Co-expression of metabolites and sensory attributes through weighted correlation network analysis to explore flavor-contributing factors in various Pyrus spp. Cultivars

Flavor profiles of various Pyrus spp. cultivars exhibit significant variations, yet the underlying flavor-contributing factors remain elusive. In this investigation, a comprehensive approach encompassing metabolomics analysis, volatile fingerprint analysis, and descriptive sensory analysis was employed to elucidate the flavor disparities among Nanguoli, Korla fragrant pear, and Qiuyueli cultivars and uncover potential flavor contributor. The study comprehensively characterized the categories and concentrations of nonvolatile and volatile metabolites, and 925 metabolites were identified. Flavonoids and esters dominated the highest cumulative response, respectively. Utilizing weighted correlation network analysis (WGCNA), seven highly correlated modules were identified, yielding 407 pivotal metabolites. Further correlation analysis of the differential substances provided potential flavor constituents strongly associated with various sensory attributes; taste factors had a certain association with olfactory characteristics. Our findings demonstrated the manifestation of flavor was a result of the synergistic effect of various compounds; evaluation olfactory flavor necessitated a comprehensive consideration of taste substances.

Pest categorisation of small-spored Alternaria carrying the genes for the AM- or AK-toxin biosynthesis

The Panel on Plant Health performed a pest categorisation of small‐spored Alternaria carrying the genes for the AM‐ or AK‐toxin biosynthesis, for the EU. The identity of the pests is clearly defined and reliable methods exist for their detection/identification. They are listed in Annex IIAI of Directive 2000/29/EC as Alternaria alternata (non‐European pathogenic isolates). Their distribution in the EU is restricted though with some uncertainty. The AM‐toxin producer Alternaria affect Malus spp. and Pyrus communis (European pear), whereas the AK‐toxin producer affect Pyrus pyrifolia, Pyrus bretschneideri and Pyrus ussuriensis (Asian pears). The pests could potentially enter the EU on host‐planting material and fruit originating in infested countries. There are no biotic/abiotic factors limiting their potential establishment and spread in the EU, as their epidemiology is similar to that of other well‐established Alternaria spp. Apples and European pears are widespread in the EU; Japanese pears are also present, but no data was found on their abundance/distribution. In the infested areas, the pests cause premature defoliation, fruit spotting and rot resulting in yield/quality losses. It is expected that the introduction and spread of the pests in the EU could impact apple and pear production, although the magnitude is unknown. Cultural practices and chemical measures may reduce the inoculum and the disease, but they cannot eliminate the pests. Phytosanitary measures are available to mitigate the risk of introduction and spread of the pests. The pests do not meet all the criteria assessed by EFSA for consideration as potential Union quarantine pests, as they are not under official control in those EU restricted areas where they have been found. The pests do not meet all the criteria assessed by EFSA to consider them as Union regulated non‐quarantine pests, as host plants for planting are not the main means of pest spread.

Pest categorisation of Venturia nashicola

The Panel on Plant Health performed a pest categorisation of Venturia nashicola, the causal agent of Asian pear scab, for the European Union (EU). The pathogen is a well‐defined, distinguishable fungal species affecting Pyrus pyrifolia var. culta, P. ussuriensis and P. bretschneideri in Asian countries. P. communis (European pear) is not a host of V. nashicola, but the host status of other Pyrus species is unclear. V. nashicola is not known to occur in the EU. It is listed in Annex IIAI of Directive 2000/29/EC. The pathogen could potentially enter the EU on host plants for planting and fruit originated in infested countries. There are no climatic factors limiting the potential establishment and spread of the pathogen in the EU, as its epidemiology is similar to those of Venturia inaequalis (apple scab) and Venturia pyrina (European pear scab), which are well‐established in the EU. The hosts are present in the EU, but no data were found on their abundance and distribution. In the infested areas, V. nashicola causes premature leaf and fruit drop and fruit distortion resulting in considerable yield/quality losses. The introduction of the pathogen into the EU could cause yield/quality losses and environmental consequences because of the additional fungicide sprays for disease control. Cultural practices and chemical measures applied in the infested areas reduce the inoculum sources but they cannot eliminate the pathogen. Phytosanitary measures are available to mitigate the risk of introduction and spread of the pathogen in the EU. All criteria assessed by EFSA for consideration as a potential Union quarantine pest are met. As V. nashicola is not known to occur in the EU, this criterion assessed by EFSA to consider it as a Union regulated non‐quarantine pest is not met.

Characterization and Phylogenetic Analysis of Ancient Italian Landraces of Pear

Pear is one of the oldest fruit tree crops and the third most important temperate fruit species. Its domestication took place independently in the Far East (China) and in the Caucasus region. While the origin of Eastern Asian cultivars is clear, that of European cultivars is still in doubt. Italy has a wealth of local varieties and genetic resources safeguarded by several public and private collections to face the erosion caused by the introduction of improved varieties in specialized orchards. The objectives of the present study were: (i) to characterize the existing germplasm through nuclear (SSR) and (ii) to clarify the genetic divergence between local and cultivated populations through chloroplast DNA (cpDNA) markers in order to provide insights into phylogenetic relationships of Pyrus spp. For this reason, 95 entries from five different germplasm collections, including nine European, Mediterranean and Eastern Asian species, were analyzed, and the intergenic accD-psaI sequences were compared to the worldwide distributed dataset encompassing a total of 298 sequences from 26 different Pyrus species. The nine nuclear SSRs were able to identify a total of 179 alleles, with a loci polymorphism P = 0.89. Most of the variation (97%) was found within groups. Five accessions from different sources were confirmed to be the same. Eight out of 20 accessions of unknown origin were identified, and six synonyms were detected. Locus NH030a was found to be monomorphic in all the cultivated accessions and in reference species interfertile with P. communis, leading to hypothesize selection pressures for adaptation to cultivation. The cpDNA sequences of the 95 accessions were represented by 14 haplotypes, six of which (derived from P. communis, P. cossonii and P. ussuriensis) are recorded here for the first time and may suggest the ancient origin of some local varieties. The network analysis of the 298 cpDNA sequences allowed two different haplogroups, Eastern and Western Eurasia, to be defined, supporting recent views of a clear division between Occidental and Oriental species. By combining the results from nuclear and uniparental markers, it was possible to better define many unknown accessions.