About

Soon Li Teh began his appointment as an Assistant Professor in October 2023 at the University of Minnesota's Department of Horticultural Science. He holds a B.Sc. in Agronomy and Biochemistry from the University of Wisconsin-Madison and completed his PhD in Plant Breeding and Molecular Genetics at the University of Minnesota in 2018. His doctoral work integrated genomics and metabolomics to characterize genetic and biochemical resistance to grape powdery mildew. After earning his PhD, he joined Washington State University as a postdoctoral researcher and later as a research assistant professor, where he led the pear rootstock breeding program focused on developing size-controlling Pyrus rootstocks. In his current role, Dr. Teh focuses on developing high-quality, cold-hardy wine and table grapes to benefit growers in Minnesota and broader cold-climate regions. His research program emphasizes integrating conventional and molecular plant breeding approaches to improve grape cultivars, targeting traits such as cold hardiness, disease and pest resistance, and desirable fruit quality and biochemistry. He aims to characterize genetic determinants of these traits to develop diagnostic DNA markers that guide breeding decisions. Additionally, Dr. Teh is involved in outreach activities, including workshops, training, conferences, and educational programs to support grape growers, winemakers, and producers in Minnesota.

Research topics

• Biology
• Horticulture
• Mathematics
• Statistics
• Genetics

Selected publications

• Asexual Propagation of Salix humilis Using Stem Cuttings I: Cutting Types

  HortScience · 2025-12-10

  articleOpen access

  Salix humilis Marsh. (prairie willow) is an underutilized native shrub willow with potential for broader application in ornamental horticulture and managed landscapes. With attractive features, winterhardiness, and adaptability to a range of site conditions, including a purported tolerance to both extremes of the soil-moisture spectrum, prairie willow may be especially valuable for urban landscapes and green infrastructure applications. Despite the broad range of settings in which the species could be used, prairie willow is unusually difficult to propagate asexually, a feature that limits clonal improvement efforts as well as its availability in the green industry. To date, there has been no formal research conducted to explore or improve asexual propagation efforts of prairie willow. Through a series of four experiments, this project aimed to help address these gaps in knowledge by evaluating different cutting types, including dormant hardwood, semihardwood, softwood, and single-node cuttings. Semihardwood cuttings rooted at 12% and dormant hardwood cuttings rooted at 56% to 88%. Single-node cuttings gradually formed roots, reaching 45% rooting at week 9, but failed to produce shoots. Plant growth regulator application significantly increased propagule rooting. Based on these findings, it is recommended that nursery production companies use dormant hardwood cuttings treated with 5000 to 10,000 ppm K-IBA.

  PublisherDOI

• Asexual Propagation of Salix humilis Using Stem Cuttings II: Stock Plant and Propagule Conditioning

  HortScience · 2025-12-10

  articleOpen access

  Salix humilis Marsh. (prairie willow) is a compact shrub willow with a native distribution throughout the eastern United States. While underutilized in horticulture, prairie willow has potential for broader application in managed landscapes due to attractive ornamental features, hardiness, and high adaptability. This multifunctionality makes prairie willow a strong candidate for use in challenging settings, including urban green spaces. However, the unique recalcitrance of prairie willow to standard asexual propagation techniques and a general lack of directed research limits clonal improvement efforts and the availability of the species in the green industry. The objective of this work was to address this gap in knowledge and contribute to an effective asexual propagation protocol for prairie willow through four separate experiments exploring stock plant regeneration techniques, fungicide application, cutting positions, source populations, and substrate selection. Using cuttings [US Department of Agriculture (USDA)–Germplasm Resources Information Network (GRIN) and wild Minnesota populations] from stem tissue closer to basal regions of stock plants, applying preventive fungicide (T-Bird ® , 1.3 mL/L), and using a well-draining perlite or bark-based medium improved propagule rooting and survival. Rooting exceeded 80% in basal dormant cuttings treated with fungicide and apical cuttings rooted at near 0%. These findings can be used to identify propagation methods suitable for prairie willow commercial production, supporting its potential use in gardens and landscapes.

  PublisherDOI

• Pear rootstock breeding in the U.S. Pacific Northwest

  Acta Horticulturae · 2024-09-01 · 2 citations

  article1st authorCorresponding
  PublisherDOI

• Breeding for fruit quality improvement in apple

  Burleigh Dodds series in agricultural science · 2024-01-30 · 1 citations

  book-chapter1st authorCorresponding

  Breeding for fruit quality improvement is critical for sustaining consumer interest and providing long-term profitability for the apple industry. Priority breeding targets consist of eating quality, appearance, and storability traits (to ensure year-round availability of fruit). Apple breeding is a resource-intensive process constrained by its heterozygosity and long generation time. Advancements in genomic research and DNA technologies are increasing our knowledge of genomic regions and diagnostic markers linked to priority traits. This chapter describes breeding for quality improvement, address challenges of phenotyping, and provide a comprehensive review of DNA markers associated with fruit quality traits.

