Pear Breeding Research Articles

Товарные качества плодов новых форм груши в условиях предгорной плодовой зоны

Abstract. The need for pear breeding in the foothills of the North Caucasus is associated with the inconsistency of varieties grown in the region, including world standards, with the requirements of modern horticulture. Continuous improvement of the breeding process has led to the creation of new varieties of fruit crops with valuable characteristics and qualities. Currently, pear breeding is actively carried out using classical and modern methods, aimed at creating new sources and donors of valuable traits. As a result of breeding work in our institute, promising pear hybrid forms (2002 year of crossing) with fruits of high commercial quality have been identified. The data of the analysis of the commercial qualities of fruits for 2020-2023 are presented. The largest fruits are marked in two combinations Talgarskaya krasavitsa (free pollination). In the first variant, Talgarskaya krasavitsa (free pollination / working name – Zul’fira/), the average fruit weight was 509 g, and the largest reached 637 g. In the second variant of the Talgarskaya krasavitsa combination (free pollination / working name – Chegemskaya/), the average fruit weight was 258,2 g, and the largest weighed 323,5 g. The content of vitamin "C" in pear fruits is small, and therefore the pear cannot serve as a source of ascorbic acid. The variation of this indicator was noted in the range of 4,0...6,0 mg/100 g. The largest number of them in the Talgarskaya krasavitsa form (free pollination / Chegemskaya/) is on average 6,0 %, and this variety also has a higher sugar content – on average 11,6 %. The presented varieties show a high degree of adaptation to the specific weather conditions of the region. Despite the prevailing meteorological conditions, they mature physiologically, accumulate a sufficient number of chemical components that contribute to the formation of fruits with good dessert taste qualities. As a result, they can not only replenish the zoned assortment, but also are of undoubted interest for further breeding work. Key words: pear, varieties, commercial qualities, fruit weight, biochemical composition

Identification of Candidate Genes Associated with Flesh Firmness by Combining QTL Mapping and Transcriptome Profiling in Pyrus pyrifolia.

Flesh firmness is an important quality of pear fruits. Breeding cultivars with suitably low flesh firmness is one of the popular pear breeding goals. At present, SNP markers related to pear flesh firmness and genes affecting flesh firmness are still uncertain. In this study, a QTL analysis was performed, and the result showed that the position of 139.857 cM in lineage group 14 (LG14) had the highest average logarithm of odds (3.41) over two years. This newly discovered locus was identified as a flesh firmness-related QTL (qFirmness-LG14). The 'C/T' SNP was found in corresponding Marker1512129. The 'C' genotype is the high-firmness genotype, which is a dominant trait. The average firmness of fruits with genotype C is 21.4% higher than genotype without the C genotype. Transcriptome profiling was obtained between 'Zaoshengxinshui' and 'Qiushui' at five time points. Three candidate genes in the interval of qFirmness-LG14 might affect firmness. A gene of xyloglucan endotransglucosylase 1 (PpXTH1) was upregulated in 'Qiushui' at all five time points. Two transcription factors (PpHY5 and PpERF113) were upregulated in 'Zaoshengxinshui', which might be negative regulatory genes for high flesh firmness. The transcriptome results also isolated a large number of cell wall-related genes (e.g., Pectate lyase, Pectin acetylesterase, Pectin methylesterase, and 4-coumarate-CoA ligase) and transcription factors (e.g., ERF, WRKY). These genes are all potential upstream and downstream genes related to flesh firmness. In conclusion, this study provides valuable insights into the QTLs and molecular mechanisms associated with fruit firmness in Pyrus pyrifolia.

A transcription factor, PbWRKY24, contributes to russet skin formation in pear fruits by modulating lignin accumulation

Abstract Skin color is one of the major traits of fruit appearance quality in pear (Pyrus), which affects the fruit commodity value. Russet skin protects pear fruits from environmental stresses and its formation process is closely linked to lignin accumulation. However, the molecular regulatory networks underlying russet skin formation in pear fruits involve complex secondary metabolic pathways and remain elusive. Here, we explored the regulatory mechanisms underlying lignin accumulation in pear skin based on transcriptome sequencing, co-expression network analysis, and gene expression profiling. We identified a WRKY transcription factor gene, PbWRKY24, that regulates russet skin formation in pear fruits. The relative expression of PbWRKY24 in russet pear skin was significantly correlated with lignin content. We then verified the function of PbWRKY24 in lignin accumulation via genetic transformation. DNA affinity purification sequencing revealed that PbWRKY24 directly binds to the promoter of a lignin biosynthesis gene, PbPRX4. This binding was confirmed by yeast one-hybrid, dual-luciferase, and electrophoretic mobility shift assays. Overexpression of PbPRX4 in pear skin stimulated lignin accumulation and consequently promoted russet skin formation. This study provides a glimpse into the intricate lignin biosynthesis mechanisms during russet skin formation in pear fruits, which is of practical significance to pear breeding for fruit quality.

