Leaf Scars Research Articles

Disease Development and Symptom Expression of Xanthomonas axonopodis pv. citri in Various Citrus Plant Tissues

ABSTRACT Experimental inoculations of Xanthomonas axonopodis pv. citri in different tissues of Tahiti lime and Pineapple sweet orange were conducted monthly under natural conditions on Réunion Island. The interactions between a set of environmental and epidemic variables associated with disease expression and 184 different factor combinations were investigated to determine the parameters needed to explain Asiatic citrus canker (ACC) disease expression. Area under the disease progress curve (AUDPC), inoculation date (Id), fruit and leaf age ratings (FAR and LAR), and number of days during the first 2 weeks postinoculation for which the temperature was less than 14 degrees C (T(min)) or more than 28 degrees C (T(max)) were retained by principal component analysis and canonical correlation analysis as the most meaningful epidemic and environmental variables, respectively. AUDPC as the strongest dependent variable and combinations of the environmental variables as independent variables were used in multiple regression analyses. Tissue age rating at the time of infection was a good predictor for disease resulting from spray inoculation on fruits and leaves and also on fruits following a wound inoculation. Temperature, as expressed by T(min) or T(max), was also a significant factor in determining disease development described by AUDPC. Mature green stems were highly susceptible after wounding, similarly to leaves, but buds and leaf scars expressed the lowest susceptibility. These variations in disease expression according to the tissues will have different impacts on ACC epidemiology.

Genetic basis of color variation in leaf scars induced by the Kanzawa spider mite

Abstract The color of scars induced on host leaves by the phytophagous spider mite Tetranychus kanzawai Kishida (Acari: Tetranychidae) can be categorized as red or white. We conducted a bi‐directional selection on the colors of leaf scars. In each of the selected strains, scars became uniformly red or white (‘Red’ and ‘White’ strains), indicating that scar color was genetically determined. Reciprocal and back‐crosses between strains suggested that the Red genotype was fully dominant over the White one and was controlled by a single locus. The performance index of adult females that induced red or white scars (‘Red’ and ‘White’ females) did not differ significantly among nine tested host plants. There seemed to be no advantages of heterozygosity at either the individual or the colony level. However, Red females defoliated host plants earlier than did White females. As a consequence, Red females dispersed from infested leaves earlier than White ones. The distribution pattern of Red and White females in the wild supported the hypothesis that genetic variation is maintained by different dispersal costs across environments.

An anatomically preserved arborescent lycopsid, Sublepidodendron songziense (Sublepidodendraceae), from the Late Devonian of Hubei, China

Sublepidodendron is a common megafossil plant in the Late Devonian of China, but historically the generic delimitation based on leaf bases masked its true systematic position. A reinvestigation of S. songziense from the Late Devonian Hsiehchingssu Formation, Hubei, China, provides new insights into its internal anatomy and reproductive morphology. This arborescent lycopsid is characterized by small, vertically elongated leaf bases arranged in spirals, presence of false leaf scars, possibly bearing separate cones, and association with a stigmarian rhizomorph. The potential for organic connections of these detached organ genera has been noted for other Sublepidodendron species. The anatomy of S. songziense axes from two levels reveals that the thinner axis may bear an ectophloic siphonostele with a filamentous pith and an outer cortex. The thicker axis has a siphonostele with a branch gap, two-zoned pith with secondary thickenings, multiseriate rays across secondary xylem, a thick periderm, and primary and secondary tracheid walls characterized by "Williamson's striations." Similarities to synapomorphies of Diaphorodendraceae and Lepidodendraceae suggest that S. songziense bears a closer affinity to Lepidodendrales rather than Protolepidodendrales, as formerly thought. Widespread occurrence of Sublepidodendron implies that phylogenetically advanced arborescent lycopsids must have diverged by the Late Devonian.

