The resistance to Cacopsylla pyri (L.) (Rhynchota Psyllidae) of different pear genotypes using phenotypical screening was evalu- ated on 33 genotypes from 2003 to 2005. Antixenosis, which arises from the settling of the adults and their reduced oviposition rate, and nymphal antibiosis were recorded using free choice tests. The transfer of resistance to C. pyri in interspecies crosses between the European pear species Pyrus communis L. and Asian pear species, such as P. ussuriensis Maximowicz and P. pyrifo- lia Nakai, to part of the progeny was possible.

Cacopsylla pyri behaviour on new pear selections for host resistance programs

Identification by suppression subtractive hybridization of genes expressed in pear (Pyrus spp.) upon infestation with Cacopsylla pyri (Homoptera: Psyllidae).

Pear psylla (Cacopsylla pyri) causes severe damage on European pear cultivars, resulting in high yield losses. Its control has become difficult since it developed resistance to a wide range of pesticides, while the number of authorized molecules for pest control has decreased. Identifying pear psylla resistance factors should help breeding new resistant pear cultivars. We analyzed the quantitative resistance to psylla inherited from the genotype NY 10355 derived from Pyrus ussuriensis. Quantitative trait locus (QTL) analysis was carried out after counting the number of nymphs and estimating the nymphal development rate using a free-choice test performed on a large segregating progeny. We mapped two new loci for pear psylla resistance on linkage groups LG01 and LG04 of NY 10355 and confirmed the QTL previously detected on LG17. A strong epistatic interaction between the two QTLs detected on LG01 and LG17 appeared to be a major factor controlling the psylla infestation in the genotype NY 10355.

Polygenic inheritance of resistance to Cacopsylla pyri in a Pyrus communis × P. ussuriensis progeny is explained by three QTLs involving an epistatic interaction

