USDA Plant Research Articles

ASM Participates in USDA Plant and Pest Biology Workshop

ASM Participates in USDA Plant and Pest Biology Workshop

Susceptibility of Fruit from Diverse Apple and Crabapple Germplasm to Attack from Apple Maggot (Diptera: Tephritidae)

Apple maggot, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), is a pest of major concern to apple, Malus x domestica (Borkh.) production in eastern North America. Host plant resistance to apple maggot among apple germplasm has been previously evaluated among a small number of exotic Malus accessions and domestic hybrid selections. However, a large number of exotic accessions housed in USDA collections have never been evaluated for their susceptibility to apple pests. Additionally, previous reports of resistance need to be confirmed under both field conditions and with more rigorous laboratory evaluations. Thus, studies were conducted to evaluate the susceptibility of a number of Malus accessions housed at the USDA Plant Genetic Resources Unit "core" collection. Contrary to earlier published reports, these results suggest that some selections previously described as "resistant" are in fact susceptible to both oviposition damage and larval feeding damage by apple maggot. One domestic, disease-resistant apple accession, 'E36-7' is resistant to survival of apple maggot larvae except when the fruit is nearly ripe in late fall. This is the first report of an apple cultivar that is confirmed to be resistant to larval feeding of apple maggot. Although adults can successfully oviposit on all accessions examined, larval survival was zero in a number of small-fruited crabapple accessions classified as resistant in previous studies and also in two accessions, Malus tschonoskii (Maxim) C. K. Schneid. and M. spectabilis (Aiton) Borkh., that have not been previously evaluated.

Rowcovers Improve Winter Survival and Production of Western Trailing ‘Siskiyou’ Blackberry in the Eastern United States

Winter injury has limited the expansion of commercial blackberry (Genus Rubus, subgenus Rubus) production into more northern latitudes in central and eastern United States. Rowcover (RC) was applied over trailing ‘Boysenberry’ and ‘Siskiyou’ and erect, thornless ‘Triple Crown’ and ‘Apache’ blackberries at Kearneysville, WV (lat. 39.5°N, USDA Plant Hardiness Zone 6b) from 2004 to 2007. The daily minimum temperatures under RC were as much as 5 °F to 10 °F higher at nights after sunny days, but were similar during nights after overcast days. On sunny days, daily maximum temperatures under RC were as much as 28 °F higher than in the open. Under RC, humidity rose more quickly and remained higher during the day than in the open, but was slightly lower at night. Mean vapor pressure deficit in late December, January, February, and early March was 100 to 250 kPa higher under RC than in the open. RC treatment significantly reduced winter injury and increased yield in ‘Siskiyou’ blackberry plants. The winter protection techniques described here would provide substantial benefits for growing blackberries in more northern areas where winter injury frequently causes crop failure.

Animals in Veterinary Medical Teaching: Compliance and Regulatory Issues, the US Perspective

Veterinary schools in the United States are regulated as research facilities under the federal Animal Welfare Act by Animal Care (AC), a division of the USDA's Animal and Plant Health Inspection Service (APHIS). The schools are inspected at least annually by AC inspectors, who are all veterinarians. In a recent poll, these inspectors identified several areas that have caused compliance problems for veterinary schools. In addition, several emerging issues also appear to be posing potential regulatory problems as societal expectations and ethical considerations change.

Susceptibility of Fruit from Diverse Apple and Crabapple Germplasm to Attack by Plum Curculio (Coleoptera: Curculionidae)

Plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), is an important apple, Malus domestica Borkh., pest that significantly hinders sustainable apple production in eastern North America. The potential for host plant resistance to plum curculio among apple germplasm has never been rigorously evaluated. Thus, studies were conducted to assess the susceptibility of a number of exotic and domestic Malus accessions housed at the USDA Plant Genetic Resources Unit (PGRU) "core" collection in Geneva, NY. Contrary to earlier published reports and promising data from a field assessment in 2005, these results suggest that there is probably little potential for genetic resistance to plum curculio among the Malus germplasm collection evaluated. More specifically, four Malus hybrid selections that have previously been released with claims of plum curculio resistance were shown to be susceptible to plum curculio attack. Because there are additional accessions housed at PGRU outside of the core collection that are currently classified as resistant, further studies are necessary to evaluate the true resistance qualities of these releases. It is also important to clarify such discrepancies in both the USDA online Germplasm Resources Information Network and in the horticultural literature. Although other Malus species exhibited some variability in fruit susceptibility, none could be classified as being truly resistant to plum curculio attack by any definition that would have relevance to commercial production and sale of apples.

