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Erwinia amylovora is the most damaging bacterial disease of quince, causing a lot of damage to this crop. In cases of severe infections, this disease could even cause the death of the tree. The climatic conditions in Bistrita region were favourable for fire blight outbreak in 2022, and gave us the opportunity to study the differences manifested by five quince cultivars ('Aromate', 'Aurii' 'Bereczki', 'Adonia' and 'Cedonia') when naturally infected with Erwinia amylovora Burrill. The second wave of infections, in September, was significantly less damaging than the first one which occurred in June. Overall, after assessing the frequency of the blighted shoots of the mentioned quince cultivars, in June and in September of the year 2022, we concluded that there were significant differences between responses to natural infection Erwinia amylovora of these cultivars. The data showed that the cultivars 'Aromate' and 'Aurii' have a better behaviour than the Hungarian cultivar 'Bereczki', while the Romanian cultivars 'Adonia' and 'Cedonia' appeared to be very susceptible under the climatic conditions of the year 2022 in Bistrita area.

Plum pox virus (PPV) is considered the most detrimental viral pathogen of stone fruits, causing important economic losses. Exhaustive studies revealed that D, M and Rec are the prevalent strains of PPV in Europe. While different experimental reports revealed that PPV-M is more aggressive than PPV-D, limited information is available about the competitiveness of PPV-Rec under field conditions. Also, symptoms developed by PPV-Rec infection are scarcely documented. To increase this knowledge, we selected and monitored an experimental plum orchard already contaminated by both PPV-D and PPV-Rec. The disease spread was monitored by visual observation and ELISA testing each year along five consecutive vegetative periods. The dynamic of single and mixed infections was assessed by molecular strain typing (IC-RT-PCR) of all newly and single-infected trees. While the disease prevalence increased almost linearly, the number of single PPV infected trees (either by PPV-Rec or by PPV-D) remained relatively stable during the five-year period of monitoring, which is explainable by the continual increase of the number of trees infected with both strains together. No significant difference in the progression rate between D and Rec strains was found when considering their presence in both single and mixed infections. Although the types of PPV symptoms developed on leaves and fruits varied among cultivars, no clear-cut D or Rec strain-specific symptoms were developed within the same cultivar. Overall results revealed that PPV-D and PPV-Rec strains had similar behaviour in terms of competitiveness and symptoms developed under our experimental field conditions.

Apple scab, caused by Venturia inaequalis is one of the most damaging pathogens that affects apple species. Cross combinations were made between Auriu de Bistrița cv. (female genitor) - a valuable local variety in terms of fruit quality but only tolerant to scab, and Florina cv. (male genitor) used as a donor of Vf resistance gene. It was first detected in Malus floribunda Clone 821, which was later transferred to commercial varieties by different breeding programs. To confirm the presence of Vf gene, progenies resulting from the mentioned combination were tested with MAS (Marker Assited Selection), using two dominant primers pairs (AM19, U1400), and another one codominant (AL07) used to distinguish homozygous and heterozygous genotypes. After the crossing combination, a number of twenty-six hybrids were obtained, of which 50% (13 hybrids) were clasified as resistant (heterozygous), respectively 50% (13 hybrids) as susceptible (recessive homozygotes), so the Mendelian ratio was confirmed.

The experiment aimed to evaluate some of organic products within a treatment scheme against Eurytoma schreineri Schreiner., on two different plum varieties: Stanley and Reine Claude d’Althan. An experimental scheme of organic treatments by using seven organic products with insecticidal effect was developed and used for evaluation in the field. There were three variants taken into account: organic, conventional and untreated, used as control. Each variant consisted of eight trees belonging to Stanley and Reine Claude d’Althan cvs., four trees for each variety. The frequency occurring of Eurytoma schreineri was evaluated along two consecutive years (2019-2020). Overall results confirmed the sensitivity of Stanley cv. to Eurytoma. schreineri. On the other hand, the results showed that the organic scheme developed was unsatisfactory and there is a risk of considerable losses for farmers who opt for this kind of scheme.

