Effect of crop plant density on critical period of weed competition in potato

A field study was conducted in Hamedan western Iran in 2006 to establish the critical period of weed competition (CPWC) in potato (Solanum tuberosum L.) for commercial and seed production plant densities. A quantitative series of treatments concerned with both increasing duration of interference and length of weed-free period were imposed within each commercial and seed potato production plant density. The beginning and end of the CPWC based on a 10% loss of tuber yield was determined by fitting logistic and Gompertz equations to the relative tuber yield data representing increasing duration of weed interference and weed-free period, respectively. At a 10% tuber yield loss level, the duration of weed interference for 571 and 676 growing degree days (GDDs) from crop emergence, corresponding to 40% and 50% canopy closure, marked out the beginning of the CPWC for commercial and seed production plant densities, respectively. When maintained weed-free for 1163 and 1014 (GDD), corresponding to 100% and 80% canopy closure, weed emerging later caused tuber yield losses of less than 10% for commercial and seed production plant densities, respectively. Practical implications of this study are that post-emergence herbicides or other weed control methods should be used in western Iran to eliminate weeds from 19–24 days post-crop emergence up to 43–51 days. Such an approach would keep yield loss levels below 10%. Interactions between plant density and weed competition durations indicated that weed management in commercial plant density of potato could be less intensive than that of seed production plant density, reducing herbicide use and risk of herbicide carryover to sensitive rotation crops.     

Allelochemicals identified from Jerusalem artichoke (Helianthus tuberosus L.) residues and their potential inhibitory activity in the field and laboratory

Weed management systems often seek biological solutions to minimize the environmental impacts related to the use of herbicides in agricultural systems. The suppressive effects of allelochemicals can sometimes be used effectively to provide biological pest and weed control. Jerusalem artichoke (Helianthus tuberosus L.) has been reported to be a highly invasive weed in European cropping systems, but this plant is also gaining interest as a cultivated crop in Italy. The aim of this study was to investigate the impact of Jerusalem artichoke and its extracts upon the germination and growth of seedling weeds and crops. HPLC coupled to MS was used for identification of the compounds associated with the observed growth inhibition. The weed suppressive activity of local biotypes of Jerusalem artichoke on weed growth and establishment was also evaluated in a field experiment. Shoot extracts of the cultivar Fuseau were consistently most inhibitory to germination and seedling growth of lettuce, particularly the diethyl ether extract. Solvent partitioning of the aqueous extracts of dried artichoke shoots resulted in greater inhibition in comparison to the aqueous extract itself. The diethyl ether extract provided 2-fold greater growth inhibition, in comparison to the aqueous extract, at concentrations of less than 0.5 mg extract per Petri dish. HPLC MS evaluation of the diethyl ether extract led to the identification of salicylic acid (o-hydroxybenzoic acid), and the closely related compound p-hydroxybenzaldehyde, as well as minor quantities of o-coumarinic acid and coumarin in the active fraction inhibiting lettuce seedling growth. Field observations provided further evidence for the allelopathic potential of H. tuberosus residues, as significant weed growth inhibition was observed in Jerusalem artichoke-infested plots with soil-incorporated residues in comparison to non-infested field sites, both in terms of weed seedling emergence and growth. The allelopathic potential of H. tuberosus may be of interest in the implementation of integrated weed management programmes by considering the suppressive ability of this plant and its residues for weed management in the field.     

