About

Al Kovaleski is an Assistant Professor in the Department of Plant and Agroecosystem Sciences at the University of Wisconsin-Madison. He is based in the Plant Sciences Building/Moore Hall in Madison, WI. His contact information includes his email al.kovaleski@wisc.edu and phone number 608-262-1390. His work is associated with the College of Agricultural & Life Sciences, and he is involved in undergraduate and graduate programs, with a focus on plant sciences and agroecosystems. The department emphasizes diversity, equity, and inclusion resources, and supports research, outreach, and educational initiatives in plant and agroecosystem sciences.

Research topics

• Botany
• Computer Science
• Biology
• Engineering
• Atmospheric sciences
• Nuclear engineering
• Environmental science
• Chemistry
• Materials science
• Physics
• Biological system
• Process engineering

Selected publications

• Integrating cold hardiness and deacclimation resistance demonstrates a conserved response to chilling accumulation in grapevines

  Journal of Experimental Botany · 2025-02-08 · 5 citations

  articleSenior author

  To survive the harsh conditions of winter, woody perennial species such as grapevine have adapted to use environmental cues to trigger physiological changes to induce dormancy, acquire cold hardiness, and measure the length of winter to properly time spring budbreak. Human-induced climate change disrupts these cues by prolonging warm temperatures in autumn, reducing the depth and consistency of midwinter, and triggering early budbreak through false spring events. We evaluated variation in dormant bud cold hardiness and chilling hour requirements of 31 different grapevine varieties over 3 years. Differential thermal analysis was used to track changes in cold hardiness, and deacclimation resistance was assessed throughout the season to track dormancy progression. Results demonstrate wide variation in the maximum deacclimation rate (1.03-2.87 °C d-1) among varieties under forcing conditions. Significant correlations were noted of wild species distributions or cultivar provenance with cold hardiness and deacclimation rates, demonstrating the likely climate-adaptive nature of these traits. When integrated with variation in cold hardiness, these rates revealed a relationship between winter cold hardiness, changes in deacclimation rate, and budbreak phenology. Standardizing rates among varieties as deacclimation potential demonstrated a conserved response to chilling exposure among varieties that alters our interpretation of the concept of high and low chill varieties and chilling requirement in grapevine.

  PublisherDOI

• Is It Cold Enough? Effects of Artificial and Natural Chilling on Budbreak and Frost Hardiness in <scp> <i>Acer saccharum</i> </scp> (Marsh.)

  Physiologia Plantarum · 2025-09-01 · 1 citations

  articleOpen access

  ABSTRACT A crucial part of the phenological cycle in temperate and boreal trees is the exposure to chilling temperatures releasing endodormancy, which allows the trees to react to external signals and resume growth in spring. We compared the effect of artificial and natural chilling on endodormancy break and frost hardiness of sugar maple ( Acer saccharum ) seedlings. Samples were either placed in growing chambers under artificial chilling conditions (4°C) or outdoors (natural temperatures, including &lt; 0°C) in Chicoutimi, Canada. During dormancy, we performed regular transfers to forcing conditions, quantified frost hardiness (LT 50 ) at the time of transfer and observed the time to budbreak (TBB). We measured chilling accumulation with classic models considering only temperatures above 0°C (Chilling Hours, Utah Model, and Dynamic Model) and with a modified model accounting for all temperatures between −10°C and 7.2°C. Samples in artificial chilling showed earlier deacclimation and initiated budbreak in late April, indicating that 4°C can both fulfill the chilling requirement and initiate ontogenetic development. Samples under natural chilling showed later deacclimation, correlating with a longer TBB. Endodormancy break point was only identified in artificial conditions, after 2715 to 3075 h at 4°C. The chilling model accounting for freezing temperatures outperformed classic chilling models. Seedling provenance did not have a significant effect. Our results indicate that including freezing temperatures can improve chilling calculations in cold climates or boreal species, where temperatures remain below 0°C during most of the winter. Moreover, measuring frost hardiness during chilling‐forcing experiments can clarify how acclimation and deacclimation influence dormancy dynamics.