A Combined Metabolome and Transcriptome Reveals the Lignin Metabolic Pathway during the Developmental Stages of Peel Coloration in the 'Xinyu' Pear.

Sand pear is the main cultivated pear species in China, and brown peel is a unique feature of sand pear. The formation of brown peel is related to the activity of the cork layer, of which lignin is an important component. The formation of brown peel is intimately associated with the biosynthesis and accumulation of lignin; however, the regulatory mechanism of lignin biosynthesis in pear peel remains unclear. In this study, we used a newly bred sand pear cultivar 'Xinyu' as the material to investigate the biosynthesis and accumulation of lignin at nine developmental stages using metabolomic and transcriptomic methods. Our results showed that the 30 days after flowering (DAF) to 50DAF were the key periods of lignin accumulation according to data analysis from the assays of lignin measurement, scanning electron microscope (SEM) observation, metabolomics, and transcriptomics. Through weighted gene co-expression network analysis (WGCNA), positively correlated modules with lignin were identified. A total of nine difference lignin components were identified and 148 differentially expressed genes (DEGs), including 10 structural genes (PAL1, C4H, two 4CL genes, HCT, CSE, two COMT genes, and two CCR genes) and MYB, NAC, ERF, and TCP transcription factor genes were involved in lignin metabolism. An analysis of RT-qPCR confirmed that these DEGs were involved in the biosynthesis and regulation of lignin. These findings further help us understand the mechanisms of lignin biosynthesis and provide a theoretical basis for peel color control and quality improvement in pear breeding and cultivation.

PbbHLH155 enhances iron deficiency tolerance in pear by directly activating PbFRO2 and PbbHLH38

Iron (Fe) deficiency is a general stress for many horticulture crops, causing leaf chlorosis and stunted growth. The basic–helix–loop–helix (bHLH) transcription factor (TF) was reported to function in Fe absorption; however, the regulatory mechanism of bHLH genes on iron absorption remains largely unclear in pear. In this study, we found that PbbHLH155 was significantly induced by Fe deficiency. Overexpression of PbbHLH155 in Arabidopsis thaliana and pear calli significantly increases resistance to Fe deficiency. The PbbHLH155-overexpressed Arabidopsis lines exhibited greener leaf color, higher Fe content, stronger Fe chelate reductase (FCR) and root acidification activity. The PbbHLH155 knockout pear calli showed lower Fe content and weaker FCR activity. Interestingly, PbbHLH155 inhibited the expressions of PbFRO2 and PbbHLH38, which were positive regulators in Fe-deficiency responses (FDR). Furthermore, yeast one-hybrid (Y1H) and Dual-Luciferase Reporter (DLR) assays revealed that PbbHLH155 directly binds to the promoters of PbFRO2 and PbbHLH38, thus activating their expression. Overall, our results showed that PbbHLH155 directly promote the expression of PbFRO2 and PbbHLH38 to activate FCR activity for iron absorption. This study provided valuable information for pear breeding.

Profiling of soluble sugar compositions in mature fruits of a diverse pear (Pyrus spp.) germplasm by UPLC

Soluble sugars play a vital role as taste components in fruits, significantly contributing to fruit quality. Here, we employed ultraperformance liquid chromatography (UPLC) to determine the sugar composition of mature pear fruits from 142 cultivars. The results revealed that fructose, sorbitol, glucose, and sucrose were the primary soluble sugars present in pear fruit, and Pyrus pyrifolia (China) exhibited the highest total sugar content, followed by Pyrus ussuriensis, Pyrus bretschneideri, Pyrus communis, and Pyrus pyrifolia (Japanese and Korean (J&K)), Pyrus sinkiangensis, and the Hybrid Breeding (HB) cultivars. Furthermore, our study uncovered that the sampling time of these pear cultivars has a significant positive correlation with the content of sorbitol and glucose, respectively. Additionally, the soluble sugar content varied among pear fruits originating from different geographic positions, and the pear cultivars originating from the South China group presented the highest content of soluble sugar. In conclusion, these findings can provide valuable phenotypic data for studying sugar genetics and can also aid in selecting suitable parent cultivars in pear breeding programs.