  PublisherDOI

• Multi-year trends of retention of fruit firmness after storage and influence of cultivar representation among apple breeding selections

  Fruit Research · 2024-01-01

  articleOpen access1st author

  Retention of fruit firmness, as an important component of fruit quality during cold storage, is one of three primary targets of Washington State University's apple breeding program. Fruit firmness is phenotyped with a penetrometer to obtain firmness measurements of outer and inner fruit cortices. Since the breeding program's inception in 1994, substantial records of fruit firmness from Phase Two selections have been amassed, as part of its routine breeding evaluation. From 2005 to 2019, firmness data from at-harvest and after-storage samples were analyzed to describe 15-year trends in fruit firmness (and its postharvest retention) of the selections. Genetic backgrounds of selections were estimated using average allelic representation to describe pedigree relatedness of selections to cultivars, and to quantify potential influence of cultivar representation on the selections' firmness traits. Results showed that the breeding program has been selecting for increased fruit firmness and retention capacity postharvest (especially inner cortex) of the selections. The selections' increased inner cortex firmness coincided with increasing average allelic representation of 'Cripps Pink', suggesting the cultivar's influence in firmness at harvest and firmness retention during storage. 'Honeycrisp', another important breeding parent (as noted from the increasing average allelic representation from 0.10 to 0.40) has likely positively impacted firmness retention in the selections. In summary, the 15-year trend analysis highlighted the influence of important cultivars, such as Cripps Pink, Gala, and Honeycrisp, in fruit firmness and/or firmness retention of breeding program Phase Two selections.

  PublisherDOI

• Rapid Assessment of Architectural Traits in Pear Rootstock Breeding Program Using Remote Sensing Techniques

  Remote Sensing · 2023-03-07

  articleOpen access

  Over the decades in the US, the introduction of rootstocks with precocity, stress tolerance, and dwarfing has increased significantly to improve the advancement in modern orchard systems for high production of tree fruits. In pear, it is difficult to establish modern high-density orchard systems due to the lack of appropriate vigor-controlling rootstocks. The measurement of traits using unmanned aerial vehicle (UAV) sensing techniques can help in identifying rootstocks suitable for higher-density plantings. The overall goal of this study is to optimize UAV flight parameters (sensor angles and direction) and preprocessing approaches to identify ideal flying parameters for data extraction and achieving maximum accuracy. In this study, five UAV missions were conducted to acquire high-resolution RGB imagery at different sensor inclination angles (90°, 65°, and 45°) and directions (forward and backward) from the pear rootstock breeding plot located at a research orchard belonging to the Washington State University (WSU) Tree Fruit Research and Extension Center in Wenatchee, WA, USA. The study evaluated the tree height and canopy volume extracted from four different integrated datasets and validated the accuracy with the ground reference data (n = 504). The results indicated that the 3D point cloud precisely measured the traits (0.89 < r < 0.92) compared to 2D datasets (0.51 < r < 0.75), especially with 95th percentile height measure. The integration of data acquired at different angles could be used to estimate the tree height and canopy volume. The integration of sensor angles during UAV flight is therefore critical for improving the accuracy of extracting architecture to account for varying tree characteristics and orchard settings and may be useful to further precision orchard management.

  PublisherOA PDFDOI

• Genetic mapping and haploblock characterization of two novel major dwarfing loci in reciprocal <i>Pyrus</i> rootstock seedling families

  Fruit Research · 2023-01-01

  articleOpen access1st author

  The U.S. pear production is constrained by the lack of dwarfing and precocious rootstocks that revolutionized other fruit crops, such as apple. While quince is used as a rootstock in global pear production, concerns about potential graft incompatibility and lack of cold hardiness limit its adoption in the U.S. This work was aimed at identifying genetic determinants of dwarfing in <italic>Pyrus</italic> backgrounds to inform future breeding for dwarfing <italic>Pyrus</italic> rootstocks. In 2018, 145 rootstock seedlings of two reciprocal crosses were budded with a standard scion variety. Rootstock seedlings were also genotyped with the 70 K <italic>Pyrus</italic> SNP array. Based on two-year orchard architectural phenotypes, quantitative trait loci (QTLs) were consistently mapped on both chromosomes 5 and 15 for dwarfing traits, namely scion trunk cross-sectional area (TCA), total scion annual growth, and central leader annual growth. QTLs for rootstock TCA were also detected on both chromosomes 5 and 15; however, the chromosome 15 QTL did not co-localize with the scion trait locus. Each dwarfing haplotype accounted for 30% to 50% reduction in vigor (<italic>p</italic> &lt; 0.05). Combined haplotype analysis showed that one dwarfing locus was sufficient to significantly reduce vigor. Presence of two dwarfing haplotypes further reduced vigor by a total of 50% to 70% (<italic>p</italic> &lt; 0.05), but their combinatory effects were not purely additive due to epistasis. Discovery of these novel dwarfing loci (named <italic>P×Dwg1</italic> and <italic>P×Dwg2</italic>) in <italic>Pyrus</italic> facilitates future DNA test development to enable informed parental and seedling selection for dwarfing potential.