Hybrid poplar stem cankers caused by Mycosphaerella populorum in Kentucky, USA

Cankers on 2-year-old stems of a hybrid poplar clone [(Populus trichocarpa × P. deltoides) × P. maximowiczii] were noted in two plantations established for clonal evaluation in Livingston County, Kentucky, USA in January 2001. These plantations are separated by approximately 35 km and are located on upland hardwood sites, dominated by Quercus spp., where no extensive native poplar stands are found. In one plantation 30% of stems had cankers; few stems were affected in the second plantation. The cankers were flattened or sunken, discoloured, and resembled those of septoria canker, a severely damaging disease caused by Mycosphaerella populorum (anamorph =Septoria musiva) (Waterman, 1954). Fungal isolates obtained from cankers collected from both plantation sites were identified as S. musiva (Sivanesan, 1990), based on morphological characteristics of pycnidia and conidia produced on V8 vegetable juice medium. Cuttings of the hybrid poplar clone NC11505, known to be susceptible to S. musiva, were rooted in pots in a greenhouse and maintained with ambient light and day and night temperatures of approximately 25 and 15°C, respectively, for 3 months. Stems were then inoculated by placing an agar plug colonized by an isolate of S. musiva on a freshly made leaf scar. Control trees were inoculated in a similar manner, but with uncolonized agar plugs. Plugs were held in place with parafilm and removed after 1 week. After 4 weeks cankers had developed on nine of 10 stems inoculated with S. musiva. The fungus was successfully reisolated and its identify confirmed. Cankers did not develop on the control stems, and S. musiva was not obtained from these trees. Mycosphaerella populorum is assumed to be widely distributed in the eastern USA and Canada (Farr et al., 1989), and reports include mention of its occurrence in states adjacent to Kentucky including Indiana (Farr et al., 1989); Missouri and Ohio (Thompson, 1941); and Tennessee (Waterman, 1954). However, this is the first confirmed report of septoria canker of poplars in Kentucky. This is noteworthy given the current interest of the local forest industry in establishing short-rotation, intensive-culture poplar plantations. The report underscores the need for disease-resistance screening and long-term testing of clones derived from highly susceptible parental species such as P. trichocarpa and P. maximowiczii.

The effect of temperature and wetness duration on infection and a warning system for European canker ( Nectria galligena) of apple in Chile

European canker ( Nectria galligena Bres.) is a major disease of apple in Chile, mainly producing cankers on twigs and branches. Disease incidence over 50% has been reported on ‘Richard Red’ apples in Southern Chile. In vitro, conidial germination of N. galligena was low at 6°C and 32°C, and optimum germination temperature was estimated between 20°C and 25°C. Ascospore germination was low at 5°C and rapidly increased as temperature increased from 5°C to 20°C. Germination rate, calculated as germination frequency over time at 20°C, was 2.3 times faster for ascospores than conidia, and germination of ascospores increased 2.6 times faster than conidia as temperature increased from 5°C to 20 °C. Infection caused by conidia of N. galligena through leaf scars was significantly dependent on temperature and free moisture duration. However, regardless of the wetness duration no infection was obtained at 5°C. This is in agreement with the lack of conidial germination obtained below 6°C by in vitro studies. Disease incidence increased linearly with temperatures between 5 and 20°C. Based on our results, a 2-h moisture period was enough to promote a significant infection at 20°C but longer moisture periods were needed at lower temperatures. An infection warning system, based on the analysis of weather parameters, was developed and implemented in the predictive software PatFrut ©. Over two seasons, the warning system was an effective tool for determination of the need of fungicide treatments against European canker. Significant differences in disease incidence and severity were obtained reducing disease incidence from over 24% in 1999 to 4.6% when treatments were schedule according to the model program. Differences in severity, but not disease incidence were found between the model program and the standard program. This forecast model assumed that conidia, produced during leaf fall were not a limiting factor. It also assumed that susceptible leaf scars were continuously available between March and July. The protective fungicide treatments applied during leaf fall significantly reduced infection in the next season suggesting that leaf scars are important infection courts for N. galligena on apples.

Reduction of olive knot disease by a bacteriocin from Pseudomonas syringae pv. ciccaronei.

A bacteriocin produced by Pseudomonas syringae pv. ciccaronei, used at different purification levels and concentrations in culture and in planta, inhibited the multiplication of P. syringae subsp. savastanoi, the causal agent of olive knot disease, and affected the epiphytic survival of the pathogen on the leaves and twigs of treated olive plants. Treatments with bacteriocin from P. syringae pv. ciccaronei inhibited the formation of overgrowths on olive plants caused by P. syringae subsp. savastanoi strains PVBa229 and PVBa304 inoculated on V-shaped slits and on leaf scars at concentrations of 10(5) and 10(8) CFU ml(-1), respectively. In particular, the application of 6,000 arbitrary units (AU) of crude bacteriocin (dialyzed ammonium sulfate precipitate of culture supernatant) ml(-1) at the inoculated V-shaped slits and leaf scars resulted in the formation of knots with weight values reduced by 81 and 51%, respectively, compared to the control, depending on the strains and inoculation method used. Crude bacteriocin (6,000 AU ml(-1)) was also effective in controlling the multiplication of epiphytic populations of the pathogen. In particular, the bacterial populations recovered after 30 days were at least 350 and 20 times lower than the control populations on twigs and on leaves, respectively. These results suggest that bacteriocin from P. syringae pv. ciccaronei can be used effectively to control the survival of the causal agent of olive knot disease and to prevent its multiplication at inoculation sites.

PARACALAMITINA STRIATA—A NEWLY RECONSTRUCTED EQUISETOPHYTE FROM THE PERMIAN OF ANGARALAND

This paper deals with Paracalamitina striata (Schmalhausen) Zalessky, 1934, an equisetophyte of the family Tschernoviaceae from the Permian of Angaraland. New material contributes to a better understanding of this plant, which now can be reconstructed. Paracalamitina striata is an equisetopsid with opposite ribs on the stem. Its main stem bears lateral shoots or shoot and leaf scars, that are located at nodes. Shoot nodes have subcylindrical leaf sheaths. The distal parts of leaves are free and acute. Generative organs are fertile zones, which are formed by numerous sporangiophores with peltate sporophylls. A terminal sterile whorl is presented above each fertile zone. An emended diagnosis of Paracalamitina Zalessky is provided on the basis of new material and re-examination of previously collected specimens as well. The nomenclature and taxonomic status of P. striata also are discussed.

