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Stellenbosch, South Africa

Campoy J.A.,CSIC - Center of Edafology and Applied Biology of the Segura | Ruiz D.,CSIC - Center of Edafology and Applied Biology of the Segura | Cook N.,Deciduous Fruit Producers Trust Research | Allderman L.,Wine and Vine Research Institute of the Agricultural Research Council | Egea J.,CSIC - Center of Edafology and Applied Biology of the Segura
South African Journal of Botany | Year: 2011

The aim of this study was to determine the bud dormancy progression in apricot at different latitudes and altitudes. Six locations in regions with a Mediterranean climate in South Africa (SA) and Spain were chosen. The study was carried out during two consecutive years, 2007 and 2008, in SA and results were compared to those obtained in Spain in 2008. Locations ranged from low-chill areas, such as Ladismith and Villiersdorp in SA and Campotéjar in Spain, to high-chill areas, such as Ceres in SA and Barranda in Spain. A number of apricot cultivars comprising the range of chilling requirements in both countries were selected. In addition, a second, parallel study was performed to evaluate the paradormancy progression in 'Palsteyn' (SA) and 'Rojo Pasión' (Spain). Deeper dormancy was not observed in high-chill cultivars located in cold areas than in low-chill cultivars in warm areas. However, low-chill cultivars located in warm areas entered and released from dormancy earlier than high chill cultivars in warm areas. Thus, a clinal variation in dormancy progression under warm temperatures in apricot cultivars is suggested. The role of photoperiod and minimum temperatures is proposed to have a key role in dormancy onset. Paradoxically, an earlier maximum depth of dormancy was found in those areas with higher minimum temperatures at the end of summer. Before the beginning of winter, all cultivars showed an important increase of budburst rate, which indicated the end of endodormancy. Afterwards an ecodormancy period followed during winter, while chilling continued to accumulate. These results contrast with the assumed concept of the breaking of dormancy through chilling accumulation during winter and suggest a possible mediation by photoperiod in overcoming of dormancy. On the other hand, paradormancy exerted a reduction in budburst rate during dormancy entry, whereas decapitation increased the budburst rate throughout the dormant season, indicating interaction between different plant parts during this period. © 2010 SAAB. Source


Campoy J.A.,CSIC - Center of Edafology and Applied Biology of the Segura | Ruiz D.,CSIC - Center of Edafology and Applied Biology of the Segura | Allderman L.,Wine and Vine Research Institute | Cook N.,Deciduous Fruit Producers Trust Research | Egea J.,CSIC - Center of Edafology and Applied Biology of the Segura
European Journal of Agronomy | Year: 2012

Different chilling requirements (CRs) are required for apricot (Prunus armeniaca L.) cultivars to overcome dormancy. In a global climate change context, knowledge of these requirements is critical; producers must select the appropriate cultivars to avoid losses caused by an inadequate cultivar adaptation in a particular area. Important differences have been reported in the CRs of cultivars of temperate fruit crops that are cultivated in different climatic conditions. However, the lack of standardisation of protocols to calculate CRs hinders the comparison of the results obtained using different methodologies. This study was aimed at analysing adaptation in terms of the CR fulfilment of commercial apricot cultivars grown successfully in different climatic conditions. Apricot-growing locations with different latitudes and altitudes and cultivars with varying CRs were chosen. The plant material spanned the CR range for this species in South Africa and Spain. Three of the examined cultivars were tested simultaneously in both countries. The Utah, Dynamic and hours below 7 °C models for estimating CR were evaluated and compared. The cultivars examined displayed different CR ranges in Spain and South Africa. We concluded that CR differences higher than 50% can be found for clonal plant material grown successfully in different climatic conditions. This variation might be associated both with different temperatures and other factors such as latitude. No significant differences in heat requirements were found among cultivars in Spain, suggesting that this variable might not be cultivar-specific. Finally, the distribution of clonal plant material provides an excellent framework for studying the climatic adaptation of crops. © 2011 Elsevier B.V.. Source


Allderman L.A.,Wine and Vine Research Institute of the Agricultural Research Council | Steyn W.J.,Stellenbosch University | Cook N.C.,Deciduous Fruit Producers Trust Research
South African Journal of Plant and Soil | Year: 2011

