Relationship between temperature and flowering in almond: effect of location

Abstract

A model for the prediction of flowering date in almond requires estimates of the chilling and heat sum requirements. We estimated hourly temperatures from daily minimum and maximum temperatures. A continuous function relating hourly temperature to rate of chilling was used to calculate daily chill unit accumulations. Heat sums were measured as growing-degree-hours: the linear accumulation of hourly temperatures above a threshold temperature. Our model was tested with estimates derived from data obtained at 1 French and 2 Australian locations. The results indicate that estimates derived from data at a single location can be successfully used for other locations with different climates. The accuracy of flowering date prediction generally improves as the number of locations and years of data on which it is based increase. The predictions for the cultivars Mission and Nonpareil were within 5 days of the observed dates in 73 and 88% respectively of the locations-years examined. We concluded that the chilling requirement in almond is (mean � s.e.) 284 � 33 chill units and 3 groups of cultivars can be identified with respect to heat sum requirement in the ranges 5300-6300; 6800-7700 and 8200-8900 degree hours above 4.5�C.

Determination of Endodormancy Break in Almond Flower Buds by a Correlation Model Using the Average Temperature of Different Day Intervals and its Application to the Estimation of Chill and Heat Requirements and Blooming Date

“…This behavior was already observed by Chandler and Brown (1951) when studying almond bloom in California. Another cause for blooming dispersion in almond could also be the base temperature for the fl ower bud development, which can be different not only depending on the species (Rattigan and Hill, 1987;Richardson et al, 1975), but also on the cultivars within a species, as has been observed for the progression of blooming in almond (Bernad and Socias i Company, 1995;DeGrandi-Hoffman et al, 1996;Hill et al, 1985). In addition, each cultivar could react in a different way to occasional extreme temperatures or to a sudden alternation of cold and warm temperatures, a typical phenomenon occurring during the spring in temperate climates (Couvillon and Erez, 1985;Erez and Couvillon, 1987), far away from any model of quantifi cation of chilling and heat requirements.…”

“…Heat requirements were measured as the addition of maximum and minimum daily temperatures (Tabuenca et al, 1972). Later, Rattigan and Hill (1986) applied in almond the method of Ashcroft et al (1977) and evaluated the chilling and heat requirements of 12 almond cultivars grown in the mild winter climate of Australia and also observed the infl uence of different locations on the blooming behavior of three cultivars (Rattigan and Hill, 1987). More recently, the chilling and heat requirements of 10 almond cultivars and breeding selections grown in the mild winter climate of southeastern Spain have also been reported by the assess of endodormacy breaking date by the bud weight method (Egea et al, 2003).…”

Genetic control of flowering time in Eucalyptus globulus ssp. globulus

“…In almond, a combined chill 5 unit:heat sum model based on data from one location could be used to predict anthesis time at 6 a different location with a different climate (Rattigan and Hill 1988). Winter chilling has a 7 role in flower bud initiation in Eucalyptus nitens (Gardner and Bertling 2005), and may also 8 have a role in subsequent growth and development of flower buds in E. globulus.…”

The Influence of Chilling and Heat Accumulation on Bloom Timing, Bloom Length and Crop Yield in Almonds (Prunus dulcis (Mill.))

“…Early studies on almonds and chilling accumulation resulted in requirements from 200 to 500 hours below 45°F, but this requirement varies by variety (Alonso, et al, 2003;Kester, et al, 1977;Rattigan & Hill, 1986). Rattigan and Hill (1987) claim that Nonpareil requires 340 CU while Mission requires 350 CU (Rattigan & Hill, 1987). Contrastingly, D.E.…”