LINKS FOR MULTIPLICATION OF PEACH PROPAGATION MATERIAL

RSFG Constanța is the owner of the mother stock for biological superior categories of peach, so in order to align us with the new legislative requirements, starting with 2016 it was introduced in the evaluation process for obtaining Prebase Candidate mother plants for cultivars to which is maintainer: ‘Catherine sel. 1‘, ‘Cecilia‘, ‘Florin‘, ‘Filip‘, ‘Iustin‘, ‘Mimi‘, ‘Minodora‘, ‘Monica‘, ‘Redhaven‘, ‘Southland‘, ‘Springcrest‘. The evaluation was performed in terms of authenticity based on the test of distinction, uniformity and stability, as well as in terms of phytoviral. The evaluation of the phytoviral status has been done visually, by the biological method and by the DAS-ELISA serological test. The following pathogen agents were identified: ACLSV, ApMV, PPV, PDV, PNRSV, ALV, PLMV, SLRSV, ACLR. The results highlighted the presence of PPV in ‘Cecilia’, ‘Redhaven’ and ‘Southland’ cultivars, PDV in ‘Florin’ and ApMV viruses in ‘Cecilia‘s peach plants. Healthy plants have been propagated. Cuvinte cheie: Prunus persica L. Batsch, testare fitovirotică, pomi fructiferi, certificare.


Introduction
Peach is one of the most valuable fruit species due to early fruiting, to the rapid growth of the vegetative organs in the nursery and in the first years after planting, and to the high and constant yields obtained when it is planted in favorable areas of cultivation. It has the capacity to recover easily if climatic accidents occur (Cociu, 1981).
In Romania, there is a large number of cultivars created or acclimatized, and with different ripening times, so that the season for fresh consumption or the possibility for fruit processing is over 100 days. As in the case of other fruit species, it is necessary to rehabilitate the peach through well-thought-out development programs (Sumedrea et all, 2014).
The planting material used to establish new orchards is the guarantee of efficient productions from the qualitative and quantitative point of view, as it must be authentic and healthy. Therefore, the quality of the mother plants from high biological categories and of the planting material obtained in the nurseries is very important.
The European Plant Protection Organization (EPPO) has set standards for the certification of Candidate plants, requirements for authenticity, including viral testing methods (PM 4/30 (1), 2001) in order to increase the quality of fruit propagating material, including for peach.
Regarding the supply with healthy planting material, for peach, the legislation in the field of production and maintenance of fruit propagation material refers to 9 viral and phytoplasmic pathogens ( The research carried out until now on planting material and implicitly on productions has established that in peach the following have the highest incidence: PPV, PDV, PNRSV and ACLR (Chirilli, et. al, 2016;Milusheva, et. al, 2005).
The serological methods of diagnosis are most preferred for the identification of viruses, because they reduce the time required for testing, allow rapid diagnosis of the virus and immediate elimination of infected plants (Nemeth, 1986).
The aim of the paper is to evaluate the peach tree cultivars for which RSFG Constanța is maintainer, from the authenticity and phytoviral point of view, in order to obtain Prebase Candidate mother plants with the purpose of supplying the required propagation material used to obtain planting material.

