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Genetic divergence between populations can lead to reproductive isolation. Hybrid incompatibilities (HI) represent intermediate points along a continuum toward speciation. In plants, genetic variation in disease resistance ( R ) genes underlies several cases of HI. The progeny of a cross between Arabidopsis ( Arabidopsis thaliana ) accessions Landsberg erecta (L er , Poland) and Kashmir2 (Kas2, central Asia) exhibits immune-related HI. This incompatibility is due to a genetic interaction between a cluster of eight TNL (TOLL/INTERLEUKIN1 RECEPTOR-NUCLEOTIDE BINDING-LEU RICH REPEAT ) RPP1 ( RECOGNITION OF PERONOSPORA PARASITICA1) - like genes ( R1 - R8 ) from L er and central Asian alleles of a Strubbelig -family receptor-like kinase ( SRF3 ) from Kas2. In characterizing mutants altered in L er /Kas2 HI, we mapped multiple mutations to the RPP1 -like L er locus. Analysis of these suppressor of Ler/Kas2 incompatibility ( sulki ) mutants reveals complex, additive and epistatic interactions underlying RPP1 - like L er locus activity. The effects of these mutations were measured on basal defense, global gene expression, primary metabolism, and disease resistance to a local Hyaloperonospora arabidopsidis isolate ( Hpa Gw) collected from Gorzów (Gw), where the Landsberg accession originated. Gene expression sectors and metabolic hallmarks identified for HI are both dependent and independent of RPP1 - like L er members. We establish that mutations suppressing immune-related L er /Kas2 HI do not compromise resistance to Hpa Gw. QTL mapping analysis of Hpa Gw resistance point to RPP7 as the causal locus. This work provides insight into the complex genetic architecture of the RPP1 - like L er locus and immune-related HI in Arabidopsis and into the contributions of RPP1 - like genes to HI and defense., (© 2018 American Society of Plant Biologists. All rights reserved.)

Among downy mildews occurring on ornamentals in Poland the most dangerous are downy mildew of rose and downy mildew of German statice (Tartarian statice). Downy mildew of rose caused by Peronospora sparsa Berk. is a serious threat to commercial cultivation of cut roses, especially grown under plastic tunnels. Peronospora statices Lobik casual agent of German statice downy mildew can causes the total losses in the second year of statice cultivation more than 70%. Both pathogens are very difficult to control. Effectiveness of azoxystrobine, cymoxanil + famoxate, mancozeb, phosethyl aluminium, phosethyl aluminium + fenamidone, propamocarb in the control of P. sparsa and P. statices was presented. In the control of statice downy mildew none of tested compounds was able to control satisfactory the pathogen. Relatively the best results were obtained with mixture of fenamidone (88 microg/cm3) and phosethyl AL (1334 microg/cm3). In the control of rose downy mildew, the best results were obtained with phosethyl Al at concentration 1600 microg/cm3.