Inoculation of growing media with the rhizobacterium Variovorax paradoxus 5C-2 reduces unwanted stress responses in hardy ornamental species

Inoculation of growing media with plant growth promoting rhizobacteria (PGPR) has a number of potential benefits for the production of ornamental plants. Certain rhizobacteria synthesise the enzyme ACC deaminase, which cleaves ACC, the precursor of the plant hormone ethylene. Bacterial metabolism is now known to lead to a reduction in [ACC] in the plant transpiration stream and bacteria are hypothesised to act on ACC exuded from roots. This in turn reduces the ethylene generated in plants growing in growing media inoculated with these bacteria. Here we tested if applications of the ACC deaminase containing rhizobacteria Variovorax paradoxus⁵C–²could be of benefit to ornamental growers by reducing ethylene generation in stressed plants. Ethylene is produced at levels that are inhibitory to growth and development under a number of abiotic stresses. The propagation and production of hardy ornamentals is deleteriously affected by abiotic stresses that involve ethylene signalling, including drought and physical wounding. Inoculation of growing media with V. paradoxus 5C-2 lowered ethylene emission from mature leaves of Cytisus × praecox experiencing drought stress. In addition, bacterial inoculation of the growing media resulted in significantly reduced abscission of the mature leaves under drought treatment. Beneficial effects of inoculation where also found in the wounding response of Fargesia murielae following divisional propagation and late season senescence in Aquilegia × hybrida in response to drought stress. Together these results demonstrate that V. paradoxus⁵C–²has real potential for use on ornamental nurseries in situations where plant stresses are unavoidable.     

Physiological responses associated to substrate water availability of Rosa ‘Eurored’ plants grown in soilless greenhouse conditions

The aim of the present study was to provide a better insight into the adaptive processes to water deficit of Rosa hybrid plants grown in soilless cultivation. Rose plants were grown in a greenhouse under two water regimes, corresponding to 100% and 67% of the irrigation needs. Watering was stopped for 0, 72, and 96 h (dry-down period) and photosynthetic parameters, water relations, chlorophyll fluorescence, carbohydrate and ion content were determined.     

Somatic embryogenesis in pepper anther culture: The effect of incubation treatments and different media

The frequency of obtained androgenic plants depends highly on the genotype; therefore the low rate of haploid recovery limits the utility of anther culture in pepper breeding. The need for incubation treatment and adequate nutrition media supplemented with plant growth regulators, especially auxins, are suggested as important factors to obtain somatic haploid embryos in pepper anther culture. The effect of three incubation treatments of the androgenic potential in pepper anther culture on MS, N, LS, NN and CP medium are summarised, and the results demonstrate that:

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by incubating treatment in cold conditions (at 7 °C) in darkness for 7 days, and then transferring the explants to light conditions (12-h photoperiod at 25 °C) for 4 weeks, on LS and NN mediums, anthers produced callus;     

Effect of alleviating products with different mode of action on physiology and yield of olive under drought

Two years old self-rooted Koroneiki olive trees (Olea europaea L.) were subjected to two irrigation regimes, i.e. the fully irrigated and the severely water stressed trees, while they were treated with three alleviating products of different mode of action. The products used were the osmolyte glycine betaine, the antioxidant Ambiol and the heat and irradiance reflecting kaolin clay particles. The effects of product application and water regime on leaf characteristics, shoot and root growth, photosynthesis, leaf compatible solids (carbohydrates) concentration and yield were evaluated. All products applied, exhibited significant alleviating action, based on the relative alleviation index. Irrigated trees exhibited greater growth than drought stressed ones, while the ameliorating products maintained the water content of the leaves under drought conditions and resulted in lower leaf tissue density. On the other hand carbon assimilation rate, stomatal conductance and intrinsic water use efficiency were significantly reduced under drought stress, while the opposite stood for intercellular CO₂. Drought stress resulted in elevated sucrose leaf concentration, while the application of Ambiol increased stachyose concentration and that of glycine betaine did the same with the mannitol concentration. Among the alleviating products tested in this experiment Ambiol and glycine betaine had a significant positive effect on leaf water content, photosynthesis and yield under both drought and well irrigated conditions.     

