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We present a spectral analysis of two XMM-Newton observations of the narrow-line Seyfert 1 galaxy UGC 11763. UGC 11763 shows very different soft X-ray spectral shapes in the two observations separated by 12 years. Three spectral models are considered to explain the multi-epoch X-ray variability of UGC 11763, one based on the relativistic disc reflection model, one based on multiple partially-covering absorbers combined with the warm corona model, and a hybrid model. In the first model, the X-ray variability of UGC 11763 is caused by the emission from a compact coronal region with a variable size. The resulting disc reflection component changes accordingly. A warm absorption model with a modest column density is required in this model too. In the partially-covering absorption scenario, the X-ray variability of UGC 11763 is caused by the variable covering factors of two absorbers located within a region of $r, 13 pages, 10 figures, accepted by MNRAS

Previously, we modelled the X-ray spectra of the narrow-line Seyfert 1 galaxy IRAS 13224$-$3809 using a disc reflection model with a fixed electron density of $10^{15}$ cm$^{-3}$. An additional blackbody component was required to fit the soft X-ray excess below 2 keV. In this work, we analyse simultaneously five flux-resolved XMM-Newton spectra of this source comprising data collected over 2 Ms. A disc reflection model with an electron density of $n_{\rm e}\approx10^{20}$ cm$^{-3}$ and an iron abundance of $Z_{\rm Fe}=3.2\pm0.5Z_{\odot}$ is used to fit the broad-band spectra of this source. No additional component is required to fit the soft excess. Our best-fit model provides consistent measurements of black hole spin and disc inclination angle as in previous models where a low disc density was assumed. In the end, we calculate the average illumination distance between the corona and the reflection region in the disc of IRAS 13224$-$3809 based on best-fit density and ionisation parameters, which changes from 0.43$\sqrt{f_{\rm AD}/f_{\rm INF}}$ $r_{\rm g}$ in the lowest flux state to 1.71$\sqrt{f_{\rm AD}/f_{\rm INF}}$ $r_{\rm g}$ in the highest flux state assuming a black hole mass of $2\times10^{6}M_{\odot}$. $f_{\rm AD}/f_{\rm INF}$ is the ratio between the flux of the coronal emission that reaches the accretion disc and infinity. This ratio depends on the geometry of the coronal region in IRAS 13224$-$3809. So we only discuss its value based on the simple `lamp-post' model, although detailed modelling of the disc emissivity profile of IRAS 13224$-$3809 is required in future to reveal the exact geometry of the corona., Comment: 17 pages, 15 figures including appendices; accepted for publication in MNRAS

We analyze three observations of GRS 1915+105 in 2017 by Insight–Hard X-ray Modulation Telescope when the source was in a spectrally soft state. We find strong absorption lines from highly ionized iron, which are due to absorption by disk wind outflowing at a velocity of ∼1000 km s−1 along our line of sight. Two of the three observations show large amplitude oscillation in their light curves and the variation pattern corresponds to state κ of GRS 1915+105. From time-averaged and flux-resolved analysis, we find that the variation in the ionization state of the disk wind follows the X-ray continuum on timescales from hundreds of seconds to months. The radial location of the disk wind is consistent with thermal driving. The mass-loss rate due to the outflowing wind is comparable to the mass accretion rate in the inner disk, which demonstrates the important role of the disk wind in the disk accretion system.

We present an analysis of the NuSTAR and Swift spectra of the black hole candidate MAXI J1813-095 in a failed-transition outburst in 2018. The NuSTAR observations show evidence of reflected emission from the inner region of the accretion disc. By modelling the reflection component in the spectra, we find a disc inner radius of $R_{\rm in}, 9 pages, 12 figures, accepted for publication in MNRAS

Biochar offers several benefits as a soil amendment, including increased soil fertility, carbon sequestration, and water-holding capacity in nutrient-poor soils. In this study, soil samples with and without biochar additives were collected for two consecutive years from an experimental field plot to examine its effect on the microbial community structure and functions in sandy soils under peach-trees (Prunus persica). The four treatments evaluated consisted of two different rates of biochar incorporated into the soil (5%, and 10%, v/v), one “dynamic” surface application of biochar, and a 0% biochar control. Fatty acid methyl ester (FAME) analysis was used to assess the microbial community structure, and enzyme activities involved in C, N, P, and S nutrient cycling were used as a means of assessing soil functionality. Total FAME and bacterial indicators increased by 18% and 12%, respectively, in the 10% incorporated and 5% surface applied treatments. Biochar applications increased β-glucosaminidase and arylsulfatase activities, 5–30% and 12–46%, respectively. β-glucosidase and acid phosphatase activities decreased by approximately 18–35% and 5–22% in the 0–15 cm soils. The overall results suggest that biochar’s addition to the sandy soils stimulated microbial activity, contributing to the increased mean weight diameter (MWD), C sequestration, and consequential soil health. The changes in microbial community structure and functions may be useful predictors of modifications in soil organic matter (SOM) dynamics due to the long-term application of pine biochar in these systems.

