Chilling Requirements and Blooming Dates of Leading Peach Cultivars and a Promising Early Maturing Peach Selection, Momo Tsukuba 127

Abstract

A major goal of peach breeding programs in Japan is to develop cultivars with lower chilling requirements than the leading cultivars. Low-chill cultivars can be grown in subtropical as well as temperate regions. We investigated the chilling requirements (chill units; CU), heat requirements (growing degree hours; GDH), and blooming dates of 7 leading Japanese peach cultivars, 3 subtropical low-chill cultivars, and a promising new selection, Momo Tsukuba 127. In general, the CU of the 7 leading cultivars were higher than those of the 3 subtropical cultivars and Momo Tsukuba 127. The chilling and heat requirements were determined for the 3 leading high-chill cultivars ('Akatsuki', 'Hikawahakuhou', and 'Kawanakajimahakutou'), the low-chill cultivar 'Okinawa 1', and Momo Tsukuba 127 during 4 seasons at a single location. The CU for 'Okinawa 1' and Momo Tsukuba 127 were significantly lower than those of the three high-chill cultivars. Because Momo Tsukuba 127 had lower chilling requirements than the 7 leading peach cultivars but higher chilling requirements than the subtropical cultivars, we classified this new selection as a mid-chill variety. We used the CU and GDH, along with local temperature data, to estimate the blooming dates of 4 cultivars and the new selection during 11 seasons at one location. Regression analyses showed high correlations between the calculated and actual blooming dates. We also compared calculated and actual blooming dates for the 3 leading cultivars and Momo Tsukuba 127 at between17 and 21 locations per genotype. A total of 25 locations were used, and these were widely spread over the temperate zones of Japan. The correlations between the calculated and actual blooming dates were close to 1:1. Our results indicated that our CU and GDH values, along with actual temperature data, could be used to reliably estimate the blooming dates of the genotypes. Because of its lower chilling requirements, the new selection, Momo Tsukuba 127, bloomed 7 or more days earlier than the leading peach cultivars in this study.

Earliness, yield, and fruit quality characteristics in low chill peach-nectarines: a comparison of protected and open area cultivation

“…These results were similar to those reported by Ben Mimoun and DeJong (1999) and Marra et al (2002). The harvest time also depended on cultivars with low chilling (Sawamura et al, 2017) and location (Marra et al, 2002). In previous studies, the harvest data for peach-nectarines were in the range of May 1-7 in Italy (Falqui et al, 1994) and May 5-16 in Turkey (Kuden et al, 2007).…”

“…Heat requirements were calculated as the accumulation of growing degree hours (GDH) based on hourly air temperatures above 4.5 °C (Sawamura et al, 2017). Trees have no additional growth advantage at temperatures above 25 °C; therefore, the temperatures above 25 °C were accepted as equal to 25 °C.…”

Impact of Chill and Heat Exposures under Diverse Climatic Conditions on Peach and Nectarine Flowering Phenology

“…Significant differences between observed and expected bloom dates were documented for the low-chill cultivars ‘Patty’ and ‘Carla’, while the smallest differences were determined for ‘Sweet Dream’, ‘Big Top’ and ‘Catherina’. In a recent study by Sawamura et al [ 31 ], observed bloom dates collected for three peach cultivars and one selection grown in different locations in Japan were compared with predicted bloom dates calculated with the Utah Model. In agreement with our results, the authors found low suitability of this model for the low-chill selection.…”

Spatial Difference of Interactive Effect Between Temperature and Daylength on Ginkgo Budburst

“…On the contrary, chilling accumulation was substantially reduced at low latitudes, causing daylength to play a more important role by interacting with temperature. The chilling threshold to break dormancy might vary across space as well, and trees from high latitudes might exhibit higher chilling requirements ( Sawamura et al, 2017 ). Since warming rates increase with latitude ( IPCC, 2021 ), chilling accumulation might also become insufficient at high latitudes in the future, and thus, daylength may affect future budburst dates at both high- and low-latitude regions.…”