Correlation of saponin content and Fusarium resistance in hybrids from different ploidy levels of Lilium Oriental

Lilium Oriental is of great commercial value, but large losses in production can result from its susceptibility to diseases caused by Fusarium ssp. Here we report a mutant of Lilium Oriental resistant to Fusarium, Cai-74, which was generated from crossing tetraploid (from ‘Star fighter’) and diploid (‘Cor. Amore’ × ‘Acapulco’) plants. Hybrid progeny were screened via inoculating Fusarium oxysporum into tissue cultured plantlets in a greenhouse. Although Cai-74 had a saponin content of 3.81 mg g⁻¹, which is much higher than its parents, the highly Fusarium-resistant wild species Lilium dauricum had the highest content of 4.11 mg g⁻¹ among the tested genotypes. Cai-74 had a 3A karyotype rather than 3B found in normal plants of Lilium Oriental. Taken together, our results suggest that Cai-74 bears a chromosomal variation in its structure, and that the saponin content in the lily scales correlate with the Fusarium resistance of Lilium Oriental. Cai-74 could be used as a gene resource for breeding Fusarium-resistant cultivars of Lilium Oriental.     

Effect of co-cultivation and crop rotation on corm rot disease of Gladiolus

Field and pot experiments were conducted to evaluate the effect of co-cultivation and crop rotation on the growth and corm rot disease of gladiolus (Gladiolus grandiflorus sect. Blandus) cv. Aarti caused by Fusarium oxysporum f.sp. gladioli (Massey) Snyd. and Hans. In the field experiment, gladiolus was co-cultivated with 10 agricultural/horticultural crops viz. Allium cepa L., Brassica campestris L., Capsicum annuum L., Eruca sativa Mill., Helianthus annuus L., Tagetes erectus L., Zea mays L., Vinca rosea L. and Rosa indica L., in a soil infested with F. oxysporum. All the crops except V. rosea and R. indica reduced disease incidence. The effect of H. annuus and T. erectus was significant and more pronounced than other co-cultivated crops. In general, root and shoot dry biomass, corm fresh weight, number of cormlets and number of flowers per spike decreased as compared to the un-inoculated monoculture gladiolus treatment (negative control) but these parameters enhanced as compared to the F. oxysporum inoculated monoculture gladiolus treatment (positive control). In a pot experiment, all the crops of the field experiment except V. rosea and R. indica were sown in rotation with gladiolus. Pot grown plants of different species were harvested at maturity and the soil was inoculated with F. oxysporum. Gladiolus was cultivated 1 week after inoculation. Disease incidence was significantly suppressed in all the treatments ranging from 29% to 53%. The highest suppression of disease incidence was recorded in T. erectus (53%) followed by B. campestris (49%). The effect of preceding crops on various vegetative parameters was similar in the pot experiment to that of the field experiment. The present study suggests that corm rot disease of gladiolus can be managed by mixed cropping of H. annuus and T. erectus or cultivation of T. erectus and B. campestris in rotation.     

Growth of rose roots and shoots is highly sensitive to anaerobic or hypoxic regions of container substrates

Commercial greenhouse cut rose plants commonly have shallow root systems, even in well-drained substrates. We studied rose plant responses to a wide range of soil air-filled porosity values to determine tolerance to low soil aeration. ‘Kardinal’ rose plants on ‘Natal Briar’ rootstock were grown for 11 weeks in containers holding 2.5 l of Yolo loam soil. The soil had been treated with a polyacrylamide soil conditioner to stabilize aggregates after they had been separated into three size fractions: coarse (1–2 mm), medium (0.1–1 mm), and fine (<0.1 mm). Plants were irrigated frequently to keep the soil at container capacity. Total new root growth was greatest in the medium and coarse soil fractions, which had average air-filled porosities of 7.6% and 15.9%, respectively. The fine soil fraction, which had an average air-filled porosity of 1.3%, had almost no root growth. In all soil fractions, roots were absent or scarce in regions of soil that were anaerobic or hypoxic. Highest root length densities occurred at air-filled porosity values of 12–17%, and no new roots grew at air-filled porosity values below 3%. Shoot yields were lower for plants in the substrate with low air-filled porosity, and their leaves had lower stomatal conductance, chlorophyll content, mid-day water potential, and macronutrient concentrations. Frequent irrigation that precludes aeration of the lower regions of the substrate profile will result in shallow root systems and could lead to decreased yields.     

