Studies of the Old Romanian Apple Varieties Involved in New Breeding Programs for Resistance to Venturia inaequalis

Breeding for resistance to Venturia inaequalis has become a major objective for many research laboratories. The use of resistant cultivars reduces production costs for apple species. This work is focused on the identification of other sources of resistance to Venturia inaequalis among the old Romanian varieties in Transilvania area (“Turnu”, “Venchi”, “Vanatori 48”, “Sângeriu”, “Costat de Albesti” varieties), on the studies of the quality of these varieties, the use of the most valuable of them in the Romanian breeding program and the screening of the hybrid progenies after artificial infection with Venturia inaequalis for a durable resistance to this important apple disease. Some older Romanian varieties: “Mohorât”, “Vieşti” and “Nobile de Geoagiu” were used like genitors in USAMVB’s breeding program. To identify specific resistance and develop the new plant material is important in this process. Using the domestic apple varieties well adapted to the climate in Romania in the breeding program can be an interesting premise on inducing natural genetic resistance to Venturia inaequalis. After artificial infection we observed that a number of varieties such as “Prescurate”, “Turnu”, “Venchi”, “Gurguiate”, “Rosu Marin” and “Sângeriu” showed some genetic resistance to Venturia inaequalis, falling within Class 0. In total there were 36 plants belonging to class 0 which means no symptoms. In Class 1, 550 plants were assigned, which is also considered resistant. The results are presented in Table 3 and in Figure 6. The variety which recorded the highest values was “Iridium” with 139 plants, followed by the variety “Rosu Marin” with 124 plants and “Venghi” with 123 young plants.


Introduction
The fungus Venturia inaequalis causes apple scab (Bénaouf et al., 1998), the most widespread diseases of apple trees (Tenzer & Gessler, 1997).Leaves attacked by scab have a lower assimilation rate (Bowen et al., 2001).They are falling off earlier, fruits do not develop to normal size and do not have the full taste quality (Dvořák et al., 1976).Breeding for resistance is one of the effective measures for a protection against this disease.Crosby et al. (1992) describe two basic types of resistance of apple trees to scab disease.The first is qualitative (monogenic) resistance that is typical of some species of the genus Malus.Segregation of susceptible and resistant progenies is guided by Mendel's laws (Hugh et al., 1953).An important source of this resistance is Malus floribunda Sieb.clone 821.Prima was the first resistant variety that was bred with a Vf gene (Dayton et al., 1970).Simultaneously with the development of apple resistance to scab new races of Venturia inaequalis were also found (Parisi et al., 1993, Bénaouf et al., 2000).Several techniques are available for controlling scab.Advantages of one method over another depend on the number of trees you are managing and whether conditions are ideal for disease development (Bogya, 1999).Fruit breeding is very time-consuming and costly.It takes at least 20 years from the first crossing to a commercial apple cultivar (Becker et al., 1990).The flower is emasculated and pollen from a known parent (father) is transferred.The selection of parents is very important.The flower is protected in a small bag after the pollination and later the fruit is collected (Carisse, 2000).The next season the seeds are sown, and thereafter selection is made among the seedlings.The juvenile period is long, at least 4 years and sometimes up to 7-8 years.Sometimes backcrossing is necessary to obtain the right characteristics.If the desired trait is under polygenic control, there will be a variation range.In this case a progeny of several thousands of seedlings would only yield one seedling with a combination of these characters

Soluble Dry Matter
Soluble dry matter is the most important part of total dry matter.It is determined by refractometer.For this method, 5 g fruit mesocarp probes were sampled for each variety, mashed in order to obtain the juice.The reading was made by refractometer.

The Content of Vitamin C
The HPLC analysis was carried out to determine the vitamin C and organic acids on a Shimadzu class LC VP HPLC system with class LC-VP software, a pump (LC-6AD), and a UV-VIS detector (SPD-10AV VP).The columns used were YMC Pack-ODS (250 mm × 4.6 mm I.D., 5 μm) for organic acids and SGE (250 mm × 4.6 mm I.D., 5 μm) for vitamin C. The mobile phases were water adjusted to pH 2.2 with trifluoroacetic acid (organic acids) and to pH 3 with phosphoric acid (vitamin C).Separation was carried out by isocratic elution with a flow rate of 0.4 ml min-1 and column temperature was ambient.The UV detector was set at 210 nm and 254 nm, respectively.The quantity was based on the peak area measurement.Sample (10 g) was extracted in 10 ml water adjusted to pH 1.5 with trifluoroacetic acid for organic acids and with 10 ml phosphoric acid-water (2%, v/v) for vitamin C. The extracts were filtered through filter paper.Then, 1.5 ml buffer (0.01 M KH 2 PO 4 , pH 8.0) was added to 1.5 ml sample extract.From this, 1.5 ml (organic acids) and 1 ml (vitamin C) of these mixtures were loaded on to C18 cartridges.After loading, 3 ml water adjusted to pH 1.5 with trifluoroacetic acid for organic acids and 2 ml phosphoric acid-water (2%, v/v) for vitamin C were passed through the cartridges.For HPLC, 20 μl of the eluents were injected.

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Discuss
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Results on the n
The hybrid combinations-va    be an s, the all of these studies.The artificial infections in these varieties and their hybrids can provide some information on the plant defence mechanism against the pathogen agent's attack.
Support and promote the culture of the apple varieties with genetic resistance to diseases constitute, for new plantations, technological links with economic performance, with immediate effect on total or partial removal treatments with fungicides, represent the main factor in obtaining organic production.
Table 3 presents the results of the number of seeds extracted from studied apple fruits varieties.In total this study started with 2391 seeds (Figure 6).The highest number of seeds extracted and taken into study was the variety "Rosu Marin" 288 seeds, followed by the variety"Gurguiate"with 252 seeds, then the variety"Turnu" with 220 seeds.Note.DL 5% -2. .
* Statistic analysis using the significant variation method values: x: significant positive; 0: significant negative; xx: distinctive significant positive; 00: distinctive significant negative; xxx: very significant positive; 000: very significant negative; N: neutral.

Table 1 .
Results on apple fruit weight and content in soluble solids

Table 3 .
(Chevalier 1991)lassification of old studied apple varieties concerning the resistance according to the classes of symptoms(Chevalier 1991)

Table 3
Change of the assortment at shorter time intervals is required by increasing susceptibility to diseases and pests in some apple varieties, the emergence of new varieties showing superior qualities of existing varieties, adaptation to new crop technologies and systems, adapting assortment climate changes-resistance or tolerance to climatic stress factors.