Elgin (34°S, 19°E; 305 m.a.s.l.), typical of South African apple growing regions, accumulates 745 Utah Chill Units (CU) p.a. The chilling requirement of'Golden Delicious' apple (Malus x domestica Borkh.) is c.a. 1100 CU. Consequently, the chilling requirement is not satisfied and delayed foliation is common. The aim of this study was to use plant growth regulators (PGR's) to manipulate the progression of dormancy in order to reduce the chilling requirement of 'Golden Delicious' shoots in mature commercial orchards. A trial was conducted in a commercial orchard in Elgin during the winters of 2004, 2006 and 2007. To advance the onset of dormancy, 250 mgl -1 abscisic acid (ABA) was sprayed several times during April and May of 2004 and 2006. To induce a shallower state of dormancy, cytokinins were applied during April and May of 2006 and 2007. Benzyl adenine (BA) was applied at concentrations between 250 and 1000 mgl -1 and forchorfenuron (CPPU) at 15 mgl -1 Progression of dormancy was assessed by harvesting shoots every 2-3 weeks from initial spray date until commercial rest breaking agents were applied in the orchard. The time interval for 50% of the shoots to exhibit budburst under controlled conditions was used as a parameter for depth of dormancy. Although shoots were sprayed on c.a. the same calendar dates each year and before any significant CU had accumulated, the physiological state of the buds at application varied from shallow to deep dormancy depending on the season. Therefore calendar dates were not a good criteria for spray applications and CU accumulation was not a prerequisite for the onset of dormancy. PGR's altered the dormancy progression of'Golden Delicious' shoots. However, their efficacy was dependant on the dormancy status of the buds at the time of application. Furthermore, the effect was not sustainable. The trees appeared to "normalize" after a short period of time and consequently the PGRs had no effect on the dormancy release or budburst the following spring. Source


North M.S.,ARC Infruitec Nietvoorbij | De Kock K.,ARC Infruitec Nietvoorbij | Cook N.,Deciduous Fruit Producers Trust Research | Allderman L.,Deciduous Fruit Producers Trust Research | Booyse M.,ARC Infruitec Nietvoorbij
Acta Horticulturae | Year: 2012

The efficacy of chemical Rest Breaking Agents (RBA's), used to reduce the negative effects of insufficient winter chilling, depends on application date, concentration, chemistry and cultivar. As environmental concerns increasingly limit the use of agricultural chemicals, RBA's must be applied more efficiently. The depth of dormancy during RBA application was determined by the rate of bud break of oneyear-old shoots forced at 25°C. Shoots were excised six times during August and September 2008 and 2009 from mature 'Royal Gala' (RG) and 'Granny Smith' (GS) apple trees. During 2008, these same trees, on the same six occasions, were treated with either DormexR/oil (0.5%/3% v/v), LiftR (3% v/v), SymphonyR (1/2 and 1/4 volume). During 2009, the same trees were again treated with the same RBA's except Oil (5% v/v) replaced Symphony (1/4 volume). Control trees were left untreated. Bud break (BB) on one-year-old pre-marked shoots and yield/tree were recorded during both seasons. Depth of dormancy varied with cultivar and season and had little effect on BB caused by the RBA. DormexR/oil and LiftR increased bud break of RG but application date had no effect. RBA's applied during early August in both seasons increased yield of larger, redder RG fruit, but no treatment increased total yield. Bud break of GS was increased by Dormex R/oil and LiftR applied during early September. Neither RBA nor application date influenced GS yield during both seasons. Source


Maguylo K.,North Carolina State University | Cook N.C.,Deciduous Fruit Producers Trust Research | Theron K.I.,Stellenbosch University
Acta Horticulturae | Year: 2014

Branch architecture in apple (Malus × domestica Borkh.) is defined according to the location, type (vegetative or reproductive), and length of lateral shoots. This is related to both an inherent genetic basis for architecture and the response of the lateral buds and shoots to environmental constraints. Architecture is typically viewed as the result of time and position bud burst and outgrowth, or branching dynamics, and therefore is related to the competition among buds within an annual shoot. However, while both differences in budburst and in branch formation have been observed, the relationship between budburst and characteristics of the reproductive bud are somewhat unknown. In warm climates, foliation and flowering are delayed and prolonged, and therefore we have used this phenomenon to better understand how branches are formed in warm areas. In a study performed in two areas with different degrees of winter chilling in South Africa, we studied differences in both climate and genotype using three apple cultivars, 'Red Delicious', 'Granny Smith' and 'Golden Delicious', grown in two different locations with differing degrees of winter chilling. Between the warmer and cooler are in the study, we observed architectural characteristics related to differences in fruit size and dry weight. Source

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