外植体中下胚轴的愈伤组织诱导率最高,达92.2%;最佳愈伤组织诱导培养基为MS＋2,4-D2.0mg·L^-1（单位下同）＋NAA1.0＋2.5%蔗糖＋0.6%琼脂,最佳分化诱导培养基为MS＋KT0.5＋NAA0.3＋2.5%蔗糖＋0.6%琼脂,成苗培养基为1/2MS＋NAA0.1＋1%蔗糖＋0.6%琼脂。     

New selective agent for isolation of Pseudomonas aeruginosa.

Results of minimal inhibitory concentration tests with a diversity of bacterial strains showed that 9-chloro-9-(4-diethylaminophenyl)-10-phenylacridan (C-390) inhibited the growth of all microorganisms tested (other than Pseudomonas aeruginosa) at 25 microgram/ml or less, whereas MICs obtained for P. aeruginosa ranged from to to greater than 100 microgram/ml. Therefore, C-390 was evaluated as a potential selective agent for P. aeruginosa in pseudomonas agar F. Recovery tests were conducted on this medium with 53 strains o P. aeruginosa, and the results were compared to those obtained in similar tests on commercially available selective media, i.e., pseudomonas isolation agar and Pseudosel agar. The results of these comparisons indicated that pseudomonas agar F with C-390 was significantly less inhibitory than Pseudosel agar and pseudomonas isolation agar and more selective than pseudomonas isolation agar. The incorporation of C-390 in pseudomonas agar F also provided a medium that was both selective and differential. Preliminary evidence also suggested that C-390 may be added to other basal media with comparable results.     

Ampicillin-dextrin agar medium for the enumeration of Aeromonas species in water by membrane filtration

Published selective media were evaluated for the isolation of Aeromonas spp. from environmental samples by membrane filtration. Satisfactory recoveries were obtained only with mA agar (Rippey & Cabelli) and dextrin-fuchsin-sulphite agar (Schubert), but neither was sufficiently selective. The positive aspects of these two media were combined in a new medium, ampicillin-dextrin agar. Recovery from pure cultures and environmental samples was optimal at an ampicillin concentration of 10 mg/l and incubation for 24 h at 30 degrees C under aerobic conditions, and specificity was high (i.e. confirmation rate usually greater than 90%, no false negative colonies encountered). The medium can also be used for isolation of Aeromonas spp. from sea water provided that the vibriostatic agent 0/129 is added at 50 mg/l.     

Penicillium viridicatum, Penicillium verrucosum, and production of ochratoxin A

The taxonomy of the important mycotoxigenic species Penicillium viridicatum and P. verrucosum was reviewed to clarify disagreements relating to the three P. viridicatum groups erected by Ciegler and coworkers (A. Ciegler, D. I. Fennell, G. A. Sansing, R. W. Detroy, and G. A. Bennett, Appl. Microbiol. 26:271-278, 1973) and the mycotoxins produced by them. Cultures derived from the types of these two species and authentic cultures from each group and from many other sources were examined culturally, microscopically, and for mycotoxin production. It was concluded that P. viridicatum group II has affinities with P. verrucosum and not with P. viridicatum, as indicated by J. I. Pitt in the 1979 monograph (The Genus Penicillium and Its Teleomorphic States Eupenicillium and Talaromyces). As a result of this study it can now be unequivocally stated that the mycotoxins ochratoxin A and citrinin are not produced by P. viridicatum. Of species in subgenus Penicillium, only P. verrucosum is known to produce ochratoxin A.     

Penicillium viridicatum, Penicillium verrucosum, and production of ochratoxin A.

The taxonomy of the important mycotoxigenic species Penicillium viridicatum and P. verrucosum was reviewed to clarify disagreements relating to the three P. viridicatum groups erected by Ciegler and coworkers (A. Ciegler, D. I. Fennell, G. A. Sansing, R. W. Detroy, and G. A. Bennett, Appl. Microbiol. 26:271-278, 1973) and the mycotoxins produced by them. Cultures derived from the types of these two species and authentic cultures from each group and from many other sources were examined culturally, microscopically, and for mycotoxin production. It was concluded that P. viridicatum group II has affinities with P. verrucosum and not with P. viridicatum, as indicated by J. I. Pitt in the 1979 monograph (The Genus Penicillium and Its Teleomorphic States Eupenicillium and Talaromyces). As a result of this study it can now be unequivocally stated that the mycotoxins ochratoxin A and citrinin are not produced by P. viridicatum. Of species in subgenus Penicillium, only P. verrucosum is known to produce ochratoxin A.     

