Characterization of Lactococcus garvieae isolated from radish and broccoli sprouts that exhibited a KG+ phenotype, lack of virulence and absence of a capsule

AIMS: To identify Lactococcus garvieae isolates from radish and broccoli sprouts and compare them with virulent and less virulent mutant strains obtained from yellowtails with regard to KG phenotype, presence of a capsule and virulence towards yellowtails and mice. METHODS AND RESULTS: Comparative 16S rRNA gene sequence analysis of six isolates obtained from radish and broccoli sprouts indicated that they were L. garvieae (similarity >99%). They were compared with KG9502, Lg2 and ATCC49156 strains obtained from yellowtails. A less virulent mutant strain Lg2-S was obtained by Lg2 subculture. Biochemical characterization of the six strains resembled that of KG9502, Lg2, ATCC49156 and Lg2-S, except for saccharose and tagatose acidification and the presence of hippuricase. These six strains were nonpathogenic towards yellowtails and mice, nonsusceptible to bacteriophages and demonstrated heterogeneity on pulsed-field gel electrophoresis analysis. Using transmission electron microscopy, a capsule was observed in KG9502 and Lg2 but not in ATCC49156 and Lg2-S. CONCLUSIONS: We isolated L. garvieae strains that lacked pathogenicity towards yellowtails and mice from radish and broccoli sprouts; these were noncapsulated and exhibited KG(+) phenotype. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first documentation of L. garvieae isolated from terrestrial plants. These isolates exhibited genetic diversity; however, they were noncapsulated and nonpathogenic towards yellowtails and mice.     

The effects of gibberellic acid,fluridone, abscisic acid and paclobutrazol on anther culture of Brussels sprouts

Both gibberellic acid (GA₃) and fluridone, a non-specific inhibitor of ABA biosynthesis, promoted embryo production in anther cultures of Brussels sprouts cv. Hal, but not in cv. Gower. Abscisic acid (ABA) and the gibberellin-biosynthesis inhibitor paclobutrazol inhibited embryo production in both cultivars.     

Structure and dynamics of Japanese beech (Fagus japonica Maxim.) stools and sprouts in the regeneration of the natural forests

Structure and spatial distribution of stools and root-collar sprouts of Japanese beech (Fagus japonica) were studied to clarify the regeneration processes of the stool and the population, and the ecological importance of this stool formation in five quadrats of the natural forests with different forest floor vegetation on the Pacific side of Japan. F. japonica dominates in the canopy of each quadrat. Most of sprouts formed a circle around the root-collar and lowest parts of the parent stems of the stool with the youngest sprouts at the periphery. The regeneration by seedlings was slight especially on the forest floor vegetation of the dwarf bamboo Sasa. The variety of size structure of stems and the existence of dead traces and/or dead center in each stool, the apparent difference in stool size, and the aggregations of stools in the forests suggest that stool expansion and long persistence of the stool at a given location may contribute to compensate for the scarcity of regeneration by seedlings inhibited by dwarf bamboo, and by the other shrubs and herbs.     

Growth patterns and endogenous indole-3-acetic acid concentrations in current-year coppice shoots and seedlings of two Betula species

Apical dominance, internode elongation, radial growth and xylem cell size in coppice and apical shoots of Betula pubescens B. Pendula were determined and related to endogenous indole-3-acetic acid (IAA) levels, measured by gas chromatography-selected ion monitoring in the apical bud and at three positions along the stem. The effects of defoliation and debudding on morphological and anatomical characters and endogenous IAA levels were also investigated. The coppice shoots displayed superior stem elongation and increased branching during the initial phase of growth, after which their growth pattern was similar to that of the seedlings; however, their radial growth was greater throughout the experiment. Both plant types produced smaller-sized xylem cells at the top of the shoot than at the bottom with coppice shoots tending to form larger tracheids and smaller vessels than the seedlings. There was no consistent difference in IAA concentration between the coppice shoots and the seedlings. Defoliation and debudding reduced the IAA level in the stem within 36 h and it was still low after 25 days. Although the extent of the IAA decrease was similar in both coppice shoots and seedlings, the treatments affected the morphological and anatomical characters differently in the two plant types. The results suggest that the observed differences between seedlings and coppice shoots were not mediated through a drastic change in IAA level.     