Environmental control of growth and flowering of Rubus idaeus L. cv. Glen Ample

Environmental control of the annual growth cycle of ‘Glen Ample’ raspberry has been studied in order to facilitate crop manipulation for out-of-season production. Plants propagated from root buds were raised in long days (LD) at 21 °C and then exposed to different temperature and daylength conditions at varying ages. Shoot growth was monitored by weekly measurements and floral initiation by regular sampling and examination of axillary bud #5. Under natural summer daylight conditions at 60°N shoot growth was nearly doubled at 21 °C compared with 15 °C, while at 9 °C one half of the plants ceased growing and formed flower buds at midsummer. Developing shoots have a juvenile phase and could not be induced to flower before the 15-leaf stage. No significant reduction in induction requirements was found in larger plants. Plants exposed to natural light conditions from 10th August, had an immediate growth suppression at 9 and 12 °C with complete cessation after 4 weeks (by September 7). This coincided with the first appearance of floral primordia. At 15 °C both growth cessation and floral initiation occurred 2 weeks later (by September 21), while at 18 °C continuous growth with no floral initiation was maintained until early November when the photoperiod had fallen below 9 h. The critical photoperiod for growth cessation and floral initiation at 15 °C was 15 h. Plants exposed to 10-h photoperiods at 9 °C for 2–4 weeks had a transient growth suppression followed by resumed growth under subsequent high temperature and LD conditions, while exposure for 5 or 6 weeks resulted in complete growth cessation and dormancy induction. The critical induction period for floral initiation was 3 weeks although no transitional changes were visible in the bud before week 4. When exposed to inductive conditions for marginal periods of 3 or 4 weeks, an increasing proportion of the plants (20% and 67%, respectively), behaved as primocane flowering cultivars with recurrent growth and terminal flowering. It is concluded that growth cessation and floral initiation in raspberry are jointly controlled by low temperature and short day conditions and coincide in time as parallel outputs from the same internal induction mechanism.     

Two potent allelopathic substances in cucumber plants

Since cucumber plants are mostly discarded as large waste after crop harvesting, allelopathy of cucumber plants was investigated for possible weed management options and utilization of the waste. Two potent growth inhibitory substances were isolated from an aqueous methanol extract of cucumber (Cucumis sativus L. cv. Phung Tuong) plants. These substances were determined as 9-hydroxy-4,7-megastigmadien-9-one (HMO) and (6S,7E,9S)-6,9,10-trihydroxy-4,7-megastigmadien-3-one (THMO) by the analysis of MS, ¹H NMR spectra and optical rotation. HMO inhibited the growth of cress (Lepidium sativum L.) and Echinochloa crus-galli (L.) Beauv seedlings at concentrations greater than 0.3 and 1 μM, respectively. THMO inhibited the growth of cress and E. crus-galli seedlings at concentrations greater than 1 and 3 μM, respectively. The concentrations required for 50% growth inhibition on roots and shoots of cress and E. crus-galli were 2.4–29.3 μM for HMO and 8.1–52.2 μM for THMO. The endogenous levels of HMO and THMO in cucumber plants were 31.8 and 43.5 μg g⁻¹ dry weight, respectively. These results suggest that HMO and THMO may be the causal factors for the growth inhibitory effect of cucumber plants. Therefore, cucumber plants may be potentially useful for weed management options in an agricultural setting, such as a cover crop and soil admixture, which should be investigated further in the field.     

Mycorrhizal colonization improves onion (Allium cepa L.) yield and water use efficiency under water deficit condition

Most plants benefit from mycorrhizal symbiosis through improvement of water status and nutrient uptake. A factorial experiment with complete randomized blocks design was carried out in greenhouse at Tabriz University, Iran in 2005–2006. Experimental treatments were (a) irrigation interval (7, 9 and 11 days), (b) soil condition (sterile and non-sterile) and (c) arbuscular mycorrhizal fungi (AMF) species (Glomus versiforme, Glomus intraradices, Glomus etunicatum) and non-mycorrhizal (NM) plants as control. Onion (Allium cepa L. cv. Azar-shahr) seeds were sown in sterile nursery and inoculated with fungi species. One nursery left uninoculated as control. Nine weeks old seedlings then were transplanted to the pots. Average pre-irrigation soil water contents reached to about 67, 61.6 and 57.5% of FC corresponding to 7, 9 and 11 days irrigation intervals, respectively. At onion bulb maturity stage (192 days after transplanting), yield, water use efficiency (WUE) and yield response factor (K_y) were determined. The results indicated that AMF colonization increased soil water depletion significantly. G. versiforme under both soil conditions (sterile and non-sterile) and G. etunicatum in sterile soil depleted soil water effectively (P < 0.05). Mycorrhizal fungi improved WUE significantly (P < 0.0001) in both soil conditions. It raised by G. versiforme about 2.4-fold (0.289 g mm⁻¹) in comparison with the control (0.117 g mm⁻¹). G. intraradices and G. etunicatum also had significantly higher WUE than control. Apparently water deficit in 11-day irrigation interval led to lower yield and WUE compared to 9-day interval; the later resulted highest WUE (0.254 g mm⁻¹). Mycorrhizal plants increased seasonal ET significantly due to enhancing in plant growth; G. versiforme in both sterile and non-sterile soil and G. etunicatum in sterile soil had the highest ET. Bulb yield was influenced by irrigation period and fungi species. G. versiforme produced higher yield than other treatments (135.27 g/pot). Mycorrhizal plants in 11-day irrigation interval in spite of suffering from water stress had more bulb yield than non-mycorrhizal plants in all irrigation intervals. Yield in general was higher in 9-day treatments than other irrigating internals significantly (P < 0.05). Onion yield response factor (K_y) was decreased by AMF colonization; implying that symbiosed plants become less responsive to water deficit (longer irrigation interval) compared to the control ones.     