  PublisherDOI

• Genetics and Breeding of Apple Scions

  Compendium of plant genomes · 2021-01-01 · 11 citations

  book-chapter1st authorCorresponding
  PublisherDOI

• Trends in Fruit Quality Improvement From 15 Years of Selection in the Apple Breeding Program of Washington State University

  Frontiers in Plant Science · 2021-10-18 · 18 citations

  articleOpen access1st author

  Washington State University's apple breeding program (WABP) was initiated in 1994 to select new apple cultivars with improved eating quality, appearance, and storability that are suitable for production in the main growing regions of the state. Fruit quality is phenotyped using various instrumental measures, such as penetrometers (texture), titrator (acidity), and refractometer (soluble solids concentration; SSC), as well as sensory assessment. The selection regime of WABP occurs in three sequential phases: phase one (P1)-single, unreplicated seedlings at one site, phase two (P2)-replicated selections at three geographically diverse sites, and phase three (P3)-highly replicated elite selections at one to two grower sites. Most of the data collection of WABP occurs in P2. Knowledge of trends/changes associated with advancing selections is essential for understanding the selection criteria and progress of WABP throughout the changing compositions of advancing and culling selections. For each post-harvest trait, P2 data from harvest years 2005 to 2019 were split across sites, and between selections and reference cultivars (e.g., Cripps Pink, Gala, and Honeycrisp). Means of instrumental crispness (Cn) and inner cortex firmness for the advancing selections increased gradually over this period and were significantly higher than those for cultivars. Means of outer cortex firmness measurements were stable for selections but significantly higher than those for cultivars. The average fruit acidity of selections increased marginally over this period and was higher than that of the cultivars. Meanwhile, the average fruit SSCs of selections and cultivars were statistically indistinguishable. These 15-year trends indicate that WABP has been selecting apples with improved eating quality and storability through increased crispness and inner cortex firmness, respectively.

  PublisherOA PDFDOI

• Fire blight QTL analysis in a multi-family apple population identifies a reduced-susceptibility allele in ‘Honeycrisp’

  Horticulture Research · 2021 · 28 citations

  • Biology
  • Genetics
  • Horticulture

  Breeding apple cultivars with resistance offers a potential solution to fire blight, a damaging bacterial disease caused by Erwinia amylovora. Most resistance alleles at quantitative trait loci (QTLs) were previously characterized in diverse Malus germplasm with poor fruit quality, which reduces breeding utility. This study utilized a pedigree-based QTL analysis approach to elucidate the genetic basis of resistance/susceptibility to fire blight from multiple genetic sources in germplasm relevant to U.S. apple breeding programs. Twenty-seven important breeding parents (IBPs) were represented by 314 offspring from 32 full-sib families, with 'Honeycrisp' being the most highly represented IBP. Analyzing resistance/susceptibility data from a two-year replicated field inoculation study and previously curated genome-wide single nucleotide polymorphism data, QTLs were consistently mapped on chromosomes (Chrs.) 6, 7, and 15. These QTLs together explained ~28% of phenotypic variation. The Chr. 6 and Chr. 15 QTLs colocalized with previously reported QTLs, while the Chr. 7 QTL is possibly novel. 'Honeycrisp' inherited a rare reduced-susceptibility allele at the Chr. 6 QTL from its grandparent 'Frostbite'. The highly resistant IBP 'Enterprise' had at least one putative reduced-susceptibility allele at all three QTLs. In general, lower susceptibility was observed for individuals with higher numbers of reduced-susceptibility alleles across QTLs. This study highlighted QTL mapping and allele characterization of resistance/susceptibility to fire blight in complex pedigree-connected apple breeding germplasm. Knowledge gained will enable more informed parental selection and development of trait-predictive DNA tests for pyramiding favorable alleles and selection of superior apple cultivars with resistance to fire blight.

  PublisherOA PDFDOI

Frequent coauthors

• Kate Evans

  Washington State University

  39 shared

• Sarah A. Kostick

  31 shared

• John L. Norelli

  United States Department of Agriculture

  18 shared

• Bonnie Schonberg

  9 shared

• Lisa Brutcher

  9 shared

• James J. Luby

  University of Minnesota

  6 shared

• Matthew D. Clark

  National Clonal Germplasm Repository

  6 shared

• Bruce H. Barritt

  5 shared

Awards & honors

• Distinguished Alumni Award