Matteo Caser

The influence of water stress on growth, ecophysiology and ornamental quality of potted Primula vulgaris ‘Heidy’ plants. New insights to increase water use efficiency in plant production.

Efficient irrigation practices are required to reduce the amount of water used. In this study, the effects of different irrigation regimes on changes in growth, ecophysiology and ornamental traits of potted Primula vulgaris ‘Heidy’ plants were investigated. Three experiments were carried out. In the first, the plants were either fully irrigated (100% of container capacity) or not. In the second, plants were watered to full irrigation (control), to 50% of the control (moderate water stress), to 25% of the control (severe water stress), or not irrigated and followed by a rehydration phase. Both experiments were conducted under controlled growth conditions. The third experiment was performed under common nursery conditions in an unheated and shaded greenhouse where plants were either irrigated with common irrigation practices (control), or with 66% of the control amount (moderate water stress), or with 33% of the control (severe water stress). In general, the percentage of senescent plants, the growth index, the number of leaves, and the aerial fresh and the dry weight were not affected by moderate water stress treatments. As expected, increasing water stress resulted in a general decrease in all studied gas exchange parameters. However, stressed plants were more efficient in using water than control plants, suggesting that stomata closed to cope with drought conditions without damaging photosynthesis events. The number of fully opened flowers during the growing season was highest in both control and moderately water stressed plants. In conclusion, moderate, but not severe, water stress could be imposed in P. vulgaris ‘Heidy’ pot production to reduce the water consumption, still maintaining plant ecophysiological performances and ornamental quality.

Pollen Grain Preservation and Fertility in Valuable Commercial Rose Cultivars

In the cut flower market, traditional breeding is still the best way to achieve new rose cultivars. The geographical delocalization of cultivar constitution (generally made in Europe and North America) and plant cultivation (large areas in Africa and South America) represents a limit point for crossing and selection. Rose breeders often need to overcome geographical distances, resulting in asynchrony in flowering among crossing parents, by storing and sending pollen. Hence, a key aspect in breeding programs is linked to pollen availability and conservation, jointly with the identification of parameters related to pollen fertility. In this study we present the results of three different trials. In the first, pollen diameter and pollen viability were chosen as fertility predictors of 10 Rosa hybrida commercial cultivars. In the second trial, aliquots of dried pollen grains of six R. hybrida cultivar were stored under two different temperatures (freezer at T = −20 °C and deep freezer at T = −80 °C) and after a wide range of conservation period, their viability was measured. In the third trial, the effective fertilization capacity of frozen pollen of 19 pollen donor cultivars was evaluated during 2015 crossing breeding plan, performing 44 hybridizations and correlating the number of seeds and the ratio seeds/crossing, obtained by each cultivar, with in vitro pollen germination ability.

Latitude and Altitude Influence Secondary Metabolite Production in Peripheral Alpine Populations of the Mediterranean Species Lavandula angustifolia Mill.

Lavandula angustifolia Mill. has a great economic importance in perfumery, cosmetics, food manufacturing, aromatherapy, and pharmaceutical industry. This species finds its phytosociological optimum in the sub-Mediterranean region. Latitudinal and altitudinal gradients are expected to affect species diversification in peripheral alpine populations. In this study, phenotypic traits including morphometric parameters, volatile organic compounds (VOCs) and essential oils (EOs) were analyzed in lavender peripheral populations selected in order to explore different ecological conditions. Plants were cultivated under uniform conditions to observe variations due to the genetic adaptation to native environments and to exclude the short-term response to environmental factors. Results showed qualitatively and quantitatively intra-specific variations in secondary metabolites, mainly along the latitudinal gradient, while minor effect was attributable to the altitude. This latter affected more the morphometric parameters. As the latitude augmented, VOCs showed lower content of monoterpene hydrocarbon (mh) and higher content of oxygenated monoterpenes (om); whereas EOs showed higher content of mh and non-terpene derivatives (nt) and lower content of sesquiterpene hydrocarbons (sh). Lavender aroma and EO composition varied in every population, for a total of 88 and 104 compounds identified, respectively. Eleven and 13 compounds were responsible for 95% of the dissimilarity, with linalool, linalyl acetate and 1,8-cineole as major contributors. As the latitude augmented, linalool decreased and 1,8-cineole increased while linalyl acetate content was unaffected. These results are discussed with regards to the potential adoption of the lavender peripheral alpine populations for the improvement of quality and productivity of lavender cultivations, especially in mountainous areas.