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In this study we examined polyhydroxyalkanoate (PHA) synthases phaC1 and phaC2 gene expression in two strains of Pseudomonas corrugata (Pc) grown in a minimum mineral medium with related (oleic acid and octanoate) or unrelated (glucose) carbon sources. Analysis of transcription was performed by Northern blot and conventional reverse transcriptase (RT) polymerase chain reaction (PCR). In addition, we developed a RT-real-time PCR method to quantitatively evaluate phaC1 (Pc) and phaC2 (Pc) gene expression. Primers and a TaqMan probe were designed for the specific detection of both synthase transcripts as well as of the housekeeping 16S rRNA, and the relative expression of target genes was calculated. We showed that phaC1 (Pc) and phaC2 (Pc) were not cotranscribed and, on the contrary, were independently regulated. In cultures grown with oleic acid as the sole carbon source, only the expression of phaC1 (Pc) was induced (a tenfold increase after 72 h of culture), whereas that of phaC2 (Pc) remained unchanged. In cultures grown with glucose or sodium octanoate, the expression of both phaC1 (Pc) and phaC2 (Pc) was upregulated but at different rates. Cellular PHA content was compared to the gene expression of the PHA synthases and significant correlations were found between PHA production and phaC1 (Pc)/phaC2 (Pc) expression.

The fungal pathogen Fusarium circinatum (Nirenberg and O’ Donnell) is the causal agent of pine pitch canker (PPC) disease, which seriously affects conifer species in forests and nurseries worldwide. In Europe, PPC is only established in the Iberian Peninsula; however, it is presumed that its range could expand through the continent in the near future. Infection caused by this fungus requires open wounds on the tree, including physical damage caused by insects. Therefore, a relationship probably occurs between PPC and a wide variety of insects. The aim of this review is to outline the taxonomic and ecological diversity of insect species with high potential association with F. circinatum in Europe and elsewhere. The insects were classified as vectors, carriers and wounding agents according to the association level with the PPC disease. In addition, we discuss the insect-mediated spreading of PPC disease in relation to the different phases of forest stand development, from seeds and seedlings in nurseries to mature stands. Lastly, to improve our predictive capacities and to design appropriate intervention measures and strategies for controlling disease dissemination by insects, variables such as geographic location, time of the year and host species should be considered. Our review provides a framework of the multiple factors that regulate the insect–host interactions and determine the success of the infection.

Mal secco is a tracheomycotic disease caused by the fungus Plenodomus tracheiphilus (Petri) Gruyter, Aveskamp, and Verkley that has caused severe damage and loss of yield in the citrus industry in the Mediterranean area, for 100 years. While the disease can affect different cultivated citrus species, lemon (C. × limon var. limon (L.) Burm. f.) and citron are the most susceptible. The identification of resistant or field-tolerant clones and hybrids is a major goal for lemon growers and breeders. To identify sources of resistance or tolerance to the disease, we performed a phenotypic survey on a lemon and lemon-like open-field germplasm planted at CREA (Research Centre for Olive, Fruit and Citrus Crops), Italy, in an area with high pathogen pressure. Phenotyping was performed visually, four times, for three consecutive years, on a total of 50 accessions, with two or three replicate trees per accession. Moreover, molecular screening based on real-time PCR was performed, for two consecutive years, on twigs, young leaves, and mature leaves of all plants, to detect the pathogen in the absence of clear symptoms. The accessions were categorized into seven groups based on the presence of visual symptoms, real-time PCR pathogen detection, and canopy volume. The results revealed sources of tolerance in lemon and citron hybrids. The molecular screening identified P. tracheiphilus in all lemon clones, with mean Ct values ranging from 17 to 39. The screening also identified P. tracheiphilus in clones without clear symptoms, indicating their ability to tolerate the disease. Moreover, a strong negative correlation was found between the Ct values in twigs and symptom severity (r = −0.72). This indicates that the DNA from twigs is the most appropriate for use in performing reliable phenotyping of mal secco susceptibility in adult plants. An autotetraploid lemon (Doppio Lentini) seems to be immune to the disease, under natural pressure, since P. tracheiphilus was not detected by real-time PCR and visual screening. Overall, the data obtained are a valuable resource for identifying both the most tolerant lemon varieties suitable for areas with high pathogen pressure and the best breeding parents for the introgression of resistance genes into lemon genotypes.