  PublisherOA PDFDOI

• Thresholds for spring freeze: measuring risk to improve predictions in a warming world

  New Phytologist · 2025-08-07 · 7 citations

  reviewOpen accessSenior authorCorresponding

  Plant distribution and productivity are shaped by environmental stressors, particularly freezing events in extra-tropical regions. In early spring, a progressive loss of cold hardiness with phenological development leaves emerging tissues vulnerable to freezing events. In many regions, climate warming is advancing phenology to a greater degree than the date of the last spring freeze, increasing the period of vulnerability to spring freezes. Studies describing critical temperatures at which spring freeze damage occurs are numerous and diverse in both the system studied and type of thresholds used (empirical vs model). Here, we review trends in previously reported thresholds for spring freeze damage across a range of plant groups (row crops, fruit trees, and forest species) over the course of phenological development in spring, and analyze potential sources of variation causing discrepancies between empirically determined and model-derived thresholds. Our analysis shows consistent reporting of higher (less-hardy) thresholds in model-based studies when compared with empirical measurements. These differences highlight a need to improve model estimations of damage by accounting for both microclimatic complexities (humidity, topography, wind speed, etc.) and physiological considerations (phenology and species) that influence the translatability between precise, empirically measured thresholds and critical temperatures used to describe damage in the field.

  PublisherOA PDFDOI

• Anthocyanin accumulation, inflorescence dry weight and total cannabidiol content have different temperature optima in Cannabis sativa

  Journal of Cannabis Research · 2025-07-29

  articleOpen access

  Limited information exists on how temperature affects phytocannabinoids and anthocyanin accumulation and inflorescence dry weight yield in Cannabis sativa. Understanding how temperature influences these traits is essential for refining cultivation practices, meeting market demands, and developing novel cannabis cultivars with improved agronomic, medicinal, and aesthetic attributes. In this study, a day-neutral inbred population with uniform expression of purple pigmentation on the leaves and flowers was used to explore how temperatures ranging from 0.5 to 22 °C impacts inflorescence dry weight, cannabidiol (CBD) percentage, and anthocyanin accumulation in cannabis. Data on inflorescence dry weight (g/plant), CBD (%), and anthocyanin concentration (mg∙L− 1) in the primary inflorescence of each plant were collected and analyzed. Total CBD concentration and inflorescence dry weight yield increased with increasing temperature– likely a result of plant maturity rather than temperature stimuli. Anthocyanin accumulation was significantly affected by temperature stimuli, exhibiting peak production levels at constant temperatures of 8 °C and 15 °C. CBD concentration and inflorescence dry weight predominantly correlate with plant maturity, whereas anthocyanin accumulation is responsive to variations in environmental temperature. Maximum anthocyanin levels at 8 °C and 15 °C, along with reduction at 0.5 °C and 22 °C, suggests distinct temperature-dependent regulatory pathways for anthocyanin biosynthesis in cannabis, separate from those influencing CBD biosynthesis and inflorescence dry weight. Modeling anthocyanin concentration, CBD concentration, and total inflorescence dry weight across various temperature treatments could optimize desired floral qualities and other traits associated with yield in cannabis.

  PublisherOA PDFDOI

• Cold hardiness dynamics predict budbreak and associated low temperature threats in grapevine

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-01-14 · 5 citations

  preprintOpen accessSenior authorCorresponding

  Temperate woody perennial plants form buds that develop into leaves or flowers that emerge in the following growth season. To survive winter, dormant buds must attain cold hardiness, and timely lose it in spring to break bud while avoiding damage from low temperatures and late frosts. Here, we use a process-based model to predict bud cold hardiness of three grapevine varieties ( V. vinifera 'Cabernet-Sauvignon' and 'Riesling', and V. hybrid 'Concord') from historical temperature records of eight different locations in North America and Europe (n=329). Based on those predictions, and thresholds of cold hardiness at budbreak from literature, timing of budbreak was extracted. Despite the model being untrained to budbreak data, the cold hardiness model resulted in good predictions (RMSE=7.3d) that were further improved based on expected delays from cold damage (RMSE=7.2d). Both increasing and decreasing trends in freeze damage risk were predicted with increasing temperature, depending on the range of mean dormant season temperature (MDST; 1 Nov-30 Apr) in each location. Predictions in timing of spring phenology in relation to MDST also showed warming to advance (MDST&lt;10°C) or delay (MDST&gt;10°C) budbreak. Cold hardiness dynamics represents an advancement in phenological modeling that provides information for the entirety of the dormant season, as well as budbreak.

