Academic literature on the topic 'Seven-weeks fern'

During July 2005, Phytophthora ramorum S. Werres & A.W.A.M. de Cock was isolated from nine native Adiantum jordanii plants growing at two forest sites (Samuel P. Taylor State Park, Marin County and Peachland Road, Mendocino County) and from seven A. aleuticum plants at one forest site (Peachland Road) in California. At both locations, symptomatic plants were distributed close to rivers and roads and in association with infected bay laurel trees (Umbellularia californica), toyon (Heteromeles arbutifolia), and tanoaks (Lithocarpus densiflorus). Symptomatic leaflets showed brown spots that sometimes coalesced, killing entire leaves, but the disease did not appear to be fatal to the ferns. Necrotic tissues were plated on PARP and maintained in the dark at 18°C for 1 to 2 weeks. Isolates were identified as P. ramorum on the basis of colony morphology, the presence of chlamydospores and caducous, semipapillate sporangia, and the internal transcribed spacer (ITS) rDNA sequences (1,2). The P. ramorum isolates, Pr-419 from A. jordanii and Pr-422 from A. aleuticum, have been deposited in the American Type Culture Collection (ATCC MYA-3677 and MYA-3679, respectively) and a region of the ITS rDNA sequence deposited in the NCBI database (GenBank Accession No. DQ173082 and DQ219821, respectively). To test the pathogenicity, the tips of freshly detached leaves of A. jordanii and A. aleuticum were dipped into a solution of 1 × 103 zoospores per ml of Pr-419 and Pr-422 for 1 min. The wounded end of the leaves was not exposed to the inoculum. The zoospores were produced by flooding agar disks (1 cm in diameter) from the margin of 8- to 14-day-old colonies growing on V8 juice agar with sterile deionized water. After 3 days of incubation at 20°C in the dark, zoospore release was induced by placing dishes at 4°C for 20 min and then at room temperature for 60 min. For each Adiantum species and P. ramorum isolate, 15 leaves collected from five potted nursery plants were tested. Control leaves were dipped in sterile deionized water. Leaves were maintained in a moist chamber at 19°C with 13 h of natural light for 9 days. Brown lesions similar to those seen in the forest developed on approximately 60 and 33% of the A. jordanii and A. aleuticum leaves, respectively, inoculated with Pr-419 and on approximately 73 and 40% of the leaves inoculated with Pr-422. Under these experimental conditions, A. aleuticum appeared to be slightly more susceptible than the A. jordanii, with a necrotic leaf area of approximately 38% compared with 20%. The pathogen was reisolated on PARP after surface sterilization from all symptomatic leaves. Control leaves did not develop symptoms and P. ramorum was not recovered. A. jordanii and A. aleuticum have already been listed as associated hosts for P. ramorum on the APHIS (USDA Animal and Plant Health Inspection Service) website ( http://www.aphis.usda.gov/ ). To our knowledge, this is the first report of ferns as natural hosts of P. ramorum. References: (1) D. M. Rizzo et al. Plant Dis. 86:205, 2002. (2) S. Werres et al. Mycol Res. 105:1155, 2001.

Mary Washington, UC157F1, and UC157F2 asparagus cultivars were grown from 1-year-old crown under greenhouse conditions in 30-liter pots containing Pro-Mix medium. The roots were cut to 10 cm prior to planting on 12 Feb. 1991. On July 12, 1991 the plants were transferred outdoors and sprayed with BA, GA4/7 and Promalin at 400 mg. liter-1 using tap water as control. On July 16, 1991 the treated ferns were cut at ground level and the plants were returned to the greenhouse, and arranged in a RCB design. Seven reps with one pot/rep were used. Data on time of emergence of first shoots were recorded daily until all pots had produced at least 1 shoot. When all plants had sprouted, cumulative number of all shoots/pots was recorded weekly thereafter over 5 weeks. BA and Promalin reduced time of emergence of shoots and increased the number of shoots/plant. GA4/7 had no effect on shoot emergence or shoot number.

