Plum pox virus (PPV) is a devastating stone fruit disease of major importance, and better understanding of the genetic control of resistance to this trait would be useful for more efficient development of resistant cultivars. Previous studies have reported a locus of major effect from PPV resistance on linkage group 1. The current study confirms these results by mapping plum pox virus resistance in a F1 progeny issued from a cross between "Harlayne", as a PPV-resistant parent, and "Vestar" as a susceptible parent. The hybrids were grafted simultaneously and subsequently inoculated with the PPV-M and D strains.The symptom scoring on leaves was performed nine times over two vegetative cycles. Marker-trait associations were analyzed using the Kruskal-Wallis (KW) non-parametric test, and the PPV resistance loci were mapped using composite interval mapping (CIM). We show that both analyses (KW and CIM) highlighted the upper part of linkage group 1 of the apricot "Harlayne" genitor.

This study evaluates the effect of the identified pathogenic races E1, E2 and E3 of the leaf rust Melampsora larici-populina on some growth traits and biomass yield in the species Populus nigra. A field trial was conducted with 8 clones of P. nigra using fungicide-sprayed and unsprayed treatments in 3 replications of 4 plants. In the course of three years the occurrence of the rust was evaluated on a six-point scale. The plant height and stem diameter were measured during the trial. In the last year the plants were harvested and the dry weight was determined. In the untreated plants a significant negative correlation was found between the intensity of rust occurrence and the values of stem diameter and dry matter yield (P < 0.05). A decline in dry matter yield caused by the rust was low (below 9%) or zero in a half of the clones while it ranged between 19% and 28% in the other half of clones. In some clones the yield decline was relatively low although the expression of rust symptoms was rather high which could be attributed to a tolerance to the given pathogen.

No abstract

No abstract

PILAŘOVÁ, P., KRŠKA, B.: Inheritance of resistance to Plum pox virus in the progeny of the apricot cv. 'Harlayne'. Acta univ. agric. et silvic. Mendel. Brun., 2009, LVII, No. 5, pp. 243-250 Natural resistance to Plum pox virus (PPV), the agent of sharka disease, is one of the most important traits of interest to stone fruit breeders, although few sources of resistance have been identifi ed. One of the few apricot cultivars which does show resistance, 'Harlayne', was chosen for a study of the genetics of PPV resistance. It was crossed with three diff erent cultivars, two susceptible ('Vestar' and 'Strepet') and one immune ('Orangered'). Four diff erent lines (since there was one reciprocal combination) were established and the F1 crosses were subsequently inoculated with the PPV-M and PPV-D strains by gra ing infected buds. A woody indicator Prunus persica 'GF 305' was then also top-gra ed onto the plants of three of these F1 populations. The observations of leaf symptoms and accompanying ELISA tests were performed over three, or in one case fi ve, growing seasons and then hybrids were classifi ed accordingly, as either resistant or susceptible. The resistant : susceptible ratios were calculated and compared with expected theoretical ratios using the χ 2 -test. The ratios of resistant to susceptible plants in the progeny derived from the four apricot crosses are compatible with the hypothesis of three dominant genes being responsible for PPV resistance, with 'Harlayne' being heterozygous for all three genes. However, the possibility that resistance is controlled by just two dominant genes can not be ruled out just yet.