Twenty-one pear cultivars and breeders’ selections with interspecific pedigrees involving Pyrus ussuriensis Max. or P. pyrifolia (Burm.) Nakai crossed with P. communis were assessed for resistance to pear psylla (Cacopsylla pyricola Förster) using a nymphal feeding antixenosis assay. The proportion of nymphs live and present on the plants varied from 0.52 for Purdue 77-73, a P. ussuriensis 3 P. communis hybrid, to 0.08 for ‘Zelinka’, a P. communis cultivar from eastern Europe. Two P. ussuriensis 3 P. communis hybrid selections (NY 10355 and NY 10359) and the P. communis landrace cultivars, Batjarka and Zelinka, were the most resistant to nymphal feeding. NJ B9 T1 T117 may also be a useful source of resistance. The most resistant germplasm should be valuable genetic resources for the breeding of new pear cultivars with resistance to pear psylla. Pear psyllids are a serious insect pest of the cultivated European pear (Pyrus communis L.) in the production regions of North America and Europe. In North America, Cacopsylla pyricola (Förster) is the only psyllid pest of pears, whereas in Europe, C. pyri (L.) and C. pyrisuga (Förster) are also endemic. Cacopsylla bidens (Šulc) is endemic to parts of southern and eastern Europe as well as the Middle East. The insect has rapidly developed resistance to most of the pesticides used for control, and biological controls alone have rarely provided sufficient control for commercial production. The annual cost per hectare of chemical control is high. Cultivars with durable resistance would enhance the economic and environmental sustainability of pear production by reducing producer costs and pesticide use. These species of pear psylla and their host apparently coevolved in Europe. Investigations of western European cultivars identified only a few moderately resistant cultivars, including ‘Spina Carpi’ (Quarta and Puggioni, 1985), ‘Triomphe de Ronchin’, ‘Joséphine des Malines’, ‘Doyenne du Poitiers’, and ‘D’Août Lamer’ (Robert et al., 2004, 2005). Higher levels of resistance have been identified in the small-fruited Asian pear species, P. betulifolia Bunge, P. calleryana Decne., P. fauriei Schneid., P. ussuriensis Maxim., and P. 3 bretschneideri Rehd. and in a few genotypes of the European ‘‘snow pear,’’ P. nivalis Jacq. (Quamme, 1984; Westigard et al., 1970), and in P. ussuriensis 3 P. communis hybrids (Harris, 1973; Harris and Lamb, 1973; Pasqualini et al., 2006; Quamme, 1984). Pomologists and breeders have also been collecting wild germplasm and landrace cultivars to identify diverse sources of resistance for use in the development of new psyllaresistant cultivars (van der Zwet et al., 1987, 1989). The behavioral and physiological responses of arthropod pests to resistant host genotypes are termed modes of host plant resistance as distinct from the underlying mechanisms of resistance. Major modes of host plant resistance are 1) antixenosis, which can be observed in terms of disruptions to insect orientation and settling (i.e., host finding) and inhibition of feeding and oviposition; 2) antibiosis, observed as delayed development, increased mortality, and reduced fecundity and egg hatchability; and 3) tolerance or the ability to withstand infestation without damage (Painter, 1951). The term antixenosis was introduced by Kogan and Ortman (1978) to define the inhibitory effects of the host plant, whereas nonpreference refers to behavior exhibited by the pest. Feeding antixenosis has been established as a key mode of resistance, because reduced feeding frequency is associated with reduced oviposition as well as increased mortality and delayed development (Bell, 1991; Bell and Puterka, 2004; Butt et al., 1988, 1989; Puterka, 1997; Robert et al., 1999). Observation of breeders’ selections in the orchard suggested that some genotypes were at least moderately resistant to pear psylla (unpublished data). The purpose of this research was to assess the degree of resistance in breeders’ selections in a controlled experiment. The overall goal was to select the most promising parents for further breeding and cultivar development. Materials and Methods Germplasm. Seven pear cultivars and 14 selections from the breeding programs of the U.S. Department of Agriculture, Cornell University, Rutgers University, University of Illinois, and Purdue University were used in this study. The cultivars and selections represented a diverse genetic background with pure Pyrus communis as well as interspecific hybrids with P. ussuriensis and P. pyrifolia. There were five P. communis cultivars and selections, six P. communis 3 P. pyrifolia hybrids, and 10 P. communis 3 P. ussuriensis hybrids. The interspecific hybrids included both first generation as well as backcross hybrids. The exact parentage of Purdue 77-73, ‘Luscious’, and ‘Summercrisp’ is unknown but is thought to be P. communis 3 P. ussuriensis backcross hybrids. Resistance assay. Five single-shoot plants of each genotype were generated by budding onto greenhouse-grown ‘Bartlett’ seedling rootstock grown in Metro Mix 510 potting soil containing a starter fertilizer (Scott’s, Marysville, OH) in standard 8-in. (20 cm) plastic pots. The trees were also fertilized weekly with Peter’s General Purpose 20-2020 fertilizer (Scott’s). All plants were grown in a pesticide-free greenhouse until they each had at least 20 cm of shoot growth. All but the top four leaves were removed just before infestation, and a band of Tangle-Trap (The Tanglefoot Company, Grand Rapids, MI) was applied to the stem just basal to the fourth node to trap nymphs migrating off of the plant. No phytotoxicity on the stem resulting from the Tangle-Trap was evident when data were collected. The top two youngest, fully expanded leaves of each plant were each infested on the abaxial side with 10 second or third instar nymphs of pear psylla from a young laboratory colony for a total of 20 nymphs per plant. The transfer was accomplished by removing an infested leaf from a colony plant, placing it under a stereomicroscope, ‘‘teasing’’ a nymph with a singlehair brush until it appeared to have withdrawn its stylet and begun to move, lifting the nymph off of the leaf with the single hair, and then transferring the nymph to a leaf of the test plant. After infestation, the plants were maintained in a growth chamber at 25 ± 1 C and a photoperiod of 16 h/8 h (light/dark) provided by a mixture of incandescent and highintensity fluorescent bulbs. The experiment was conducted as a randomized complete block design with five sets of genotypes as Received for publication 19 Oct. 2011. Accepted for publication 17 Dec. 2012. I thank Wayne Zook, Gabriel Wilmoth, and Natalie Carpenter for technical assistance and data collection. I also thank Dr. Robert C. Lamb of Cornell University, Dr. L. Fredric Hough of Rutgers University, Dr. Herb Barrett of the University of Illinois, and Dr. Jules Janick of Purdue University for providing their pear selections. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable. USDA is an equal opportunity provider and employer. Research Horticulturist. To whom reprint requests should be addressed; e-mail richard.bell@ars.usda.gov. HORTSCIENCE VOL. 48(2) FEBRUARY 2013 143 individual tree replicates. As a result of ‘‘bud misses,’’ only three or four trees were available for six of the selections/cultivars. The numbers of live, actively feeding and dead nymphs were counted after 72 h. Active feeding was indicated by the presence of excreted ‘‘honeydew’’ associated with the nymph. Missing nymphs as well as those that migrated off the four test leaves and down the plant stem were presumed to be reacting to the antixenotic property of the host genotype. Counts on individual leaves and stems were summed for a total per plant. The numbers of live, feeding, and dead nymphs were divided by the original 20 nymphs to compute the corresponding proportions. Statistical analysis. Data for all experiments were analyzed to determine whether the residuals met the assumptions underlying the analysis. Homogeneity of variances was tested by an examination of residual plots. Normality was tested using the Shapiro-Wilk test in SAS PROC UNIVARIATE (SAS Institute Inc., 1990) and examination of box and normal probability plots. A histogram with a fitted normal curve was also used to visually assess deviation from normality. Correlation of mean and residuals was examined using a plot of residual vs. predicted values and tested by SAS PROC CORR option SPEARMAN. Type IV sums of squares were computed. All analyses were performed using SAS PROC MIXED (Littell et al., 1996). The linear model for the analyses of genotype differences for each response variable was a mixed effects models with replication as a random effect and genotype as a fixed effect. Least-squares means and SEs were computed. Mean separation for this procedure was performed using the Tukey-Kramer honestly significant difference method. The Tukey option was used to adjust for multiple comparisons. Mean separation letters for main effects were assigned by the SAS macro PDMIX 800 (Saxton, 1998). Differences among broad species pedigree classes were also analyzed. Firstgeneration interspecific hybrids were grouped with interspecific backcross hybrids. In this case, species was the fixed effect, and genotype within species and replication were random effects. Assumptions were tested as described previously. The rank correlation between proportion of live nymphs and proportion of feeding nymphs was computed using SAS PROC CORR with the SPEARMAN option. The preliminary analysis of proportion feeding and proportion alive to test whether the data met the assumptions detected four outliers in the feeding data (single replicates for NJ A2 R59 T69, NJ Rock R