Genetic and molecular regulation of chilling requirements in pear: breeding for climate change resilience.

Pear (Pyrus spp.) is a deciduous fruit tree that requires exposure to sufficient chilling hours during the winter to establish dormancy, followed by favorable heat conditions during the spring for normal vegetative and floral budbreak. In contrast to most temperate woody species, apples and pears of the Rosaceae family are insensitive to photoperiod, and low temperature is the major factor that induces growth cessation and dormancy. Most European pear (Pyrus Communis L.) cultivars need to be grown in regions with high chilling unit (CU) accumulation to ensure early vegetative budbreak. Adequate vegetative budbreak time will ensure suitable metabolite accumulation, such as sugars, to support fruit set and vegetative development, providing the necessary metabolites for optimal fruit set and development. Many regions that were suitable for pear production suffer from a reduction in CU accumulation. According to climate prediction models, many temperate regions currently suitable for pear cultivation will experience a similar accumulation of CUs as observed in Mediterranean regions. Consequently, the Mediterranean region can serve as a suitable location for conducting pear breeding trials aimed at developing cultivars that will thrive in temperate regions in the decades to come. Due to recent climatic changes, bud dormancy attracts more attention, and several studies have been carried out aiming to discover the genetic and physiological factors associated with dormancy in deciduous fruit trees, including pears, along with their related biosynthetic pathways. In this review, current knowledge of the genetic mechanisms associated with bud dormancy in European pear and other Pyrus species is summarized, along with metabolites and physiological factors affecting dormancy establishment and release and chilling requirement determination. The genetic and physiological insights gained into the factors regulating pear dormancy phase transition and determining chilling requirements can accelerate the development of new pear cultivars better suited to both current and predicted future climatic conditions.

Transcriptomic Database Analysis of Magnesium Transporter (MGT) Gene Family in Pear (Pyrus bretschneideri) Revealed Its Role in Reproductive Stage Development

The membrane proteins of the magnesium transporter (MGT) family are essential to Mg homeostasis. However, there has not been a comprehensive study of MGT in pear. The 17 MGT that were renamed to PbMGT1–17 in this study were found in the pear genome database. Phylogenetically, PbMGT proteins were categorized into three groups, namely NIPA, MRS2, and CorA. The majority of PbMGT were hydrophobic proteins situated on the chloroplast, according to the characterization study. Members of the same group shared comparable conserved motifs and gene structure, as revealed by motif and exon/intron analysis. The application of gene ontology (GO) and cis-elements has demonstrated that PbMGT genes exhibit a high degree of sensitivity to stressors and take part in chloroplast development and Mg+ ion transport. It was discovered by tissue-specific expression analysis that PbMGT genes might have a role in the development of organs. The critical significance of PbMGT was shown through comprehensive expression in five pear cultivars at various fruit developmental stages. The PbMGT5 gene was significantly expressed throughout fruit development, suggesting a role in the setting and ripening processes of pear fruits. For the first time, our research brought attention to the function of PbMGT genes as they relate to fruit development. Our research is likely to serve as an incentive for the development of pear breeding initiatives in the future.

A self-compatible pear mutant derived from γ-irradiated pollen carries an 11-Mb duplication in chromosome 17.

Self-compatibility is a highly desirable trait for pear breeding programs. Our breeding program previously developed a novel self-compatible pollen-part Japanese pear mutant (Pyrus pyrifolia Nakai), '415-1', by using γ-irradiated pollen. '415-1' carries the S-genotype S4dS5S5, with "d" indicating a duplication of S 5 responsible for breakdown of self-incompatibility. Until now, the size and inheritance of the duplicated segment was undetermined, and a reliable detection method was lacking. Here, we examined genome duplications and their inheritance in 140 F1 seedlings resulting from a cross between '515-20' (S1S3) and '415-1'. Amplicon sequencing of S-RNase and SFBB18 clearly detected S-haplotype duplications in the seedlings. Intriguingly, 30 partially triploid seedlings including genotypes S1S4dS5, S3S4dS5, S1S5dS5, S3S5dS5, and S3S4dS4 were detected among the 140 seedlings. Depth-of-coverage analysis using ddRAD-seq showed that the duplications in those individuals were limited to chromosome 17. Further analysis through resequencing confirmed an 11-Mb chromosome duplication spanning the middle to the end of chromosome 17. The duplicated segment remained consistent in size across generations. The presence of an S3S4dS4 seedling provided evidence for recombination between the duplicated S5 segment and the original S4haplotype, suggesting that the duplicated segment can pair with other parts of chromosome 17. This research provides valuable insights for improving pear breeding programs using partially triploid individuals.