A preliminary study examining soil microbiology and nutrient dynamics in year three of a peach orchard at the Sandhills Research Station‎, North Carolina, USA found that maintaining a 3.6-m vegetation-free strip in the tree row reduced microbial biomass and associated activities in the soil, compared with a 0 m strip, and that the use of under tree micro-sprinkler irrigation increased peach root colonization by endomycorrhizal fungi as well as microbial biomass and associated activities. The current study was conducted in years four and five of that orchard and examined vegetation-free strip widths of 0, 1.2, 2.4, and 3.6 m, with and without irrigation, to determine their effects on endomycorrhizal fungal colonization of peach roots, soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), soil microbial respiration (SMR), and net nitrogen mineralization (NNM). There were no significant differences between treatments for endomycorrhizal fungal colonization or MBC by year four. The 3.6 m vegetation-free strip had the lowest MBN and SMR in year four with no significant difference between strip treatments in year five. NNM decreased with greater vegetation-free strip widths in years four and five. Irrigated plots had significantly higher MBN and lower SMR in the spring of year five with no other significant differences due to irrigation. These important findings show that under standard commercial management of a bearing peach orchard there is little impairment of soil ecological function in the rhizosphere, allowing for maximum peach yield and quality while supporting the health of trees and soil.

From 14 to 18 Prunus rootstocks budded with ‘Redhaven’ peach were planted at 16 locations in North America in 2009. Seven-year performance from 12 remaining locations in 11 states showed that significant differences among rootstocks and sites were found for survival, root suckers, growth, bloom date, fruit maturity date, fruit size, cumulative yield, and yield efficiency. Survival was highest for peach seedling rootstocks at all locations. In contrast, survival of non-peach species and hybrid rootstocks was poor to fair in Missouri (winter cold, wet feet conditions) and Alabama, Georgia, North Carolina, and South Carolina due to bacterial canker. Krymsk®1, Krymsk®86, Penta, Controller(TM) 5 and Mirobac (a.k.a. Replantpac or Rootpac®R) were the most susceptible to tree death from Pseudomonas syringae canker in the four southeastern states. Overall, Imperial California had the lowest survival followed by Fortuna and Krymsk®1. Rootstock suckering was excessive on Prunus americana seedlings with lesser suckering noted on, Mirobac, Krymsk®1 and Penta. Largest trees were three Prunus × almond hybrids (Viking, Atlas, Brights Hybrid #5) and Guardian®. Fruit size varied with location and crop load (i.e., some rootstocks had few fruit). Atlas produced the largest fruit and Fortuna the smallest fruit across all sites. Cumulative yields were highest in the peach rootstocks such as Guardian®, Lovell and KV010127 and on Atlas. The lowest yields were from plum hybrids and plum species. Cumulative yield efficiency was higher on the non-peach rootstocks, but these rootstocks also produced trees much smaller than the peach and almond hybrid cultivars. The clonal P. persica rootstocks HBOK 10 (Controller(TM) 8) and HBOK 32 (Controller(TM) 7) appeared to be the most promising of the size-controlling rootstocks tested. These data suggest there was no demonstrated advantage to increase yield ha-1 by using clonal interspecific Prunus hybrids for peach production under current cultural practices. However, on higher pH soils in Colorado and Utah, peach seedlings were not the superior rootstocks for production so continuing evaluation of non-peach rootstocks is warranted.

Biochar may enhance soil health in sandy soils under peach [Prunus persica (L.) Batsch] tree production. A study was initiated in the Sandhills of North Carolina by applying pine‐biochar at two different rates (5 and 10%, v/v) and types of application (incorporation to 30 cm [‐Inc] and surface [‐Sur]) in 2017. Soil organic matter (SOM) dynamics was assessed via soil organic carbon (SOC), total nitrogen (TN), permanganate‐oxidizable carbon (POXC), aggregate fractions (macro‐, micro‐aggregates, and clay + silt particles), and enzyme activities (CNPS activity) at 0–15 and 15–30 cm in 2018 and 2019. After the first year of pine‐biochar application, POXC decreased in all biochar treatments, SOC was higher in the 10%‐Inc treatment, whereas CNPS activities and macroaggregates were highest in the 5%‐Sur compared with the non‐treated control. These results suggest early changes in SOM dynamics and biogeochemical cycling and have the potential to guide producers with the long‐term application of pine‐biochar to sandy soils.