/pdf/host-resistance-to-pear-psylla-of-breeding-program-136dutoya5.pdf

Host Resistance to Pear Psylla of Breeding Program Selections and Cultivars

Cacopsylla pyri est l’un des principaux ravageurs du poirier en France. L’utilisation de varietes de poirier resistantes au psylle pourrait constituer une alternative a la lutte chimique, mais actuellement, toutes les varietes d’importance economique sont sensibles a ce psylle. Afin d’identifier des geniteurs de resistance, quatre methodes de criblage ont ete testees en 1996. La premiere est fondee sur une notation de presence ou d’absence de larves sur les feuilles et la deuxieme sur les parties ligneuses. La troisieme repose sur une evaluation du nombre de larves a l’extremite des pousses et la quatrieme sur l’observation de l’etat du vegetal (quantite de fumagine et etat des pousses). Cette derniere methode a ete retenue pour evaluer une collection de Pyrus. Les classes de notation des symptomes vont de 1 (pas de degât apparent) a 5 (une ou plusieurs pousses mortes). Le criblage de 82 genotypes de Pyrus a ete realise de 1996 a 1999 dans un tunnel grillage. La variete Williams, connue comme etant sensible au psylle du poirier, est notre temoin. La plus grande partie des genotypes sont sensibles. Cependant, 21 genotypes ont ete evalues comme etant resistants a C. pyri. La plupart sont des hybrides interspecifiques entre P. communis et P. ussuriensis ou P. longipes ou P. pyrifolia, et possedent un haut niveau de resistance au psylle du poirier.

/pdf/criblage-de-genotypes-de-pyrus-vis-a-vis-de-la-resistance-au-4lgxq8lzm0.pdf

Criblage de génotypes de Pyrus vis‐à‐vis de la résistance au psylle du poirier Cacopsylla pyri (L.)

The development of Cacopsylla pyri larvae was observed on three Pyrus genotypes: cv. "Katman" and "NY 10355", identified as resistant to pear psylla, and cv. "William's" pear as control. The study was conducted under controlled conditions, on trees grafted one year earlier. One psylla female was placed on each plant and removed after 50 eggs on average had been laid. To record C. pyri development, the number of different instars was counted each week on each plant. On "William's", larvae completed their development and adults started emerging after one month. Larval mortality was 68 /. On "Katman" and on "NY 10355", young larvae started feeding but all larvae died before completion of their development. In conclusion, under these experimental conditions, complete larval resistance to C. pyri was observed on "Katman" and "NY 10355"

Larval development of Cacopsylla pyri (L.) (Homoptera: Psyllidae) on two resistant Pyrus genotypes

Popular Tasks used by Researchers

How can I help with your research?

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

We encountered an error while loading the panel. Please try refreshing the page.

Something went wrong

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

Anyone with the link can view this chat. You can switch it back to private anytime.

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

M. Le Lezec

Author Tools

Chat about Author

Papers

Larval development of Cacopsylla pyri (L.) (Homoptera: Psyllidae) on two resistant Pyrus genotypes