Effects of plant growth promoting rhizobacteria (PGPR) on yield,growth and nutrient contents in organically growing raspberry

During 2003 and 2005, plant growth promoting effects of two Bacillus strains OSU-142 (N₂-fixing) and M3 (N₂-fixing and phosphate solubilizing) were tested alone or in combinations on organically grown primocane fruiting raspberry (cv. Heritage) plants in terms of yield, growth, nutrient composition of leaves and variation of soil nutrient element composition in the province of Erzurum, Turkey. The results showed that Bacillus M3 treatment stimulated plant growth and resulted in significant yield increase. Inoculation of raspberry plant roots and rhizosphere with M3 and/or OSU-142 + M3, significantly increased yield (33.9% and 74.9%), cane length (13.6% and 15.0%), number of cluster per cane (25.4% and 28.7%) and number of berries per cane (25.1% and 36.0%) compared with the control, respectively. In addition, N, P and Ca contents of raspberry leaves with OSU-142 + M3 treatment, and Fe and Mn contents of the leaves of raspberry with M3 and OSU-142 + M3 applications significantly improved under organic growing conditions. Bacterial applications also significantly effected soil total N, available P, K, Ca, Mg, Fe, Mn, Zn contents and pH. Available P contents in soil was determined to be increased from 1.55 kg P₂O₅/da at the beginning of the study to 2.83 kg P₂O₅/da by OSU-142, to 5.36 kg P₂O₅/da by M3 and to 4.71 kg P₂O₅/da by OSU-142 + M3 treatments. The results of this study suggest that Bacillus M3 alone or in combination with Bacillus OSU-142 have the potential to increase the yield, growth and nutrition of raspberry plant under organic growing conditions.     

Daily and seasonal variation of water relationship in sugar apple (Annona squamosa L.) under different irrigation regimes at semi-arid Brazil

In the northeast of Brazil the drought period determines the yield period of the sugar apple (Annona squamosa L.). As a result, the use of irrigation is essential to stagger production over the course of the year. The results shown here represent an analysis of water status levels in sugar apples in daylight and seasonal periods in semi-arid regions. Two plant groups were studied: one without irrigation and the other with irrigation during drought months. This study showed that younger leaves displayed greater stomatal conductance and transpiration. In drought months, even in irrigated plants, the high air moisture deficit had a strong influence on the stomatal closure, which did not translate into a reduction in transpiration. Over the same period, the leaf water potential was −1.8 and −2.9 MPa at mid-day in irrigated and non-irrigated plants, respectively, and only the irrigated plants could recover their leaf hydration level at night. With a water deficit, plants showed greater control of transpiration through stomatal closure, with a linear relationship between stomatal conductance and transpiration.     

Influence of nitrogen form,growing season and sulfur fertilization on yield and the content of nitrate and vitamin C of broccoli

The objective of this study was to determine the effects of nitrogen (N) sources, sulfur (S) and growing seasons on yield and the content of nitrate and vitamin C of broccoli (Brassica oleracea L. spp. Italica). Three N fertilizers (ammonium sulfate, ammonium nitrate and urea) were side-dressed while two levels of sulfur (0.0 and 0.5%) were sprayed on broccoli plants grown in both spring and fall-winter seasons. Here, we report on the interaction between N-source and S supply, yield, and nitrate content and discuss the relevance of this interaction in relation to crop-management strategies under different growing seasons. In the fall-winter season, broccoli yield of “Sultan F1”, “Majestic F1” and “Marathon F1” were 21.23%, 128.52% and 88.53% higher than spring season. Furthermore, S application increased the yield by 9% average over growing seasons, cultivars and N-forms. Also, application of urea as N-source decreased the yield by approximately 13–15% than other N-sources. High curd nitrate accumulation was attributed with spring season and “Marathon F1”, however, less accumulation was found in fall-winter season and “Majestic F1”. Fertilizers containing N forms that not ready available to the crop, i.e. ammonium sulfate and urea, decreased nitrate than fast N-release fertilizer (ammonium nitrate), but their effect on the yield was different. Highest yield with low content of nitrate was achieved when ammonium sulfate combined with sulfur were used during fall-winter season, especially in cv. “Marathon F1”. N-source and sulfur application had no effect on vitamin C, conversely, it was affected by growing season and tested genotypes. Therefore, additions of ammonium sulfate and sulfur application in the field of broccoli were essential to produce higher yield with good quality curds that pose minimum health risk to human.     