The results of the implementation of the pear breeding program in the conditions of Adygea

The article describes the results of work on the creation of low-growing pear varieties with a red outer color of a fruit, adapted to the conditions of the foothill zone of the North-Western Caucasus (the Republic of Adygea). Many years of studying and selection pear variety were carried out by employees of the Maikop Experimental Station, a branch of VIR. The breeding task was to combine a number of valuable traits in the genotype of new varieties: small size of trees, early onset of fruiting, high yield, bright color of fruits, their good taste and late ripening, as well as resistance to fungal diseases. A comprehensive assessment of the source material was carried out and genotypes that were promising for breeding were identified. To obtain weak-growing hybrids, the weak-growing varieties of Obilnaya, Jacques Tellier, Triomphe de Vienne, Amiral Gervais, De ľAssomption and others were used. The variety of Max Red Bartlett (Max Red Bartlett, Williams Red) and its descendants became the donors of the red outer color of the fruit. To improve the quality of fruits and late ripening, high-quality varieties of Abbé Fetel, Doyenné d'Hiver, Martin and others were used. As a result of simple and multi-stage crossings, a hybrid fund of more than 100 samples was created, from which genotypes were isolated that had a complex of positive economically valuable traits that were promising for production and selection. Their brief characteristics are given.

Quantitative 2D fruit shape analysis of a wide range of pear genetic resources toward shape design breeding

The shape of a fruit is one of the main characteristics of fruit morphology, and its quantitative description is crucial to improve fruit quality. However, the shape of a pear fruit is relatively complex, and difficult to describe comprehensively. This study aimed to quantitatively analyze the morphological diversity of 2D fruit shapes of 276 cultivars, covering 6 groups including Pyrus pyrifolia, Pyrus bretschneideri, Pyrus ussuriensis, Pyrus sinkiangensis, Pyrus communis and interspecific hybridization, and discover shape traits with high heritability. Through an automated image processing method, the fruit contour was first accurately extracted, and then geometrical parameters and Fourier descriptors of the pear fruit shape were obtained. Furthermore, principal components (PCs) of the Fourier descriptors were analyzed, and the broad-sense heritability (H2) of the PCs and standardized width (WSD) were estimated. After that, the pear shape stability was calculated, and cultivars were clustered by their shape characteristics. This paper mainly discusses the longitudinal section, as the cross-section variation among cultivars is small. For the longitudinal section, the results showed more than 95 % of the two-dimensional shape variation can be explained by only six principal components; WSD20, WSD30 and PC1 have high H2; the shape stability of western pear was the lowest; a new class of shape was found by clustering the shape traits. The results indicated that the proposed pipeline can provide an objective and comprehensive quantitative description of pear fruit shape for a wide range of cultivars, which is necessary to discover the key genes determining pear shape. This approach is also beneficial for research on pear breeding and germplasm resource management.

Over a century of pear breeding at the USDA.

The U.S. Department of Agriculture (USDA) has performed European pear (Pyrus communis L.) scion breeding for over a century. The breeding program started in the early 1900s by Merton B. Waite in the Washington D.C. area and the program's main goal was to develop host resistance to the devastating disease fire blight, caused by Erwinia amylovora. Most of the historic European pear cultivars being produced in the U.S. were susceptible to fire blight, prompting a need to breed for resistance. More than six generations of USDA breeders have continued this effort to breed disease-resistant European pears. Along with fire blight resistance, the pear breeding programs sought improved fruit quality, cold hardiness, and resistance to psylla (Cacopsylla pyricola Foërster), a significant insect pest of pear. Herein, we discuss the history of the program through each generation of breeder(s). We also present breeding aims, parental selection, and releases. In total, the program has released ten named pear varieties between 1938 and 2022.

Seed Germination and Growth Improvement for Early Maturing Pear Breeding.