Orchard floor vegetation competes with peach trees for water and nutrients and may harbor pathogens and insects. Tree growth, fruit yield, and fruit size can be optimized through management of vegetation in the tree row and irrigation. Under-tree vegetation-free strip widths (0, 0.6, 1.2, 2.4, 3.0, and 3.6 m) and irrigation were studied in years four through eight of a young peach orchard to determine their effects on peach tree growth and fruit yield, harvest maturity, and fruit size. Immature fruit samples were collected during thinning in years four through six to determine the effect of the treatments on the incidence of hemipteran (catfacing) insect damage. Trunk cross-sectional area (TCSA), as a measure of tree growth, increased with increasing vegetation-free strip width; trees grown in the 3.6-m vegetation-free strip had TCSAs 2.2 times greater, on average, than trees grown in the 0-m vegetation-free strip. TCSA also increased with irrigation; trees grown with irrigation had TCSAs 1.2 times greater, on average, than trees grown without irrigation. Yield increased with increasing vegetation-free strip width, from 9.6 kg per tree in the 0-m plot to 26.5 kg per tree in the 3.6-m plot in year four, to 24.3 kg per tree in the 0-m plot and 39.6 kg per tree in the 3.6-m plot in year eight, for a total yield over years 4–8 per tree of 100 kg in the 0-m plot compared with 210 kg per tree in the 3.6-m plot. Yield, average fruit weight, and average fruit diameter increased with irrigation in three of 5 years; the other 2 years had higher than average rainfall reducing the need for supplemental irrigation. In 3 out of 5 years fruit in irrigated plots matured earlier than fruit in nonirrigated plots. In all years, fruit grown in the 0-m strip matured earliest and had the smallest diameter. Establishing a vegetation-free strip of as narrow as 0.6 m reduced the incidence of catfacing damage compared with the 0-m treatment, even though the orchard was on a commercial pesticide spray schedule. The least damage was seen with the industry standard vegetation-free strip widths greater than 3.0 m with or without irrigation.

With the registration of 1-methylcyclopropene (1-MCP) in the USA and large scale use on apples, the question was posed of how effective the product would be in maintaining the flesh firmness of tree ripened peaches. In NC where peaches are sold primarily through retail outlets immediately after harvest, high quality tree-ripened peaches are expected. However, to meet this expectation peaches are picked at a more advanced stage of maturity and they are softer with a reduced shelf life. Six peach (Prunus persica L. Batsch) cultivars and one nectarine cultivar were harvested at tree-ripe maturity. The cultivars were selected to represent a range of maturity from early to late season. The cultivars included in this study were: 'Candor', 'Goldprince', 'Carolina Red', 'Redhaven', 'Contender', 'China Pearl', and 'Big Red'. After harvest the fruit were cooled overnight to remove field heat and then treated with 1-MCP for 24 h at 5°C. After treatment with one µL/L 1-MCP the fruit were held at 21°C for up to 8 days to simulate retail and consumer conditions after purchase. Treatment with 1-MCP resulted in fruit with higher flesh firmness, particularly during the first 5 days at 21°C, compared to untreated fruit. Treated fruit were significantly firmer than the untreated fruit after approximately seven days, but this was somewhat dependent on harvest maturity. On fruit harvested at a later stage of maturity that had significantly softened, 1-MCP had little effect. One µl/L reduced the respiration rate of the fruit. Effect on soluble solid concentration was not consistent. It was concluded that use of 1-MCP would allow a tree-ripened peach to maintain slightly greater flesh firmness for a longer period of time when held under room temperature conditions. However, the commercial economics of this treatment need to be determined.

Researchers have collected a considerable amount of data relating to apple (Malus ×domestica) cultivars and rootstocks over the past 30 years, but much of this information is not easily accessible. The long-term goal of our working group is to increase access to this information using online technology available through eXtension. In eXtension, researchers and extension personnel are developing a community of practice (CoP) to increase the quality and amount of online information for individuals interested in our work [referred to as a community of interest (CoI)]. For this project, our CoI is broadly defined as commercial apple producers, nursery professionals, county extension educators, Extension Master Gardeners, home gardeners, and consumers. Our CoP is developing diverse educational tools, with the goals of increasing productivity, profitability, and sustainability for commercial apple production. Additionally, we will provide other members of our CoI access to research-based, reliable information on the culture of apples. We chose to begin our focus on cultivars and rootstocks adapted to the eastern United States and will add other U.S. regions as our resources and interest in our project grows.