In vitro asymbiotic seed germination and seedling growth of Ansellia africana Lindl.

The effects of sodium hypochlorite treatment and growth medium on in vitro seed germination and seedling growth of the leopard orchid (Ansellia africana Lindl.) were investigated. Forty minutes treatment of seeds with 1.75% sodium hypochlorite stimulated germination (70.6%) and seedling development when measured at Stage 5 (emergence of first leaf) on P668 medium after 8 weeks of culture. The growth medium played a significant role in determining the germination response of A. africana seeds. Dark pretreatment of seed cultures significantly enhanced the germination percentage and the growth of rhizoids on the protocorms. Leaf growth in terms of length was substantially enhanced on P668 medium. It was significantly reduced in modified Knudson C medium after 16 weeks of culture. Seedlings developed on P668 medium showed a significantly better growth performance in relation to leaf length, leaf number, root length, fresh and dry weights per plant in vermiculite after 12 weeks of ex vitro growth in a mist house with 90% relative humidity. Further studies developing a suitable method for in vitro symbiotic germination could assist in reintroduction of this threatened orchid species into the wild.     

Weed management in onion using chemical,non-chemical,and manual methods

Summary

Weed management studies in onions grown from seedlings were conducted during 2006 and 2007 at the National Agricultural Research Centre, Islamabad, Pakistan. Applications of pendimethalin at 0.825 l a.i. ha^–1, or oxadiazon at 0.240 l a.i. ha^–1, 2 d after transplanting (DAT) seedlings were evaluated alone, and in combination with one manual weeding, for their effects on weed competition and bulb yields. Other weed control treatments included the application of rice straw mulch 2 weeks after transplanting (WAT) combined with one manual weeding at 9 WAT, or a newspaper and rice straw mulch applied 2 WAT. Compared to the weed-free situation, competition with weeds caused reductions in bulb yields of 62% and 68% during the first and second year, respectively. Polygonum plebejum, Amaranthus viridis, Cyperus rotundus, and Coronopus didymus were the dominant weeds recorded in the field. Mulching reduced weeds by 56 – 60% compared to the chemical weed treatments. Compared to the weed-free treatment (four manual weedings at monthly intervals), which is a traditional method to control weeds in onion, bulb yields increased significantly under the rice straw mulch or when treated with pendimethalin in combination with one manual weeding at 9 WAT. The latter two treatments, on average, resulted in the highest increases of 26 t ha^–1 and 24 t ha^–1 in bulb yields with net returns of US$ 1,522 ha^–1 and US$ 1,486 ha^–1, respectively over the non-treated control.     

Effect of Glomus mosseae and Entrophospora colombiana on plant growth,production, and fruit quality of ‘Maradol’ papaya (Carica papaya L.)

The effect of inoculating ‘Maradol’ papaya plants with arbuscular mycorrhizal fungi (AMF) Glomus mosseae (GM) and Entrophospora colombiana (EC) was assessed. The results showed that both mycorrhizae species increased the number of fruits and yield in papaya plants by 41.9 and 105.2% for GM and 22.1 and 44.1% for EC, respectively, with respect to control plants. GM significantly increased plant height. Sugar content, firmness, color (°Hue), and ripening process of mycorrhized plant fruits were similar to those of the control. Weight loss of mycorrhized plant fruits was considerably less than that of the control. Inoculation of papaya with AMF is recommended, particularly with GM since it increases yield, and fruit weight (45.1%), furthermore, it reduced fruit weight loss during ripening.     