Breeding early maturing cultivars is one of the most important objectives in pear breeding. Very early maturing pears provide an excellent parental material for crossing, but the immature embryo and low seed germination of their hybrid progenies often limit the selection and breeding of new early maturing pear cultivars. In this study, we choose a very early maturing pear cultivar 'Pearl Pear' as the study object and investigate the effects of cold stratification, the culture medium, and the seed coat on the germination and growth of early maturing pear seeds. Our results show that cold stratification (4 °C) treatment could significantly improve the germination rates of early maturing pear seeds. A total of 100 days of cold-temperature treatment in 4 °C and in vitro germination on White medium increased the germination rate to 84.54%. We also observed that seed coat removal improved the germination of early maturing pear seeds, with middle seed coat removal representing the optimal method, with a high germination rate and low contamination. The results of our study led to the establishment of an improved protocol for the germination of early maturing pear, which will greatly facilitate the breeding of new very early maturing pear cultivars.

A MADS-box gene-induced early flowering pear (Pyrus communis L.) for accelerated pear breeding.

There have been a considerable number of studies that have successfully sped up the flowering cycle in woody perennial horticultural species. One particularly successful study in apple (Malus domestica) accelerated flowering using a silver birch (Betula pendula) APETALA1/FRUITFULL MADS-box gene BpMADS4, which yielded a good balance of vegetative growth to support subsequent flower and fruit development. In this study, BpMADS4 was constitutively expressed in European pear (Pyrus communis) to establish whether this could be used as a tool in a rapid pear breeding program. Transformed pear lines flowered within 6-18 months after grafting onto a quince (Cydonia oblonga) rootstock. Unlike the spindly habit of early flowering apples, the early flowering pear lines displayed a normal tree-like habit. Like apple, the flower appearance was normal, and the flowers were fertile, producing fruit and seed upon pollination. Seed from these transformed lines were germinated and 50% of the progeny flowered within 3 months of sowing, demonstrating a use for these in a fast breeding program.

Identification and Characterization of ABCG15-A Gene Required for Exocarp Color Differentiation in Pear.

Exocarp color is a commercially essential quality for pear which can be divided into two types: green and russet. The occurrence of russet color is associated with deficiencies and defects in the cuticular and epidermal layers, which affect the structure of the cell wall and the deposition of suberin. Until now, the genetic basics triggering this trait have not been well understood, and limited genes have been identified for the trait. To figure out the gene controlling the trait of exocarp color, we perform a comprehensive genome-wide association study, and we describe the candidate genes. One gene encoding the ABCG protein has been verified to be associated with the trait, using an integrative analysis of the metabolomic and transcriptomic data. This review covers a variety of omics resources, which provide a valuable resource for identifying gene-controlled traits of interest. The findings in this study help to elucidate the genetic components responsible for the trait of exocarp color in pear, and the implications of these findings for future pear breeding are evaluated.

Genetic mapping of the pear scab resistance gene Vnlf using a pseudo-BC3 population derived from Japanese pear cultivars and European pear ‘La France’

Pear scab disease caused by Venturia nashicola is one of the most serious diseases of Asian pears. To facilitate the breeding of scab-resistant cultivars, we mapped and developed markers for a resistance gene from the European pear (Pyrus communis) cultivar ‘La France’. By using a pseudo-backcross strategy to introduce genes from ‘La France’ into Japanese pear (P. pyrifolia) cultivars, we developed a mapping population from a cross between Japanese pear ‘Akiakari’ and interspecific hybrid progeny line 537–14. The individuals in the mapping population were evaluated for resistance by inoculation testing in 2020 and 2021. The segregation ratio of resistant to susceptible individuals was 1:1, indicating that resistance is inherited as a single dominant gene, which we named Vnlf. A genetic linkage map was constructed using single-nucleotide polymorphism (SNP) and simple sequence repeat (SSR) markers. On the basis of the genetic map of 537–14, we narrowed down the putative region carrying Vnlf to 959 kb on chromosome 2 between SNPs Chr2_20220913 and Chr2_21180341. To facilitate marker-assisted selection in Japanese pear breeding programs, we developed SSRs closely linked to Vnlf, one of which (LFA02a09) showed complete linkage to the resistance phenotype in an inoculation test of 175 individuals. These linked markers will enable introgression of Vnlf into breeding materials without the need for inoculation tests and will facilitate pyramiding Vnlf with other scab resistance loci.