Many of the apples (Malus ×domestica) grown in the southeastern United States are sold to consumers through direct farm markets and roadside stands. Fruit in these markets may be exposed to high temperatures (>68 °F), which cause the fruit to ripen quickly, limiting their shelf life and consumer appeal and increasing their susceptibility to decay pathogens. Studies were undertaken in 2009 and 2010 to determine the effects of a 1-μL·L−1 postharvest 1-methylcyclopropene (1-MCP) treatment on the maintenance of flesh firmness and the incidence of rots in fruit held at elevated temperatures for up to 8 weeks. 1-MCP-treated fruit of three apple cultivars (Ginger Gold, Gala, and Golden Delicious) held in three retail farm markets in the southeastern United States maintained their firmness for 3 to 5 weeks. The firmness of non-treated ‘Ginger Gold’ fruit declined to less than 12 lbf after 1 week in each market, whereas the firmness of treated fruit remained greater than 16 lbf after 3 weeks. Treated ‘Gala’ fruit maintained their firmness at 14 lbf during 4 weeks in each farm market, whereas the firmness of non-treated fruit declined to less than 12 lbf after 2 weeks. The firmness of non-treated ‘Golden Delicious’ fruit declined to less than 12 lbf after 1 week in each farm market, whereas treated fruit maintained their firmness for up to 4 weeks. ‘Golden Delicious’ fruit treated with 1-MCP exhibited almost no loss of firmness during 4 weeks at 32, 50, or 70 °F, or even up to 8 weeks at 32 or 50 °F. The incidence of fruit rots increased with temperature, and 1-MCP reduced the incidence of fruit rots after 4 weeks at 70 °F in 2009 or after 8 weeks at 70 °F in 2010. These data show that 1-MCP may be of great benefit to producers who sell their fruit directly to the consumer by delaying the loss in firmness and reducing the incidence of rots in fruit kept at elevated temperatures.

Experiments were conducted to compare the effects of different preharvest and postharvest 1-methylcyclopropene (1-MCP) treatment combinations on ‘Law Rome’ and ‘Golden Delicious’ apple fruit. Preharvest 1-MCP sprays had minimal effects on maturity as determined by flesh firmness, starch index, internal ethylene concentration, and soluble solids concentration. Fruit internal ethylene concentration and firmness loss after 30- to 40-days storage at 0 °C plus 7 days at 20 °C were reduced by preharvest and postharvest 1-MCP treatments. The positive effects of preharvest 1-MCP on postharvest quality of ‘Law Rome’ declined in fruit that were harvested 3 days or more after spraying, whereas preharvest 1-MCP continued to have a positive effect on postharvest fruit quality of ‘Golden Delicious’ that were harvested up to 9 days after spraying. The loss in postharvest effects of preharvest 1-MCP treatment on ‘Law Rome’ at delayed harvests was reinstated by exposing fruit to gaseous 1-MCP on the day of harvest. These findings suggest that attached apple fruit of some cultivars may be capable of rapidly generating new ethylene receptors.

Three experiments were undertaken to evaluate the effects of different preharvest 1-methylcyclopropene (1-MCP) spray treatments on apple (Malus × domestica Borkh.) fruit maturity at harvest and quality after long-term storage in a regular atmosphere or controlled atmosphere (CA). Trees were sprayed within 7 days of the anticipated harvest date (H) and fruit for long-term storage were sampled at either H in the case of ‘Law Rome’ or at harvest dates that were delayed by up to 21 days (H + 21) in the case of ‘Golden Delicious’ and ‘Law Rome’. Preharvest 1-MCP sprays within 7 days of H reduced fruit drop, internal ethylene concentration, and starch index and reduced firmness loss during long-term storage of fruit at delayed harvest dates but had only minor effects on fruit maturity at H. Preharvest 1-MCP sprays reduced the incidence of superficial scald on ‘Law Rome’ apples more effectively than either diphenylamine or CA storage. Application of 1-MCP within 7 days of H may be used to delay harvest date, thereby allowing continued fruit growth without a concomitant advance in fruit maturity and to reduce firmness loss and superficial scald during long-term storage both for normal and delayed harvests.

