Blooming under Mediterranean Climate: Estimating Cultivar-Specific Chill and Heat Requirements of Almond and Apple Trees Using a Statistical Approach

Xavier Miarnau,Felicidad de Herralde,Isabel Díez-Palet,Inmaculada Funes,Glòria Àvila,Robert Savé,Francisco Vargas,Xavier Aranda,Joaquim Carbó,Carmen Biel

doi:10.3390/agronomy9110760

Xavier Miarnau, Felicidad de Herralde + Show 8 more

Open Access

https://doi.org/10.3390/agronomy9110760

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Journal: Agronomy	Publication Date: Nov 15, 2019
Citations: 37	License type: CC BY 4.0

Affiliation: Institute of Agrifood Research and Technology

Abstract

Climate change, and specifically global temperature increase, is expected to alter plant phenology. Temperate deciduous fruit trees have cultivar-specific chill and heat requirements to break dormancy and bloom. In this study, we aimed to estimate chill and heat requirements (in chill portions, CP, and growing degree hours, GDH, respectively) of 25 almond (30–36 years) and 12 apple (14–26 years) cultivars grown under a Mediterranean climate. The set included early and late blooming genotypes. Long-term phenological and temperature records were analyzed by means of partial least squares (PLS) regression. The main difference between early and late genotypes was chill requirement, ranging from 8.40 CP of early genotypes to 55.41 CP of extra-late genotypes. However, as chill requirements are quite easily attained by all almond cultivars in this study, year-to-year variations in actual blooming dates for each genotype are governed by variability of mean forcing temperatures. In contrast, different chill and heat combinations resulted in similar mean blooming dates for the studied apple cultivars. Mean temperature in both chilling and forcing phases determined their blooming time in the location studied. Overlaps and gaps between both phases were obtained. Despite some limitations, the PLS analysis has proven to be a useful tool to define both chilling and forcing phases. Nevertheless, since the delineation of these phases determine the total amount of CP and GDH, further efforts are needed to investigate the transition of these phases.

Highlights

Dormancy in temperate deciduous fruit trees is a phase of the ontogenetic development that allows trees to survive unfavorable conditions, like cold damage during winter [1], while helping to preserve nutrients assimilated over the preceding season [2] and delaying the reproductive processes to guarantee the reproduction of the individual [3].Flowering time results from the sum of two traits: chill and heat requirements (CR and HR, respectively [4])
No significant trends were observed in the phenological traits for any species, indicating that recorded blooming dates were independently distributed over the study period (Supplementary Tables S2 and S3)
As mean bloom dates did not differ much between the 12 apple cultivars analyzed no clear relationship could be found between the chill requirements (CR) or the length of the chill/forcing phase and their bloom dates like those we found for almond

Summary

Introduction

Dormancy in temperate deciduous fruit trees is a phase of the ontogenetic development that allows trees to survive unfavorable conditions, like cold damage during winter [1], while helping to preserve nutrients assimilated over the preceding season [2] and delaying the reproductive processes to guarantee the reproduction of the individual [3]. Flowering time results from the sum of two traits: chill and heat requirements (CR and HR, respectively [4]). The adaptation of a crop to a specific location is intrinsic to the fulfilment of these agro-climatic requirements [3], which are known to be cultivar-specific. 2 ofwinter chill and heat is related to an adequate flower bud development and budburst. Theirregular, adaptationdelayed of a cropand to areduced specific location is intrinsic the fulfilment of [5]

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