Steve van Nocker

Steve van Nocker

Contact Me

Department of Horticulture

(517) 353-0394


Developmental Genetics of Horticultural Crop Plants

The research group that I lead focuses on identifying genes that control development and form of horticultural crop plants and understanding how these genes interact with the environment to determine final plant form. Our research should lead to better understanding of the genetic mechanisms of processes such as flowering, as well as the developmental remodeling of new cultivars with traits more compatible with changing societal needs, production systems, and climate.

Current Projects

  • Juvenility in woody perennial plants
    Many fruit and nut crops are woody perennial plants. These typically pass through several years of vegetative growth before flowering is possible - a phenomenon called juvenility. The length of the juvenile phase is now the major impediment to the rapid development of new cultivars because breeders must wait several years to obtain seed from crosses. We are using a wild apple species, Malus hupehensis, as a model to understand the molecular-genetic control of juvenility. This species shows a very short juvenile phase (as little as seven months) and is easy to research in the lab and field. We are also developing new ways to artificially shorten the juvenile phase of domesticated apple (Malus x domestica) and have decreased the flowering time of this species from 5-8 years to under 2 years in the lab!
  • Understanding biennial bearing and the control of flowering in apple by gibberellins
    Apple cultivars typically bear flowers and fruit only every other year, a phenomenon termed alternate or biennial bearing. In the bearing year, the presence of developing fruit has a repressive effect on the initiation of flowers, which would bloom the following year to generate fruit. In apple and other woody perennial plants, bioactive gibberellins (GAs) also generally have a repressive effect on floral initiation. This project encompasses several synergistic lines of inquiry integrating molecular, genetic and genomic approaches designed to dissect the molecular-genetic bases of biennial bearing in apple. At the applied level, this work will generate tools and knowledge to combat one of the major challenges to the sustainability of the U.S. apple industry. At the fundamental level, the work will address one of the most significant unanswered problems in plant biology - the mechanisms by which GAs repress flowering in woody perennial plants.


  • Ph.D., Cell and Molecular Biology, University of Wisconsin
  • B.S. Genetics, Cornell University


HRT860 Scientific Writing: Workshop (Spring semesters, class time arranged by students)

This small-group workshop trains graduate students in scientific writing through reading and analysis of representative publications from a variety of general and plant-related journals. Optionally, students writing a paper, thesis or grant proposal  bring drafts and distribute these to other students in the group. The writing is discussed and suggestions for improvement are made collectively by instructor and class members.


(last five years; See Google Scholar for more recent)

Mansfield B, Yocca A, Ou Shujun, Harkess A, Burchard E, Gutierrez B, van Nocker S, Gottschalk C.  2023. A haplotype resolved chromosome-scale assembly of North American wild apple Malus fusca and comparative genomics of the fire blight Mfu10 locus. The Plant J. in press;

Xu Y, Fu Q, Wang Y, Yang J, Jiao Y, Li W, Yang F, Yin X, Shang B, Liu R, Zhang Y, Saileke A, Liu G, van Nocker S, Hu H. Plasmopara viticola RxLR effector PvAvh77 triggers cell death and governs immunity responses in grapevine. J Exp Bot. 74(6), 2047-2066;

Zhang S, Gottschalk C, van Nocker S. 2023. Conservation and divergence of expression of GA2-oxidase homeologs in apple (Malus x domestica Borkh). Front Plant Sci. 14:1117069;

Wang L, Yao W, Zhang X, Tang Y, van Nocker S, Wang Y, Li Y, Zhang C. In press. The putative ABCG transporter VviABCG20 from grapevine (Vitis vinifera) is strongly expressed in the seed coat of developing seeds and may participate in suberin biosynthesis. Physiol Mol Biol Plants 29(1):23-34;

Zhang S, Yao J, Wang L, Wu N, van Nocker S, Li Z, Gao M, Wang X. 2022. Role of grapevine SEPALLATA-related MADS box gene VvMADS39 in flower and ovule development. The Plant J.