Plant regeneration from leaf protoplasts of Solanum torvum

A protocol to obtain regenerated plants from protoplasts of Solanum torvum Sw a wild species of eggplant resistant to Verticillium wilt is reported. Leaf protoplasts were enzymatically isolated from six-week old seedlings grown in a controlled environment chamber. Protoplasts were plated on modified KM medium (0.4 M glucose)+(mg/l): 1.0 p-chlorophenoxyacetic acid (CPA)+1.0 naphthaleneacetic acid (NAA)+0.5 6-benzylaminopurine (BAP) and 0.02 abscisic acid (ABA). The protoplast density was 5×10⁴ per ml with 5 ml placed in each of two quadrants in X-dishes (100×15 mm). The reservoir medium was modified KM+(mg/l): 0.1 NAA+0.5 BAP+0.1 M sucrose+0.1 M mannitol+0.6% washed agar+1% activated charcoal. Dishes were initially placed in the dark at 27°C. Protoplast division was initiated in 1–2 weeks and 4 weeks later p-calli were 1–3 mm. Plating efficiency was 11% when measured at 3 weeks. Six-week old p-calli were transferred individually onto Whatman No. 1 filter paper layered on modified KM (0.15 M sucrose)+mg/l: 2.0 indoleacetic acid (IAA)+2.0 zeatin+0.5% washed agar for 2 weeks. Subsequently, shoots occurred within 4 weeks at 70% efficiency on MS+30 g/l sucrose+2 mg/l zeatin. Shoots were rooted on half strength MS+10 g/l sucrose.Abbreviations ABA abscisic acid - BAP 6-benzylaminopurine - CPA p-chlorophenoxyacetic acid - IAA indoleacetic acid - KM Kao and Michayluk - MS Murashige and Skoog - NAA naphthaleneacetic acid - 2ip 6-dimethylallyamino purine Michigan Agricultural Experiment Station Journal Article No. 12167     

Classification of terverticillate penicillia based on profiles of mycotoxins and other secondary metabolites

Strains of available terverticillate penicillium species and varieties were analyzed for profiles of known mycotoxins and other secondary metabolites produced on Czapek yeast autolysate agar (intracellular metabolites) and yeast extract-sucrose agar (extracellular metabolites) by using simple thin-layer chromatography screening techniques. These strains (2,473 in all) could be classified into 29 groups based on profiles of secondary metabolites. Most of these profiles of secondary metabolites were distinct, containing several biosynthetically different mycotoxins and unknown metabolites characterized by distinct colors and retardation factors on thin-layer chromatography plates. Some species (P. italicum and P. atramentosum) only produced one or two metabolites by the simple screening methods. The 29 groups based on profiles of secondary metabolites were known species or subgroups thereof. These species and subgroups were independently identifiable by using morphological and physiological criteria. The species accepted, the number of isolates in each species investigated, and the mycotoxins they produced were: P. atramentosum, 4; P. aurantiogriseum, 510 (group I: penicillic acid and S-toxin and group II: penicillic acid, penitrem A [low frequency], terrestric acid [low frequency], viomellein, and xanthomegnin); P. brevicompactum, 81 (brevianamid A and mycophenolic acid); P. camembertii group I, 38, and group II, 114 (cyclopiazonic acid); P. chrysogenum, 87 (penicillin, roquefortine C, and PR-toxin); P. claviforme, 4 (patulin and roquefortine C); P. clavigerum, 4 (penitrem A); P. concentricum group I, 10 (griseofulvin and roquefortine C), and group II, 3 (patulin and roquefortine C); P. crustosum, 123 (penitrem A, roquefortine C, and terrestric acid); P. echinulatum, 13; P. expansum, 91 (citrinin, patulin, and roquefortine C); P. granulatum, 6 (patulin, penitrem A, and roquefortine C [traces]); P. griseofulvum, 21 (cyclopiazonic acid, griseofulvin, patulin, and roquefortine C); P. hirsutum, 100 (group I: terrestric acid; group II: citrinin, penicillic acid , roquefortine C, and terrestric acid; and group III: roquefortine C and terrestric acid), P. hirsutum group IV, 2 (chaetoglobosin C); P. isariiforme, 1; P. italicum, 41; P. mali, 104; P. roquefortii, 78 (group I: mycophenolic acid, PR-toxin, and roquefortine C and group II: mycophenolic acid, patulin, penicillic acid [low frequency], and roquefortine C); P. viridicatum group I, 634 (brevianamid A [low frequency], penicillic acid, viomellein, and xanthomegnin), P. viridicatum group II and III, 494 (citrinin and ochratoxin A), P. viridicatum group IV, 12 (griseofulvin and viridicatumtoxin). It is proposed that profiles of secondary metabolites be strongly emphasized in any future revision of the penicillia.     