Identification and distribution of S haplotypes in Brassica vegetables from China

The amplification efficiency and identification diversity with gene-specific primers derived from S locus glycoprotein gene (SLG) and S locus receptor kinase gene (SRK) were compared, and the geographical distribution for S haplotypes was investigated by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) in 72 genotypes of 5 Brassica vegetables from China. The amplification efficiency and identification diversity with class I SRK primers were generally higher than that with class I SLG in most crops tested. Class I alleles were found in total 66 genotypes and they were classified into 16, 10, 7 and 10 groups for Chinese cabbage, purple flowering stalk, cauliflower and cabbage respectively. The number of amplification accessions and identification diversity using the primers of class II SLG and SRK were quite similar. Class II alleles were detected in 55 genotypes and further grouped into one type in mustard and three in other crops. The nucleotide sequences showed high similarity between identical S haplotypes determined by reciprocal pollination and PCR-RFLP tests. It demonstrated that the PCR-RFLP analysis was feasible for identification of S alleles, and SRK should be considered as a better marker for the identification of S haplotypes than SLG. The types of S haplotypes are highly diverse in Brassica vegetables from China. Nevertheless, they were geographically limited in some Brassica vegetables, so the exchange of germplasm resources should be enhanced for breeding.     

Combined effects of leaf/fruit ratios and N and K fertigation levels on growth and distribution of nutrients in pot-grown persimmon trees

Responses of pot-grown persimmon trees (Diospyros kaki cv. ‘Fuyu’) with two different leaf/fruit (L/F) ratios and three different fertigation levels were studied. On July 2, the L/F ratios of 4-year-old trees were adjusted to 20 and 10 by fruit thinning. From July 4 to August 26, each pot was fertigated with a solution containing 0–0 g (none), 10–8 g (medium), or 20–16 g (high) of nitrogen (N) and potassium (K), respectively. The L/F ratio of 10 resulted in higher yields but smaller fruits containing lower soluble solids than the ratio of 20. The non-fertigated trees with the L/F ratio of 10 produced the smallest fruits, but the medium fertigation increased the size of the fruit at this ratio. The high fertigation level decreased fruit skin color at both ratios. Fruit dry weight increased the most among the tree components, accounting for 48–57% of the tree total dry weight at the L/F ratio of 20 and for 64–72% at the ratio of 10. The increase in tree total dry weight at the ratio of 10 was greater than that at the ratio of 20. The trees receiving medium fertigation had higher tree total dry weights than those receiving high fertigation, especially at the ratio of 10. As the L/F ratio changed to 10 from 20, the percentages of N and K partitioned to fruits in the non-fertigated trees increased from 38% to 51% and from 67% to 96%, respectively, of the tree total N and K increases; the percentage decreased with increasing fertigation level. Although fertigation significantly increased total N and K contents of the tree, the increase in K at the ratio of 10 was less in high fertigation rather than in the medium level. The results indicated that adjusting supplemental N and K was necessary to ensure fruit growth and N and K accumulation for trees with high fruit loads, but high levels of fertigation are not necessarily preferable.     

Effect of different girdling dates on tree growth,fruit characteristics and reserve accumulation in a late-maturing persimmon

Trunks of 8-year-old vigorous ‘Fuyu’ persimmon (Diospyros kaki Thunb.) were girdled to a 1 cm width on April 20 and June 10 2004. Tree growth and fruit characteristics were monitored for two years, with special emphasis on the carry-over effect in 2005. Girdling reduced trunk and shoot growth especially of April-girdled trees over two consecutive years. However, the most significant effect of girdling was in the occurrence of water sprouts: a control tree had 29.5 in 2004 and 27.3 in 2005, whereas the April-girdled trees had only 0.3 and 5.3, respectively. Girdling increased fruit set by nearly 50% and enhanced fruit colour in 2004 only. Girdling date did not significantly affect fruit size and soluble solids for two years. Fruit flesh of girdled trees in 2004, especially in the April-girdled trees, had lower N and P concentrations. The levels of starch, soluble sugars, and inorganic elements in flower-bearing distal buds measured just before new growth in 2005 were not significantly altered by the girdling in 2004.     