An experiment was conducted at one location in 1999 and two locations in 2000 to determine the critical weed-free period for peach in North Carolina. The cultivars for the three locations were ‘Contender’, ‘Norman’, and ‘Summerprince’. Weed-free intervals of 0, 3, 6, 9, 12, and 15 wk after peach tree bloom were established. Paraquat at 1.1 kg ai/ha plus nonionic surfactant at 0.25% v/v was applied every 10 d, after treatments were initiated at peach bloom, to maintain weed-free plots. Large crabgrass, hairy vetch, and smooth crabgrass were the primary weeds in Contender. Horseweed, smooth crabgrass, and large crabgrass were the primary weeds in Norman. Bermudagrass, smooth pigweed, and common lambsquarters were the primary weeds in Summerprince. No differences in trunk cross-sectional area were observed between the weed-free periods. Maintaining the orchard floor weed-free for 12 wk after peach tree bloom resulted in the greatest fruit size (individual fruit weight and diameter), total yield, and fruit number.

White clover is a weed in apple orchards that competes with the crop; also, flowers of this weed are unwanted attractants of honey bees at times when insecticides, which are harmful to these pollinators, are being applied. In 1997 and 1998, white clover flower head and plant control by clopyralid alone and with 2,4-D and apple tolerance to these herbicides were determined. Treatments consisted of clopyralid at 0.10 and 0.21 kg ae/ha, 2,4-D at 1.1 kg ae/ha, and 2,4-D at 1.1 kg ae/ha plus 0.03 or 0.05 kg ae/ha clopyralid, which were applied 2 wk before full apple bloom and 2 wk after full apple bloom, and a nontreated check. No crop injury occurred with any treatment. All herbicide treatments provided some white clover control and flower head suppression. No differences in white clover bloom reduction were observed through May among treatments containing clopyralid. As summer progressed, the effect of clopyralid rate became more apparent. Clopyralid at 0.21, regardless of application time, provided 99% vegetative control and 100% flower head reduction through July. Clopyralid plus 2,4-D controlled white clover better than 2,4-D alone. However, vegetative control and flower head reduction with clopyralid at reduced rates (0.03 or 0.05 kg ae/ha) plus 2,4-D were not acceptable (76% or less and 78% or less, respectively). Thus, clopyralid at 0.10 and 0.21 kg ae/ha will be necessary for acceptable white clover vegetation control and flower head reduction.

In two orchard experiments, interplanting wheat (Triticum aestivum cv. Stacy) around either newly planted or 4-year-old well-established peach trees did not suppress (P ≤ 0.05) the population density of the ring nematode, Criconemella xenoplax, after 3 years. Furthermore, inter-planting wheat around newly planted trees reduced tree growth, perhaps the result of competition for water and (or) nutrients. Wheat root exudate was not as attractive to C. xenoplax as peach root exudate, but wheat root exudate did not repel the nematode either. Stacy wheat appeared to be more beneficial as a preplant rather than as a postplant ground cover management tool for suppressing the population density of C. xenoplax.

Peach (Prunus persica L. Batsch. `Biscoe'/Lovell) trees were grown in a sandy loam soil under six orchard floor management systems, including five vegetative covers (continuous under the tree) and a vegetation-free control (bare ground). At the end of the fifth year, trees grown in bare ground and nimblewill grass (Muhlenbergia schreberi J.F. Gmel.) had a significantly larger trunk cross-sectional area (TCSA) than trees grown in weedy plots, centipedegrass [Eremochloa ophiuroides (Munro) Hack.], or bahiagrass (Paspalum notatum Flugge). Trees grown in brome (Bromus mollis L.) did not differ significantly in TCSA from any other treatment. Soil profile excavations of the root system revealed that trees grown in bare ground or with nimblewill had significantly higher root densities than those in the weedy plots or grown with bahiagrass. Vector analysis of root distribution indicated that trees grown in bare ground or nimblewill rooted deeper than trees in all other treatments. The greatest reduction in deep rooting occurred with bahiagrass.

