Reaction of peach tree genotypes to bacterial leaf spot caused by Xanthomonas arboricola pv. prunis

Bacterial leaf spot (BLS), caused by Xanthomonas arboricola pv. pruni, is one of the most important diseases in Brazilian peach [Prunus persica (L.) Batsch] orchards and all over the world. The main objective of this study was to evaluate for BLS sensitivity of peach genotypes. Evaluations of thirty genotypes were carried out during the onset of the disease, for incidence, severity and defoliation, in field conditions. Pearson's correlations between the percentage of defoliation and leaf severity rating were performed. Genotypes 'Conserva 985', 'Conserva 871', 'Conserva 1129', and 'Tropic Snow', as resistance sources, and 'Conserva 1153', 'Bonão', 'Conserva 1125', and 'Atenas', as susceptible to BLS, were submitted to detached-leaf bioassay and greenhouse evaluation. The peach genotypes showed different reactions to the BLS, and none was immune to the pathogen. 'Conserva 985' and 'Conserva 1129' confirmed resistance responsiveness while 'Conserva 1153', 'Conserva 1125' and 'Atenas' were found susceptible for the detached-leaf bioassay

Evolution of transition metal charge states in correlation with the structural and magnetic properties in disordered double perovskites Ca2 xLaxFeRuO6 0.5 lt; x lt; 2

A series of disordered Ca1.5La0.5FeRuO6, CaLaFeRuO6 and La2FeRuO6 double perovskites were prepared by the solid state reaction method and investigated by neutron powder diffraction, X ray absorption near edge structure XANES analysis at the Ru K edge, Mössbauer spectroscopy, DC magnetization and resistivity measurements. All compounds crystallize in the orthorhombic crystal structure with the space group Pbnm down to 3 K, showing a random distribution of Fe and Ru at the B site. Thermogravimetric analysis indicates oxygen deficiency in the Ca rich and formal oxygen hyperstoichiometry in the La rich members of the present series. While Mössbauer spectra verify the Fe3 state for all compositions, the XANES study reveals a variable Run oxidation state which decreases with increasing La content. The end member actually is a Ru3 Ru4 compound with possibly some cation vacancies. From magnetic susceptibility and neutron diffraction measurements, the presence of a G type antiferromagnetic ordering was observed with a drastic increase in transition temperature from 275 K Ca1.5La0.5FeRuO6 to 570 K La2FeRuO6 . Mössbauer spectroscopy confirms the presence of long range ordering but, due to local variations in the exchange interactions, the magnetic states are microscopically inhomogeneous. All the samples are variable range hopping semiconductors. A complex interplay between structural features, charge states, anion or cation defects, and atomic disorder determines the magnetic properties of the present disordered 3d 4d double perovskite serie