Structure and stem growth of multi-stemmed trees of Fagus engleriana in China

Fagus engleriana Seem. occurs in the mountains of southern China. It has a multi-stemmed form at several sites, but it is single-stemmed at other sites. It is not known whether this tree naturally develops the multi-stemmed form at all sites of its range. This paper describes the occurrences of multi-stemmed F. engleriana at eight sites that are spread over its range. The clonal structure and stem growth patterns for selected F. engleriana individuals are also given. Our results suggest that F. engleriana is able to develop a multi-stemmed form at all sites of its range. The beech clones examined usually had closed centres, suggesting that they were younger than the Japanese Fagus japonica clones that have open centres. There were usually dominant and suppressed stems within the F. engleriana clones. Often, the dominant and some suppressed stems within a clone were of similar-age and had strong initial stem-radial growth rates. These similar-aged stems probably emerged in a large opening. The suppressed stems usually had radial growth rates that were initially similar to, but later much less than that of the dominant ones. At one site that was intensively studied, decrease of stem growth with increase of stem size was found in the multi-stemmed beech but not in single-stemmed Fagus hayatae Palibin ex Hayata. Both species had comparable initial radial growth rates. At this latter site there were two large peaks in the ages of all F. engleriana stems sampled, suggesting two major disturbances occurred in the past. F. engleriana occurs mainly in the northern part of Chinese Fagus range, where beech seed production is rather low, and in forests where dense bamboo undergrowth restricts establishment and survival of seedlings. Vigorous sprouting is probably beneficial to F. engleriana enabling it to persist in these habitats.     

Micropropagation of nodal explants from adult trees of Cleistanthus collinus

The micropropagation of adult Cleistanthus collinus was accomplished. The nodal segments from terminal twigs of a 15-year-old tree and basal sprouts of a comparable chronological age were used for initiating shoot bud cultures. Washing explants with sterile mixtures of citric acid (520.5 μM) and PVP 40 (3.75 μM) three to four times controlled the leaching of brown inhibitory substances into the establishment medium. Axillary shoots proliferated best on MS medium containing citric acid (104.1 μM), and PVP 40 (12.5 or 25 μM) supplemented with 0.44 μM BA. The number of new shoots from nodal segments of explants placed on MS medium supplemented with 0.44 μM BA increased when the remaining lengths of nodal segments were transferred to fresh medium after the longer microshoots were harvested. The microshoots derived from basal sprouts rooted best (50%) when treated with 11.4 mM IAA for 2 min, whereas only 40% of the microshoots derived from terminal twigs produced roots after a 2-min exposure to 28.5 mM IAA. The placement of BA-soaked agar cubes on the apex-decapitated shoots controlled shoot-tip necrosis considerably. In general, explants from basal sprouts were more suitable than terminal twig explants for the micropropagation of adult trees of C. collinus. Received: 26 February 1997 / Revision received: 13 September 1997 / Accepted: 29 September 1997     

Comparison of an immunochromatographic method and the TaqMan E. coli O157:H7 assay for detection of Escherichia coli O157:H7 in alfalfa sprout spent irrigation water and in sprouts after blanching