Paracalamitina striata—a newly reconstructed equisetophyte from the Permian of Angaraland

This paper deals with Paracalamitina striata (Schmalhausen) Zalessky, 1934, an equisetophyte of the family Tschernoviaceae from the Permian of Angaraland. New material contributes to a better understanding of this plant, which now can be reconstructed. Paracalamitina striata is an equisetopsid with opposite ribs on the stem. Its main stem bears lateral shoots or shoot and leaf scars, that are located at nodes. Shoot nodes have subcylindrical leaf sheaths. The distal parts of leaves are free and acute. Generative organs are fertile zones, which are formed by numerous sporangiophores with peltate sporophylls. A terminal sterile whorl is presented above each fertile zone. An emended diagnosis of Paracalamitina Zalessky is provided on the basis of new material and re-examination of previously collected specimens as well. The nomenclature and taxonomic status of P. striata also are discussed.

Differences in salt sensitivity of four deciduous tree species to soil or airborne salt.

Seedlings of four deciduous tree species maple (Acer pseudoplatanus), beech (Fagus sylvatica), horse chestnut (Aesculus hippocastanum) and lime (Tilia cordata) were exposed to de-icing salt (NaCl) either through the soil or applied to the above ground plant parts. A soil solution of 1.65 g l-1 NaCl was maintained from the start of the experiment in January 1999 until termination in June 1999. The main effects caused by salt treatment through the soil were a reduction in photosynthesis of up to 50% and the development of leaf chlorosis or necrosis covering up to 50% of the total leaf area for the most sensitive species (lime and beech); maple and horse chestnut were relatively tolerant. There was no significant correlation between Cl or Na concentration in leaves and the relative sensitivity of the species. Saturated salt solution was applied to bark, buds or leaf scars on two occasions three weeks apart during the winter season. This affected the timing of bud break with delays of up to eight days compared with the controls. In the most sensitive species the above ground salt treatments partly prevented bud break (beech) or reduced photosynthesis (lime). Uptake through the bark was most important for the development of stress effects, compared with uptake through the other above ground plant parts.

Submerged Aquatic Bryophytes in Colour Lake, a Naturally Acidic Polar Lake with Occasional Year-round Ice-cover

Colour Lake is a small, naturally acidic (pH 3.7) lake on Axel Heiberg Island (Canadian High Arctic) that experiences occasional year-round ice cover. We investigated the benthic vegetation of this lake, with a specific aim of determining whether the annual growth of benthic bryophytes reflects the state of summer ice cover. We found the bed of the lake to be almost completely covered by mosses or liverworts to a depth of 22 m. The mosses showed annual growth bands 10-30 mm in length, visible as changes in leaf density and size. Four to five bands retained recognizable leaves and measurable amounts of chlorophyll-a (chla), and up to 12 bands were recognizable from leaf scars. We could not find a consistent relationship between band length and persistence of ice cover for a given year. We suggest that this lack is due to the complex effects of ice cover on moss growth conditions, specifically on the water temperature and irradiance at depth. Photosynthetic characteristics of Calliergon over a range of light and temperature conditions, determined using pulse amplitude-modulated fluorometry, are presented in support of this argument. We conclude that moss banding patterns are an unreliable method of hindcasting episodic failure of ice to melt in Arctic lakes.

Test of Populus x euramericana cv. Pannònia resistance to the attack of Discoporium populeum (Sacc) Sutton by artificial infections

Populus x euramericana cv. Pann?nia is an artificial hybrid, created in the Sarvar research station (Hungary), by crosses made by Kopecky Ferenc. It was registered in Hungary and its identification is H 490-31. Its parents are: Populus deltoides S-1-54 & Belgium (P. deltoides A 42 Iowa ? P. deltoides A148 Missouri) x P. nigra L?b?ny 211%. Inoculations were implanted by spore suspension and mycelium of the fungus, grown on the MEA medium, by standard method. The experiments were performed on the plants 1/2, especially singled out for the experiment and on the plants in the second year after transplanting (2/2 and 2/3), at the locality Siget. The inoculations were replicated three times: 15.05.2000, 14.10.2000 and 31.03. 2001 The study shows that the newly introduced cultivar Populus ? euramericana cv. Pann?nia is not immune to the attack of the fungus Discosporium populeum. The highest percentage of realised infections in the experiment with mycelium was realised in October (89.7%), and the lowest percentage in May (22.6%). Inoculations with spore suspension had the same trend, only the percentage of realised infections was considerably lower, with the maximal value for October, 23.5%. Infection with spore suspension implanted in leaf scar produced the positive results, with 10.4% percentage of infection. A very significant fact is that the percentage of random infections of the plants monitored during the experiment was only 4.4%. Only one plant was girdled and killed during the research. It must be emphasised that all the necrotised spots were callused and remedied in a short period after infection, which indicates the presence of the defence mechanisms in this cultivar The study results are a good base of further research. To be able to bring correct conclusions and recommendations to the practice regarding this cultivar in the study area, it is necessary to assess the degree of Discosporium populeum presence on one-year and two-year old trees .