Phenmedipham in the establishment of strawberries as solid beds

Solid-bed culture of strawberries results in much greater yields than the more usual matted rows. One of the reasons that solid beds are not commercially popular is that weeds, particularly Veronica spp., which are resistant to simazine and lenacil, may establish during the period of runner growth and rooting when weed control by cultivation is impossible. To allow the formation of a clean solid bed, these weeds were controlled by phenmedipham applied immediately after harvesting the first crop from autumn planted strawberries. Yield (up to 50 tonnes per hectare) and berry weight data are presented for 2 years and 4 commercially important cultivars managed in this way. Once established, a weed-free solid bed was found to need only slight attention for satisfactory maintenance.     

Genetic transformation of Prunus domestica L. using the hpt gene coding for hygromycin resistance as the selectable marker

The study and development of transformation technology with new selection schemes is important for various fundamental studies and for crop trait improvement via genetic engineering. Here we have shown that hygromycin resistance is an effective system for plum genetic transformation. Embryonic axes of mature seeds were co-cultivated with Agrobacterium strain LBA4404 containing the pC1381 plasmid carrying the hygromycin phosphotranferase gene (hpt) and β-glucuronidase (GUS) gene or with strain EHA105 containing the plasmid pC1301 carrying the same marker and reporter genes. The latter strain containing a pC2301 plasmid carrying the neomycin phosphotransferase gene (nptII) gene was used as a control. Infected explants were placed on shoot induction medium containing either 5 mg L⁻¹ hygromycin or 75 mg L⁻¹ kanamycin for selection. Green shoots developed from the explants under hygromycin pressure. These shoots showed continued and vigorous growth and development upon transfer onto fresh hygromycin medium. PCR using hpt sequence primers, and Southern blot analysis using a probe from the hpt gene, confirmed the presence of the transgenes and their stable integration in regenerated plants. Full transgenic plants were obtained in a greenhouse. Hygromycin selection was very effective and no escapes were observed. The study demonstrated that hygromycin resistance can be used as an effective selectable marker for plum transformation. The new system developed here is important and useful for multiple gene transformation in plum.     

Potent herbicidal activity of Inula crithmoïdes L.

Aqueous (10, 20, 30 and 40 g/L) and organic (hexane, chloroform and methanol, at 3000 and 6000 ppm) extracts of Inula crithmoïdes L. (roots, stems, leaves and flowers) were evaluated for their allelopathic activities on radish, lettuce, peganum and thistle. Pot cultures were conducted by incorporation of I. crithmoïdes leaves and flowers powder (1.25 and 2.5 g/kg) in soil and by irrigation with their aqueous extracts at 40 g/L. PEG (polyethylene glycol) solutions, with similar osmotic potentials of aqueous extracts, at the highest concentration, were without effect on target species, this eliminates the extracts osmotic effect. Germination index was not affected by root and stem extracts and significantly decreased by the two other ones. For growth, leaf and flower extracts had the most significant toxicity at 40 g/L, inducing up to a total inhibition. For organic extracts, a strong toxicity was recorded for the three fractions at 6000 ppm, thistle seedling growth was more sensitive, especially to chloroform fractions. Soil incorporation of residues (at 2.5 g/kg) significantly decreased root (35–100%) and shoot (0–100%) length of target species. Irrigation soil with leaves and flower aqueous extracts was harmful for peganum and thistle, respective inhibition percentages were 100% and 66.5%. I. crithmoïdes may be favorably used for incorporating in agricultural systems for sustainable weed management.     

In vitro proliferation from axillary buds and ex vitro protocol for effective propagation of Syringa × hyacinthiflora ‘Luo Lan Zi’

As a precondition for lilac mass propagation, the optimal shoot-multiplication medium for Syringa × hyacinthiflora ‘Luo Lan Zi’ was ascertained mainly based on clustered microshoot inducement and large leaf area establishment in 6-benzyladenine (BAP) (1.00 mg L⁻¹) and zeatin (Z) (0.10 mg L⁻¹) combination. Medium supplied with lower level of BAP (0.50 mg L⁻¹) and auxin (IAA) (0.25 mg L⁻¹) was not suitable for lilac shoot proliferation, but it could be competent for long-term preservation of the un-rooted shoots so that subsequent proliferation culture could be carried out at anytime. In addition, excess height growth which resulted in low transplanting survival rate was effectively controlled by decrease in node number when paclobutrazol (PBZ) was applied in rooting medium at a concentration of 1.00 mg L⁻¹ after taking into account the effects on shoot height, rooting, persistent leaf area and PBZ carry-over. An important overwintering treatment was to use a plastic chamber covering for plants in the greenhouse prior to field planting to ensure adequate biomass of stem and underground parts not only in the current growing season but also in the subsequent years.     

