During the last years, many evidences have been accumulating about the phytohormone indole-3-acetic acid (IAA) as a multifaceted compound in the microbial world, with IAA playing a role as a bacterial intra and intercellular signaling molecule or as an effector during pathogenic or beneficial plant–bacteria interactions. However, pretty much nothing is known on the mechanisms that bacteria use to modulate IAA homeostasis, in particular on IAA active transport systems. Here, by an approach combining in silico three-dimensional (3D) structural modeling and docking, mutagenesis, quantitative gene expression analysis, and HPLC FLD auxin quantitative detection, for the first time a bacterial multidrug and toxic compound extrusion (MATE) transporter was demonstrated to be involved in the efflux of IAA, as well as of its conjugate IAA–Lysine, in the plant pathogenic hyperplastic bacterium Pseudomonas savastanoi pv. nerii strain Psn23. Furthermore, according to the role proved to be played by Psn23 MatE in the development of plant disease, and to the presence of Psn23 MatE homologs in all the genomospecies of the P. syringae complex, this membrane transporter could likely represent a promising target for the design of novel and selective anti-infective molecules for plant disease control.

The cultivation of cacao represents an income option and a source of employment for thousands of small producers in Central America. In Honduras, due to the demand for fine flavor cacao to produce high-quality chocolate, the number of hectares planted is increasing. In addition, cacao clones belonging to the genetic group named Criollo are in great demand since their white beans lack of bitterness and excellent aroma are used in the manufacturing of premium chocolate. Unfortunately, the low resistance to pests and diseases and less productive potential of Criollo cacao leads to the replacement with vigorous new cultivars belonging to the other genetic groups or admixture of them. In this study, 89 samples showing phenotypic traits of Criollo cacao from four regions of Honduras (Copán, Santa Bárbara, Intibucá, and Olancho) were selected to study their genetic purity using 16 SSR molecular markers. The results showed that some samples belong to the Criollo group while other accessions have genetic characteristics of “Trinitario” or other admixtures cacao types. These results confirm the genetic purity of Criollo cacao in Honduras, reaffirming the theory that Mesoamerica is a cacao domestication center and also serves to generate interest in the conservation of this genetic wealth both in-situ and ex-situ.

Feijoa sellowiana (O. Berg) is a broadly widespread fruit tree species at a very early stage of domestication. Although appreciated for its flavored berries rich in nutrients and nutraceuticals, and as an ornamental plant, feijoa is still considered an underutilized species and little information is available about its genetic background, cultivar traceability and divergence. This study aimed to investigate, for the first time, the genetic diversity of feijoa through the application of AFLPs. Specifically, twenty cultivars from different countries and six wild types (WTs) from their area of origin (Misiones, Argentina) were analyzed. The AFLPs proved to be informative, revealing the values of the percentage of polymorphic loci (PPB), Nei’s genetic diversity (h), and the Shannon index (I) at 69.36%, 0.27, and 0.43, respectively, consistent with the average of long-lived perennial and outcrossing species. However, despite the limited number of WTs examined, the genetic variability (h) was higher (approximately 37%) within the six samples compared to cultivars. The population structure analysis identified three clusters, with WTs forming a separated cluster (III) as expected. Cultivars were divided into two clusters (I and II), with cluster I exhibiting a closer genetic proximity to WTs compared to cluster II. This finding was further confirmed using the UPGMA dendrogram based on Provesti distances. This work raised awareness of the genetic variability among the feijoa’s widespread cultivars and demonstrated that the limited genetic breeding programs over the last decades resulted in low diversity among them. Moreover, these results confirm the hypothesis that all varieties are derived from a single narrow ancestral population. The potential of this species is considerable and needs to be further investigated to exploit its peculiarities.

