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Research Project: Grapevine Genetics, Genomics and Molecular Breeding for Disease Resistance, Abiotic Stress Tolerance, and Improved Fruit Quality

Location: Grape Genetics Research Unit (GGRU)

Title: Vein-to-blade ratio is an allometric indicator of climate-induced changes in grapevine leaf size and shape

Author
item MULLINS, JOEY - Michigan State University
item MIGICOVSKY, ZOE - Dalhousie University
item FRANK, MARGARET - Cornell University - New York
item VANBUREN, ROBERT - Michigan State University
item Londo, Jason
item CHITWOOD, DANIEL - Michigan State University

Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2020
Publication Date: 5/20/2020
Citation: Mullins, J., Migicovsky, Z., Frank, M., Vanburen, R., Londo, J.P., Chitwood, D.H. 2020. Vein-to-blade ratio is an allometric indicator of climate-induced changes in grapevine leaf size and shape. American Journal of Botany. 1. https://doi.org/10.1101/2020.05.20.106906..
DOI: https://doi.org/10.1101/2020.05.20.106906.

Interpretive Summary: Leaf shape dynamically changes as leaves grow and expand from earlybudburst to fully formed leaves. But how do the shapes of leaves change in response to climate variation such as heat or drought?  This study aimed to understand how leaf shape is impacted by climate variation and to help identify a metric for measuring year to year variation in shape.  We measured the ratio of leaf vein and leaf blade area from 208 grapevines in 4 growing seasons.  In total, 8,412 leaves were examined and their leaf shape parameters correlated with changes in climate in each of the four years.  Maximum daily temperature and precipitation were the most correlated with changes in leaf shape, with hot dry years resulting in smaller leaves.  Additionally, we found that the previous year climate impacts the shape of leaves in the following year.  Together we found that heat and drought effects have a strong and measurable impact on the shape of leaves.

Technical Abstract: As a leaf expands, its shape dynamically changes. Previously, we documented an allometric relationship between vein and blade area in grapevine leaves. Larger leaves have a smaller ratio of primary and secondary vein area relative to blade area compared to smaller leaves. We sought to use allometry as an indicator of leaf size to measure the environmental effects of climate on grapevine leaf morphology. We measure the ratio of vein-to-blade area in 8,412 leaves from the same 208 vines across four growing seasons (2013, 2015, 2016, and 2017) using 21 homologous landmarks. Matching leaves by vine and node, we correlate size and shape of grapevine leaves with climate variables. Vein-to-blade ratio varies strongly between years in ways that blade or vein area do not. Maximum daily temperature and to a lesser degree precipitation are the most strongly correlated climate variables with vein-to-blade ratio, indicating that smaller leaves are associated with heat waves and drought. Leaf count and overall leaf area of shoots and the vineyard population studied also diminish with heat and drought. Grapevine leaf primordia initiate in buds the year prior to when they emerge, and we find that climate during the previous growing season exerts the largest statistical effects over these relationships. Our results demonstrate the profound effects of heat and drought on the vegetative morphology of grapevines and show that vein-to-blade ratio is a strong allometric indicator of the effects of climate on grapevine leaf morphology.