Material and methods
The The data were recorded between 2016 and 2018; 10 trees were evaluated for each cultivar in the maximum fruiting period (year 5 after planting). The analyzed fruit trees are located in the experimental lots from RSFG Constanța.
The paper presents 11 characters considered the most important for the international harmonization of the description of peach cultivars, as follows: Fruit tree: type-normal; -spur. The characters regarding the tree were observed during the dormancy period, those referring to the flower were noted at full flowering, by collecting and analyzing the flowers from the central part of the annual branches. Similarly, for leaves, fully developed ones from the middle area of the shoots were analyzed. The shape of the nectaries glands was determined on the mature leaves in late July. In order to be able to make an accurate assessment of the characteristics of the flesh color, the fruits of each peach cultivar analyzed were harvested at consumption maturity.
The determination of the viral status was accomplished by combining several methods: 1. Field assessment: visual inspections were carried out several times a year. 2. The biological testing was performed according to the recommendations of the International Working Group on Fruit Tree Viruses, (Jelkmann, 2001).
The biological testing was performed on 'GF 305' and 'Elberta' seedlings and in accordance with the recommended diagrams, using the structure: number of repetitions / temperature / observation period (w = weeks), as follows: - 3. The serological testing was performed to highlight the following viruses: ACLSV, ApMV, PPV, PDV, PNRSV, SLRSV, by using the DAS-ELISA method (Clark and Adams, 1977), in accordance with the protocol recommended by the kit manufacturer. The sampling of the test samples was performed at the end of May and beginning of June, in order to avoid high temperatures that would lead to a decrease in viral concentration.

A. Assessment of authenticity
The analyzed peach cultivars displayed standard branches, with the exception of the Cecilia cultivar (dwarf) that had spur branches, table 1.
The flowering season is an important criterion in choosing peach cultivars, because the climatic accidents (late frosts or hoar) that occur in the second half of March or early April are becoming more frequent in recent years.
The flowering duration and rhythm depend on temperatures and cultivar (Popescu et al., 1992). According to Baldini, quoted by Cepoiu (2006), the critical temperatures for peach are -1. The nectaries glands are located at the base of the leaves on the petiole or on the edge of the leaf blade and secrete a sweet liquid (nectar), attractive to bees. The lack of glands on the petiole is correlated with the sensitivity of peach cultivars to powdery mildew (Asănică and Hoza, 2013). They are present in all the analyzed varieties, and the reniform nectaries glands were noted in most of the studied peach cultivars, table 2.
The ground color of the flesh and the flesh to stone adherence are important indicators in the evaluation of peach cultivars. The consistency of the pulp is correlated with its color. The white flesh found in 'Filip' 'and 'Monica' is softer at fruit maturity, the yellow or orange-yellow one is firm or very firm, similar to the 'Mimi', 'Minodora' and 'Catherine sel. 1'.
The assessment performed on the characters mentioned in Tables 1 and 2 coincides with the characteristics from the examination sheets used for registration with the purpose of description of the peach cultivars studied.

B. Evaluation of the phytovirotic status
The visual field monitoring carried out over the years of observations of the selected plants did not reveal the existence of symptoms that could be associated with diseases caused by viruses, viroids or phytoplasmas.
1) The visual field monitoring carried out over the years of observations on the selected plants, did not revealed the existence of symptoms that could be associated with diseases caused by viruses, viroids or phytoplasmas.
There was a good expression of ACLR phytoplasma symptoms in the 'Filip' variety for the selected tree coded T5, on both biological indicators used: GF 305 and Elberta. Also, positive results expressing symptoms produced by the ACLR phytoplasma were identified both on the biological indicator 'GF 305' and on the biological indicator 'Elberta' at the 'Monica' cultivar in the case of the trees coded T3 and T7. The positive plants were eliminated by burning.
3) The serological testing by DAS-ELISA to detect viral infections revealed individual infections ( Table  4). The PPV virus was identified in most samples (trees), namely T3 'Cecilia', T2 and T4 'Redhaven' and T3 'Southland'. PDV was highlighted on 3 trees, namely T1 'Florin', T6 'Filip' 'and T6 'Southland'. The positive samples were also identified with ApMV in T2 'Cecilia' and with PNRSV in T5 'Redhaven'. The trees identified as positive were removed from the selection process and burned.

Conclusions
The analyzed peach cultivars are very diverse in terms of fruit appearance and can be used fresh or in the canning industry from June to mid-August, being a sort that can be recommended to peach growers.
Trees of all studied peach varieties correspond in terms of distinctiveness, uniformity and stability. The increased incidence of peach infections caused by PPV, PDV, ACLR pathogens, identified by testing even in the absence of symptoms in the selected plants is reconfirmed.