The root distribution of peach trees (Prunus persica (L.) Batsch cv. Redhaven/Halford) as affected by six orchard floor management treatments was evaluated after 3 years of growth. Two treatments were maintained vegetation-free and four had vegetative covers in the alleyway with a 1.2-m-wide herbicide strip in the tree row. The profile wall method was used to determine root distribution. Trees maintained vegetation-free with herbicide had the most roots. Trees in the vegetation-free plots, maintained with herbicide or cultivation, produced more roots 1.2 m from the tree than trees in the vegetative covers. The number of roots, 1.2 m from the tree, was lowest in the tall fescue treatment. The number of roots were higher in the Kentucky bluegrass (Poa pratensis L.) or alfalfa (Medicago sativa L.) than with tall fescue (Festuca arundinacea, Schreb.). Michigan peach orchard floor management is primarily clean cultivation with cover crops planted in the fall, or vegetative covers with herbicide strips in the tree row. Several reviews have docu- mented the effects of orchard floor management on tree growth and soil characteristics (Haynes, 1980; Hogue and Nielsen, 1987), but little has been reported about the effect on root growth and distribution (Atkinson, 1980). Root distribution of various fruit crops differs in response to cultural management practices of tree spacing, fertility level, irrigation, and cultivar (Lyons and Krezdorn, 1962; Castle, 1980; Perry et al., 1983). Root distribution of orange (Citrus sinensis Osb.) trees was affected by tree density (Boswell et al., 1975; Castle, 1980). Nonirrigated peach trees had more roots than irrigated trees (Layne et al., 1986). Perry et al. (1983) reported large differences in the number of roots and root dry weight at various depths and lateral distances from the trunk of four Vitis cultivars. A vegetation-free area around fruit trees had a significant effect on tree rooting (Atkinson and White, 1976). Apple (Malus domestica Borkh.) trees grown in grass had fewer roots and lower root weights than total vegetation-free treatments, which had the most roots. Ten-year-old apple trees maintained with a herbicide strip had higher root densities under the herbicide strip than under the vegetative alley. Tree roots under the vegetative alley grew deeper than those under the herbicide strip (Atkinson et al., 1977). Glenn and Welker (1989) reported tall fescue sod resulted in reduced peach root length for roots

Apple (Malus domestica Borkh.) cultivars Spur Galagored (#42) (`Gala'), Jonagored (`Morren's'), and Red Fuji (B.C. #2) (`Fuji') on Mark rootstock and `Gala' on Malling 26 EMLA (M.26) and Malling 9 EMLA (M.9) were planted in the four major apple-production regions of western North Carolina. Three leader management techniques, weak leader renewal, snaked leader, and heading with partial terminal leaf removal (H + PTLR), were applied to five-tree plots beginning the spring after planting. Leader management techniques, weak leader renewal or H + PTLR, which involved dormant pruning or vegetation removal and an interruption in vegetative vigor, reduced total branching and yield during the third year. Fumigation with methyl bromide increased lateral branching and yield in the third year. No significant yield differences were detected for `Gala' grown on M.9, M.26, or Mark rootstocks. Trees grown in the most western region of the state, Haywood County, had smaller trees and reduced yields compared to the other three regions due to a shorter growing season.

An overview description of the WR-21 Intercooled Recuperated Gas Turbine Engine System (ICR), currently being designed, built and tested for the U.S. Navy Surface Fleet is presented. The paper describes a development program which reduces development risk and results in a modem, affordable engine that reduces propulsion fuel costs by 30 percent. Major system components and their functions are outlined. Environmental and performance requirements are discussed together with trade-offs which lead to the current configuration as the best combination of cost, performance, reliability, maintainability and other attributes. Then the configuration design is presented. A key to the low-risk design is commonality with the commercial RB211 aircraft engine family. Inherited from the RB211 modular engine are the flexible ICR maintenance features. Modularity also allows mixing and matching to achieve a variety of engines ranging up to 37.3 MW (50,000 bhp). Finally, the ship integration aspects of the WR-21 are discussed.

Peach tree short life (PTSL), a major disease complex impacting peach culture in the southeastern United States for decades, accounts for millions of dollars of losses annually. In spite of the overwhelming amount of research that has been conducted on PTSL, many uncertainties still exist regarding the factors involved in the syndrome and the true cause of tree death. As a consequence, we examined the wood structure and anatomy of 6-year-old peach trees, some showing the initial visible symptoms of PTSL, and others that appeared unaffected and healthy. Very dramatic differences in wood anatomy were observed between healthy and stricken trees. Stricken trees showed a total lack of vessel formation in some earlywood zones, a decrease in vessel formation in latewood, and a marked increase in ray parenchyma cells. Healthy trees showed normal vessel and ray formation. Preliminary results indicate that in some way PTSL may be associated with increased gum production in the xylem and decreased earlywood vessel production, thereby significantly reducing water conduction, leading to tree death. Results of studies currently in progress to further investigate this hypothesis will also be presented.

With the current situation facing land grant universities of declining resources and a portion of federal funding being dependent upon multistate activities, the search for means to successfully address clientele needs may be handled through multistate activity. In the Southeast, the tree fruit programs, both research and extension, have been evaluating areas that could be addressed with multistate programming. To date, most of the tree fruit multistate activities have been informal in nature. The apple program was the first to look at multistate activity because of the heavy concentration of the industry in the mountains of NC, SC, GA, and TN. The formation of the Southeastern Apple Growers Meeting, which combined the annual educational meeting for apple growers in NC, GA, SC, and TN, was the first initiative. It proved to be very successful with the completion of the eighth joint meeting. In addition, the pest management guides for both apple and peach have been combined for many of the southeastern (five states) and southern states (11 states), respectively. Numerous working groups, workshops, tours, and field days are held on a regional scale as well. However, in order for multistate programming to succeed, our experience suggest the need for several key components. The technical competence in the program to be addressed, a supportive university administration, backing of the industry groups, and personnel that are neither territorial nor resistant to change must be present. From our experience multistate programming can be very successful!