Comparison of an Improved Rose Bengal-Chlortetracycline Agar with Other Media for the Selective Isolation and Enumeration of Moulds and Yeasts in Foods

S ummary . A modification of the medium (RBC) of Overcast & Weakley (1969) containing 50 p/m of rose bengal and 10 p/m of chlortetracycline was compared with the oxytetracycline-glucose-yeast extract medium (OGY) of Mossel, Visser & Mengerink (1962) and with acidified (pH 4·5) malt extract agar for the selective isolation and enumeration of moulds and yeasts in foods. The results obtained from several foods confirm earlier observations that media containing antibacterial agents are superior to acidified ones for isolating moulds from foods. Little difference in counts was observed for yeasts on the 3 media and there was no significant difference in the counts of moulds or the incidence of recovery of moulds on the RBC or OGY. Both media suppressed growth of bacteria but the RBC medium restricted the diameter of mould colonies thereby aiding counting and preventing overgrowth of slowly growing strains by more luxuriant species such as occurs on OGY.     

Ampicillin-dextrin agar medium for the enumeration of Aeromonas species in water by membrane filtration

Published selective media were evaluated for the isolation of Aeromonas spp. from environmental samples by membrane filtration. Satisfactory recoveries were obtained only with mA agar (Rippey & Cabelli) and dextrin-fuchsin-sulphite agar (Schubert), but neither was sufficiently selective. The positive aspects of these two media were combined in a new medium, ampicillin-dextrin agar. Recovery from pure cultures and environmental samples was optimal at an ampicillin concentration of 10 mg/l and incubation for 24 h at 30°C under aerobic conditions, and specificity was high (i.e. confirmation rate usually <90%, no false negative colonies encountered). The medium can also be used for isolation of Aeromonas spp. from sea water provided that the vibriostatic agent 0/129 is added at 50 mg/1.     

Direct identification of the common cheese contaminant Penicillium commune in factory air samples as an aid to factory hygiene

F. LUND. 1996. Creatine sucrose dichloran agar (CREAD) was used as a selective medium for Penicillium commune and related species found in air samples in a cheese factory. Using growth and simple colony characters on CREAD together with detection of indole metabolites with a filter paper method, it was possible to identify all 22 P. commune isolates from a total of 43 Penicillium isolates. Penicillium commune numbers on CREAD were compared with those found on a general isolation medium, dichloran 18% glycerol agar.     

`Isubgol' as an alternative gelling agent in plant tissue culture media

`Isubgol', the mucilaginous husk derived from the seeds of Plantago ovata, was successfully used as a gelling agent in tissue culture media for in vitro seed germination, shoot formation and rooting in Syzygium cuminii and anther culture in Datura innoxia. For seed germination, Knop's basal medium supplemented with 1% sucrose was employed, whereas for the development of shoots the epicotyl segments excised from in vitro-developed seedlings were cultured on MS basal medium supplemented with 4% sucrose and 1 mg/l 6-benzyladenine. Shoots that developed from the epicotyl segments were rooted on Knop's medium enriched with 2% sucrose and 1 mg/l indole-3-acetic acid. The anthers of D. innoxia excised at the late uninucleate to early binucleate stages of microspore development were cultured on Nitsch's basal medium containing 2% sucrose. Media were either gelled with 0.9% agar or 3% `Isubgol'. The response on media gelled with `Isubgol' in each of the cases was similar to that on media solidified with agar. Received: 9 October 1996 / Revision received: 22 July 1996 / Accepted: 30 July 1997     

麝香石竹花芽离体发育的阶段控制

在离体条件下,利用不同的培养基对麝香石竹顶芽外植体的花芽发育进行了阶段控制的研究.结果表明,麝香石竹的顶芽外植体在MS+KT1.0mg/L+IAA1.0mg/L+蔗糖3.0%+琼脂0.8%的Ⅰ级培养基上能被诱导花芽发育的启动;然后,将已诱导花芽发育启动的顶芽外植体,转接到MS+KT1.0mg/L+IAA0.5mg/L+蔗糖1.5%+葡萄糖1.5%+琼脂0.8%的Ⅱ级培养基上能进行花芽的进一步发育形成花蕾,且能从一个花蕾继续分化发育重新产生2—3个花蕾;把花蕾再转接到改良的MS+BA2.0mg/L+NAA0.2mg/L+蔗糖1.5%+葡萄糖1.5%+琼脂0.8%的Ⅲ级培养基上,培养一周后花蕾的花瓣张开,花朵全部开放.不同麝香石竹品种,诱导花芽发育启动的效果不同,Scania品种诱导效果最好.花芽发育初期可溶性蛋白含量较高,但随着花芽发育的进程而迅速下降,不同花芽发育时期的过氧化物酶活性均强于营养器官.本文为花芽分化发育机理的研究创造了条件,也为鲜花生产探索了新路子.