Susceptibility of Fruit from Diverse Apple and Crabapple Germplasm to Attack by Plum Curculio (Coleoptera: Curculionidae)

Plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), is an important apple, Malus domestica Borkh., pest that significantly hinders sustainable apple production in eastern North America. The potential for host plant resistance to plum curculio among apple germplasm has never been rigorously evaluated. Thus, studies were conducted to assess the susceptibility of a number of exotic and domestic Malus accessions housed at the USDA Plant Genetic Resources Unit (PGRU) “core” collection in Geneva, NY. Contrary to earlier published reports and promising data from a field assessment in 2005, these results suggest that there is probably little potential for genetic resistance to plum curculio among the Malus germplasm collection evaluated. More specifically, four Malus hybrid selections that have previously been released with claims of plum curculio resistance were shown to be susceptible to plum curculio attack. Because there are additional accessions housed at PGRU outside of the core collection that are currently classified as resistant, further studies are necessary to evaluate the true resistance qualities of these releases. It is also important to clarify such discrepancies in both the USDA online Germplasm Resources Information Network and in the horticultural literature. Although other Malus species exhibited some variability in fruit susceptibility, none could be classified as being truly resistant to plum curculio attack by any definition that would have relevance to commercial production and sale of apples.

A Worldwide Survey of Cultivated Metasequoia glyptostroboides Hu & Cheng (Taxodiaceae: Cupressaceae) from 1947 to 2007

Since the first seeds were sent from China in December 1947, the famous “living fossil” Metasequoia glyptostroboides Hu & Cheng has been cultivated for 60 years throughout the world. The comprehensive survey of Metasequoia cultivation presented herein has been conducted over the past five years, yielding 2535 accessions from nearly 50 countries on every continent. Optimal growth seems to be in the USDA Plant Hardiness Zones 5 through 9 in North America and Europe, as well as comparable areas in East Asia. The tallest individual reported is approximately 38 m in height, and the largest is approximately 6.2 m in girth. The details of each accession are summarized, including place cultivated, recent growth statistics, and information about the source of introduction.

Gladiolus Rust Caused by Uromyces transversalis Makes First Nearctic Appearance in Florida.

The most serious rust pathogen of gladiolus (Gladiolus × hortulanus), Uromyces transversalis, has been listed as an exotic pathogen of concern for the United States for more than 80 years (4). Native to South Africa, the pathogen was reported in the Western Hemisphere for the first time in Brazil (2) and Argentina (1). Reports of gladiolus rust in several central Mexican states from 2004 to 2005 (3; http://www.pestalert.org/espanol/oprDetail.cfm?oprID=138 ) and interceptions at Mexican border stations and in Brazilian imports in 2005 at the port of Miami, FL collectively raised the alert level in the United States to high. In April 2006, the Hawaii Department of Agriculture notified the USDA of rust-infected gladiolus in a cut-flower shipment that was traced back to a 1,400-acre (565 ha) farm in Manatee County, FL. Inspection at the farm yielded samples that were quickly confirmed as U. transversalis by FDACS-DPI and USDA plant pathologists. The disease was identified in eight residential gardens near the commercial find and in another 700-acre (285 ha) farm in remote Hendry County, 100 miles to the southeast. In May 2006, gladiolus rust was detected in residential and commercial gladiolus in San Diego County, CA (see companion publication). On the advice of a USDA-assembled panel of experts, strict rust management guidelines and fallow host-free periods were implemented with the ultimate goal of eradication. Subsequent summer, fall, and now winter surveys in the infested commercial and residential areas have uncovered diminishing amounts of rust, with last traces detected on 9 September 2006. Commercial planting resumed at both farms in late summer, and crops remained rust free under weekly inspection until 15 February 2007 in Manatee County and 29 March 2007 in Hendry County. To insure a rust-free product, cut flowers are carefully inspected and foliage stripped at the packinghouse. Eradication will be attempted once more with a fallow host-free period before the 2007 season. U. transversalis is an autoecious rust that mainly infects Gladiolus spp., but has been known to infect other members of the Iridaceae: Anomatheca, Crocosmia, Melasphaerula, Tritonia, and Watsonia. Amphigenous uredinia form in transverse lines across gladiolus foliage and also on flower spikes under heavy disease pressure. The isolate present in Florida fits the literature description of U. transversalis in every respect (uredinia 0.5 to 1.5 mm in diameter, subglobose to ellipsoid verruculose yellow-amber urediniospores, 15 to 28 × 14 to 20 μm with wall 1.5 to 2.5 μm thick; telia also amphigenous, 0.5 to 1.3 μm in diameter, dark brown-black, subglobose to pyriform smooth amber teliospores, 20 to 30 × 15 to 20 μm with wall 1.5 to 2.0 μm thick, 4 to 6 μm thick at apex, pale brown to hyaline pedicel 30 to 40 μm long, yellow-brown paraphyses in pustule) ( http://nt.ars-grin.gov/fungaldatabases/new_allView.cfm?whichone=all&thisName=Uro myces%20transversalis&organismtype=Fungus ). Urediniospores initiated typical foliar lesions on transplanted gladiolus samples kept in the FDACS-DPI quarantine greenhouse during the diagnostic process.