VanderWeide J, van Nocker S, Gottschalk C. 2022. Meta-analysis of apple (Malus x domestica Borkh.) fruit and juice quality traits for potential use in hard cider production. Plants People Planet 4, 463-475.

Wang L, Zhang X, Qu Z, Guo W, van Nocker S, Zhang C. 2022. Grapevine VviERF105 promotes tolerance to abiotic stress and is degraded by the E3 ubiquitin ligase VviPUB19. Environ Experim Bot 201:

Zhang Y, Zhang L, Ma H, Zhang Y, Zhang X, Ji M, van Nocker S, Ahmad B, Zhao Z, Wang X, Gao H. 2021. Overexpression of the Apple (Malus × domestica) MdERF100 in Arabidopsis Increases Resistance to Powdery Mildew. Int J Mol Sci. 22(11):5713. doi: 10.3390/ijms22115713

Gottschalk C, Zhang S, Schwallier P, Rogers S, Bukovac MJ, van Nocker S. 2021. Genetic mechanisms associated with floral initiation and the repressive effect of fruit on flowering in apple (Malus x domestica Borkh). PLoS One 16(2):e0245487. doi: 10.1371/journal.pone.0245487

Liu Z, Zhu H, Chen P-Y, Zhong S, Dardick C, Callahan A, An Y-Q, van Nocker S, Yang Y, Zhong G-Y, Abbot A. 2020. Thermal-responsive genetic and epigenetic regulation of DAM cluster controlling dormancy and chilling requirement in peach floral buds. Horticulture Research 7:114.

Gao T, Zhang Z, Liu X, Wu Q, Chen Q, Liu Q, van Nocker S, Ma, F, Li C. 2020. Physiological and transcriptome analyses of the effects of exogenous dopamine on drought tolerance in apple. Plant Physiol Biochem 148 DOI 10.1016/j.plaphy.2020.01.022

Tang Y, Liu B, Li Y, van Nocker S., Wang Y, Zhan C. 2020. Differential expression of the seed-specific gene ABCG20 between seedless and seeded grapes and its roles in tomato seed development. South African Journal of Botany 131:428-436

Wang Q, Liu C, Huang D, Dong Q, Li P, van Nocker S, Ma F. 2020. Physiological evaluation of nitrogen use efficiency of different apple cultivars under various nitrogen and water supply conditions. J Integrative Agriculture 19(3):709-720.

Miles C, Alexander T, Peck G, Galinato S, Gottschalk C, van Nocker S. 2020. Growing apples for hard cider production in the U.S. - Trends and research opportunities. HortTechnology 30(2):148-155.

Li X, Xie Y, Lu L, Yan M, Fang N, Xu J, Wang L, Yan Y, Zhao T, van Nocker S, Ma F, Liang D, Guan Q. 2019. Contribution of methylation regulation of MpDREB2A promoter to drought resistance of Malus prunifolia. Plant and Soil 441. DOI 10.1007/s11104-019-04149-z

Huang D, Wang Q, Duan D, Dong Q, Zhao S, Zhang M, Jing G, Liu C, van Nocker S, Ma F, Li C. 2019. Overexpression of MdIAA9 confers high tolerance to osmotic stress in transgenic tobacco. PeerJ 7:e7935 DOI 10.7717/peerj.7935

Zhang S, Gottschalk C, van Nocker S. 2019. Genetic mechanisms in the repression of flowering by gibberellins in apple (Malus x domestica Borkh.). BMC Genomics 20-747. doi:10.1186/s12864-019-6090-6

Li Y, Zhang S, Dong R, Wang L, Yao J, van Nocker S, Wang X. 2019. The grapevine homeobox gene VvHB58 influences seed and fruit development through multiple hormonal signaling pathways. BMC Plant Biology 19. DOI 10.21203/rs.2.11184/v4 DOI 10.1186/s12870-019-2144-9

Zhang G, Yan X, Zhang S, Zhu Y, Zhang X, Qiao  H, van Nocker S, Li Z, Wang X. 2019. The jasmonate-ZIM domain gene VqJAZ4 from the Chinese wild grape Vitis quinquangularis improves resistance to podery mildew in Arabidopsis thaliana. Plant Physiol Biochem 143. DOI 10.1016/j.plaphy.2019.09.018

