Retrospection of century-long peach chill, yield and other production data and implications for breeding programs

Authors: Chen, Chunxian

Submitted to: Acta Horticulture Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2022
Publication Date: 12/8/2022
Citation: Chen, C. 2022. Retrospection of century-long peach chill, yield and other production data and implications for breeding programs. Acta Horticulture Proceedings. 1352(1):385-389. https://doi.org/10.17660/ActaHortic.2022.1352.54.
DOI: https://doi.org/10.17660/ActaHortic.2022.1352.54

Interpretive Summary: Commercial peach production depends on many cultivars of different chill requirements and harvest seasons and cooperation of favorable weather conditions. The chilling requirements must be satisfied during winter dormancy to ensure timely bud break in spring and maximize potential yield for harvest. In this report, we analyzed some century-long peach chill, yield, and farm value datasets from GA and/or the U.S. and revealed the trends and relationships among those factors, as they relate to breeding prospects for peaches. Chill hours at Byron, GA, varied greatly year by year, but the averages of every three, five, and ten years all showed a declining trend. The declines in January and February contributed most to the declining annual chill hours. Peach production yields both in GA and the U.S. changed from year to year and also steadily declined over the past century. However, both farm values increased steadily over time, suggesting that increasing prices might sustain similar market values and profits with smaller yields. Improvement of genetic traits with resilience to unfavorable weather conditions is likely among the priorities to minimize the negative impact on peach yield.

Technical Abstract: Peach (Prunus persica) production is complicated. Seasonal yield depends on the performance of a sequence of many cultivars with the cooperation of favorable climatic conditions. Peach chilling requirements, in terms of cumulative chill hours, must be satisfied during winter dormancy to ensure timely bud break and maximize potential yield. In this report, some century-long peach chill, yield, and other production datasets from Byron, GA and the U.S. were analyzed to show the trends and relationships among those factors, as they relate to breeding prospects for peaches. Chill hours at Byron, GA, varied greatly year by year, but the averages of every three, five, and ten years all showed a declining trend. Viewed by months, the smallest to largest declining slopes in turn were October, November, December, January, and February, suggesting declines in the last two months contributed most to the declining annual chill hours. Annual chill hours over the last century approximated a normal distribution using 100-hour bands ranging between 500 and 1700 chill hours, with a mean of 1044. Years with chill hours below 700, 700-899, 900-1299, 1300-1499, and above 1500 accounted for 3.2%, 21.3%, 62.3%, 9.8%, and 3.2% of the total years, respectively. It appeared that chill hours in the higher ranges occurred more in the earlier 5 decades (average 1087 hours) than the more recent 5 decades (959). Peach production yields both in GA and the U.S. changed from year to year and also steadily declined over the past century. The significantly lowest yields occurred mostly in years with spring freeze and/or chill inadequacy. However, both farm values and price per ton increased steadily over time, suggesting that increasing prices might sustain similar market values and profits with smaller yields. The potential use of the data and results in determining future peach cultivar breeding objectives was discussed. Improvement of genetic traits with resilience to unfavorable weather conditions is likely among the priorities to offset or minimize the negative impact on peach yield.