Large‐scale patterns in seagrass (Thalassia testudinum) demographics in south Florida

An examination of the population age structure of 118 spatially separated subpopulations of Thalassia testudinum over the extent of the Florida Keys National Marine Sanctuary (FKNMS) during a 2‐yr period revealed significant spatial variation in short shoot (SS) demographic characteristics and population dynamics. Shoot age was determined for 12,031 SS. The number of leaf scars on individual shoots was converted to shoot age by use of observed seasonally and spatially variable leaf emergence rates. The yearly mean leaf emergence rate was 0.0295 ± 0.0128 leaves SS−1 d−1 (±1 SD), and the median age of counted shoots was ~5 yr. A significant relationship between asexual reproductive effort and gross recruitment of SS into the populations (r2 = 0.15, P < 0.001) and between mortality of SS and gross recruitment (r2 = 0.72, P < 0.001) existed. Thus, the greatest risk of mortality occurred in areas where gross recruitment was highest. The net population growth for T. testudinum within the boundaries of FKNMS was stable (mean = −0.006 ± 0.089 yr−1). However, areas within FKNMS fluctuated between positive and negative net growth rates (−0.20–0.50 yr−1). The power of such large‐scale observations is the ability to identify areas of management concern and to frame questions that address the controlling mechanisms that influence these regions of fluctuating population growth.

Age determination of individuals of Corydalis species and other perennial herbs

In only a few perennial herbs is age determination of individual plants possible. The life cycle of Corydalis intermedia and C. solida is described. Plants have an age in years identical to the number of dead sheaths outside their underground tuber. Various ways to determine age in other species are reviewed: No. of dead layers around corm: Corydalis cava; no. of dead layers around tuber: Corydalis pumila, Drosera erythrorhiza, D. bulbosa; no. of dead remains of leaves/inflorescence stalks to the side of the corm: Philydrella pygmaea; no. of collaterals in corm: Liatris aspera; no. of nodes on rootstock: Trillium erectum; and no. of bands of high and low density of leaf scars on stems: Aeonium species.

Three New Brazilian Species in the Genus Marcetia (Melastomataceae, Melastomeae)

Three new species of Marcetia are described and illustrated. Marcetia semiriana occurs only in Serra do Cip6, Minas Gerais. Marcetia shepherdii, collected in Marai1, at sea level, and M. lychnophoroides, from Chapada Diamantina, are both endemic to Bahia. The new species Marcetia shepherdii and M. lychnophoroides, together with M. luetzelburgii Markgraf, constitute a group of closely related species. They share in common subcoriaceous, fleshy, imbricate to subimbricate, revolute leaves. Marcetia shepherdii is distinguished by its rigid, erect branchlets, yellowish green leaves that are glabrous on the adaxial surface, unappendaged and broadly dilated connectives, linear-oblong thecae with a ventrally inclined pore, and a unique 2locular ovary. Marcetia lychnophoroides has velutinous to sublanate branchlets, cinereous-green leaves that are densely puberulous-sericeous on the abaxial surface, unprolonged and inconspicuously bilobulate connectives, and a 3or 4-locular ovary. Marcetia semiriana is very similar to M. taxifolia (A. Saint-Hilaire) DC., differing in the prostrate branches, long pedunculate flowers, and straight anthers. Marcetia is a neotropical genus of 27 species largely endemic to Brazil. Except for the widespread Marcetia taxifolia, which has a bicentric distribution in eastern Brazil and northwestern South America (Colombia, Venezuela, and Guyana), all other species of Marcetia have restricted distributions. Marcetia species are usually shrubs or subshrubs that occur in campo rupestre in the Serra do Espinhago, Minas Gerais, in the mountains of Goi s, and especially in the Chapada Diamantina, Bahia. Campo rupestre is an exclusively Brazilian complex mosaic of vegetation types characterized by extensive outcrops of highly acidic rocks, nutrient-poor soils, and local variations in topography, slope, aspect, and moisture regime. A few Marcetia species occur in both montane and littoral areas, such as M. ericoides (Sprengel) 0. Berg ex Cogniaux and M. canescens Naudin. Marcetia shepherdii is the only species in the genus that is endemic to coastal Bahia, where it occurs in the sandy vegetational formation commonly referred to as restinga. The genus Marcetia can be distinguished within the tribe Melastomeae mainly by the combination of tetramerous flowers and simple anthers that lack basally prolonged connectives (except in M. shepherdii) and, in some species, may have short ventral tuberculate appendages. Three of the species studied in my taxonomic revision of Marcetia (Martins, 1989) are new. They are described and illustrated here. Marcetia shepherdii A. B. Martins, sp. nov. TYPE: Brazil. Bahia: Maraui, 4 km de Mara6, 12 Mar. 1977 (fl, fr), G. J. Shepherd, L. S. Kinoshita, J. B. Andrade & N. Taroda 4550 (holotype, UEC). Figure 1. Haec species Marcetiae luetzelburgii affinis, sed ab ea foliis arcte adpressis sessilibus revolutis dense imbricatis internodia brevia occultantibus, ramis basin versus denudatis, conspicue annulis foliorum delapsorum praeditis, lamina foliari supra glabra in sicco flavovirescenti, staminum filamentis ter longioribus, antheris apice rotundato ventraliter minute dehiscenti atque ovario biloculari differt. Erect subshrub ca. 60 cm, compactly branched; branchlets rigid, subterete to inconspicuously quadrangular, moderately puberulous or nearly glabrous, at the base defoliating with age and with conspicuous leaf scars. Leaves opposite, sessile, appressed, densely imbricate and concealing the short internodes; blade lanceolate-ovate, 2.5-3 x 1 mm, fleshy-coriaceous, basally cordate, apically recurved and mucronulate, margins revolute, glabrous on the adaxial surface, glandular-pubescent abaxially, obscurely 1-nerved. Flowers 4-merous, subsessile, solitary in upper leaf axils resembling a terminal foliaceous spiciform inflorescence, becomNOVON 10: 224-229. 2000. This content downloaded from 157.55.39.45 on Fri, 02 Sep 2016 06:22:09 UTC All use subject to http://about.jstor.org/terms Volume 10, Number 3 2000 Luckow & Du Puy Gagnebina bakoliae from Madagascar 225