Growth,yield and essential oil content of three cultivars of basil grown under different levels of nitrogen in the field

A field experiment was conducted in Southern Italy to investigate the effect of different nitrogen (N) rates (0, 100 or 300 kg ha⁻¹) on the number of branchings and leaves per plant, plant height, yield of above-ground fresh biomass, total leaf area, dry weight, leaf-to-stem ratio, leaf essential oil content and the essential oil quality at commercial harvest (full bloom) of the three cultivars of basil (Ocimum basilicum L.): (i) “Mostruoso mammouth” (MM); (ii) “Genovese profumatissimo” (GP); (iii) “Napoletano a foglia di lattuga” (NFL). Nitrogen fertilization up to 300 kg ha⁻¹ increased yield of above-ground and leaf fresh biomass, leaf essential oil yield, but it did not affect leaf-to-stem ratio, plant height and the number of branchings per plant. The increase in essential oil yield induced by N fertilization depended on an increase in both leaf essential oil concentration and leaf biomass. The increase in LAI with increasing N fertilization was due to an increase in leaf number per plant rather than in individual leaf expansion. The cultivar GP was different in morphology from MM and NFL, since it had greater leaf number and plant height, but lower leaf-to-stem ratio and LAI. The physiological efficiency of N use (PE) in producing above-ground biomass was not related to N application whereas PE in producing essential oil (PE-oil) tended to increase with increasing levels of N applied. With regard to the effect of the cultivar, GP was less efficient in N use for oil production than MM and NFL since PE-oil of GP was lower while leaf N and PE-biomass were higher than the other cultivars. NFL was the richest in methyl chavicol but the lowest in linalool, whereas MM and GP contained linalool and eugenol.     

Root development of Thuja plicata in peat-substitute rooting media

In this study we investigated the potential usefulness of different substrates produced from gorse (Ulex europaeus L.) for propagating cuttings of Thuja plicata ‘Atrovirens’. The gorse was composted by different methods, to produce four types of compost. These composts were then used as such (100% compost) or in mixes with coarse sand and pine bark compost (25% compost, 25% coarse sand and 50% pine bark compost, v/v/v) to prepare eight different substrates. The substrates were compared in cutting propagation trials carried out in a greenhouse, with a standard rooting medium consisting of 25% Sphagnum peat moss, 25% coarse sand and 50% pine bark compost (v/v/v). Cuttings were taken from a garden hedge in March 2003, and comprised shoots of the previous year's growth. The bases of the cuttings were treated with a 0.4% solution of IBA rooting hormone, then inserted into cells filled with the corresponding substrate and placed on a propagation bench. Rooting percentage and visual rooting score were determined in July. The quality of roots was evaluated, as total root length and number of root tips, in July, September and November 2003, by use of a Delta-T Scan system. The rooting success of the cuttings ranged from 75% to 90%, except when the substrate comprised the pure composted gorse, obtained after the shorter period in an enclosed composting system with addition of fertilizer and reuse of leachates. Most of the cuttings in this substrate died and only 4% of the cuttings rooted successfully. Physicochemical characteristics of this rooting medium included very high electrical conductivity, low C/N ratio and high water retention. Addition of coarse sand and pine bark compost to the composted gorse significantly increased the rooting success. The root quality variables differed depending on the substrate considered and date of harvest. The results showed that substrates made from gorse compost are of potential use as a peat substitute for propagating cuttings of T. plicata ‘Atrovirens’. The physicochemical properties of the composted gorse should be determined before its use to establish whether it can be used pure as a substrate for rooting or whether it should be mixed with other substances.     

Study on nutraceutical properties of different cultivars Ipomoea aquatica Forsskal (‘Chunbai’ and ‘Liulv’) in an eutrophic water body

Ipomoea aquatica Forsskal is a fast-growing aquatic economic plant and has been applied widely to purify eutrophic water, but little is known about the edible safety of it for humans or animals. The main purpose of our research was to assess the metal (copper, zinc, lead, cadmium and chromium) concentration and nutritional quality in the edible part of I. aquatica Forsskal (‘Chunbai’ and ‘Liulv’) growing in eutrophic water. The results showed that all levels of these metals were within the acceptable levels in our present studies, and the metal accumulating potential varied mainly depending upon levels of metal contamination in the water body in which they were growing. In the present investigation, nitrate content (NO₃–N) had no significant differences between ‘Chunbai’ and ‘Liulv’, but had significant differences (p < 0.001) between eutrophic water and Hoagland nutrient solution. Soluble protein, soluble sugar, and vitamin C content were affected greatly by variety and solution (treatments). The soluble protein and vitamin C content in ‘Liulv’ were one time higher but the soluble sugar content was one time lower than that in ‘Chunbai.’ The soluble protein and soluble sugar of plants cultivated in nutrient solutions were one time lower than that in eutrophic water. In addition, the vitamin C content of plants grown in Hoagland nutrient solution was approximately two times higher than that in eutrophic water. The possible utilization of these aquatic vegetables to meet the demands of food and health perspectives for consumers is discussed.     