Castanea sativa Mill. is a valuable species with historical and economic importance in Europe, particularly in the Mediterranean area. In Italy, chestnut cultivation has been developed for centuries, leading to the recognition of more than 300 varieties. Nevertheless, a profusion of local names has been assigned by growers, causing the occurrence of synonyms and homonyms across the country. This research focused on genetic characterization and identification using 21 single sequence repeats (SSRs) for four chestnut varieties (i.e., Pastinese, Nerattino, Carpinese, and Rossola) commonly used for flour production in the Tuscan Apennine Mountains (Pistoia Province). A comprehensive number of 55 accessions identified by local growers as belonging to the four varieties were analyzed, in addition to a few “Marrone” accessions as outgroups. The 21 microsatellites were highly informative, detecting 98 alleles and displaying an average polymorphism information content (PIC) equal to 0.582. In addition, a considerable amount of genetic diversity was revealed, as shown by the heterozygosity levels (He = 0.634 and Ho = 0.475). The STRUCTURE analysis provided clear distinctions among the different varieties, splitting them into four separate groups. This result was also confirmed by UPGMA dendrogram and principal co-ordinates analysis (PCoA). However, one accession (Carp_5), previously identified as Carpinese, showed an allelic profile attributable to Pastinese, suggesting that farmers might have performed mislabeling or grafting propagation errors. Thus, our results confirm the use of SSRs to allocate the accessions of different varieties, uncovering possible synonyms and homonyms. Specifically, in the context of the Pistoiese mountain region, this tool can favor the traceability of processed products, such as flour, enhancing the quality and economic value of the local market. Lastly, our findings have revealed a considerable genetic variability within the Tuscan chestnut varieties whose preservation is mandatory to face climate change challenges through sustainable forest management practices.

In the Mediterranean area, the species of the genus Helichrysum Mill. (Asteraceae) have very similar genetic traits despite they may show different morphological characteristics. A first genetic and morphological assessment on twelve populations of Helichrysum from Elba, Capraia and Giglio Islands, in the Tuscan Archipelago (Italy) was carried out. To determine their taxonomic identity, additional reference specimens belonging to the three Helichrysum species reported from the Tuscan Islands in the literature -H. italicum (Roth) G. Don subsp. italicum, H. litoreum Guss., and H. stoechas L.-, were also included in the assessments. Our results show that the Tuscan Archipelago populations have low levels of morphological and genetic variation. In particular, the variability was mainly observed at the intra-population level, as revealed by the coefficient of variation and AMOVA-Gst in the morphological and genetic analyses, respectively. Basing on our results, all examined populations from the Tuscan Archipelago seem fit in H. italicum subsp. italicum. However, we detect and discuss the existence of some intermediate specimens, mainly with H. litoreum, reflecting the complexity of Helichrysum’s taxonomy and highlighting the need for additional studies to fully understand the various patterns and the underlying evolutionary events that originated them.

Climate change is causing a decline in the availability of crucial resources such as water and fertile soil, leading to a detrimental impact on crop yields. Basil (Ocimum basilicum L.), an annual aromatic plant used worldwide for culinary, cosmetic, and medicinal purposes, is especially at risk due to its high water demand and specific growing requirements typical of the Mediterranean climate. In Italy, basil is an essential part of any herb garden and is also commonly found in households as a potted plant. Nowadays, the conventional practice of growing basil in pots with peat as the primary medium is not environmentally sustainable, which underscores the need for alternative and sustainable cultivation techniques to ensure the continued growth of this majestic king of herbs. A greenhouse factorial experiment was conducted to study the impact of peat replacement and reduced water supply on the growth and biochemical traits of basil plants. The study included two cultivars (‘Genovese’ and ‘Valentino’), three substrate mixes with phytoremediated dredged sediment (TS) at varying volume percentages (0%, 12.5%, and 25%), and three levels of water irrigation (normal, reduced by 25%, and reduced by 37.8%). Increasing the TS percentage resulted in higher germination rates and greater biomass production in both cultivars compared with the control. ‘Valentino’ potted plants produced a higher yield than those of ‘Genovese’, while the latter had higher pigment contents due to its genetic characteristics. All combinations of substrates mixed with the highest water amounts of irrigation positively impacted seed germination and biomass-based outputs, while control peat with reduced water availability led to lower plant yields and germination capacity. Substrates with TS had suitable physicochemical characteristics for plant development. Our findings suggest that using peat–TS mixtures can produce quality results comparable to or even better than conventional soilless culture using only peat. Thus, replacing peat with moderate percentages of TS can be an effective and sustainable practice for recycling phytoremediated sediments.