Zhang S, Wang L, Sun X, Li Y, Yao J, van Nocker S, Wang X. 2019. Genome-wide analysis of the YABBY gene family in grapevine and functional characterization of VvYABBY4. Frontiers in Plant Science, published online Oct 8, 2019

Peace CP, Bianco L, Troggio M, van de Weg E, Howard NP, Cornille A, Durel CE, Myles S, Migicovsky Z, Schaffer RJ, Costes E, Fazio G, Yamane H, van Nocker S, Gottschalk C, Costa F, Chagné D, Zhang X, Patocchi A, Gardiner SE, Hardner C, Kumar S, Laurens F, Bucher E, Main D, Jung S, Vanderzande S. 2019. Apple whole genome sequences: recent advances and new prospects. Hortic Res. 6-59 doi:10.1038/s41438-019-0141-7

Guo T, Wang N, Xue Y, Guan Q, van Nocker S, Liu C, Ma F. 2019. Overexpression of the RNA binding protein MhYTP1 in transgenic apple enhances drought tolerance and WUE by imprvoing ABA level under drought conditions. Plant Sci 280:397-407.

Jia D, Jiang Q, van Nocker S, Gong X, Ma F. 2019. An apple (Malus domestica) NAC transcription factor enhances drought tolerance in transgenic apple plants. Plant Physiol Biochem 139:504-512.

Shao Y, Zhang X, van Nocker S, Gong X. Ma F. 2019. Overexpression of a protein kinase gene MpSnRK2.10 from Malus prunifolia confers tolerance to drought stress in transgenic Arabidopsis thaliana and apple. Gene 692:26-34.

Inês Pratas M, Aguiar B, Vieira J, Nunes V, Teixeira V, Fonseca N, Iezzoni AF, van Nocker S, Vieira C. 2018. Inferences on specificity recognition at the Malus × domestica gametophytic self-incompatibility system. Scientific Reports 8-1717.

Wang H, Dong Q, Duan D, Zhao S, Li M, van Nocker S, Ma F, Mao K. 2018. Comprehensive genomic analysis of the TYROSINE AMINOTRANSFERASE (TAT)genes in apple (Malus domestica) allows the identification of MdTAT2 conferring tolerance to drought and osmotic stress in plants. Plant Physiol Biochem. 133:81-91.

van Nocker, S. 2018. Hybrids without hybridization - can it revolutionize horticulture? Hortic Res 5:76

Xie Y, Chen P, yan Y, Bao C, Li X, Wang L, Shen X, Li H, Liu X, Niu C, Zhu C, Fang N, Shao Y, Zhao T, Yu J, Zhu J, Xu L, van Nocker S, Ma F, Guan Q. 2o18. An atypical R2R3 MYB transcription factor increases cold hardiness by CBF-dependent and CBF-independent pathways in apple. New Phytol 218:201-218.

Xu J, Zhou S, Gong X, Song Y, van Nocker S, Ma F, Guan Q. 2017. Single-base methylome analysis reveals dynamic epigenomic differences associated with water deficit in apple. Plant Biotechnol J.

Li Y, Zhu Y, Yao J, Zhang S, Wang L, Guo C, van Nocker S, Wang X. 2017. Genome-wide identification and expression analyses of the homeobox transcription factor family during ovule development in seedless and seeded grapes. Sci Rep. 7(1):12638

Wang Y, Wang D, Wang F, Huang L, Tian X, van Nocker S, Gao H, Wang X. 2017. Expression of the Grape VaSTS19 Gene in Arabidopsis Improves Resistance to Powdery Mildew and Botrytis cinerea but Increases Susceptibility to Pseudomonas syringe pv Tomato DC3000. Int J Mol Sci. 18(9) pii: E2000

Yang J, Gao M, Huang L, Wang Y, van Nocker S, Wan R, Guo C, Wang X, Gao H. 2017. Identification and expression analysis of the apple (Malus × domestica) basic helix-loop-helix transcription factor family. Sci Rep. 7(1):28