Exotic Pest Information Collection and Analysis (EPICA) – gathering information on exotic pests from the World Wide Web*

This paper describes the Exotic Pest Information Collection and Analysis (EPICA) project, a cooperative effort of the United States Department of Agriculture's (USDA) Center for Plant Health Science and Technology (CPHST) and the National Science Foundation's Center for Integrated Pest Management (CIPM). The EPICA team identifies, archives, evaluates, and communicates relevant information about exotic plant pests from around the world that potentially threaten US agriculture and the environment. The goal of the EPICA project is to provide key groups within USDA's Plant Protection and Quarantine (PPQ) with regular updates of vital pest information to enable a proactive safeguarding approach.

Fruit Exploration Supported by the National Plant Germplasm System, 1980 to 2004

The National Plant Germplasm System (NPGS) of the U.S. Department of Agriculture (UDSA), Agricultural Research Service (ARS), has greatly expanded since 1980. Foremost in this expansion was the addition of seven repositories for clonally propagated fruit and specialty crops. Many collections at state agricultural experiment station sites were in jeopardy as breeders retired. These collections can now be preserved by the NPGS. The NPGS has provided funding for plant exploration and exchange. From 1980 to 2004, 37 exploration/exchange proposals for fruit crops were funded, and over 3000 accessions introduced as a result. Crop Germplasm Committees (CGCs), established for each commodity have prepared genetic vulnerability statements and prioritized collection activities. The USDA ARS, National Germplasm Resources Laboratory (NGRL), facilitates international relationships, and the USDA Animal and Plant Health Inspection Service (APHIS), National Plant Germplasm Quarantine Center (NPGQC), tests and makes pathogen-tested germplasm available. As a result of the Convention on Biological Diversity (1993) and the International Treaty on Plant Genetic Resource for Food and Agriculture (2004), the USDA now pursues germplasm collection through the establishment of bilateral agreements of mutual benefit.

First Report of the Pale Cyst Nematode, Globodera pallida, in the United States.

In 2006, a cyst nematode was discovered in tare dirt at a potato (Solanum tuberosum) processing facility in eastern Idaho. The nematode was found during a routine survey conducted jointly by the Idaho State Department of Agriculture and the USDA Animal and Plant Health Inspection Service through the Cooperative Agricultural Pest Survey program. Extensive additional sampling from two suspect fields led to the identification of the same nematode in a 45-acre (18.2-ha) field located in northern Bingham County. The morphology of cysts and second-stage juveniles and molecular analyses established the identity of the species as the pale cyst nematode Globodera pallida (Stone 1973) Behrens 1975. Morphological characters used for identification included cyst shape, characteristics of cyst terminal cone including nature of fenestration, cyst wall pattern, anal-vulval distance, number of cuticular ridges between anus and vulva, and Granek's ratio (1,4). The second-stage juvenile morphologies critical for identification were the following: body and stylet length, shape of stylet knobs, shape and length of tail and hyaline tail terminus, and number of refractive bodies in the hyaline part of tail (1,4). Diagnosis as G. pallida was clearly confirmed by two molecular tests. First, PCR-RFLP (restriction fragment length polymorphism) profiles of a ribosomal DNA fragment using restriction enzymes RsaI, TaqI, and AluI (2) were consistent with a G. pallida control and not G. rostochiensis. Second, the ribosomal DNA region that extends from the 3' end of the 18S ribosomal subunit and includes all of ITS1, 5.8S, and ITS2 to the 5' end of the 28S ribosomal subunit was used to generate sequence for the most accurate species determination. Sequences obtained from three individual juveniles were compared with those from several Globodera species (3), revealing unequivocal similarity to G. pallida. This detection represents a new country record for G. pallida in the United States. Collection of additional information regarding distribution of this nematode within the region is underway.

