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ABSTRACT:The submitted work deals with the relation between the sum of active temperatures above 7°C and important phenological phases in peach tree cultivation. The aim of the paper is to provide information for growers, especially regarding anticipated harvest dates, which is important for marketing. Data has been compiled for the period 1998-2007 for the variety Catherine, grown in the locality of Velké Bílovice in the Czech Republic. A relationship between the sum of active temperatures above 7°C from the beginning of the year up to the start of blossoming has been identified, and a model determining the harvest date on the basis of the sum of active temperatures in the periods of 30 days and 60 days after blossoming has been tested. conditions. We can also assume that an increase in weather variability, as it is suggested in some studies concerning climate change, will lead to an increase in variation in the start of individual phenophases.The goals of this study were as follows: to test the possibility of using the sum of effective hourly temperatures for a model of the onset of peach tree phenophases and to predict the date of harvest for the selected cultivar. MATERIAL AND METHODSIn assessing the relationship between meteorological factors and the start of phenophases in peaches, we have used average hourly air temperatures. The compiled phenological observations refer to the variety Catherine (synonym Frederika-Catharina, Čepička et al. 1999) in Velké Bílovice, where air temperatures were precisely recorded at fifteenminute intervals with the aid of a HOBO recorder (see e.g. Litschmann 1999) placed close to the observed orchard. The study period comprised the years 1998-2007.We focused on the assessment of the start of blossoming and the start of harvest; these dates were carefully recorded every year. Blossoming was determined as stage F by Baggiolini (1952) (or 65 by BBCH, i.e. at least 50% of flowers open, first petals falling). The beginning of harvest was determined as the period when most fruits reached the optimum market maturity.From the meteorological data, we calculated the sum of active hourly temperatures above the base of 7°C (SAT7), starting from 1 st January every year. In the published literature this index is referred to as GDH (Growing Degree Hours); though, Peréz-Pastor et al. (2004) used it with a base of 6°C. DeJong (2005) used a combination of two cosine curves to calculate GDH, as follows: t ≤ 25: GDH = 10.5 (1 + cos (3.14 + 3.14 (t -4)/(25 -4))) t > 25: GDH = 21 (1 + cos (3.14/2 + 3.14/2 (t -25)/(36 -25))) where: t -temperature (°C).We tried to use this method in our own study, but we failed to reach more exact results. The retarding influence of higher temperatures on phenological development is probably not so critical under the conditions of South Moravia, where the relatively cooler climate prevails. RESULTS AND DISCUSSION Start dates of individual phenophases and temperature characteristics in individual yearsThe average blossoming start date (period 1994 to 2007) of the se...

Differences in reactions to infection and different development of Plum pox virus (PPV) symptoms were observed in leaves and fruits of one hundred sixty-five apricot and seventy-nine peach cultivars and hybrids. A very broad spectrum of reactions from high susceptibility to high resistance and immunity was proved in apricot cultivars and hybrids and the results were published (POLÁK et al. 1997). A much narrower spectrum of reactions was proved in peach cultivars. Relative concentrations of PPV by ELISA in flowers, intensity of virus symptoms in leaves and fruits of peach cultivars were evaluated. The relative concentration of PPV coat protein (PPV-CP) in flowers was found to be positively correlated with the intensity of leaf and fruit symptoms in most cultivars. On the basis of obtained results cultivars of peaches were divided into four groups and classified as medium resistant, tolerant, medium susceptible and susceptible to PPV. None of the investigated cultivars was immune, highly resistant or resistant to PPV. Eighteen peach cultivars were classified to be medium resistant to PPV. Nine peach cultivars were characterized as tolerant to PPV, with high relative concentration of PPV-CP protein in flowers and mild symptoms in leaves and fruits. Twenty-seven peach cultivars were characterized as medium susceptible to PPV. Twenty-five peach cultivars were rated as susceptible to PPV. It is recommended to grow medium resistant peach cultivars in the areas where PPV is widely distributed.

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The presence and distribution of PPV-M strain of Plum pox virus were investigated in selected orchards of apricots and peaches in the Czech Republic. PPV-M was found to be distributed in apricot and peach orchards planted with nursery material imported from abroad. The presence of PPV-M was not proved in orchards planted with trees from local nurseries. The absence of PPV-M in a majority of spontaneous PPV hosts was proved previously. PPV-M strain appears to have been introduced recently. K rozšíření kmenu PPV-M ve vybraných sadech meruněk a broskvoní v České republice ABSTRAKT: Ve vybraných sadech meruněk a broskvoní v České republice byla zjišťována přítomnost a rozšíření kmenu PPV-M viru šarky švestky. Bylo zjištěno, že PPV-M je rozšířen v sadech meruňky a broskvoně vysazených školkařským materiálem importovaným ze zahraničí. Přítomnost PPV-M nebyla prokázána v sadech osázených stromy z místních ovocných školek. Již dříve byla prokázána absence kmenu PPV-M ve většině spontánních hostitelů viru šarky švestky. Ukazuje se, že kmen PPV-M byl introdukován nedávno. Klíčová slova: meruňka; broskvoň; sady; virus šarky švestky; kmen PPV-M; rozšíření; ELISA; polyklonální a monoklonální protilátky Corresponding author: Doc. Ing. JAROSLAV POLÁK, DrSc., Výzkumný ústav rostlinné výroby, odbor rostlinolékařství, Drnovská 507, 161 06 Praha 6-Ruzyně, Česká republika tel.: + 420 233 022 402,