Wild asparagus (Asparagus acutifolius L.) is becoming an interesting niche crop for marginal areas in Europe, but little information is available regarding cultivation techniques, which differ from those of cultivated asparagus (A. officinalis). We experimented with the cultivation of wild asparagus using two different ecotypes planted at two plant densities. We measured yield and number of spears per hectare and spear quality (average weight, portion of edible part, diameter, and dry matter content). There were no significant effects of either genotype or density on the spear yield and number per hectare. No differences among treatments were found on spear quality parameters. Spear yield and number per plant decreased proportionally with increasing plant density, resulting in constant spear yield and number per hectare. Harvest efficiency was ≈1.2 kg of spears per hour of labor when the prickly evergreen vegetation was not removed before harvest and ≈3 kg per hour when the vegetation was cut and removed. In the latter case, harvest would cost approximately one-third of the gross income of the crop suggesting that the crop could easily be economically viable. Further studies are needed to assess whether cutting the vegetation affects plant vigor and longevity in the following years, but also to further study suitable techniques for crop cultivation, especially weed control.
Paolo Benincasa, Francesco Tei and Adolfo Rosati
Dario Mantovani, Adolfo Rosati and Domenico Perrone
The wild asparagus species Asparagus acutifolius L. is widespread in Mediterranean and subtropical environments, where its spears are consumed regularly. The species is known to have ecophysiologic plasticity, however there is no literature on this subject. This work aimed at assessing the photosynthetic characteristics of this wild species of asparagus, grown under full light (FL) and partial (i.e., about 40%) light (PL) conditions, and evaluating its ecophysiologic response to drought and temperature stress. The photosynthetic response to light of spears and of new cladodes (NC; current year) and old cladodes (OC; previous year) was measured using an infrared gas analyzer coupled with a climatized cuvette chamber. Cladodes net photosynthesis at high irradiance was also measured at varying air temperatures and decreasing soil water availability. Results indicate that developing spears were photosynthetically active with no difference between FL and PL treatments. Photosynthetic rates did not differ between NCs and OCs and were greater for FL cladodes, except at low irradiance. Well-watered plants were photosynthetically active from 0 to 45 °C, with a maximum photosynthetic rate of up to 9 µmol·m–2·s–1 at 30 °C and a decrease of about 60% at 45 °C. The species also demonstrated high tolerance to drought, with positive net photosynthesis even at predawn leaf water potential values of –2.4 MPa. Showing great ecophysiologic plasticity, this wild asparagus could be an interesting species in areas were conventional crop species are not profitable economically, or as an intercrop in agroforestry systems.
Adolfo Rosati, Andrea Paoletti, Giorgio Pannelli and Franco Famiani
The modern olive industry is increasingly interested in olive cultivars that start producing early and remain relatively small, because they are suitable for super high-density orchards. Some cultivars are better suited to this than others but it is not clear why. Understanding the mechanisms that lead to early production and reduced canopy size is therefore important. The object of this study was to investigate whether differences in vigor across olive cultivars are related to earliness and abundance of bearing. We analyzed tree growth and productivity in young coetaneous trees of 12 olive cultivars, grown together in the same orchard. Trunk diameter increased over the observation period, reaching significantly different values across cultivars. Canopy volume also increased, reaching 2-fold differences between the minimum and the maximum values. Cumulative yield increased, reaching up to 3-fold differences. When the cumulative yield at the end of the experiment was plotted against the final trunk diameter, no correlation was found. A significant correlation was found when cumulative yield was plotted against the increment in trunk diameter during the observation period for which yield data were collected. This relationship improved (i.e., R 2 rose from 0.57 to 0.83) when yield efficiency [i.e., cumulative yield per unit of final trunk cross-sectional area (TCSA) or per unit of canopy volume] was used instead of yield. These results clearly showed that trees that produced proportionally more (i.e., higher yield efficiencies) grew less. We conclude that, in young olive trees, vigor is inversely related to early bearing efficiency, which differs significantly across cultivars. The results support the hypothesis that early and abundant bearing is a major factor in explaining differences in vigor across olive cultivars.
Adolfo Rosati, Andrea Paoletti, Raeed Al Hariri, Alessio Morelli and Franco Famiani
Low vigor and early and abundant production are desirable traits for modern tree crops. In olive, most cultivars are too vigorous and cannot be successfully constrained in the small volume allowed by the straddle harvester used in the so-called superhigh-density (SHD) orchards. Only few cultivars appear to have sufficiently low vigor to be suitable for this system. These cultivars combine low vigor with earlier and higher yield. This study investigated the hypothesis that differences in vigor between Arbequina, a low vigor and the most commonly used cultivar in SHD orchards, and Frantoio, a highly vigorous cultivar not suitable for such orchards, are related to their differences in early bearing and consequent differences in dry matter partitioning into fruit. Young trees of both cultivars were deflowered either in 2014, 2015, both years, or neither one, resulting in a range of cumulative yields over the 2 years. Tree trunk cross-sectional area (TCSA) was measured at the beginning of each year. This was closely related to total tree mass, as assessed at the beginning and at the end of the experiment. Cumulative yield, in terms of fruit dry matter, was also assessed. TCSA increased less in fruiting trees in both years. As expected, when not deflowered, ‘Frantoio’ was less productive and more vigorous than ‘Arbequina’. However, there was no difference in TCSA increment when both cultivars were completely deflowered. TCSA increments were closely inversely related to yield across all treatments and cultivars (R 2 = 0.90). The regressions improved further when data from 2015 only were used (R 2 = 0.99). The results represent the first quantitative report showing that differences in vigor among cultivars can be completely explained in terms of different dry matter partitioning into fruit, supporting the hypothesis that early bearing is a major cause, rather than merely a consequence, of lower vigor in young ‘Arbequina’ trees. These results provide new understanding on vigor differences across cultivars, which will be useful for breeding and selection of new genotypes.