Base temperature as a function of genotype: a foundation for modeling phenology of temperate fruit species

Abstract

To complete each phase of the growing season, plants must accumulate thermal time at lower base temperature (Tb). Little information exists on Tb variation between either fruit species or cultivars of the same species. We therefore aimed to determine the lower base temperature for contrasting genotypes in precocity of peach, plum, grape, pear, and kiwi. Twigs 25-35 cm long for the following cultivars: peach, Tropic Beauty (TB) and Eragil (ER); plum, Gulf Blaze (GB) and Letícia (LE); grape, Chardonnay (CH) and Cabernet Sauvignon (CS); pear, Smith (SM) and Packham's (PA); and kiwi, Golden King (GK) and Hayward (HA) were collected in orchards in Veranópolis, RS Estate, on 06/13/2014, with 0 h at temperatures ≤ 7.2°C (chilling hours; H C ) in the field. Intact twigs packed in black plastic film were subjected to 1,008 H C at 0°C in incubators to overcome dormancy and then transferred to temperatures of 2, 4, 6, 8, 10, and 12°C on single-node cuttings planted in phenolic foam to define effective heat temperature for the genotypes. Over 110 d, budburst of the buds was evaluated in 2-3-d intervals in the green-tip stage. The resulting inverse data of number of days to budburst (1/days to budburst) was inserted into regression curves to estimate Tb for each genotype. Historical phonological series comprised of 10 years for the analyzed cultivars and meteorological data of the cultivation sites were used to determine thermal time (degree-days) for the fruit trees during the growing season, considering different phenological phases. Temperate fruit species exhibited different Tb behaviors: Tb was lower for early cultivars (TB and GB = 2.2°C; CH = 2.1°C; SM = 4.4°C; GK = 4.3°C) and higher for late cultivars (ER = 6.3°C; LE = 6.2°C; CS = 4.3°C; HA and PA = 8.2°C) for all cultures. The Tb f fruit cultivars related directly with genotype chilling requirements: the higher the chilling requirement, the higher the Tb of the cultivar. Cultivars of the same fruit species yielded a sum of degree-days almost equal to finalize the growing season, regardless of the degree of precocity (TB = 1720; ER = 1801; GB = 1680; LE = 1718; CH = 2310; CS = 2369; SM = 2096; PA = 2003 GD; GK = 2775; HA = 2691). Regarding phenological phases, 82% of the assessed cases responded more to thermal time (degree-days) than to chronological time (d) to complete phenological steps. Differences in Tb between genotypes are a relevant factor for improving the accuracy and applicability of phenology models in agriculture. Key words: Growing season. Dormancy. Thermal sum. Degree-days. ResumoPara completar cada subperíodo do ciclo vegetativo, as plantas necessitam de uma soma térmica acumulada a partir da temperatura-base inferior (Tb). Há pouca informação que mostre variação da Tb, considerando espécies e cultivares de uma mesma espécie frutífera. O objetivo deste estudo foi determinar a temperatura-base inferior para genótipos contrastantes em precocidade de pessegueiro, ameixeira, videira, pereira e quivizeiro. Estacas com 25-35 cm de comprimento das c...

Base Temperature Comparisons for Leafing Date, Pistillate Flower Receptivity, and Pollen Shedding in Persian Walnut

“…This study confirms the findings of other researchers (Baker et al, 1986;Gallagher 1979;Sayed 1995;Stinner et al 1974) that changes in the phenological stages are the best markers for the fruit species for forecasting their behaviour with the increasing outside air temperature; however, there are differences in the base temperature values among the species, cultivars, and phenological states (Borges et al 2017;Kerr et al 1981;Rafael and Biasi 2016;Ribeiro et al 2009;Salinger and Kenny 1995;Souza et al 2011;Taghavi et al 2017). The strongest correlation of the observed phenological data was always on the same threshold values in both countries; in the case of leafing, the best correlation was at Tb5.5.…”

“…The strongest correlation of the observed phenological data was always on the same threshold values in both countries; in the case of leafing, the best correlation was at Tb5.5. This value is higher than the amount predicted for grape cultivars 'Chardonnay' (Tb = 2.1 °C) and 'Cabernet Sauvignon' (Tb = 4.3 °C), kiwifruit 'Golden King' (Tb = 4.3 °C), plum 'Gulf Blaze' (Tb = 2.2 °C), pear 'Smith' (Tb = 4.4 °C), peach 'Tropic beauty' (Tb = 2 °C) (Rafael and Biasi 2016), and hazelnut cultivars (Tb = 2 °C) (Taghavi et al 2017). The kiwifruit cultivar 'Hayward' (Tb = 10 °C, Kerr et al 1981;Salinger and Kenny 1995;Tb = 8.2 °C, Rafael and Biasi 2016), the pear cultivar 'Packham's' (Tb = 8.2 °C, Rafael and Biasi 2016), the plum cultivar 'Letícia' (Tb = 6.2 °C, Rafael and Biasi 2016), the grape cultivars 'BRS Victo-K Souza et al 2011), were found to require higher base temperature values than the Persian walnut cultivars involved in our study.…”

“…The walnut cultivars from both countries need less heat accumulation than some wine grape and kiwifruit cultivars (Rafael and Biasi 2016). The walnut cultivars grown in Hungarian climatic conditions needed 20% to 30% less GDD demand for leafing than those under the Iranian conditions.…”

“…Previous studies in pome fruits, stone fruits, and berries showed that the minimum base temperature varied not only by fruit tree species but also by cultivars among species. Studies for determining the base temperatures for growth, sprouting, or leafing of peach and nectarine showed that, for Prunus persica sprouting, the base temperature (Tb) varied from 2.2 °C in 'Tropic Beauty' to 8 °C in 'Sunblaze' nectarine cultivar (Rafael and Biasi 2016;Souza et al 2011). Table 1 contains data for the Tb of phenological stages for several fruit tree species.…”

Base temperature estimates for lisianthus cultivars grown in different planting seasons

“…The determination of the base temperature is an expensive process, since each species has a base temperature which may very in accordance with the plant genotype and the growing season (Anzanello & Biasi, 2016). In temperate species, leaf growth and expansion start before reaching the temperature of 10°C and, in subtropical species, growth does not occur below 12 to 15°C (Hatfield & Prueger, 2015).…”