T. La Mantia

Epicuticular changes and storage potential of cactus pear (Opuntia ficus-indica Miller (L.)) fruit following gibberellic acid preharvest sprays and postharvest heat treatment

Abstract Cactus pear [Opuntia ficus-indica Mill. (L.) cv. Gialla] fruit were treated 10 weeks after the second induced-bloom flush with 10 ppm gibberellic acid (GA3) or were heated at 37°C for 30 h under saturated humidity after harvest. The two treatments were also combined before storage at 6°C for 45 days plus 4 additional days at 20°C to simulate a marketing period (SMP). Fruit not treated with GA3 and unheated were used as controls. GA3 spray delayed fruit ripening as evaluated by peel colour change and scanning electron microscopic observations of epicuticular wax morphology, decreased ethanol levels in the flesh during storage and SMP, and reduced decay development during storage. Postharvest heat treatment (HT) reduced decay during storage and SMP, retained visual quality of fruit, prevented chilling injury and resulted in a higher ethylene production rate after SMP in comparison with untreated fruit. The combined treatments (GA3+HT) did not produce any further beneficial effects in chilling injury and decay control or in maintaining fruit quality. Heat treatment caused a partial melting of the epicuticular wax layers. This caused the disappearance of platelets normally present on the skin surface of unheated fruit and sealed micro-wounds and cracks. The covering of wounds and cracks by melted wax following heat treatment was considered a contributing factor in protection against wound pathogens.

Do island plant populations really have lower genetic variation than mainland populations? Effects of selection and distribution range on genetic diversity estimates

Ecological and evolutionary studies largely assume that island populations display low levels of neutral genetic variation. However, this notion has only been formally tested in a few cases involving plant taxa, and the confounding effect of selection on genetic diversity (GD) estimates based on putatively neutral markers has typically been overlooked. Here, we generated nuclear microsatellite and plastid DNA sequence data in Periploca laevigata, a plant taxon with an island–mainland distribution area, to (i) investigate whether selection affects GD estimates of populations across contrasting habitats; and (ii) test the long‐standing idea that island populations have lower GD than their mainland counterparts. Plastid data showed that colonization of the Canary Islands promoted strong lineage divergence within P. laevigata, which was accompanied by selective sweeps at several nuclear microsatellite loci. Inclusion of loci affected by strong divergent selection produced a significant downward bias in the GD estimates of the mainland lineage, but such underestimates were substantial (>14%) only when more than one loci under selection were included in the computations. When loci affected by selection were removed, we did not find evidence that insular Periploca populations have less GD than their mainland counterparts. The analysis of data obtained from a comprehensive literature survey reinforced this result, as overall comparisons of GD estimates between island and mainland populations were not significant across plant taxa (N = 66), with the only exception of island endemics with narrow distributions. This study suggests that identification and removal of markers potentially affected by selection should be routinely implemented in estimates of GD, particularly if different lineages are compared. Furthermore, it provides compelling evidence that the expectation of low GD cannot be generalized to island plant populations.

Research strategies for the improvement of cactuspear (Opuntia ficus-indica) fruit quality and production

Abstract Cactus pear ( Opuntia ficus-indica L.) is cultivated worldwide for fruit production either in the subsistence agriculture of dryland areas or as a cash crop. However, little horticultural research has been devoted to this species so far. Research needs related to reproductive biology as well as productivity and orchard management are outlined. A better knowledge of the environmental influence on reproductive biology and fruit quality, the control of fluctuations in plant cropping, as well as the reduction of seed number and size, are the major challenges for future research. Cactus pear will transcend the ethnical markets only if adequate marketing strategies can be promoted and fruit quality enhanced and standardized.

Seed content and fruit characteristics in cactus pear (Opuntia ficus-indica Mill.)

Abstract A positive correlation between seed content (number and weight) and fruit weight has been determined for summer and late fruits of the two major Italian cultivars of Opuntia ficus-indica , ‘Gialla’ and ‘Rossa’. In late ripening fruits, the number of aborted seeds was not related to fruit and core weight. The bigger size of the late fruits is related to a higher seed number.

Olive agroforestry systems in Sicily: Cultivated typologies and secondary succession processes after abandonment

Abstract The first part of this study provides an overview on Sicilian olive systems. Subsequently, the study describes the different typologies of cultivated agroforestry systems present in South-Eastern Sicily employing olive trees in association with other Mediterranean tree species, in particular for the production of firewood, coal and animal food (downy or pubescent oak, holm oak, cork oak), but also in association with forage or grazing species (oat, barley, vetch, etc.) or cereals. The study shows that Sicilian agroforestry systems are much more diversified than it was known so far. In the second part, the study describes the spontaneous colonization processes by plants, observed in abandoned olive agroforestry systems and leading to the formation of more complex ecosystems (renaturation). Most of the previously described agroforestry systems are at present subject to abandonment. Our analysis of secondary succession dynamics shows how woody species, and above all those species which are part of the cultivated system, rapidly colonize abandoned areas, so that a maquis-wood is formed within few decades.