  PublisherOA PDFDOI

• Cold hardiness-informed budbreak reveals role of freezing temperatures and daily fluctuation in chill accumulation model

  bioRxiv (Cold Spring Harbor Laboratory) · 2024-02-27 · 2 citations

  preprintOpen accessSenior authorCorresponding

  Abstract Fundamental questions in bud dormancy remain, including what temperatures fulfill dormancy requirements (i.e., chill accumulation). Recent studies demonstrate freezing temperatures promote chill accumulation and cold hardiness influences time to budbreak – the phenotype used for dormancy evaluations. Here we evaluated bud cold hardiness ( CH ) and budbreak responses of grapevines ( Vitis hybrids) throughout chill accumulation under three treatments: constant (5°C), fluctuating (−3.5 to 6.5 °C daily), and field conditions (Madison, WI, USA). Chill treatments experiencing lower temperatures promoted greater gains in cold hardiness ( CH field &gt; CH fluctuating &gt; CH constant ). All treatments decreased observed time to budbreak with increased chill accumulation. However, perceived treatment effectiveness changed when time to budbreak was adjusted to remove cold acclimation effects. Among three classic chill models (North Carolina, Utah, and Dynamic), none were able to correctly describe adjusted time to budbreak responses to chill accumulation. Thus, a new model is proposed that expands the range of chill accumulation temperatures to include freezing temperatures and enhances chill accumulation under fluctuating temperature conditions. Most importantly, our analysis demonstrates adjustments for uneven acclimation change the perceived effectiveness of chill treatments. Therefore, future work in bud dormancy would benefit from simultaneously evaluating cold hardiness. Highlight A new chill accumulation model demonstrates how bud cold hardiness changes elicited by chill treatments affect the interpretation of thermal effectiveness in promoting dormancy progression and release.

  PublisherOA PDFDOI

• Cold hardiness-informed budbreak reveals role of freezing temperatures and daily fluctuation in a chill accumulation model

  Journal of Experimental Botany · 2024-06-28 · 7 citations

  articleSenior author

  Fundamental questions in bud dormancy remain, including what temperatures fulfill dormancy requirements (i.e. chill accumulation). Recent studies demonstrate freezing temperatures promote chill accumulation and cold hardiness influences time to budbreak-the phenotype used for dormancy evaluations. Here we evaluated bud cold hardiness and budbreak responses of grapevines (Vitis hybrids) throughout chill accumulation under three treatments: constant (5 °C), fluctuating (-3.5 to 6.5 °C daily), and field conditions (Madison, WI, USA). Chill treatments experiencing lower temperatures promoted greater gains in cold hardiness (field>fluctuating>constant). All treatments decreased observed time to budbreak with increased chill accumulation. However, perceived treatment effectiveness changed when time to budbreak was adjusted to remove cold acclimation effects. Among three classic chill models (North Carolina, Utah, and Dynamic), none was able to correctly describe adjusted time to budbreak responses to chill accumulation. Thus, a new model is proposed that expands the range of chill accumulation temperatures to include freezing temperatures and enhances chill accumulation under fluctuating temperature conditions. Most importantly, our analysis demonstrates that adjustments for uneven acclimation change the perceived effectiveness of chill treatments. Therefore, future work in bud dormancy would benefit from simultaneously evaluating cold hardiness.

  PublisherDOI

• The potential for an increasing threat of unseasonal temperature cycles to dormant plants

  New Phytologist · 2024-08-17 · 15 citations

  reviewOpen access1st authorCorresponding

  Two functional responses largely guide woody plants' survival to winter conditions: cold hardiness and dormancy. Dormancy affects budbreak timing based on chill accumulation. Effects of warming on dormancy may appear time-shifted: fall and winter warming events decrease chill accumulation, delaying budbreak observed in spring. The same warming events also affect cold hardiness dynamics, having immediate implications. As cold deacclimation rates increase with dormancy progression, the same amount of warming has greater damage risk the later it occurs in the season, depending on return of low temperatures. Should frequency of erratic weather increase with climate change, more instances of risk are expected. However, understanding how plants fare through seasons now and in future climates still requires better knowledge of winter physiology.