Genetic and Pathogenic Diversity of Pseudomonas avellanae Strains Isolated from Corylus avellana Trees in North-west of Italy, and Comparison with Strains from Other Regions

Forty strains of Pseudomonas avellanae isolated from hazelnut (Corylus avellana L.) trees in the Langhe district of Italy were compared with 15 strains collected from various geographic areas. All strains were assessed by rep-PCR genomic fingerprinting using ERIC, REP and BOX primer sets. Cluster analysis was performed by means of UPGMA. To check the possible differential virulence of the strains, pathogenicity tests were carried out by inoculating leaf scars of hazelnut trees in early autumn. Cluster analysis indicated that, during a four-year study, at least five groups of strains were isolated from different hazelnut orchards located in the small district of Langhe. Two groups were isolated from the same twig. Such strains showed around 20% similarity with other P. avellanae strains collected from northern Greece and central Italy. The strains from Langhe were less aggressive to hazelnut than strains from northern Greece and central Italy. These results and previous genomic characterizations indicate a possible correlation between genomic profile type and regional geographic distribution of P. avellanae strains. In addition, the genetic variability found in the strains from Langhe indicates that such populations are older than the more homogenous P. avellanae populations from other regions.

Critical assessment of Thalassia testudinum (turtle grass) aging techniques:implications for demographic inferences

Variability in the time interval between the formation of successive leaves (i.e. the plastochron) directly influences estimates of seagrass shoot age. Age-frequency distributions were constructed for Thalassia testudinum short shoots from a shallow and a deep site in the Lower Laguna Madre, Texas, during the summers of 1995 and 1996. In each year the ages of 200 to 250 shoots, collected by coring, were estimated from leaf scars and annual leaf production rates. Two years of monthly leaf production measurements were used to calculate annual leaf production. The leaf production rate was site-specific: plants at the shallow site produced about 13 leaves yr -1 while plants from the deep site produced about 10 leaves yr -1 ; the 95% confidence limits around the mean were ±20 to 25%. At the shallow site, the mean annual leaf formation rate during 1996 was 15% higher than during 1995, indicating substantial interannual variability. Age-frequency distributions were adjusted to account for misclassification errors as a result of age-specific leaf initiation rates. The oldest shoot was estimated to be between 8 and 12 yr. Long-term leaf marking indicates that the seagrass T testudinum in Lower Laguna Madre violates the assumption that the leaf production rate is constant and successive plastochrons are of equal duration. Reduced leaf formation rates during summer were likely caused by resource allocation to developing fruits and seeds. As a result of site-specific, seasonal, and interannual variability in annual leaf formation rates, the application of the plastochron method to estimate T. testudinum short shoot age is limited. Furthermore, a review of the literature indicates that age-frequency distributions cannot be used to predict population growth. Predicting population growth requires traditional demographic methods (e.g. mapping individuals through time).

