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One hundred ninety clonal accessions of Corylus, including species and various interspecific hybrids of C. avellana, C. americana, C. heterophylla, C. colurna, and C. fargesii, were assessed for their response to field exposure to the eastern filbert blight (EFB) pathogen, Anisogramma anomala, in New Jersey, where the fungus is native. Plants were obtained from the U.S. Department of Agriculture Agricultural Research Service National Clonal Germplasm Repository and Oregon State University, the University of Nebraska, Lincoln, and the National Arbor Day Foundation. Additional plant material was acquired from the Morris and Holden Arboreta and from private nurseries in Amherst, NY, and Niagara-on-the-Lake, Ontario, Canada. The accessions were chosen based on their resistance to EFB in Oregon, a region where A. anomala is not native, or anecdotal reports and grower observations of tolerance or resistance to the disease. Trees were planted in the field from 2002 through 2009 in New Jersey where they were exposed to EFB yearly through field inoculations and natural spread. In Jan. 2012, they were visually evaluated for the presence of EFB. The cankers were measured, and the proportion of diseased wood was calculated for susceptible trees. Nearly all accessions reported to be resistant to EFB in Oregon maintained at least a useful level of tolerance in New Jersey with a number remaining free of cankers. However, several accessions developed small to medium-sized cankers and showed branch dieback, including offspring of C. avellana ‘Gasaway’. Most C. americana and C. heterophylla accessions remained free of EFB, although variation in EFB response was found in hybrids of these species with C. avellana, ranging from no signs or symptoms to severe EFB. Nearly half of the C. colurna × C. avellana hybrids developed cankers, whereas each of the C. fargesii accessions and most grower selections developed in eastern North America remained free of EFB. The results document the existence of a wide diversity of Corylus germplasm that expresses resistance or a high level of tolerance to EFB in New Jersey and confirms previous reports that C. americana is highly resistant to the disease. Interestingly, most C. heterophylla and the C. fargesii were also found to be resistant despite originating in Asia where A. anomala has not been found. The various interspecific hybrids show the potential for incorporating EFB resistance from wild species through breeding. The results provide further evidence of differences in disease expression in Oregon and New Jersey, where isolates differ and disease pressure may be higher.

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Temperature sensitivity of CO2 assimilation (ACO2), dark respiration, and chlorophyll fluorescence was evaluated among three taxa of hollies including I. aquifolium L., I. cornuta Lindl. & Paxt., and I. rugosa Friedr. Schmidt. Variations in foliar heat tolerance among these species were manifested in temperature responses for ACO2. Temperature optima of ACO2 for I. rugosa, I. cornuta, and I. aquifolium were 22.0, 26.3, and 27.9 °C, respectively (LSD0.05 = 2.9). Temperature responses of respiration were similar among taxa and did not appear to be contributing factors to variations in ACO2. At 40 °C, potential photosynthetic capacity, measured under saturating CO2, was 4.1, 9.4, and 14.8 μmol·m-2·s-1 for I. rugosa, I. aquifolium, and I. cornuta, respectively (LSD0.05 = 5.1). Variations in the relative dark-acclimated fluorescence temperature curves were used to assess thresholds for irreversible heat injury. The critical fluorescence temperature threshold (TC) was similar (48.0 °C) for all taxa. The fluorescence temperature peaks (TP) were 52.0, 52.8, and 53.5 °C for I. rugosa, I. cornuta, and I. aquifolium, respectively (LSD0.05 = 0.9). Based on these results, I. rugosa was the most heat-sensitive species, followed by I. aquifolium and I. cornuta. Ilex cornuta also had substantially greater potential photosynthetic capacity than the other species at 40 °C, indicating superior metabolic tolerance to high temperatures.

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Hazelnuts (Corylus sp.) are monoecious and wind-pollinated with reproduction limited by a sporophytic self-incompatibility system. They flower during the winter and are dichogamous with the dates of flowering ranging from December to March in New Jersey depending on the genotype, geographic location, and year. Successful, consistent nut production depends on both genetic compatibility and the appropriate timing of flowering between pollinizing and nut-producing cultivars. While the disease eastern filbert blight (EFB), caused by Anisogramma anomala, has severely limited past hazelnut production in the eastern United States, resistant and tolerant genotypes are now available for testing. However, little is known of their flowering phenology in this region. In this study, the flower and budbreak phenology of 19 different EFB-resistant and EFB-tolerant hazelnut accessions was evaluated over 4 years, and the results compared with air temperature data collected during bloom. Results showed that the accessions followed a similar progression of bloom each year (both staminate and pistillate flowers), which allowed their placement into early-, mid-, and late-flowering groups. However, the date of bloom and duration of bloom, especially for pollen shed, differed each year, largely corresponding to average air temperature trends. Confirming previous reports from other cold regions, it was shown that consistently colder average temperatures delayed bloom until later in the winter, which then led to a compressed period of flowering once temperatures warmed. In contrast, relatively warm temperatures over the season led to earlier flowering as well as a significant lengthening of the duration of bloom, similar to responses reported in Mediterranean climates. Our study documents hazelnut flowering phenology under New Jersey’s variable winter climate, and the results provide a benchmark for selecting suitable pollenizers and breeding parents for future nut production, flowering research, and/or genetic improvement in this region.