  PublisherOA PDFDOI

• Physiological and transcriptomic characterization of cold acclimation in endodormant grapevine under different temperature regimes

  Physiologia Plantarum · 2024-11-01 · 9 citations

  articleOpen access

  It is essential for the survival of grapevines in cool climate viticultural regions where vines properly acclimate in late fall and early winter and develop freezing tolerance. Climate change-associated abnormities in temperature during the dormant season, including oscillations between prolonged warmth in late fall and extreme cold in midwinter, impact cold acclimation and threaten the sustainability of the grape and wine industry. We conducted two experiments in controlled environment to investigate the impacts of different temperature regimes on cold acclimation ability in endodormant grapevine buds through a combination of freezing tolerance-based physiological and RNA-seq-based transcriptomic monitoring. Results show that exposure to a constant temperature, whether warm (22 and 11°C), moderate (7°C), or cool (4 and 2°C) was insufficient for triggering cold acclimation and increasing freezing tolerance in dormant buds. However, when the same buds were exposed to temperature cycling (7±5°C), acclimation occurred, and freezing tolerance was increased by 5°C. We characterized the transcriptomic response of endodormant buds to high and low temperatures and temperature cycling and identified new potential roles for the ethylene pathway, starch and sugar metabolism, phenylpropanoid regulation, and protein metabolism in the genetic control of endodormancy maintenance. Despite clear evidence of temperature-responsive transcription in endodormant buds, our current understanding of the genetic control of cold acclimation remains a challenge when generalizing across grapevine tissues and phenological stages.

  PublisherOA PDFDOI

• Integrating cold hardiness and deacclimation resistance demonstrates a conserved response to chilling accumulation in grapevines

  bioRxiv (Cold Spring Harbor Laboratory) · 2024-09-30 · 3 citations

  preprintOpen accessSenior author

  Abstract To survive the harsh conditions of winter, woody perennial species such as grapevine have adapted to use environmental cues to trigger physiological changes to induce dormancy, acquire cold hardiness, and measure the length of winter to properly time spring budbreak. Human induced climate change disrupts these cues by prolonging warm temperatures in fall, reducing the depth and consistency of midwinter, and triggering early budbreak through false spring events. We evaluated variation in dormant bud cold hardiness and chilling hour requirements of 31 different grapevine varieties over 3 years. Differential thermal analysis was used to track changes in cold hardiness and deacclimation resistance was assessed throughout the season to track dormancy progression. Results demonstrate wide variation in maximum deacclimation rate (1.03 – 2.87 °C/day) among varieties under forcing conditions. Absolute maximum rates of deacclimation show signatures of species-level responses to forcing temperatures. When integrated with variation in cold hardiness, these rates revealed a relationship between winter cold hardiness, changes in deacclimation rate and budbreak phenology. Standardizing rates among varieties as deacclimation potential demonstrated a conserved response to chilling exposure among varieties that alters our interpretation of the concept of high and low chill varieties and chilling requirement in grapevine.

  PublisherDOI

Frequent coauthors

• Jason P. Londo

  85 shared

• Hongrui Wang

  Central South University

  10 shared

• Rebecca L. Darnell

  University of Florida

  10 shared

• Bruno Casamali

  9 shared

• Michael G. North

  University of Wisconsin–Madison

  8 shared

• Jeffrey G. Williamson

  Washington University in St. Louis

  8 shared

• Bruce I. Reisch

  Cornell University

  8 shared

• Lance Cadle‐Davidson

  6 shared

Education

• Ph.D., Plant Pathology

  University of Wisconsin-Madison

  1990

• M.S., Plant Pathology

  University of Wisconsin-Madison

  1986

• B.S., Botany

  University of Wisconsin-Madison

  1982