L. Andreini

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.

Gas Exchange, Stem Water Potential and Xylem Flux on Some Grapevine Cultivars Affected by Esca Disease

The effect of esca disease on gas exchange, stem water potential and xylem flux of adult grapevines of Cabernet Sauvignon, Sangiovese and Trebbiano cultivars was studied over three growing seasons. Water relations were measured at veraison and cluster ripening on three types of vines: i) healthy (control); ii) symptomatic and iii) apparently healthy in the year of measurements but that had showed esca symptoms in the previous season. Xylem flux was determined on cane segments by perfusion using a tracing dye before and after the appearance of esca symptoms. Esca induced a marked reduction (about 70%) in carbon assimilation and stomatal conductance, especially in Cabernet Sauvignon and Sangiovese. Esca did not affect the stem water potential. Gas exchange parameters measured before the symptoms appeared in plants affected by esca were similar to those of healthy plants. Measurements made one month before the appearance of the symptoms cannot be used as screening method to determine whether the vine will show esca. No differences in dye translocation were found before the symptoms’ appearance. However, a decrease in xylem flux was measured in symptomatic vines of Cabernet Sauvignon. After the appearance of esca symptoms, only the Trebbiano had a lower xylem flux than the healthy vines.

Influence of canopy fruit location on morphological, histochemical and biochemical changes in two oil olive cultivars

The influence of different irradiance conditions was evaluated under natural solar radiation by comparing well-exposed (in) and shaded fruit (out) in canopies of olive trees (Olea europaea L). Over a 2-year period, from 50 days after full bloom up to harvest time, “in” and “out” olive samples of two genotypes (“Frantoio Millennio” and “Coratina 5/19”) were periodically collected. Morphological, histochemical, and biochemical analysis were performed to study the changes on fruit morphometric traits, oil body accumulation, and β-glucosidase enzyme activity. Some parameters were modified by shading inside the canopy in which the proportion of incident photosynthetically active radiation intercepted by the crop was 47%. Shaded fruits developed at slow rate and were characterized by late darkgoing time, reduced size, with a tendency toward oblong shape. The rapid histochemical procedure proposed to estimate the oil body accumulation during fruit ripening showed that a reduced irradiance caused a decrease in oil body density. The canopy position influenced, in a different way, the β-glucosidase activity in relation to the fruit-ripening stage in both genotypes. These findings indicate that providing an adequate and uniform lighting of the olive canopy by careful choices of orchard management practices can be a key factor for several yield components.

Preliminary histological observations on grapevine affected by esca disease

Esca is a destructive disease of the woody tissues of grapevine (Vitis vinifera L.) and due to the complexity of disease many aspects of host-pathogen interactions are not clearly understood. The histological characteristics of esca symptomatic petioles and internodes, collected from Cabernet Sauvignon and Sangiovese grapevine were studied. The tissues were fixed in FAA, dehydrated and embedded in Histoplast. To identify the lignified cell walls the sections were stained by Crystal violet and Erythrosin B and observed using an optical microscope. The main feature of tissues infected by esca disease was the minor lignification of vascular tissues, which was observed in petiole tissues before appearance of esca symptoms. The opportunity to utilize the histological examination of tissues as a method for the early detection of esca infections is hypothesized for the future application.

Influence of rootstock on fruit entity, quality and antioxidant properties of fresh apricots (cv. ‘Pisana’)

The influence of two commercial Prunus rootstocks (‘Myrabolan 29/C’ and apricot ‘Seedling’) on fruit entity and quality of ‘Pisana’ apricot cultivar (Prunus armeniaca L.) was evaluated over two consecutive crop seasons. The effect of rootstock on the total antioxidant capacity, total phenols and physical-chemical traits of fresh apricots was studied at the ready-to-eat stage and after 14 days at 4 °C cold storage. The rootstocks had no significant influence on the flowering and fruiting entity but affected some fruit quality traits. The ‘Myrabolan 29/C’ appeared to induce the highest fruit weight, total antioxidant capacity and total phenols. The results showed an important role of the climatic conditions in determining the fruit antioxidant content. A drought ripening period improved the antioxidant potential of fruit independently of the rootstock. After cold storage, apricot fruits maintained good levels of antioxidants.