Southeastern peach and pecan orchards weathered hurricanes in the 1980s and 1990s that left long-term effects on tree health and productivity. Pecan trees were affected the most, due to being blown down from strong winds and wet soils or suffering considerable damage to branches and immature nuts resulting in massive nut drops. Premature nut drop triggered or enhanced alternate bearing problems. Cultivar differences were evident in the ability of trees to withstand wind damage, with open-canopy trees being most resistant, but essentially all trees were damaged when they exceeded ≈17m in height. Hurricanes in older, alternate-bearing orchards sometimes broke enough limbs to induce sufficient vegetative regrowth to reestablish an equilibrium between sink (nuts) and source (foliage), thus enhancing yields in subsequent years. Peach trees which were less than 4.5 m tall and already harvested usually did not blow over unless the soil was very wet. However, peach trees were often twisted about the tree axis from the change in wind directions as the hurricane passed over. Afterwards, many trees leaned more than 30 °, especially trees less than 6 to 7 years of age. Root damage was significant and increased when trees were manually repositioned as additional root breakage occured from which these trees often later died. Trees not repositioned but instead retrained to vertical by pruning lived longer. Ambrosia beetles also attacked wind-stressed trees and caused a long-term decline. Slow moving hurricanes significantly damaged peach trees by waterlogging the soil, which killed roots and helped primary pathogens such as Phytophthora sp. to attack the tree crown. This was followed by secondary pathogens like Oxyporous sp., which attacked the internal woody cylinder. Initial trunk damage appeared localized; however, trees continued to die over a number of years. Experience showed that whole orchard removal on severe waterlogged sites was the best economical response.

A problem facing the peach industry is the ability to harvest field-ripened peaches and get them to market without significant softening or damage. However, getting mature peaches into marketing channels before significant softening occurs is a challenge. Our objectives were to evaluate two growth regulators to determine the effect on fruit quality and softening at harvest and after 1, 2, or 3 weeks in cold storage and to evaluate the effect on harvest date. The two products evaluated in this study were ReTain (aminoethoxyvinylglycine (AVG)—Abbott Labs) and EthylBloc (1-methylcyclopropene (MCP)—Biotechnologies for Horticulture). ReTain is a growth regulator that inhibits ethylene production and is used in commercial apple production to delay harvest. EthylBloc is applied as a gas and attaches to ethylene receptor sites which inhibits ethylene effects. A trial with preharvest foliar applications of ReTain and postharvest gassing with EthylBloc was initiated in July 1998 on `Contender' peaches. ReTain applications were made at 3-day intervals beginning 19 days before first harvest at the rate of 50 g a.i./acre. Applications 3 days before harvest resulted in increased flesh firmness at harvest and decreased ethylene evolution, which continued for up to 3 weeks in cold storage. Fruit were also gassed with 1 μl•L-1 (1ppm) EthylBloc in the laboratory the day following harvest for 24 h. Fruit treated with ReTain and EthylBloc had twice the flesh firmness of peaches that were not treated after 1 week in storage. ReTain applied 3 days before harvest delayed maturity. Further evaluation will be conducted in 1999.

Thinning peach fruit in the spring of the year is one of the most labor- and capital-intensive operations for peach growers in the southeast. In addition, fruit size can be negatively affected if peach thinning is delayed. The objective of this study was to evaluate the application of gibberellic acid (4% GA3, Ralex—Abbott Labs) in June to reduce peach bloom the following spring. Ralex was applied in June 1995 and 1996 to `Contender' peaches. Bloom density was evaluated in Spring 1996 and 1997 from long and short shoots from the higher and lower portions of the tree's canopy. Applications in 1995 were to trees with a crop load while applications in 1996 were to trees without a crop due to a spring freeze. Bloom densities in 1997 were 300% greater than bloom densities in 1996. The five rates of material evaluated were 0, 59, 79, 99, and 119 g/ha. In 1996, bloom density was significantly reduced with Ralex applications with the greatest reduction with the 99 and 119 g/ha application rates. However, in 1997 only slight differences were detected between all treatments with no difference between the control and 79-g/ha rate.

