ASSESSMENT OF THE PHYTOVIRAL STATUS OF SOME PLUM ORCHARDS IN THE MUNTENIA REGION

To reduce the damage caused by plum virus infections, were evaluated phytoviral, plantations aged between 1 and 13 years in different areas of Muntenia: Breasta-Dolj, Dobrețu-Olt, Nicolae Bălcescu-Vâlcea, Cepari and Bălilești-Argeș, Bucov-Prahova, Săhăteni/Istrița-Buzău, SăruleștiCălărași, Pietroșani-Teleorman, in order to identify viruses with special economic implications for this species: PPV, PDV, PNRSV, ACLSV and ApMV. The varieties, included in the 10 orchards analyzed were: ‘Anna Spath’, ‘d'Agen’, ‘Stanley’, ‘Cacanska Lepotica’, ‘Centenar’, ‘President’, ‘Topend’ and ‘Tophit’.They were followed: the symptomatology, the highlighting by the serological method DAS-ELISA as well as the etiology of the viruses. The results of the diagnosis by the DASELISA test, highlighted the presence of positive samples: 14.7% PPV, 0.3% ApMV and 0.05% PDV. The cause of infection of the plants found positive was established as depending on circumstances both in the nursery and occurred during life in the orchard. Cuvinte cheie: virus, metoda ELISA, plantatie, prun.


Introduction
The stone fruit species are hosts for a large number of viruses that can cause substantial economic losses (Nemeth, 1986;Desvignes, 1999;Myrta et al., 2003). Plum pox virus (PPV), is considered the most harmful virus that attacks the stone species and causes losses of up to 80-100% (Nemeth, 1986; Cambra et al., 2006). PPV is transmitted by vegetative and natural propagation through vector aphid species. In addition to PPV, Prunus necrotic ringspot virus (PNRSV), Prune dwarf (PDV) and Apple mosaic virus (ApMV) also, cause significant damage with different distribution worldwide (Matic et al., 2008). Apple chlorotic leaf spot (ACLSV) is also an economically important virus due to its high prevalence and effects even if the infection caused by this virus is not externalized by symptoms in most varieties. All these viruses can seriously affect the yield of production and the development of trees (Uyemoto et al., 1992). The use of infected plant material for propagation is the main cause of long-distance spread, as at short distances, the spread is mediated by a number of aphid species in a non-persistent manner (Labonne et al., 1995;Isac et al., 1998). Control measures depend on the identification of diseases and their etiological agents. Diagnosis is the most important aspect of controlling fruit plant viruses. Early detection of viruses in fruit trees or in propagating material is a prerequisite for their control and to guarantee a sustainable agriculture (Barba et al., 2014). Vector control plays an important role in the management of systemic diseases, but should be used in conjunction with other control measures such as the eradication of infected plants and the use of certified propagating material.
virus, pollen or seed PDV virus, the success of transmission also depends on various factors: concentration in the virus, temperature, etc. Gilmer (1961;1963) explains the very poor spread of pollen compared to the seed transmission of PDV, in that in some varieties, eggs pollinated with infected pollen die before the virus invades neighboring cells.
The strategies for managing infection and the spread of orchard infections are based on the factors that lead to this risk. Thus, after viral evaluation performed, by analyzing the influencing factors of the spread of viruses in the 10 plantations studied, was established the cause / origin of the disease of the trees. Plantation 1. The plum plantation has PPV infections. Infection rate by 23% with PPV, generalization of infection in the crown of trees, plantation age (4 years), use of CAC planting material, untested virotically, the existence of old apricot and plum plantations nearby, indicates a high probability that the trees, was infected from the nursery as well as in the orchard with a high rate of spread in the orchard. Plantation 2. The virotic condition is very good, it shows infections with PPV, on a single tree, isolated on the leaves of a shoot. Concidering the age of the plantation (2 years), the use of CAC seedlings, it can be concluded that the source of infection is from the nursery. Plantation 3. The plum plantation is infected with PPV in a proportion of 20%, the presence of both generalized and isolated infections and the infection with ApMV in a proportion of 0.5%, the age of the plantation (4 years), the presence of scattered plums in the family gardens, use of CAC planting material, without viral evaluation, indicates that the material was mainly infected in the nursery. Plantation 4. The plum plantation is 11% infected with PPV. The infections in the crown of the trees are mostly generalized, the age of the plantation (7 years), the use of planting material CAC, suggests that some of the material was infected in the nursery, but can not be excluded and infections that occurred after the establishment of the plantation, provided that, there are scattered plums in family gardens that have PPV infections.
Plantation 5. The infection rate (0.5%) is low, indicates a good phytovirotic status, but the PDV infection most likely occurred in the nursery, provided that, this virus is transmitted through pollen and seed and the plantation is only 2 years old. Plantation 9. The plum plantation established with planting material, biological category Certificate, is massively infected with PPV. Provided that partial infections predominate in the crown of trees and there is a source of inoculation nearby, there is a high probability that within 8 years since the plantation was established, most of the infection has occurred. However provided that, high infection rate of 57.5%, there is also the probability that another part of the infections occurred in the nursery. Plantation 10. The plum plantation established with planting material, biological category Certificate, is massively infected with PPV. Provided that partial infections predominate in the crown of trees and there is a source of inoculation nearby, there is a high probability that within 8 years since the plantation was established, most of the infection has occurred. However provided that, high infection rate of 29,5 %, there is also the probability that another part of the infections occurred in the nursery.

Conclusions
In the case of very young plantations with a low infection rate, the main measure to limit the spread of the virus is to eliminate of the infected trees and extend monitoring throughout the plantation and in the event of infections to replace diseased trees with healthy trees; In the case of medium and high rates of PPV infection, eliminating infected trees to limit the impact of PPV is not an economical solution, although profitability will be affected. The maintenance of the plantation is based on the fact that there are also tolerant varieties in the plantation: Stanley, Anna Spath, Cacanska lepotica and it is recommended to respect the cultivation technology, insisting on phytosanitary treatments to limit / slow down the propagation of PPV to healthy plants; Assessing the spread of plum viruses will promote the rationale for the effectiveness of the monitoring system.