Chemical compositions and insecticidal effects of essential oils isolated from Achillea gypsicola, Satureja hortensis, Origanum acutidens and Hypericum scabrum against broadbean weevil (Bruchus dentipes)

The essential oils of aerial parts of Achillea gypsicola Hub.-Mor., Hypericum scabrum L., Satureja hortensis L., and Origanum acutidens (Hand.-Mazz.) Letswaart were analyzed in this study by GC and GC–MS and their oils were tested for toxicity against broadbean weevil (Bruchus dentipes). A. gypsicola oil contained camphor (40.17%), 1,8-cineole (22.01%), piperitone (11.29%), borneol (9.50%) and α-terpineol (1.56%) as major components. A total of 74 components were identified by GC–MS in H. scabrum oil, including α-pinene (9.26%), terpinen-4-ol (5.12%), camphor (5.94%), δ-cadinene (4.52%), pulegone (4.45%), γ-muurolene (4.12%), pinocarvone (3.97%) and β-caryophyllene (3.42%) as predominant components. The essential oils of O. acutidens and S. hortensis were characterized by high contents of carvacrol (86.99% and 55.74%), γ-terpinene (0.71% and 20.94%), p-cymene (1.95% and 12.30%), α-terpinene (0.13% and 2.04%) and β-caryophyllene (1.30% and 1.08%). All of the essential oils were toxic to adults of B. dentipes and insect mortality increased with increasing concentration of each oil. The oils (20 μl dose) brought about 100% mortality in 36 h. Although desirable insecticidal activities against the pest were achieved with the oils from all four plant species, S. hortensis and O. acutidens oils were more effective, particularly after 6 h of treatment. The current results concluded that the essential oils, in particular O. acutidens and S. hortensis oils, may be used as potential botanical insecticides against B. dentipes.     

Characterization of a new fungal antagonist of Phytophthora capsici

The capacity of many microorganisms for antagonism towards pathogens is unknown and previously uncharacterized species may be potentially useful in this respect. This work presents the evaluation of the capacity of a previously uncharacterized Ascomycete, denominated here as UA to protect chili pepper (Capsicum annuum) against Phytophthora capsici, and other soil-borne plant pathogens and establishes the role of UA as a biocontrol agent. Inoculation of UA 2 days before the inoculation of P. capsici led to 77.8% survival of pepper plants. Simultaneous confrontation of both microorganisms in vitro led to 53.1% growth inhibition of P. capsici, while the inoculation of P. capsici 3 days after the inoculation with UA improved growth inhibition up to 73%. Simultaneous confrontation in vitro of UA with Fusarium oxysporum and Fusarium solani led to 41.2 and 50% growth inhibition, respectively, but had no effect on Rhizoctonia solani or a binucleate Rhizoctonia isolate. Moreover, formation of zoosporangia and the germination of zoospores were completely inhibited by exposure to undiluted filter sterilized filtrate. UA produces septate mycelia, but could not be classified in detail due to a lack of spores or reproductive structures. However, sequencing of Internal Transcribed Spacer 1, 2 and the 5.8S genes indicated that this fungus is a member of the Ascomycetes.     

Application method and rate of Trichoderma species as a biological control against Pythium aphanidermatum (Edson) Fitzp. in the production of microgreen table beets (Beta vulgaris L.)