A study was initiated in 1994 to evaluate the performance of the recently released peach rootstock Guardian TM (BY-5209-9), compared to Lovell, the commercial standard in North Carolina. `Redhaven' was the scion for both rootstocks. Guardian&™ is reported to be tolerant to root-knot nematodes and not affected by ring nematodes, which contribute to the incidence of peach tree short life (PTSL). The site of this study has a history of poor peach tree survival. Six-year-old trees were removed because of tree mortality from PTSL in Spring 1993. After tree removal, one-half of each existing row was pre-plant fumigated and trees were replanted over the rows of the previous orchard in Feb. 1994. In Spring 1996, tree mortality for the trees planted on Lovell was 30%, compared to 10% for the trees planted on GuardianTM. Trunk cross-sectional area for trees grown in the fumigated soil was approximately double that of trees grown in the unfumigated soil for both GuardianTM and Lovell. The 1996 fruit crop was eliminated from frost/freeze conditions and 1997 yields will be discussed. In Fall 1996, one-half of the trees were treated with a post-plant nematicide to determine if such treatments are necessary or beneficial with the GuardianTM rootstock.

Managing vegetative growth in higher density apple systems in the Southeast can be difficult due to the longer growing season. This study was initiated in 1990 to evaluate leader management techniques that have commercial potential for high-density systems in the Southeast. `Spur Galagored', `Jonagored', and `Red Fuji' apples on Mark root-stock were planted in the four major apple production regions of western North Carolina. The three leader management techniques evaluated were weak leader renewal, banding of the leader during the growing season (snaked leader), and leader heading with partial terminal leaf removal (H + PTLR) every 25 cm of leader growth. In the third year, branching was greatest for the snaked leader. In the fifth year, no differences in trunk cross-sectional area were detected between the leader management techniques. However, yields were significantly greater for trees managed with the snaked leader. Trees with the snaked leader yielded 44 kg/tree compared to 35 and 34 kg/tree for the H + PTLR and weak leader renewal, respectively. This illustrates that leader management techniques that use pruning or vegetation removal reduce the early production required of profitable high-density systems.

Controlling vegetative growth resulting from a long growing season in the southeast is difficult while trying to promote early fruiting. This study was initiated in 1990 to evaluate higher density leader training techniques, cultivar interactions, and the benefits of pre-plant fumigation on apple replant sites. Another objective was to evaluate these management parameters in four regions with very different climates and elevations. The training techniques evaluated were, weak leader renewal, bending of the leader during the growing season, and partial terminal leaf removal every 10 inches of leader growth (without injuring the apical meristem). The cultivars used were Jonagored, Spur Gala, and Red Fuji, all on Mark rootstock. First and second year branching was not significantly different between the various training techniques. Yields during the third year did not appear to differ between the leader training techniques. Pre-plant fumigation appeared to be beneficial in increasing tree growth in only two of the four sites.

Peach trees (`Biscoe'/Lovell) were planted in March, 1988 in ten different ground cover management systems. The trees were planted at the Sandhills Research Station in Southeastern North Carolina on a Candor sand and Eunola sandy loam. In December, 1991 the trench profile method was used to evaluate root distribution under the six orchard floor management systems of nimblewill, bare ground control, centipedegrass, brome, bahiagrass, and weedy control. Trenches were dug parallel to the tree row 60 cm from the center of the row on both sides of the tree. Grids 1 meter square, sectioned into 10 cm squares, were placed on the profile walls and root distribution (in three size categories) was recorded for 1 meter on each side of the tree in each trench. Root numbers were greatly reduced under the vegetative covers that provided the greatest suppression of vegetative tree growth. Total root densities under the trees in the vegetative covers were ranked into three size categories which were correlated with the amount of vegetative tree growth.

Saccharomyces cerevisiae a cells secrete an extracellular protein, called "barrier" activity, that acts as an antagonist of alpha factor, the peptide mating pheromone produced by mating-type alpha cells. We report here the DNA sequence of BAR1, the structural gene for barrier activity. The deduced primary translation product of 587 amino acids has a putative signal peptide, nine potential asparagine-linked glycosylation sites, and marked sequence similarity of the first two-thirds of the protein with pepsin-like proteases. Barrier activity was abolished by in vitro mutation of an aspartic acid predicted from this sequence homology to be in the active site. Therefore, barrier protein is probably a protease that cleaves alpha factor. The sequence similarity suggests that the first two-thirds of the barrier protein is organized into two distinct structural domains like those of the pepsin-like proteases. However, the BAR1 gene product has a third carboxyl-terminal domain of unknown function; deletion of at least 166 of the 191 amino acids of this region has no significant effect on barrier activity.