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Eastern filbert blight (EFB), caused by Anisogramma anomala, is a devastating disease of Corylus avellana, the European hazelnut of commerce, and is considered the primary limiting factor of production in eastern North America. Conversely, C. americana, the wild American hazelnut, is generally highly tolerant of EFB, although it lacks many horticultural attributes necessary for commercial nut production. Hybrids of C. americana and C. avellana combine the EFB resistance of the wild species with the improved nut quality of the European species. However, inheritance of EFB resistance from C. americana remains unclear with existing hybrids derived from a very limited selection of parents. To investigate this topic, C. americana and advanced-generation C. americana × C. avellana hybrids were crossed with susceptible C. avellana and the resulting seedlings exposed to EFB through field inoculations and natural disease spread. In the winter after their fifth growing season, plants were rated for the presence of EFB using an index of 0 (no disease) through 5 (all stems containing cankers). The three progeny related to C. americana ‘Rush’ segregated for resistance in a ratio of one resistant to one susceptible, suggesting the presence of a single dominant R gene. A wide array of disease responses was observed for the other progenies with some expressing little EFB resistance or tolerance and others showing a distribution of disease phenotypes typical of control by multiple genes. Overall, the results indicate that both qualitative and quantitative resistance is present in C. americana. They also suggest that the choice of C. americana parent as well as the C. avellana parent will play a significant role in obtaining useful levels of EFB resistance in hybrid offspring, although the degree of disease expression in the parents may not be a useful predictor of progeny performance. Thus, more research is needed to understand inheritance of resistance, especially in advanced-generation backcrosses to susceptible C. avellana.

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The leaf nutrient status and stoichiometry of nitrogen (N), phosphorus (P), and potassium (K) were determined for Elaeocarpus joga trees in Guam’s dominant calcareous soils to understand nutrient limitations in limestone soils of Oceania and contribute to global databases on leaf economic spectrum studies. Supplemental N, P, or K was added to soils to determine plant growth and nutrient concentration responses. Leaf and soil quantifications of nutrients enabled multiple trait comparisons. Supplemental N stimulated growth of young cultivated plants without affecting leaf N concentrations. Supplemental K increased leaf K concentration but did not generate a growth response. Supplemental P did not affect growth or leaf P concentration. N:P, N:K, and K:P were most influenced by K additions. Leaf N and P concentrations of mature trees in unmanaged settings were similar to unfertilized young plants in the controlled study, but leaf K concentration was greater in the mature trees. Leaf nutrient relations were not overtly related to soil nutrient relations for mature trees. Results indicate that N and K are the limiting factors in calcareous soils of the Mariana Islands for this endemic tree species, age and size of trees do not greatly influence leaf nutrient content, and leaf stoichiometry is constrained and less variable than soil stoichiometry.

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Abstract

Apical shoot tips and axillary buds of buffalo gourd (Cucurbita foetidissima HBK.) when cultured on Murashige and Skoog (MS) medium supplemented with 4.4-22.2 μm (1-5 mg/liter) BA and 0-0.54 μM (0-0.1 mg/liter) NAA produced 4-9 multiple shoots within 4 weeks. The individual shoots subcultured on MS medium containing 4.9 μm (1 mg/liter) IBA produced a healthy root system in 4 weeks. Rooted cultures were successfully transferred to soil in a greenhouse. Chemical names used. BA:N-(phenylmethyl)-1H-purin-6-amine. NAA:l-naphthaleneacetic acid. IBA: lH-indole-3-butanoic acid.

Open Access

Abstract

Shoot tips and stem nodes of Asclepias erosa Torr., cultured on a modified (0.5 × major salts) Murashige and Skoog (MS) medium containing 0.54 µm (0.1 mg/liter) NAA and 44.4 µm (10 mg/liter) BA, produced multiple shoots in 5 weeks. Subcultures of the individual shoots on the same medium produced 5-12 new shoots 4 weeks later. Rooting of the resultant shoots was best accomplished by preculturing them for 48 hr on MS medium containing 246 or 492 µm (50 or 100 mg/liter) IB A prior to subculturing for 4 weeks on MS medium devoid of growth regulators. The rooted cultures were established successfully in soil. Chemical names used. NAA: 1-naphthaleneacetic acid. BA:N-(phenylmethyl)-lH-purin-6-amine. IBA: lH-indole-3-butanoic acid.

Open Access

A novel combination of in vitro and in vivo approaches was employed to generate sufficient stock of an introduced grape (Vitis vinifera L.) cv. Arka Neelamani which significantly accelerated the multiplication rate. The in vitro part included induction of root and shoot growth in shoot tip and nodal microcuttings in MS medium containing 1 μm IAA, sequential pruning of shoots at 1, 1.5, and 2 months, leaving the basal one to two nodes, resulting in fresh sprouts on the stump, and use of remaining stumps for in vivo establishment. The in vivo part included acclimatization of in vitro rooted plantlets and stumps, use of single node cuttings from 1.5- to 2-month-old in vivo shoots for the subsequent propagation, and utilizing the fresh sprout growth from these cuttings and in vivo stumps for further propagation. Employing both in vitro and in vivo approaches, we achieved a multiplication rate unparalleled to the general micropropagation or conventional propagation and significant stock was obtained within 6 months of introducing the material. The in vivo plants exhibited adult characters like distichous phyllotaxy, three lobed leaves and normal pattern of tendril development within 2 months from planting.

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Abstract

A plant nutrient delivery system that uses a microporous, hydrophilic tube was developed with potential application for crop production in the microgravity of space. The tube contains a nutrient solution and delivers it to the roots. Pumps attached to the tubing create a very small suction that holds the solution within the tube. This system was used to grow wheat (Triticum aestivum cv. Yecora Rojo) for 107 days in a controlled environment at suctions of 0.40, 1.48, or 2.58 kPa. The water absorbed through the pores of the tube by baby diaper sections decreased as suction increased. Correspondingly, final plant biomass, seed number, and spikelet number also tended to decrease as suction increased. The reduced yield at higher suction suggests that the plants experienced water stress, although all suctions were below those typical of soils at field capacity.

Open Access