Pre-germination Seed Treatments and Stratification Affect Germination of Montezuma Cypress

Abstract Taxodium distichum (L.) Richard var. mexicanum Gordon (syn. T. mucronatum), Montezuma cypress, is a valuable ornamental tree species tolerant of a wide range of cultural conditions. However, little is know about the propagation requirements of this species. The objectives of this study were 1) to determine the effect of previously recommended seed treatments for baldcypress (T. distichum (L.) Richard var. distichum) or pondcypress (T. distichum (L.) Richard var. imbricarium (Nutt.) Croom; syn. T. ascendens, T.d. var. nutans) on Montezuma cypress seeds, and 2) to determine the effects of stratification in combination with pre-germination treatments on germination of Montezuma cypress seeds. Open pollinated seeds were collected from a single tree in Southmost, TX (25° 52.576’ N, 97° 27 .083’ W, elevation 4.5 m, USDA Plant Hardiness Zone 9b). Seven pre-germination treatments and three stratification periods were applied to the seeds. If immediate germination of ripe seed is desired, then the best treatments are the citric acid soak and the hot water baths, however, if seeds can be stratified, then no pre-germination seed treatment is needed. Citric acid scarification and hot water baths produced the best germination. Stratification hastened germination rates and cumulative mean germination percentages. Stratification for 45 d appears to be sufficient, although for the best pre-germination treatments stratification requirements were less pronounced.

New strain of Verticillium dahliae in North America

A new strain of Verticillium dahliae, the fungus causing Verticillium leaf mottle and wilt, was identified from northwestern Minesota in 2002. The new strain or biotype is characterized by its ability to overcome the single, dominant V-1 resistance gene employed in oilseed and confection hybrids. Samples collected in 2003 from diseased plants confirmed the new biotype also exists in Manitoba, Canada. Limited survey, conducted in September 2004, identified the new strain in roughly one-quarter of fields showing Verticillium wilt in North Dakota. In greenhouse trials in 2004/5 we tested 221 cultivars for reaction to the new Verticillium strain. One entry from the USDA Plant Introduction collection, developed in Russia as VNIIMK 8883, was immune and would be an ideal source of resistance. Other commercial oilseed hybrids from the U.S., Argentina and Europe, were also noted with ratings of 0.5 or lower on a 0 to 5 scale. On a related note, another fungus, Phialophora asteris F. sp. helianthi, was isolated from oilseed sunflower plants showing leaf mottle symptoms in Minot, North Dakota in 2002, and presumed to be due to Verticilliumdahliae. In greenhouse inoculations, Phialophora produced leaf mottle symptoms on sunflower lines with and without the V-1 gene, which were very similar to those incited by V. dahliae. Proper identification of this pathogen from plants displaying leaf mottle symptoms will be necessary to avoid confusion between the two pathogens.

The generation of USDA-equivalent extreme minimum temperature models and a comparison with Canada’s plant hardiness zones

Hardiness zones are widely used in North America to support the trade of plants and recommendations on local use of perennial plant species. In Canada, two zonation approaches are in use, a made-in-Canada model that integrates seven climate variables and the United States Department of Agriculture’s (USDA) extreme minimum temperature map/model. In this paper we develop and present several extreme minimum temperature models for the 1961–1990 and 1971–2000 climate normal periods and annual models for the winter seasons of 1961 through 2000. These models are similar in nature to the USDA plant hardiness model/map. We compare these models with a recent update of the Canadian plant hardiness zones developed with the same mathematical interpolation techniques (thin plate smoothing splines). Individual Canadian zones typically span five to nine USDA equivalent sub-zones in total, although most of the area (>75%) of each zone generally spans 3–4 USDA sub-zones. We note that there is no simple transformation of one zonation approach to the other, but values for both systems can now be obtained for any location in Canada using an internet mapping tool. Over the period of 1961–2000 extreme minimum temperature has been trending upward in most provinces. These trends may be affecting plants in some locations, but a lack of survival and/or hardiness data is a significant impediment to assessing this. Variation in extreme minimum temperature over the 1961 to 2000 period was greatest in western North America, particularly interior British Columbia. Key words: Climate mapping and trends, spatial analysis, ANUSPLIN

Hydrocotyle ranunculoides

<i>Hydrocotyle ranunculoides</i>

First Report of Infection of Maiden-Hair Fern (Adiantum jordanii and A. aleuticum) by Phytophthora ramorum in California.