Comparative Evaluation of Pyrus Species to Identify Possible Resources of Interest in Pear Breeding

Pear is one of the most important fruit species grown in the temperate zones of the globe. Besides fruit production, pear species are highly valued in forestry and agroforestry systems; in landscaping, as ornamental features; as fruits of ecological value, and in other areas. The Pyrus species, obtained from a gene bank, were evaluated for the different morphological traits of the trees, leaves, flowers, and fruits, as well as their responses to attacks from principal diseases and pests. Phenotypic data were examined using correlation and multivariate analyses, and a dendrogram of morphological traits was completed via molecular investigations at the DNA level using the RAPD markers. The findings revealed the complexities of the phenotypic and genetic connections among Pyrus species, as well as the difficulty in establishing phylogenetic relationships among pear species. The findings also demonstrated that the wide variability between species with different geographical origins, and their multiple peculiarities of interest, represents a cornerstone as the source of genes of great utility for pear breeding or for utilizing trees for different edible crops and for silvocultural, landscape, or ecological purposes.

Identification and genetic mapping of novel resistance gene, Rvn4, for pear scab in Chinese pear

Pear scab, caused by Venturia nashicola, is one of the most harmful diseases of pears, especially of Japanese and Chinese pears. The breeding of new cultivars resistant to pear scab has long been an aim of the Asian pear breeding programs. Although loci for pear scab disease resistance have been identified in Japanese and European pears, information on the genes controlling scab resistance in Chinese pears is limited. Genetic control of scab resistance in Chinese pear is reported to involve a single dominant gene. Here, we reaffirmed the scab resistance in the Chinese pear ‘Hong Li’ controls a single dominant gene and identified the exact location of a scab resistance gene, Rvn4. We first mapped Rvn4 at the top of linkage group (LG) 7 and then used public genome sequences to develop novel simple sequence repeat (SSR) markers to enrich the target region. Using these novel SSRs and the previously published SSR markers, we constructed a LG 7 of ‘Hong Li’ with an average marker density of 1.4 cM per marker. The novel SSR marker Pbr.chr07.20 had a significant linkage to Rvn4, with a genetic distance of 1.3 cM. The identification of the precise locus of Rvn4 in Chinese pear, together with previous studies in Japanese and European pear, will enhance our understanding of the mechanisms of pear scab resistance. DNA markers linked to the novel gene may also allow efficient selection of scab-resistant seedlings in pear breeding programs and the pyramiding of multiple resistance genes.

Performance of an Expert Sensory Panel and Instrumental Measures for Assessing Eating Fruit Quality Attributes in a Pear Breeding Programme

Breeding programmes count on stable trained panels that support breeding evaluation selections. This work aimed to evaluate the performance of a small expert panel in the join IRTA-PFR breeding programme to validate its use in the sensory assessments of fruit pear genotypes during the selection process. A breeding F1 population of 80 pear seedlings from this programme was used. Descriptors and standard references used for sensory evaluations of pear attributes were previously defined by the four members of the expert panel. A General Procrustes Analysis (GPA) was applied to analyse the relations between instrumental and sensory traits. The results showed a good relationship between sensory attributes such as firmness and crispness with penetrometer measures. A high correlation was also found between sensory sourness and titratable acidity (TA). Panel performance was evaluated in terms of reproducibility, homogeneity, and panel consonance. The results indicated that the experts were very consistent and had a good performance. The work demonstrates, for the first time, that a small expert trained panel could be efficiently used in pear breeding programmes and allows for the selection process in a more economical and available way in contrast to the larger sensory panels conventionally used.

Comparative Analysis of Phenotypic and Molecular Data on Response to Main Pear Diseases and Pest Attack in a Germplasm Collection

The pear is an important fruit tree in temperate areas, but due to its sensitivity, fruit yield and quality are often affected by disease and pest attacks. Pear genotypes from a germplasm collection comprising 13 Pyrus species, 17 Romanian varieties, and 50 non-Romanian varieties from a worldwide assortment were investigated in this study. Throughout four years, response to attack of the principal pathogens and pests was investigated phenotypically under natural conditions of infection and infestation. SSR markers were used to analyze the genetic diversity of the genotypes. A standardized method for the evaluation of responses to biotic stressors was proposed, which highlighted significant differences between genotypes. The species and varieties with the lowest degrees of attack (DA%), calculated based on the frequency and intensity of attack, were identified for pear scab (Venturia pyrina), septoria (Septoria pyricola), fire blight (Erwinia amylovora), and psyllids (Psylla sp.). These accessions could provide valuable sources of genes of interest to develop resistant varieties in new pear breeding programs. By combining phenotypic and molecular analyses, significant information was obtained that can be exploited to generate high variability for selection through artificial hybridization by harnessing accessions with complementary molecular fingerprints and high genetic distances.