Can Biological Control Agents Reduce Multiple Fungal Infections Causing Decline of Milkwort in Ornamental Nursery?

This research evaluates biological control agents (BCAs) and fungicide alone and in combination for the management of decline caused by multiple fungi on milkwort (Polygala myrtifolia). Four experiments were performed in a greenhouse within a nursery located in Catania province (southern Italy). The activity of fungicides and biological control agents was evaluated by calculating the plant mortality (%) and recovery frequency (%) of different fungi associated with symptomatic tissue. Comprehensively, boscalid + pyraclostrobin and fosetyl-Al showed the best results in managing disease complex on milkwort. Biological control agents provided, on average, the lowest performances; nevertheless, in most cases, they were able to significantly reduce multiple infections and sometimes when combined with fungicide enhanced the effectiveness. The molecular analysis of 86 isolates obtained from symptomatic tissue allowed to identify the fungi involved in the disease as Calonectriapauciramosa, C. pseudomexicana, Fusariumoxysporum, Neocosmospora solani (syn. F. solani) and binucleate Rhizoctonia AG-R. Calonectriapseudomexicana never reported on milkwort and in Europe was inoculated on P. myrtifolia potted healthy cuttings and produced crown and root rot after 40 days. Our findings represent the first worldwide report about disease complex of milkwort caused by several fungi (Calonectria spp., Fusarium spp. and binucleate Rhizoctonia) and on the effects of integrated control strategies to manage this disease in the nursery.

Effects of Water Stress on Gas Exchange, Water Relations and Leaf Structure in Two Ornamental Shrubs in the Mediterranean Area

One of the main problems in the Mediterranean area is the long dry season, and hence there is a need to individuate plants that are tolerant to low water availability. The mechanisms adopted by different plant species to overcome drought stress conditions and reduce water loss could allow the identification of tolerant species to drought stress, thereby increasing the sustainability of ornamental plant utilization in green areas. In this regard, the aim of this study was to investigate the morphological, physiological, and anatomical responses of Polygala myrtifolia L. and Viburnum tinus L. ‘Lucidum’ irrigated under different irrigation deficits. In pot plants, four water regimes were adopted (10%, 20%, 30% and 40% of water container capacity (WC)). Drought stress significantly reduced the biomass accumulation in both shrubs. In Viburnum, total dry biomass reduction was observed only in 10% WC with a reduction by 33%, while in Polygala, this was observed both in 20% WC and 10% WC (~48%). The higher deficit irrigation conditions improve the root-to-shoot ratio, which was increased in Polygala 20% WC (by 20%) but not in Viburnum ones. The latter species shows higher drought tolerance, as demonstrated by the gas exchange values, chlorophyll fluorescence, leaf structure, and water relationship.

Xylella fastidiosa subsp. multiplex. [Distribution map].

A new distribution map is provided for Xylella fastidiosa subsp. multiplex Schaad et al. Gammaproteobacteria: Xanthomonadales: Xanthomonadaceae. Hosts: olive (Olea europaea), Prunus persica, coffee (Coffea spp.), Citrus, Polygala myrtifolia, many tree species. Information is given on the geographical distribution in Europe (France, Mainland France, Corsica, Spain, Mainland Spain, Balearic Islands), North America (USA, Alabama, California, District of Columbia, Florida, Georgia, Indiana, Kentucky Louisiana, North Carolina, Tennessee, Texas, Virginia), South America (Argentina, Brazil, Minas Gerais, Parana, Rio Grande do Sul, Santa Catarina, Sao Paulo, Paraguay).

Xylella fastidiosa subsp. pauca. [Distribution map].

A new distribution map is provided for Xylella fastidiosa subsp. pauca Schaad et al. Gammaproteobacteria: Xanthomonadales: Xanthomonadaceae. Hosts: olive (Olea europaea), coffee (Coffea) Citrus, Polygala myrtifolia. Information is given on the geographical distribution in Europe (France, Mainland France, Italy, Spain, Balearic Islands), Central America & Caribbean (Costa Rica), South America (Argentina, Brazil, Bahia, Minas Gerais, Sao Paulo, Ecuador).

Linking root traits to superior phosphorus uptake and utilisation efficiency in three Fabales in the Core Cape Subregion, South Africa

In the low-P soil of the fynbos biome, plants have evolved several morphological and physiological P acquisition and use mechanisms, leading to variable uptake and use efficiencies. We expected that plants grown in low-P soils would exhibit greater P acquisition traits and hypothesised that Aspalathus linearis (Burm. f.) R. Dahlgren, a cluster-root-forming species adapted to drier and infertile soils, would be the most efficient at P acquisition compared with other species. Three fynbos Fabales species were studied: A. linearis and Podalyria calyptrata (Retz.) Willd, both legumes, and Polygala myrtifolia L., a nonlegume. A potted experiment was conducted where the species were grown in two soil types with high P (41.18 mg kg–1) and low P (9.79 mg kg–1). At harvest, biomass accumulation, foliar nutrients and P acquisition mechanisms were assessed. Polygala myrtifolia developed a root system with greater specific root length, root hair width and an average root diameter that exuded a greater amount of citrate and, contrary to the hypothesis, exhibited greater whole-plant P uptake efficiency. However, P. calyptrata had higher P use efficiency, influenced by N availability through N2 fixation. Specific root length, root length and root : shoot ratio were promising morphological traits for efficient foraging of P, whereas acid phosphatase exudation was the best physiological trait for solubilisation of P.

An improved encapsulation protocol for regrowth and conservation of four ornamental species

The encapsulation technology, initially developed for clonal propagation through the production of synthetic seeds with somatic embryos, is currently proposed for use with non-embryogenic explants, such as buds and nodal segments (unipolar propagules). In the present study, the encapsulation procedure and its effect on shoot regeneration were evaluated. Apical buds isolated from shoot cultures of four ornamental species (<em>Photinia × fraseri</em> Dress., <em>Polygala myrtifolia</em> L., <em>Metrosideros excelsa</em> Soland. ex Gaertn., and <em>Rosa</em>) were encapsulated in 3% sodium alginate. Effects of complexation time, sucrose concentration, and storage temperature on the regrowth ability of propagules were assessed. With the appropriate combination of sucrose concentration and polymerization time, the encapsulated explants proved to have a better regrowth (80–100%) after sowing than the naked ones. In addition, medium-term storage of <em>Metrosideros</em> encapsulated explants promoted a high level of regrowth (74%) after 4 months in the dark at 10°C; while polygala beads were preserved up to 8 months regardless of storage temperatures. Potential current applications of encapsulation technology and the future use of beads in vivo conditions are also discussed.