Perspectives on the adaptation of Japanese plum-type cultivars to reduced winter chilling in two regions of Spain

Abstract

Japanese plum, like other temperate fruit tree species, has cultivar-specific temperature requirements during dormancy for proper flowering. Knowing the temperature requirements of this species is of increasing interest due to the great genetic variability that exists among the available Japanese plum-type cultivars, since most of them are interspecific hybrids. The reduction of winter chilling caused by climate change is threatening their cultivation in many regions. In this work, the adaptation perspectives of 21 Japanese plum-type cultivars were analyzed in two of the main plum-growing regions in Spain, Badajoz and Zaragoza, to future climate conditions. Endodormancy release for subsequent estimation of chilling and heat requirements was determined through empirical experiments conducted during dormancy at least over two years. Chill requirements were calculated using three models [chilling hours (CH), chilling units (CU) and chilling portions (CP)] and heat requirements using growing degree hours (GDH). Chilling requirements ranged 277-851 CH, 412-1,030 CU and 26-51 CP, and heat requirements ranged from 4,343 to 9,525 GDH. The potential adaption of the cultivars to future warmer conditions in both regions was assessed using climate projections under two Representative Concentration Pathways (RCP), RCP4.5 (effective reduction of greenhouse gas emissions) and RCP8.5 (continuous increase in greenhouse gas emissions), in two time horizons, from the middle to the end of 21st century, with temperature projections from 15 Global Climate Models. The probability of satisfying the estimated cultivar-specific chilling requirements in Badajoz was lower than in Zaragoza, because of the lower chill availability predicted. In this region, the cultivars analyzed herein may have limited cultivation because the predicted reduction in winter chill may result in the chilling requirements not being successfully fulfilled.

Chilling and heat requirement for dormancy breaking and flowering of the plum accessions belonging to the living collection of Morocco

“…The other groups showed intermediate heat requirements. Our results showed some similarities with previous investigations reported by Ruiz et al, (2018) and Guerrero et al, (2024), which have showed that accumulated heat requirements for plum cultivars grown in Spain were 7,609 GDH and 6,934 on average, respectively. Besides, the cultivar Santa Rosa showed the earliest owering and the cultivar Singlobe showed the latest owering.…”

“…in Spain,Alburquerque et al, (2008) in the USA,Campoy et al, (2012) in South Africa andGuerrero et al, (2024) in Spain, recording low chilling accumulation during November and high accumulation from December to mid-February. The heat accumulation, estimated in GDH, between February and May during the two years of the experiment 2020-2021 and 2021-2022 were 15,000 and 13,800 GDH, respectively which showed increased heat availability from March.…”