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Flyspeck disease caused by the Ascomycete fungus Schizothyrium pomi is a major component of a summer disease complex that has become an increasing problem on apple in the northeastern United States. This study describes the development of thyriothecia of S. pomi on one of its major reservoir hosts, wild blackberry, and suggests that temperature drives thyriothecium maturation. An empirical model relating thyriothecium maturity to degree-days from apple leaf budbreak in Massachusetts had a high coefficient of determination, R2 = 0.90. Ninety percent of thyriothecia matured between 540 and 1,625 degree-days from the budbreak biofix. S. pomi produced one generation of asci per year on blackberry. This discrete maturation period occurred well before signs of disease developed on apple fruit and before production of conidia. Considering that fungicide applications for scab management in commercial apple orchards also will protect fruit from flyspeck during early fruit development, it is unlikely that ascospores produced on reservoir hosts directly infect fruit. Instead, they probably initiate infections in reservoir hosts adjacent to commercial orchards, which produce conidia that are the inoculum which infects apple fruit in commercial production.

Few studies with random amplified polymorphic DNA (RAPD) markers have focused on blackberry genotypes. In this study we attempted to differentiate several blackberry and raspberry cultivars for genetic identification by pedigree and RAPD analyses. Rubus allegheniensis was present in 14 of 16 cultivars and had a mean genetic contribution of 15.9%. The cultivar 'Brewer' and R. argutus were also recurrent founding clones. The raspberry cultivars in this study ('Dormanred' and 'Heritage') participated as the outlier group and were identified as such in relation to the blackberry cultivars both in terms of RAPD and pedigree analysis. One hundred fifty-seven RAPD loci were used to identify 10 of 16 genotypes with unique banding patterns. Blackberries averaged 55% similarity amongst themselves, and 22% to raspberries. Overall, pedigree and RAPD data should be interpreted separately, with the RAPD data likely being more reliable.

Summary 1 Seed banks are dynamic entities, with input occurring through dispersal and loss occurring through germination and various sources of mortality. Measures of abundance of seeds in the soil at one point in time cannot distinguish those seeds destined to germinate or die in the next growing season from those entering the long-term seed bank, and cannot therefore reveal the proportion of seeds that are carried over from year to year. 2 We studied seed bank dynamics in a 2.5-ha deciduous forest gap by following the fate of a single year’s cohort of seeds over 2 years. Seed input for 1 year, subsequent in situ germination and survivorship were measured at 60 locations. We examined how temporal changes in seed bank composition were affected by the presence of the dominant gap colonizing species Rubus allegheniensis. 3 Over the course of 2 years, both mean seed density and its variance declined. The temporal changes in density were not, however, accompanied by detectable changes in diversity. 4 Three species (R. allegheniensis, Phytolacca americana and Paulownia tomentosa) dominated the seed bank. Seed bank accumulation patterns in Rubus and Phytolacca showed contrasting responses to the presence of Rubus, with Phytolacca excluded from seed banks in such patches through reduced input and increased mortality. 5 First year germination and post-dispersal mortality interact with seed input to influence the spatial distribution of density and diversity in the long-term seed bank. Substantial long-term seed banks do form within temperate forest gaps and patterns of above-ground vegetation can have substantial effects on their dynamics.