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

ASM Participates in USDA Plant and Pest Biology Workshop

ASM Participates in USDA Plant and Pest Biology Workshop

Exotic bark- and wood-boring Coleoptera in the United States: recent establishments and interceptions

Summary data are given for the 25 new species of exotic bark- and wood-boring Coleoptera first reported in the continental United States between 1985 and 2005, including 2 Buprestidae (Agrilus planipennis and Agrilus prionurus), 5 Cerambycidae (Anoplophora glabripennis, Callidiellum rufipenne, Phoracantha recurva, Sybra alternans, and Tetrops praeusta), and 18 Scolytidae (Ambrosiodmus lewisi, Euwallacea fornicatus, Hylastes opacus, Hylurgops palliatus, Hylurgus ligniperda, Orthotomicus erosus, Phloeosinus armatus, Pityogenes bidentatus, Scolytus schevyrewi, Tomicus piniperda, Xyleborinus alni, Xyleborus atratus, Xyleborus glabratus, Xyleborus pelliculosus, Xyleborus pfeilii, Xyleborus seriatus, Xyleborus similis, and Xylosandrus mutilatus). In addition, summary interception data are presented for the wood-associated beetles in the families Bostrichidae, Buprestidae, Cerambycidae, Curculionidae, Lyctidae, Platypodidae, and Scolytidae, based on the USDA Animal and Plant Health Inspection Service "Port Information Network" database for plant pests intercepted at US ports of entry from 1985 to 2000. Wood-associated insects were most often intercepted on crating, followed by dunnage and pallets. The five imported products most often associated with these 8341 interceptions were tiles, machinery, marble, steel, and ironware. A significantly higher proportion of the most frequently intercepted true bark beetles have become established in the United States compared with the less frequently intercepted species.

(113) Quantifying Landscape Microclimates and Related Cold Injury

It is generally accepted that plants closer to structures benefit from the warmth emitted via imperfect insulation and solar energy reemitted as long-wave, thermal radiation. However, while claims of protection are given, little quantifiable information exists on the extent or pattern of this protection. We studied existing plantings of Trachelospermum asiaticum, an evergreen groundcover that is frequently damaged in northeast Texas. The plantings studied were part of a landscape with at least five different identifiable microclimates: 1) near building (NB); 2) mid-bed (MB); 3) bed edge (BE); 4) beneath Quercus virginiana (LO); and 5) beneath Pyrus calleryana`Bradford' (BP). We placed HOBO temperature data loggers recording one temperature per minute in each location. Following our first damaging freeze, we waited 7 days before collecting leaf samples. Leaf samples were collected by using a 25-cm square, 2 cm deep on two sides. The square was placed on the groundcover so that the top of the groundcover was level with the top of the square. All leaves and stems that extruded through the top 2 cm of the square were excised. Four samples were taken from each location, and the number of damaged and nondamaged leaves were counted for each sample. Leaves that were at least 50% discolored were considered damaged. Leaf damage data were analyzed using SAS Proc ANOVA. Leaves in the BE and BP locations showed significantly fewer live leaves than any other locations. NB leaves were virtually undamaged. Average temperatures in the BE and BP locations were 4.5 to 5 °F colder than the “near building” locations, comparable to an a or b zone in the current USDA Plant Hardiness Zone map.

(18) Biodiversity of the Flavonoid Phlorizin in a Subset of the USDA Apple Germplasm Core Collection

Phlorizin is known for its role in reducing glucotoxicity and has a long history of use in diabetes research. In addition, its contribution to the pool of total phenolics adds to the overall health benefits attributed to fruit. Phlorizin is limited to Rosaceae family plants, of which apple comprises its current commercial source; however, limited information exists regarding its biodiversity among apple taxa. A subset of 22 taxa from a core collection of apple accessions representative of the global genetic diversity of apple was used to investigate the biodiversity of phlorizin present in apple shoots and in fruit relative to total phenolic content and free radical scavenging capacity. Fruit and shoots were harvested from the USDA Plant Genetic Resources Unit in Geneva, N.Y. Validation and quantification of phlorizin was conducted using a rigorous high-pressure liquid chromatography (HPLC) procedure. Total phenolics in fruit, assayed using a Folin-Ciocalteu method and expressed as gallic acid equivalents, ranged from 227 to 7181 mg·L-1 and were strongly related to 2,2' azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) antioxidant capacity for the core collection (r= 0.778). On a molar basis, phlorizin had lower antioxidant capacity than other major phenolic compounds present in apple fruit, but was more effective than ascorbic acid. Phlorizin yield in dormant apple shoots, expressed as percent weight, ranged from 0.9% to 5.5%. A rapid, 96 well micro-plate spectrophotometric assay was also developed to aid in the screening of multiple samples for selection of high phlorizin yielding apple taxa. Spectrophotometry overestimated phlorizin content as expected, but the calibration curve between HPLC and spectrophotometry was acceptable, r2 = 0.88.