Performance of peach and plum based rootstocks of different vigour on a late peach cultivar in replant and calcareous conditions

The field performance of fifteen peach and plum based rootstocks of different vigour (Adesoto, Evrica, Garnem, GF 677, HM-2, Krymsk^® 1, PAC 9801-02, PAC 960, PAC 9907-02, PAC 9917-26, PAC-MUT, PADAC 9907-23, ROOTPAC^® 40, ROOTPAC^® 70 and Tetra) grafted with ‘Calrico’ cultivar was compared after 7 years of establishment on an Armillaria infested replant site. ‘Calrico’ is a selected clone of “Calanda” late peach cultivar. Differences in parameters such as tree survival, leaf chlorophyll content, vigour, yield, cumulative yield, yield efficiency and fruit size were analyzed among rootstocks. All PAC 9801-02 and Tetra trees survived and the mortality rate was low in Evrica, PADAC 9907-23 and ROOTPAC^® 40. The rest of genotypes showed higher mortality rates. Leaf chlorophyll concentration was higher when grafted on Adesoto and Evrica and lower when grafted on PAC 9907-02 and PAC 9917-26. Garnem and PADAC 9907-23 were the most vigorous rootstocks. The highest yield efficiency was induced by Krymsk^® 1 and PAC 9801-02 due to their lower vigour. The highest fruit weight was also induced by Krymsk^® 1 but its cumulative yield was low. Other rootstocks that showed high fruit weight and cumulative yields were ROOTPAC^® 70 and Tetra. Overall, Evrica, PAC 9801-02, ROOTPAC^® 40 and Tetra were among the best adapted to soil sickness and calcareous soil showing a good agronomic performance. The first three rootstocks (Evrica, PAC 9801-02, ROOTPAC^® 40) also exhibited a high capacity to control tree vigour associated with high yield efficiency.     

Effect of different biodegradable and polyethylene mulches on soil properties and production in a tomato crop

The use of plastic materials for mulching is a very common practice for vegetable crops. Black polyethylene is the most widely used due to its excellent properties and low cost. However, the massive use of these materials supposes an environmental risk. In the last few years, the use of starch-based biodegradable films has been introduced as an alternative to conventional mulches. These materials can be incorporated into the soil at the end of the crop season and undergo biodegradation by soil microorganisms. A 2-year study was conducted to determine the response of a tomato crop to seven mulch materials (polyethylene and biodegradable) in open fields in Central Spain. Biodegradable films underwent early decomposition, but in general remained functional during use and did not affect yield and the fruit quality attributes (total soluble solids, firmness, dry weight, juice content and shape). The temperatures reached under polyethylene films were always higher than under biodegradable films, which could be a disadvantage in certain circumstances, especially in hot climates, although may be advantageous in cool conditions. The use of polyethylene films resulted in the lowest values of soil microbial biomass C and soil organic matter mineralization, probably due to the increase of temperature registered under mulches. The analysis of the marketable yield components indicates that the variability in yield mainly depended on the number of fruits, with mean fruit weight being practically constant in the different treatments and seasons, which suggests the strong varietal character of this parameter.     

Pollination with laser-irradiated pollens breaks cross-incompatibility between zicaitai (Brassica campestris var. purpurea) and ornamental kale (Brassica oleracea var. acephala) to produce hybrids with the aid of ovule culture

The objective of this study was to produce interspecific hybrids between an Ogura-cytoplasmic male sterile (CMS) line of zicaitai (Brassica campestris var. purupurea, 2n = 20) and cultivars of ornamental kale (Brassica oleracea var. acephala, 2n = 18) to develop a CMS system for hybrid seed production. Pollination with pollen grains of ornamental kales irradiated at a power output of 9.0 mW with a He–Ne laser for 3 min could overcome the cross-incompatibility between the species concerned. Intact hybrids could be efficiently produced from ovules cultured on Murashige and Skoog media supplemented by 0.2 mg l⁻¹ 6-benzyladenine. Chromosome number of hybrids was confirmed to be 2n = 19. Hybrids resembled ornamental kales in leaf morphology and in vernalization response. Pollens of hybrids had a sterile appearance. Moreover the hybridity of the putative hybrids was confirmed by RAPD data on a DNA fragment of 820 bp.