Most blackberry plants cultivated in Finland closely resemble the American species Rubus allegheniensis. Thirty nine such blackberry accessions in the University of Helsinki clone collection were studied by hybridization-based DNA fingerprinting and compared with some known cultivars of R. allegheniensis derivation. ‘lmperial’ appears to be identical to the old cultivar ‘Majestät’, but ‘Earliest of All’ differs considerably. In addition, 37 of the accessions analysed also have DNA fingerprints that appear to be completely identical to that of ‘Majestät’! The remaining two accessions, although identical to each other, exhibit one band not found in ‘Majestät’ that is probably caused by a somatic mutation., Saatavilla olevien taimien heikko talvenkestävyys ja marjojen myöhäinen kypsyminen vaikeuttavat karhunvatukoiden (Rubus spp.) viljelyä Suomessa. Viksten etsi tutkimuksessaan Suomessa menestyviä karhunvatukoita tiedotusvälineissä julkistettujen kyselyjen avulla. Vastausten perusteella Helsingin yliopistolle kerättiin n. 100 karhunvatukkanäytteen kloonikokoelma. Näistä 74 kloonia muistuttaa läheisesti Pohjois-Amerikassa laajalle levinnyttä Rubus allegheniesis -lajia. Lajiketiedot puuttuivat suurimmalta osalta kerätyistä näytteistä. Tämän tutkimuksen tarkoituksena on tunnistaa lajikkeita vertaamalla tuntemattomien näytteiden ja tunnettujen lajikkeiden DNA-sormenjälkiä keskenään. Kaikista 39 toistaiseksi tuntemattomasta R. allegheniensis -tyyppisestä kloonista ja kokoelmassa olevista ‘Majestät’, ’Imprial’ ja ‘Earliesti of All’ -lajikkeista kerättiin lehtinäytteet. DNA eristettiin hiukan muunnellun Nybomin ja Schaalin ohjeen mukaan. DNA-sormenjälkitekniikka tuotti kaikille tutkituille _Rubus-suvun näytteille selkeät kuviot. ‘Majestät’ ja ‘Earliest of All’ -lajikkeiden DNA-sormenjäljet erosivat selkeästi toisistaan usean viivan osalta. Tässä tutkimuksessa mukana ollut ‘Imperial‘-lajikkeen näyte osoittautui puolestaan täysin samanlaiseksi ‘Majestät’-lajikkeen kanssa. Jotta taimimateriaalin sekaantuminen tai väärä nimeäminen voitaisiin varmistaa, olisi analysoitava useampia eri lähteistä peräisin olevia ‘Imperial‘-lajikkeen näytteitä. Aiemmin tuntemattomasta 39 näytteestä 37 osoittautui täysin samanlaiseksi ‘Majestät‘-lajikkeen kanssa. Kahden näytteen sormenjälkikuvioista löytyi samalta kohdalta yksi ylimääräinen viiva muutoin täysin samanlaiseen ‘Majestät‘-lajikkeen kuvioon verrattuna. Muutoksen aiheuttaa todennäköisesti yksittäinen somaattinen mutaatio, mikä yleensä tuottaa hyvin vähäistä vaihtelua DNA-sormenjälkikuvioihin, kuten on todettu esim. omenoilla. ‘Majestät‘-lajikkeen on aikaisemmin todettu lisääntyvän apomiktisesti, eli suurin osa sen siemenjälkeläisistä on täysin emokasvin kaltaisia. Tämä saattaa olla yksi selitys ‘Majestät’ ja ‘Imperial‘-lajikkeiden identtisille DNA-sormenjälkikuvioille. Immonen mainitsee vielä yhden karhunvatukkalajikkeen, ‘Wilson’s Frühe’, joka on ilmeisesti myös samanlainen kuin ‘Majestät’. Hämet-Ahdin ja muiden mukaan suurin osa Suomessa viljeltävistä karhunvatukoista muistuttaa R. allegheniensis -lajia, ja tämän tutkimuksen tulosten mukaan vain ‘Majestät‘-lajike tästä ryhmästä on todella menestynyt.

The soil seed bank (seed and vegetative propagules) of a jack pine (Pinus banksiana Lamb.) ecosystem was investigated using direct propagule emergence from soil cores in greenhouse experiments, and visual examination of rhizome/rooting systems in situ. Of the 985 emergents observed from soil cores 643 (65%) originated from seeds whereas 342 (35%) arose from rhizomes. Grasses and sedge comprised 89% of the seed emergents while shrubs comprised 75% of the vegetative emergents. In situ examination of root systems revealed that Linnaea borealis L., Carex houghtonii Torr., Gaultheria procumbens L., and Maianthemum canadense Desf. had rhizomes buried at or above the duff/mineral interface while Lycopodium obscurum L., Lycopodium complanatum L. and Pteridium aquilinum L. (Kuhn) were predominately buried within the upper- layers of mineral soil. All other vegetatively reproducing species examined, with the exception of Rubus alleghaniensis Porter, had rhizomes buried deeper than 25 cm into mineral soil. Rubus allegheniensis (reproductive roots) had no discrete area of burial and were located in duff, upper mineral, and deep mineral soil. Depth of burial of reproductive material is used to explain plant succession after disturbance.

The effect of unincorporated and incorporated litter and extracts of broom-sedge, fescue, and blackberry on the mycorrhizal development and growth of black walnut seedlings was investigated in two greenhouse experiments. Seedling growth varied with method of litter application. Only fescue extract decreased growth in the extract experiment, but unincorporated and incorporated broom-sedge litter significantly (P ≤ 0.05) reduced seedling total dry weight below that of mycorrhizal control seedlings. The total dry weight of seedlings in incorporated fescue litter was reduced by 47%. The number of mycorrhizal infected root segments on seedlings grown in unincorporated litter was more than twice the number of infected roots on seedlings grown in incorporated litters. Significantly fewer mycorrhizal roots were found on seedlings grown with fescue and broom-sedge litters than on mycorrhizal control seedlings. On the average, incorporation of litter increased the percentage of leaf phosphorus, but the shoot absorption of phosphorus was considerably less for seedlings grown in incorporated fescue litter compared with unincorporated fescue litter. Seedlings grown in fescue extract had 33% less phosphorus than control seedlings. Except for possible interference with mycorrhizal development when litter was incorporated, there was no evidence to suggest that blackberry litter contains substances that are allelopathic to black walnut.

