José Antonio Campoy

Developing Microsatellite Multiplex and Megaplex PCR Systems for High-Throughput Characterization of Breeding Progenies and Linkage Maps Spanning the Apricot (Prunus armeciaca L.) Genome

One hundred and twenty apricot and peach simple sequence repeat (SSR) markers have been used in the molecular characterization of a BC1 apricot progeny of 73 seedlings derived from the cross between the F1 selection “Z506-07” (“Orange Red” × “Currot”) and the Spanish cultivar “Currot.” To reduce costs and improve the capacity of molecular characterization assays using SSR markers, a series of seven megaplex PCRs containing between six and 20 SSR markers were developed for the molecular characterization of the apricot breeding progeny studied. Amplification was successful in apricot progenitors and in the progeny with 114 of the 120 (95%) SSR markers with a suitable level of polymorphism (1.7 alleles/marker) detected in the BC1 descendants studied. In addition, the implementation of megaplex PCR increased the efficiency and reduced the cost of this type of molecular studies. The implications of these results for apricot-breeding programs and the construction of genetic linkage maps have been also discussed.

The relationship between xylem differentiation and dormancy evolution in apricot flower buds (Prunus armeniaca L.): the influence of environmental conditions in two Mediterranean areas

Environmental and climatic conditions affect the flower bud growth, flowering and yield performance of fruit species. Temperature and water availability appear to be important factors for temperate fruit trees in mild climates. The aim of this research was to study the involvement of temperature regime on biological processes, such as xylem differentiation and dormancy evolution, in apricot flower buds (Prunus armeniaca L.). Over 3 consecutive years, biological and anatomical investigations were carried out in Tuscany (Italy) and Murcia (Spain) on two cultivars characterized by a different chilling requirement (CR): Currot, a traditional Spanish cultivar with a very low CR, and Stark Early Orange (SEO), a North American cultivar with a very high CR. Currot had a regular bearing, and was characterized by a synchronism between endodormancy release and xylem differentiation. On the other hand, SEO showed an irregular flower bud growth leading to flowering and fruit-set failure, even with a high level of chilling accumulation. No relationship was found in SEO between xylem development and flower bud growth reactivation. The de-synchronism between these processes could determine the poor adaptability to different environmental areas of SEO cultivar, and its very high CR is not the main hypothesised cause of the altered flower bud development.

Seasonal progression of bud dormancy in apricot (Prunus armeniaca L.) in a Mediterranean climate: A single-node cutting approach

Abstract The progression of the dormancy of apricot (Prunus armeniaca L.) vegetative and reproductive buds in the summer–winter period (June–March) was analysed with the single-node cutting method during two consecutive years in a Mediterranean climate. The progression of the mean time to budbreak (MTB) was studied. Low MTB values were obtained, which show endodormancy intensity under climatic conditions in the South East of Spain only reached a shallow level in apricot. The onset of bud dormancy occurred prior to the advent of chilling accumulation. Although an oscillating pattern on dormancy progression was observed, MTB increased progressively from summer until January and declined rapidly thereafter coinciding with dormancy breaking, although in 2006–2007, maximum endodormancy intensity was observed at beginning of October. Vegetative and reproductive buds showed a similar pattern of seasonal progression of MTB, although after flower differentiation (ca. September) vegetative buds always showed a deeper dormancy than reproductive buds. Autumn and early winter temperatures seem to play a crucial role over dormancy intensity and dormancy progression. A gradient of increasingly deep dormancy from shoot apex to base is suggested by the gradual increment of MTB in a basipetal direction, although it was influenced by the year.

Temperature efficiency for dormancy release in apricot varies when applied at different amounts of chill accumulation

Our aim was to assess the possible differential effect of increasing temperatures due to global warming on dormancy progression in apricot. The effect of a range of chilling temperatures on vegetative and reproductive bud dormancy progression in excised shoots was examined during two seasons. Temperature treatments were applied in different dormant stages to evaluate the possible interaction of date × temperature for dormancy release in apricot. During sampling, chill accumulated in the field ranged from 0 to 49 chill portions (CPs), corresponding to 0-100% of the chilling requirement (CR) of the apricot selection Z505-2. Forcing conditions were applied after a 60-day chill treatment on each sampling date, and rate to budbreak (1/mean time to bud break: MTB(-1) ) was established in vegetative (terminal and lateral) and reproductive buds to determine depth of dormancy. Results showed that the stage of dormancy has a strong influence on the effect of different temperatures on dormancy progression in apricot. For the first time, a non-linear effect of different chilling temperatures during the dormancy cycle in apricot was obtained, especially in the superior range of temperatures traditionally considered to release dormancy. Thus, introduction of this differential effect could help to improve the models to estimate dormancy release in the context of climate change.