Valeriana tajuvensis (Valerianaceae), a New Species from Southern Brazil

Valeriana tajuvensis, a species from the Serra Geral massif in Rio Grande do Sul and Santa Catarina, Brazil, is described and compared with related Brazilian species of the genus. RESUMEN. Valeriana tajuvensis, especie de las montafias de Serra Geral en Rio Grande do Sul y Santa Catarina, Brasil, es descrita y comparada con las especies brasilefias afines del g~nero. The last specific study of the genus Valeriana in Brazil (Borsini, 1962) listed 15 species, all of them consisting of herbs restricted to the southern and southeastern states of the country and generally collected in montane or submontane habitats. During recent fieldwork on a montane massif in the southernmost Brazilian state of Rio Grande do Sul, a strikingly distinct, arborescent, and somewhat uncommon species of Valeriana was collected; it is described here. Valeriana tajuvensis Sobral, sp. nov. TYPE: Brazil. Rio Grande do Sul: Tajuva, mun. Morrinhos do Sul (29?21'S, 49?58'W), 19 Aug. 1995 (hermaphrodite fl), J. A. Jarenkow 2708 & M. Sobral (holotype, ICN; isotypes, MBM, PEL, SP). Figures 1, 2. Species haec V polystachyae et V kurtzianae proxima, a quarum habitus arborescenti, ramificatione sympodialis foliisque apici ramorum aggregatis distincta est. Gynodioecious shrub 1-3 m high, profusely sympodially ramified, the branches bearing conspicuous leaf scars; canopy 2.5-3 m diam. Leaves opposite, somewhat tufted at the apex of the branches; blades pinnatisect with elliptic-obovate profile, 8.5-18 cm long, 4-7 cm wide, 15-24-lobed (discounting 4-5 strongly reduced proximal lobes at the base of pseudopetioles), the abaxial face very sparsely glandular-punctate, the glands less than 0.1 mm diam., lobes with the margin slightly revolute, unequal in size, the 4-5 proximal pairs at the base of the pseudopetioles (1-)3-10 mm long, (0.3)1-1.5 mm wide, the others 30-45 mm long and 4-5 mm wide, markedly asymmetrical, the terminal 30-40 mm long and 3-3.5 mm wide, symmetrical; ps udopetioles 4-15 mm long, each pair of leaves connected at base forming a continuous nodal sheath. Inflorescences paniculiform with the final units dichasial, in hermaphrodite plants 20-30 cm long and 10-15 cm wide, in pistillate ones 15-20 cm long and 5-8 cm wide, due to the reduction of secondary ramifications (paracladia sensu Larsen, 1989); proximal bracts similar to leaves, about 6 cm long and 3 cm wide; distal bracts simple and lanceolate, 8-10 mm long and 1-1.5 mm wide; bracteoles lanceolate, 1.5-1.8 mm long and 0.5 mm wide, sometimes with sparse tufts of hairs 0.1 mm long in the base. Flowers sessile, pentamerous, the calyx with 4-5 loosely distinct to completely fused segments, forming a hyaline ring 0.2-0.4 mm high; corolla white, campanulate, with straight tube. Hermaphrodite flowers with corolla about 2 mm long and 2 mm wide, lobes 0.8 mm long and 0.6-0.7 mm wide; stamens attached at about the middle of the corolla, 2-4, generally 3, exserted, filaments about 2 mm long, anthers 2-lobed, globose, the locules in a same anther slightly unequal, about 0.3 mm long; style included, about 1 mm long, stigmas 3, 0.2-0.3 mm; ovary inferior, triquetrous in shape, filled with parenchymatous tissue, unilocular, uniovulate; ovule pendulous. Pistillate flowers with corolla 0.5-0.8 mm long and 0.5 mm wide, the lobes about 0.3 mm long and wide; stamens 3, included, 0.2-0.3 mm long, anthers globose with somewhat unequal locules, about 0.2 mm long, not producing pollen in the flowers examined; style 1.3-1.5 mm long, stigmas 3, exserted, 0.1-0.2 mm long; ovary the same as in hermaphrodite flowers. Fruits triquetrous, asymmetrical in transversal view, 2-2.3 mm long and 1.1-1.3 mm wide, uniseminate, sparsely pilose, eventually somewhat more densely so at the edges. Seeds examined immature. Arborescent species of Valeriana are quite common in the Andean highlands of Colombia, Peru, and Venezuela (Killip, 1925, 1928; Cuatrecasas, 1941; Xena, 1992), the region where Valeriana atNovoN 9: 114-117. 1999. This content downloaded from 207.46.13.101 on Sun, 09 Oct 2016 05:47:53 UTC All use subject to http://about.jstor.org/terms Volume 9, Number 1 1999 Sobral Valeriana tajuvensis from Brazil 115