Seed balls of ‘Early Wonder Tall Top’ table beet (Beta vulgaris L.) were incubated for 2 days at 21 °C in moist exfoliated grade 3 vermiculite (3 g seed balls [168 seed balls] and 1.1 g vermiculite) containing equal weights of Trichoderma harzianum Rifai strain KRL-AG2 G41 and T. virens strain G-41 (ThTv) at 0, 0.25, 0.50, 0.75 or 1.00 mg ThTv per seed ball. ThTv also was applied to the peat-lite growth medium 14 days before planting, at the same rates per seed ball as the seed ball treatments. Four days before planting, the peat-lite was inoculated with Pythium aphanidermatum (Edson) Fitzp. (Pa) at 0, 0.5 and 1.0× the rate that resulted in 96% damping-off when non-ThTv-treated dry seed balls were sown in peat-lite containing 1.0 Pa. Increasing ThTv level per seed ball decreased percentage damping-off, with 1.0 Pa giving greater percentage damping-off than 0.5 Pa. At 1 mg ThTv per seed ball, damping-off was 5% and 19% at 0.5 and 1.0 Pa, respectively. Including Agro-Lig UF (mostly humic acids) in the incubating seed-ball-ThTv mixture further decreased damping-off by an average 13 and 10 percentage points in 0.5 and 1.0 Pa, respectively. Increasing ThTv per seed ball in growth media decreased percentage damping-off, but not to the extent achieved with seed ball treatment, with 1 mg ThTv per seed ball giving 20% and 55% damping-off in 0.5 and 1.0 Pa, respectively. Decreasing incidence of damping-off with increasing ThTv application to seed balls or growth media was associated with increasing shoot fresh weight m⁻² at 14 days after planting, a response attributable to increased percentage plant survival and not to a ThTv growth-promoting effect.     

Piriformospora indica promotes adventitious root formation in cuttings

Adventitious root formation in excised plant shoots is a crucial process in the vegetative propagation of many plant species, and insufficient rooting causes substantial losses in the propagation industry. Based on the various physiological effects on whole plants described for the basidiomycete Piriformospora indica, it was hypothesized that inoculation of the substrate with this endophyte should promote the generation and growth of adventitious roots in cuttings. Inoculation experiments were conducted to study the effects of P. indica on adventitious rooting in three plant species. Inoculation with P. indica dramatically enhanced the number and length of the adventitious roots in pelargonium and poinsettia. Root colonization parameters suggest that the interaction between the endophyte and cuttings had already occurred before physical contact. In contrast, petunia showed no rooting response to P. indica inoculation. Very fast root formation in this plant indicates that a minimum time period for the fungus–plant interaction is required for establishment of a promoting effect. P. indica-based biotechnology is proposed as a new tool for improving plant propagation systems of plant species or cultivars with low to moderate capacity of adventitious root formation.     

Towards crop improvement in bell pepper (Capsicum annuum L.): Transgenics (uid A::hpt II) by a tissue-culture-independent Agrobacterium-mediated in planta approach

Agrobacterium tumefaciens-mediated transformation has been one of the methods used to generate transgenic plants in bell pepper. An alternate transformation method that avoids/minimizes tissue culture would be beneficial for the improvement of bell pepper due to its recalcitrant nature. In this report, transgenic bell pepper plants have been developed by a tissue-culture-independent A. tumefaciens-mediated in planta transformation procedure. In the present study, two open pollinated varieties viz., Arka Gaurav and Arka Mohini were used for transformation. Agrobacterium strain EHA105 harboring the binary vector pCAMBIA1301 that carries the genes for β-glucuronidase (uid A) and hygromycin phosphotransferase II (hpt II) was used for transformation. GUS histochemical analysis of T₀ and T₁ plants at various stages of growth followed by molecular analysis using PCR, Southern analysis and RT-PCR allowed selection of transgenics. The method resulted in 17.8% and 11.4% of the T₀ plants in Arka Gaurav and Arka Mohini being selected as chimeric and 35.0% and 29.7%, respectively, were identified as stable transformants in the T₁ generation based on PCR analysis.     

In vitro tuberisation of Gloriosa superba L. on basal medium

A suitable protocol for in vitro tuber production using non-dormant tubers of Gloriosa superba L. on Murashige and Skoog (MS) medium without addition of plant growth regulators is reported in the present study. Among the different basal media tested MS medium was found to be suitable for induction and development of secondary tubers; one in vitro tuber per explant was obtained after 6 weeks and 3 tubers per explant after 12 weeks of culture. These tubers produced healthy green shoots that rooted on basal medium. Best rooting was noted in half strength (half organics and inorganics) MS medium with one-fifth nitrates.     

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.