AFRIKAANS: Rumohra adiantiformis (G. Forst.) Ching, die seweweeks- ofknysnavaring se gewildheid as loof in die snyblombedryf neem vinnig toe. Onder natuurlike groeitoestande ontwikkel die seweweeksvaring slegs beperkte hoeveelhede sori op blare, terwyl groot hoeveelhede sori ontwikkel wanneer die varing onder skadunet verbou word. Die teenwoordigheid van oormatige sori lei tot bemarkingsprobleme. Die navorsing is op die perseel van Bergland Tuine kwekery te Krugersdorp uitgevoer om die invloed van etefon, paklobutrasool (PP333), gibberelliensuur (GA3) , sitokiniene en verskillende skaduvlakke op sorivoorkoms en grootte van seweweeksvaringblare te bepaal. Behandeling van PP333 teen 500 mg dm-3 of met etefon teen 144 en 480 mg dm-3 in die blaarknopstadium het die getal sori by volwassenheid van blare betekenisvol verlaag. PP333-behandelings teen 1 000 en 1 500 mg dm-3 in die blaarknopstadium het die sori by volwassenheid van blare hoogs betekenisvol verlaag. Bespuitings met behandelings GA3 teen 57,6 mg dm-3 of sitokiniene teen 0,00062 en 0,0155 mg dm-3 op die blaarknopstadium het tot 'n betekenisvolle verhoging van sori op volwasse blare gelei. PP333 of etefon beinvloed nie die blaargrootte van volwasse blare wat in die jongblaar-, oopgevoudeblaar- en blaarknopstadium behandel is nie. Blare van al drie blaarstadia wat met sitokiniene of GA3 behandel is, was by volwassenheid nie-betekenisvol groter. Die 70% skadunet met bykomstige swartplastiekstroke in 'n noordsuidrigting onderaan gespan het die getal sori op blare verlaag en die blaaroppervlakte betekenisvol vergroot. Faktore soos seisoenale variasie, oesfrekwensie, plantdigtheid, grondvogstatus, waterkwaliteit, peste en plae was nie by hierdie ondersoek ingesluit nie en behoort ondersoek te word. ENGLISH: Rumohra adiantiformis (0. Forst.) Ching, the seven-weeks or knysna fern is a relatively new floral greenery of increasing importance. In its natural habitat the seven-weeks fern produces small numbers of sori on leaves, while commercially cultivated ferns under shade produce large numbers. The presence of excessive numbers of sori have a detrimental influence on the market value of the product. A trial was conducted on the premises of Bergland Tuine nursery in Krugersdorp to determine the effect of ethephon, paclobutrazol (PP333), gibberellic acid (GA3), cytokinins and different shade levels on the presence of sori and size of seven-weeks fern leaves. Leaves treated in the leafbud stage with PP333 at 500 mg dm-3 or ethephon at 144 and 480 mg dm-3 significantly reduced the number of sori on the leaves at maturity. Highly significant reduction of sori on mature leaves were found when PP333 was applied at I 000 and 1 500 mg dm-3 on the leaves in the leafbud stage. Sori numbers on mature leaves significantly increased after treatment of bud stage leaves with GA3 at 57,6 mg dm-3 or cytokinins at 0,00062 and 0,0155 mg dm-3. The leaf size of mature leaves was not influenced when PP333 or ethephon was applied on the leaves at the young leaf, unfolded leaf and leafbud stage. Leaves in all three leaf stages treated with cytokinins or GA3 showed a non-significant increase in leaf size at maturity. The 70% shade net with additional black plastic strips suspended underneath the net in a north-south direction, reduced the number of sori on the leaves and increased the leaf area significantly. Factors such as seasonal variation, harvest frequency, plant density, ground moisture levels, water quality, diseases and pests were not included in this investigation but should be researched.<br>Dissertation (MSc(Agric))--University of Pretoria, 2011.<br>Plant Production and Soil Science<br>unrestricted