A New Marsdenia (Apocynaceae, Asclepiadoideae) from Baja California

Marsdenia carterae, a new species of Apocynaceae (Asclepiadoideae, Marsdenieae) from Baja California Sur, Mexico, is described and illustrated. This is the first North American species of Marsdenia with verticillate leaves and is also notable in lacking a developed corona and for its non-twining habit. Marsdenia carterae W. D. Stevens & Ju6rez-Jaimes, sp. nov. TYPE: Mexico. Baja California Sur: eastern escarpment of Cerro Mechudo between Portezuelo de San Antonio and La Sabanilla, Sierra de la Giganta, 675 m, 24?49'N, 110?44'W, occasional on cliffs and talus, 4 Nov. 1971, R. Moran 18990 (holotype, UC; isotype, MO). Figure 1. Distribution map and additional images can be found in W3TROPICOS (http://mobot.mobot.org/ Pick/Search/pick.html). A speciebus ceteris Marsdeniae regionis foliis verticillatis habitu haud volubili corona obsoleta distinguenda. Shrub to 1.5 m tall and 2.5 m wide, branches decumbent or pendent, stems with thick, dark, corky bark on older wood, bark thinner and whitish on younger wood, branchlets roughened by raised leaf scars, densely pubescent with appressed, ? curly, multicellular hairs to ca. 0.15 mm long, internodes 1-5(-25) mm long, ribbed except when still herbaceous; latex white; roots unknown. Leaves 3, rarely 1 or 2, per node, without pseudostipules but with 1-3 colleters in each stipular area, blades 5-8.5 cm long, 4-8 mm wide, very narrowly lanceolate to lorate or linear, apex acute to rounded or minutely mucronate, base acute, minutely pubescent when young, glabrescent except hairs + persistent along midrib of both sides, midrib prominent below, sulcate above, especially near petiole, venation pinnate, lateral veins obscure, ca. 7-13 pairs, middle veins arising ca. 550 to midrib, margin thickened and + revolute, colleters 0-3, at adaxial base of blade; petiole 4-6 mm long, with indumentum of stem. Inflorescence extra-axillary, 1 per node and mostly not on adjacent nodes, cymose, congested-racemiform, or congested-paniculiform, sometimes bearing a fully formed leaf opposite the first flower or branch, 5-15-flowered, with indumentum of stem, peduncle 2-5 mm long, pedicel 3-4 mm long, bracts to 2.5 mm long, 1.1 mm wide, lanceolate; calyx divided to base, with 1-2 colleters below each sinus within, lobes 2.22.5 mm long, 0.9-1.4 mm wide, ovate or elliptic, with rounded tips, green with scarious margins, pubescent outside, glabrous inside; corolla rotate with ascending lobes, aestivation narrowly imbricate and dextrorse, glabrous outside, glabrous inside except throat densely barbate with stiff, white, unicellular hairs to ca. 0.5 mm long, these spreading at sinuses and retrorse between, cream-white, tube 1.2-1.4 mm long, lobes 2.3-3.1 mm long, 1.5-2.2 mm wide, elliptic with obliquely rounded tips; gynostegium ca. 2.2 mm tall, stipe ca. 1.7 mm long, corona obsolete, anthers rectangular, ca. 1.0 mm long, 1.5 mm wide, terminal appendages ovate, ca. 0.8 mm long, 0.6 mm wide, + erect and appressed to style apex, wings straight, parallel, ca. 0.5 mm long, 0.3 mm wide; corpusculum ca. 0.25 mm long, 0.08 mm wide, linear, dark red-brown, translator ca. 0.08 mm long, translucent and unwinged, pollinia erect, ca. 0.25 mm long, 0.15 mm wide, obovate, pale yellow; style apex conical, smooth, shallowly 2-lobed at apex, ca. 0.4 mm wide. Follicles single or occasionally paired, divergent when paired, fusiform-attenuate to napiform, somewhat asymmetrical, smooth, 7-12 cm long, 1.3-1.8 cm wide, densely tomentose, follicle wall ca. 0.5 mm thick, herbaceous; seeds obovate, flat, ca. 11 mm long, 7 mm wide, pale yellow-brown with a pale brown margin 0.4-0.5 mm wide, margin smooth and entire, surface smooth and glossy, coma about 2.5 cm long, pale tawny. NOVON 9: 565-567. 1999. This content downloaded from 207.46.13.60 on Thu, 21 Apr 2016 07:10:49 UTC All use subject to http://about.jstor.org/terms

Seasonal Development of Phomopsis Shoot Blight of Peach and Effects of Selective Pruning and Shoot Debris Management on Disease Incidence.

Seasonal development of shoot blight of peach caused by a Phomopsis sp. was evaluated in Oconee, Hall, and Peach counties in Georgia from April 1994 through May 1996. The frequency of infected buds in all three locations was highest during spring (mid-March to mid-May) and fall (early September to mid-October). The frequency of infected buds was highest in Hall County, which is the northernmost sampling location, followed by Oconee and Peach counties, which are located further south. During the same period of time, the effects of selective pruning and shoot debris management on disease incidence were evaluated in orchards in Oconee and Hall counties from May 1994 through May 1996. Selective pruning of infected shoots in May and October each year, following the major periods of infection, significantly reduced disease incidence during the following seasons in both locations. Disease incidence was similar regardless of whether shoot debris were left under the tree or removed from the orchard and destroyed. Our study indicates that major periods of infection of peach shoots by the Phomopsis sp. occur in the spring during the period of bud break, and in the fall when dormant buds and leaf scars are present. Additionally, our study indicates that reduction of inoculum by selectively removing infected shoots from the trees following the major periods of infection may significantly reduce disease incidence, although it may not eliminate the disease. Removal of infected shoot debris from the orchard does not appear to be necessary following pruning.