Studies conducted from May through Nov., 1979 determined that the distribution and abundance of Scaphylopius acutus acutus (Say) (Homoptera: Cicadellidae), a vector of peach ( Prunus persica Batsch) X-disease, in a Connecticut peach orchard were related to the distance from wild host species at the orchard edge and to the relative abundance of wild host plants in the orchard ground cover. Greatest numbers of adult S. acutus for spring and summer generations were captured on yellow sticky traps located among wild host plants at the orchard edge while fewest were caught on traps in peach trees furthest from the edge. Density of nymphs and adults on peach trees and in ground cover in 32 plots along a transect through the orchard increased with the relative abundance of wild host plants in the ground cover and decreased with distance from the orchard edge. Host preference experiments conducted in the laboratory revealed that both generations of S. acutus were most highly attracted to red clover, Trifolium pratense L. (Leguminosae), for feeding and oviposition. However, this plant comprised less than 1% of the orchard ground cover. Peach was preferred as a food host by both generations over 8 wild host species, which comprised 94% of the ground cover. Oviposition preference experiments indicated that peach was among the least preferred hosts for both generations while several rosaceous species, in particular strawberry, Fragaria virginiana Duchesne and blackberry, Rubus allegheniensis Porter, comprising 65% of the ground cover, were most highly preferred for oviposition. The differential utilization of peach and wild rosaceous hosts by S. acutus for feeding and oviposition would encourage frequent movement of adults between peach and the ground cover.

Excess nitrogen (N) in terrestrial ecosystems can arise from anthropogenically-increased atmospheric N deposition, a phenomenon common in eastern US forests. In spite of decreased N emissions over recent years, atmospheric concentrations of reactive N remain high in areas within this region. Excess N in forests has been shown to alter biogeochemical cycling of essential plant nutrients primarily via enhanced production and leaching of nitrate, which leads to loss of base cations from the soil. The purpose of our study was to investigate this phenomenon using a multifaceted approach to examine foliar nutrients of two herbaceous layer species in one N-treated watershed (WS3—receiving aerial applications of 35 kg N/ha/yr as ammonium sulfate, from 1989 to the present) and two untreated reference watersheds at the Fernow Experimental Forest, WV, USA. In 1993, we analyzed foliar tissue of Viola rotundifolia, a dominant herb layer species and prominent on all seven sample plots in each watershed. In 2013 and 2014, we used foliar tissue from Rubus allegheniensis, which had become the predominant species on WS3 and had increased, though to a lesser extent, in cover on both reference watersheds. Foliar N and potassium (K) were higher and foliar calcium (Ca) was lower on WS3 than on the reference watersheds for both species. Magnesium (Mg) was lower on WS3 for Viola, but was not different among watersheds for Rubus. Results support the stream chemistry-based observation that excess N lowers plant-available Ca and, to a lesser degree, Mg, but not of K. Foliar manganese (Mn) of Rubus averaged >4 times that of Viola, and was >50% higher on WS3 than on the reference watersheds. A Mn-based mechanism is proposed for the N-meditated increase in Rubus on WS3. Data suggest that excess N deposition not only alters herb community composition and biogeochemical cycling of forest ecosystems, but can do so simultaneously and interactively.

Diploid Rubus allegheniensis Porter and R. rusticanus Merc. shoot tips were proliferated in tissue culture and treated with 0.02 to 0.08% colchicine to induce non-chimeral polyploidy. About 20 shoot tips of each treatment were transferred to test tubes containing modified Anderson's medium for shoot proliferation. Shoots at the 3- or 4-leaf stage were transplanted into Jiffy-7 peat pellets and placed under intermittent mist for rooting. Root tip squashes were made for chromosome counts. Thirteen R. allegheniensis and 7 R. rusticanus plants proved to be autotetraploids (28 chromosomes). Stomata of the autotetraploids were significantly larger than those of the diploids but stomatal conductance of CO2 and photosynthesis rate were reduced significantly as compared to diploids. Pollen grains in tetraploid were larger than those in diploid R. allegheniensis plants. These results indicate that tissue culture can facilitate the production of non-chimeral colchiploids in Rubus spp.