The evaluation of occurrence of PPV symptoms in young peach orchard according to the used rootstock

GOGOLKOVA, K., HORSAKOVA, J., ONDRASEK, I., KRSKA, B.: The evaluation of occurrence of PPV symptoms in young peach orchard according to the used rootstock. Acta univ. agric. et silvic. Mendel. Brun., 2012, LX, No. 8, pp. 59–66 The degree of PPV occurrence was monitored in a young peach orchard during 2010–2011. This study evaluates the percentage of infected trees in 2010 as well as the intensity of PPV symptoms in 2011 in two peach varieties „Royal Glory“ and „Symphony“ gra ed on seven diff erent rootstocks of Prunus species a er the natural infection. The diff erent intensity of PPV symptoms was proved on infected parts such as fl owers, leaves, fruits and from rootstocks’ point of view. In 2010 were PPV symptoms most o en detected in variety ’Royal Glory’ gra ed on rootstock Julior where 100% of trees were infected. No visible symptoms were observed in trees of variety ’Symphony’ on Pumiselect rootstock. As for the rootstocks evaluation, PPV symptoms were most numerous in trees gra ed on MRS 2/5 rootstock (94.78%), at least were monitored on Lesiberian rootstock (28.47%). The intensity of PPV symptoms on fl owers, leaves and fruits in each combination was evaluated in 2011. Generally, the PPV symptoms were present mainly on fl owers and less on fruits. Peaches, P. persica L., intensity of PPV symptoms, fl ower, leaf, fruit, rootstock Plum pox virus (PPV) represents the major threat in production of plums, peaches and apricots. Eradication of this pathogen in the infected areas seems to be impossible (Hamdorf, 1986) and thus there are only two alternatives how to eliminate the PPV occurrence – either a complete removal of the infected trees or breeding new resistant varieties (Dicenta et al., 1999). Currently, the offi cial sources have reported the PPV spread in peach orchards through the Czech Republic (Polak, 2004) as well as in other EU countries. Moreover, PPV virus is widely spread in natural environment of the Czech Republic (Polak, 2002; Polak and Kominek, 2009) so it is unlikely to guarantee a PPV–free area (Hnizdil, 2010). Finding a source of immunity or resistance within genus Prunus persica L., or in the wide gene pool in various geographical groups seems impossibly, the strategy to breed PPV resistant peaches gets even more complicated. Prunus davidiana (Carriere) Franch represents the only source of resistance from related species, and it is used in INRA Avignon breeding program (Rubio et al., 2010). As Polak et al. (1998) reports, no immune or even resistant variety was identifi ed from 34 naturally infected varieties. However, varieties Envoy and Favorita Morettini 3 were recommended for the conditions of the Czech Republic where PPV infection is widely spread. Other varieties such as Candor, Flamencrest, Harcrest, Harmony, Maycrest, Spring Lady, Friestina and Velvet were classifi ed as medium resistant. In other work Polak et al. (2003) identifi ed the following peach varieties as medium resistant to PPV a er PPV-D inoculation (Flame Prince, Cotender, Newhaven, Ruby Prince, Sun Prince, Jeff erson, Camden a Jersey Queen), and as tolerant varieties Loring, Blaze Prince, June Prince and Legend. In the course of years 2003–2007 Pollini et al. (2008) carried out the research of PPV symptoms 60 K. Gogolkova, J. Horsakova, I. Ondrasek, B. Krska present in 21 peach varieties a er the inoculation. Varieties such as ’Morsiani 90’, ’Summer Lady’ and ’Maria Dolce’ did not show any PPV symptoms, unlike the rest of varieties where typical PPV symptoms such as foliage discoloration and diff use spots, colour breaking of the petals, deformed fruits with light rings on the skin were reported. The rootstock eff ect on PPV spread in peach varieties has not been studied yet. The aim of this study is to assess the presence and intensity of PPV symptoms in natural environment in young peach orchards. Primarily, PPV symptoms will be evaluated visually and then will be the occurrence of pathogen in leaves confi rmed by ELISA test. MATERIAL AND METHODS Between the years 2010 and 2011 the PPV (Plum pox virus) symptoms were evaluated in peach rootstock orchard on fl owers, leaves and fruits of peach trees (Prunus persica L.). The symptoms were evaluated in two varieties gra ed on diff erent rootstocks – variety Royal Glory on 7 rootstocks: GF 677 (148 pcs), Lesiberian (62 pcs), Ishtara (68 pcs), Pumiselect (47 pcs), St. Julien A (13 pcs), MRS 2/5 (72 pcs) and Julior (92 pcs) and variety Symphony on 6 rootstocks: GF 677 (120 pcs), Lesiberian (82 pcs), Ishtara (61 pcs), Pumiselect (31 pcs), MRS 2/5 (43 pcs) a Julior (75 pcs). A total of 13 variety/rootstock combinations were included in the study (altogether 914 trees). The planting was set up in 2004 on the premises of Faculty of Horticulture, Department of Fruit Growing in Lednice. Trees were planted with 5 x 1.5 m spacing. The training system of the trees was maintained by long american pruning to form the modifi ed leader (one half of the evaluated collection) and the open centre (second half of the evaluated trees). As for agro-technical measures, common treatment and spraying methods were applied, especially against leaf curl (treatment by Champion), aphids (treatment by Pirimor), powdery mildew (treatment by Kumulus), infection of Monilinia laxa (treatment by Horizon). Monitoring of PPV virus occurrence on fruits was carried out for the fi rst time in 2010. The trees with distinct symptoms of the pathogen were marked and the percentage of infected trees showing PPV symptoms was calculated accordingly. The occurrence of symptoms of the pathogen was graded by points 0–3 in the year 2011, where 0 stands for no symptoms, 1 for mild symptoms, 2 for medium symptoms and 3 for severe symptoms. ELISA test confi rmed the presence of the pathogen in leaves in combination ’Symphony’/ Julior and in combination ’Royal Glory’/Julior in 2010–2011. Source of infection can not be unambiguously specifi ed, but the fi rst symptoms (already in the third year a er plantation) were observed in small quantities (5%) in both varieties on rootstock MRS 2/5. These lines were planted on the border, closed to the old very infected peach plantation from 1988 with varieties ’Redhaven’ and ’Sunhaven’. The obtained data were subjected to statistical analysis using the so ware Statistica, ANOVA multi-factor analysis. Scheff e test was applied to evaluate signifi cance of diff erences among multiple combinations. Compared combinations were divided into two groups: a – with no signifi cant diff erences, b – with signifi cant diff erences or highly signifi cant diff erences.