A New Species of Dubautia (Asteraceae-Madiinae) from Kaua'i, Hawaiian Islands

Dubautia kenwoodii G. Carr from the Hawaiian Island of Kaua'i is described and illustrated. The new species is distinguished from congeners by virtue of its combination of uniseriate, peripheral, very firmly coalescent receptacular bracts, cymose-glomerate capitula, and coriaceous, lustrous leaves with sharply cartilaginous-toothed margins and abruptly narrowed, broadly clasping bases. Intensive botanical exploration of Kaua'i over the last several years has led to increased understanding of many plant groups and to the discovery of many species not previously known to science. For example, the publication of a new species of Dubautia from Kaua'i by Carr and Lorence (1998, this issue), brings the total number of species currently recognized in that genus to 22 (cf. Carr, 1985). The substantial body of new information about Dubautia on Kaua'i warrants a detailed reassessment of the genus on that island. However, it seems more prudent to formally recognize another new, exceedingly rare species of Dubautia in a timely fashion in order to encourage efforts to find additional populations of this critically endangered taxon and to make it eligible for legal protection and conservation. Dubautia kenwoodii G. Carr, sp. nov. TYPE: Hawaiian Islands (U.S.A.). Kaua'i: Hanalei District, Kalalau Rim, N of Kahuama'a Flat, steep, diverse Lowland Mesic Forest, 800 m, 4 July 1991. K. R. Wood & M. Query 1004 (holotype, PTBG). Figures 1, 2. A speciebus aliis Dubautiae sectionis Dulbautiae bracteis receptaculi uniseriatis peripheralil)us firmissimis coalescentibus, c(apitulis cymnoso-glomerulaltis. foliis (o?riaceis nitidis margine acute cartilaginidentata l)asi al)rupte contracta dliffert. Shrub 5 dm tall, vegetative stems apparently glabrous except for a tuft of trichomes on the upper border of some leaf scars, woody and brown below; flowering stems becoming increasingly hispid in the region of the capitulescence. Leaves opposite, coriaceous, commonly 4-12 cm long, 0.8-2.0 cm broad, narrowly elliptic to sometimes narrowly lanceolate, surfaces nearly concolorous in dried material, gray-green, lustrous above, only slightly paler and duller beneath, glabrous, or becoming medially hispidulous in proximity to the capitulescence: margins with very conspicuous sharply pointed, narrow, somewhat cartilaginous teeth from apex to about the middle, often ciliolate basally; apex usually slightly acuminate; base rather abruptly narrowed and somewhat broadly clasping the stem at point of insertion; venation parallelodromous, with mostly 7 basal veins visible above, sometimes with additional parallel veins and usually fainter elongate-areolate reticulations visible beneath. Heads numerous, disposed in elongatepaniculiform, cymose-glomerate congested capitulescences about 14 cm long and 10 cm broad; peduncles increasingly hispidulous above, the ultimate ones mostly less than 1 mm long; receptacular bracts about 9-12, linear-oblanceolate, gray-green, densely hispidulous and obscurely minutely glandular, peripheral, uniseriate, the lower 23 very strongly and uniformly coalescent (remaining so and becoming sub-indurate on drying), forming a cone about 5 mm long, the lanceolate free tips up to 3 mm long, apparently reflexed in age; receptacle flat, moderately hirsute between the fruit scars; florets mostly 12-18, the corolla rusty yellow in age, 3.0-4.0 mm long, apparently commonly slightly exceeded by the pappus, moderately glandular on the tubular portion, rather abruptly dilated distally, ending in 5 triangular lobes about 1 mm long; pappus stramineous, comprising about 21 unequal, very narrowly linear-lanceolate, shortly fimbriate aristae 3.75-4.5 mm long; achenes conspicuously grayish-strigose, straight or only slightly curved, mostly 3.5-4.5 mm long. Distribution. This taxon is known only from a single collection on the steep slopes of the Kalalau Rim where it was reached by rappelling. Based on extremely limited phenological data, flowering appears to occur in June. Habitat. Dubautia kenwoodii is found in a diverse Lowland Mesic Forest community with Chamaesvce eleanoriae Lorence & W. L. Wagner, HedNovoN 8: 8-11. 1998. This content downloaded from 207.46.13.133 on Fri, 22 Jul 2016 03:58:58 UTC All use subject to http://about.jstor.org/terms 9 Volume 8, Number 1 1998 Carr Dubautia kenwoodii from Kaua'i