An immunochromatographic-based assay (Quixtrade mark E. coli O157 Sprout Assay) and a polymerase chain reaction (PCR)-based assay (TaqMan E. coli O157:H7 Kit) were used to detect Escherichia coli O157:H7 strain 380-94 in spent irrigation water from alfalfa sprouts grown from artificially contaminated seeds. Ten, 25, 60, or 100 seeds contaminated by immersion for 15 min in a suspension of E. coli O157:H7 at concentrations of 10(6) or 10(8) cfu/ml were mixed with 20 g of non-inoculated seeds in plastic trays for sprouting. The seeds were sprayed with tap water for 15 s every hour and spent irrigation water was collected at intervals and tested. E. coli O157:H7 was detected in non-enriched water by both the TaqMan PCR (30 of 30 samples) and the immunoassay (9 of 24 samples) in water collected 30 h from the start of the sprouting process. However, enrichment of the spent irrigation water in brain heart infusion (BHI) broth at 37 degrees C for 20 h permitted detection of E. coli O157:H7 in water collected 8 h from the start of sprouting using both methods, even in trays containing as few as 10 inoculated seeds. The TaqMan PCR assay was more sensitive (more positive samples were observed earlier in the sprouting process) than the immunoassay; however, the immunoassay was easier to perform and was more rapid. At 72 h after the start of the sprouting process, the sprouts were heated at 100 degrees C for 30 s to determine the effectiveness of blanching for inactivation of E. coli O157:H7. All of the 32 samples tested with the TaqMan assay and 16 of 32 samples tested with the Quixtrade mark assay gave positive results for E. coli O157:H7 after enrichment of the blanched sprouts at 37 degrees C for 24 h. In addition, the organism was detected on Rainbow Agar O157 in 9 of 32 samples after 24 h of enrichment of the blanched sprouts. In conclusion, E. coli O157:H7 was detected in spent irrigation water collected from sprouts grown from artificially contaminated seeds by both the TaqMan and Quixtrade mark assays. The data also revealed that blanching may not be effective to completely inactivate all the E. coli O157:H7 that may be present in sprouts.     

Analysis of natural Fagus sylvatica L. s.l. regeneration in low elevation stands located in the central part of the Evros region in northeastern Greece: Is sprout origin regeneration significant for species maintenance?

Abstract

The aim of this study was (a) to analyse natural Fagus sylvatica L. s.l. regeneration in low elevation stands located in the central part of Evros region in northeastern Greece in relation to factors such as site productivity, type of silvicultural treatment and regeneration origin and (b) to determine whether or not sprout origin regeneration is significant for the maintenance of beech stands. One hundred and twenty plots (3 m × 3 m) were established in areas where thinnings and regeneration fellings had taken place, and in two site productivity regimes. In each plot, the number of beech seedlings, saplings, and stump or root sprouts (regeneration plants) with a height of up to 3 m was counted, and their height measured. Our findings indicate that even though reproduction by seed is the predominant regeneration mechanism in our stands, in the medium productivity sites sprouts represent a significant percentage of the total number of plants. Moreover, sprouting functions as a mechanism of maintenance of beech stands in medium productivity sites. During the regeneration fellings practised in this area, it is advisable to cut the seedlings and saplings of the advanced regeneration in order to supplement the seed-derived plants with seedling sprouts.     

Occurrence and pathogenicity of Enterobacter sp. causing sprout decay and seedling stunting of upland cotton (Gossypium hirsutum L.)

A new sprout decay and seedling stunting disease of unknown aetiology in upland cotton (Gossypium hirsutum L.) affecting nearly 5%–10% of young seedlings was noticed in vertisols of central Vidarbha (Maharashtra state, India) in July of 2017. The bacterium was consistently isolated from diseased seedlings and identified with a polyphasic method of characterization, including morphological, physiological, biochemical and 16S rRNA gene sequence analysis. The bacterium strain CICR-MGMG1 was isolated from diseased plants identified as Enterobacter sp. Inoculation of healthy cotton seed with an axenic culture of strain CICR-MGMG1 isolated from diseased young seedling reproduced disease symptoms of yellowing, stunting and deformed growth similar to the symptoms reported from infected field condition. The strain CICR-MGMG1 was consistently isolated from both diseased seedlings and stunted plants. Thus, the pathogenicity test of Koch's postulates was confirmed with the bacterium Enterobacter sp. strain CICR-MGMG1 as the causal organism of sprout decay and seedling stunting. To the best of our knowledge, this is the first record of Enterobacter sp. causing sprouts decay and seedling stunting of cotton.