Structural analysis of woody species in Mediterranean old fields

Abstract The study analyses the changes in vegetation structure and composition within a sere of secondary succession at Pantelleria Island (Sicilian Channel, Italy). It aims to show that not only phytosociological data but also structural parameters, like woody species’ height and spatial distribution indices are useful to describe and interpret renaturation processes. Woody species structure was recorded on abandoned terraces, both on north-facing and on south-facing slopes. Relevés were made in fallows representing five different stages of succession. The pace of succession, measured through the analysis of woody species cover, basal area, height distribution and spatial indices, resulted quite rapid: already after 50 years of abandonment terraces are covered by dense maquis communities. Our study also revealed that different plant species or groups prevail during colonisation dynamics, mostly depending on exposition, a factor which strongly influences also the speed of colonisation by woody species. In this case study, human activity seems to be unnecessary to accelerate the process of renaturation, except in some unfavourable contexts. Species turnover rate, biodiversity value, and structural evolution along progressive succession must be taken into account in nature management and conservation policies of terraced landscapes, which are nowadays one of the most endangered landscape types throughout the Mediterranean area.

Microbial Inoculants on Woody Legumes to Recover a Municipal Landfill Site

Tree and shrubby legumes have great potential in degraded land rehabilitation because of their ability to form symbiotic associations with nitrogen fixing rhizobia and mycorrhizal fungi. Extensive soil disturbance reduces natural microbial propagules thus preventing the formation of beneficial plant-microbes symbiosis. Reintroduction of selected microbial symbionts may improve the recovery rate of disturbed ecosystems. We inoculated selected rhizobia and arbuscular mycorrhizal fungi on two woody legume species, the mediterranean shrub Spartium junceumL. and the exotic tree Acacia cyanophylla Lindl. in order to recover a sealed municipal landfill (Palermo, Sicily, Italy). Inoculated plants showed shoot growth parameters 2 to 12-fold higher than uninoculated plants. After transplanting on the municipal landfill site, inoculated plants showed no transplant shock and low mortality (6–15%). The chemical analysis of P and N plant content showed no differences between inoculated and uninoculated plants suggesting that a dilution effect occurred due to higher biomass production of the inoculated plants. The beneficial effects of mycorrhization and rhizobium inoculum on growth parameters were still detectable one year after transplanting in S. junceum.

Assessing the biomass of shrubs typical of Mediterranean pre-forest communities

Abstract One of the most outstanding issues of current environmental research is the need of reliable assessments of carbon stock (i.e. above-ground (a.g.) and below-ground biomass, deadwood, litter, and organic soil matter) within forest ecosystems. Although shrub vegetation plays an important role in accumulating carbon in many Mediterranean environments, there is still very little knowledge on the carbon they store. In this article, we analyze the a.g. carbon stock of several Mediterranean shrubby communities in Sicily (Italy), dominated by Pistacia lentiscus, Chamaerops humilis, Euphorbia dendroides and Spartium junceum. Plant samples for each species were selected, and morphometric attributes (height, crown diameter, diameter at breast height, etc.) were measured to establish models for estimating a.g. biomass. Dendrometric data were also used to support the assessment of shrub biomass at community level by coupling them with the coverage of the considered woody species estimated from several hundreds of phytosociological relevés carried out on pre-forest Sicilian communities. Although the results of such an approach have to be considered as rough assessments, the trial proves interesting, given the lack of information on stand biomass of pre-forest vegetation within the Mediterraean region.

Evolution of endogenous gibberellins at different stages of flowering in relation to return bloom of cactus pear (Opuntia ficus-indica L. Miller)

Abstract The effect of flower emasculation, flower injection with paclobutrazol and the complete removal of the spring flush of flowers and cladodes on the changes in GA 3 concentration at different stages of bloom in flowers and fertile cladodes of Opuntia ficus-indica has been determined. Throughout the bloom period, the concentration of GA 3 was higher in intact flowers and the cladode than in flowers emasculated or injected with paclobutrazol. With the onset of blooming, GA 3 started to accumulate both in the flower and in the fertile cladode, and the highest concentration was measured at full bloom in the flower and in the cladodes whose flowers were not removed. Flower emasculation or removal similarly affected GA 3 concentration at any stage of bloom. Until petal shedding GA 3 concentration was higher in the flowers than in the fertile cladodes. Consistent return bloom occurred only when the spring flush was removed before bloom. Fruit resulting from flowers emasculated or treated with paclobutrazol had a smaller size, percent flesh and seed content than fruits produced by untreated flowers.

The Role of Vineyards in the Carbon Balance Throughout Italy

A common belief is that agricultural fields cannot be net carbon sinks, but perennial tree crops, growing a permanent woody structure with a life cycle of decades could act as carbon sink. Vineyards are good candidates to test this hypothesis, because they are often grown with limited soil cultivation and produce plenty of woody pruning material that can be left on the ground. Three Eddy Covariance sites were established in different vineyards, along a north-south transect, in Italy, to study the role of vine cultivation in the carbon balance of the Italian penisula. The year 2009 was chosen as a reference year for the three sites, in order to compare carbon budget estimates in areas characterized by different meteorological, pedological and geomorphological conditions. In the three sites a carbon sink ranging between 814 (Negrisia site) and 89 (Serdiana site) g C m−2 y−1 was measured. Both climate (water availability and PAR) and management (in particular the presence of permanent grass cover) have a strong impact on the carbon balance of the ecosystems. Even if it can be argued that this sink may be only temporary and the built-up can be substantially disrupted at the end of the vineyard life cycle, these results show that there is a concrete possibility of storing carbon in agricultural soils. Proper practices can be defined to preserve this storage at best, greatly contributing to the global carbon budget.