Four young plum orchards from Iaşi county, two of these established by using propagated material in Romania, and the other two with material from Austria, Czech Republic and Netherlands, were surveyed by visual observation of viral symptoms. Then, trees were sampled and tested for the presence of six viruses (PPV, PDV, PNRSV, ACLSV, ApMV and MLRSV) by serologic assays. A high rate of PPV infection (78% and 79%, respectively) was determinated in the two orchards established with planting material propagated in Romania, and a rate of 5% PDV infection was found in one of them. A rate of 2.5% PPV infection was determined in the orchard established with propagated material in Austria and Czech Republic, and no PPV infected tree was found in the orchard set up with material propagated in Netherlands. The infections with PNRSV, ACLSV, ApMV and MLRSV were not detected in the four orchards surveyed.

The European plum (Prunus domestica L.) is one of the most important cultivated species among fruit trees in the world, and the dominant in Romania. Regarding the development of new plum cultivars derived from Prunus domestica, the following characteristics are taken into consideration most of the time: high yield performance, good quality fruits and last but not least, the resistance to PPV. “HoneySweet” is a transgenic clone of Prunus domestica transformed with Plum pox virus coat protein gene making it highly resistant to the virus. This study presents preliminary results on the chemical composition of HoneySweet transgenic plum and two conventional ones: Reine Claude d’Althan and Stanley. The most important nutritional factors were determined. HoneySweet had balanced individual carbohydrates content but lower soluble solids in comparison with the two conventional cultivars. Total lipids content in HoneySweet fruits was similar to Stanley, higher than in Reine Claude d’Althan. HoneySweet is distinguished by the highest total protein content. Similar amounts of magnesium and calcium were recorded in the three varieties. Overall, our preliminary results revealed that the quality and nutritional value of “Honey Sweet” genetic engineered plum is in the range of other valuable plum cultivars.

Plum pox virus (PPV) is considered the most destructive viral pathogen of stone fruits. Although PPV is widespread in all plum growing areas from Romania and causes serious yield losses, little is known about the virus variability. For this reason we investigated 100 PPV isolates collected from 13 different plum orchards in the Transylvania - Romania. PPV detection was made by DAS-ELISA and by IC-RT-PCR. PPV strains were serologically determined by TAS-ELISA using PPV-D and PPV-M specific monoclonal antibodies. Molecular strain typing was done by RT-PCR targeting three different genomic segments corresponding to (Cter)CP, (Cter)NIb/(Nter)CP and CI. RFLP analysis was used to distinguish the two major strains, D and M based on a RsaI polymorphism located in (Cter)CP. All PCR products targeting (Cter)CP and 10 PCR products spanning the (Cter)NIb/(Nter)CP were sequenced. All PPV isolates typed as PPV-M by serological analysis and by molecular differentiation in the genomic region corresponding to (C-ter)CP proved to be PPV recombinant (PPV-Rec) when the molecular analysis were performed in the region corresponding to NIb/CP. Sequencing confirmed a high similarity with different sequences of PPV-Rec previously reported. All these recombinant isolates share the same recombination breakpoint and conserve the DAG motif, which is considered essential for aphid transmission. Overall results provided that in Transylvania the predominant strain is PPV-D, followed by PPV-Rec which shares the CP gene with M strain and, therefore, it is serologically detected as PPV-M with M-specific monoclonal antibodies. In this big plum growing area, mixed infections (PPV-D+PPV-Rec), which might generate additional variation by recombination, are also frequent.

To assess the durability of resistance to PPV of HoneySweet transgenic plum harbouring plum pox virus (PPV) capsid gene, a new field trial was recently established in Romania at Fruit Research & Development Station Bistrita. Stanley and Reine Claude d’Althan cvs. are used as control. PPV inoculum source is secured within the experimental plot. PPV monitoring was made by visual observation of symptoms development on leaves and by serological (DAS-ELISA) and molecular (IC/-RT-PCR) testings. Three years after planting PPV was observed and detected only on Stanley. 'HoneySweet' and Reine Claude d’Althan cultivars remained PPV free.