Entwicklung eines In-vitro-Resistenztests für den Erreger des Schwarzrostes (<em>Puccinia graminis</em> ssp. <em>graminicola</em>) an Deutschem Weidelgras (<em>Lolium perenne</em> L.) und molekulare Charakterisierung eines dominanten Resistenzgens

Abstract

Stem rust caused by Puccinia graminis ssp. graminicola is a dramatic problem for grass seed production in many areas of the world. Higher temperatures in summer and mild winters as a consequence of the climatic change lead to an increased occurrence of stem rust in the field over the last years. Infections lead to yield reduction and reduced seed quality. In Germany, resistant varieties are failing and treatments with fungicides are difficult and expensive. The reduced benefit of grass seed production makes the cultivation of other crops more and more attractive. The amount of stem rust infection depends on the climatic conditions in spring and summer, therefore an evaluation of stem rust in field trials is not always possible. A detached-leaf test for resistance of Lolium perenne to stem rust has been developed, which is easy to use and gives the opportunity of a stem-rust evaluation independent of environment and climatic conditions. Its results indicate a high robustness of the test and show, despite difficult evaluation in the field trials, good correlations to the field results. Field trials with 340 single plants of a population showing 1:1 segregation in the leaf segment test for stem rust resistance were carried out over two years on three locations with two replications. Using the leaf segment test, the monogenic, dominantly inherited resistance to stem rust in Lolium perenne LpPg1 was found and characterised. Correlation coefficients obtained for infestation scores in independent tests and with plants of varying age indicated satisfactory robustness of the test procedure and stage-independency of the resistance. Reaction to different inoculi of the pathogen indicated a broad effectiveness of the resistance. Analysis with 82 genomic resistance gene analogs (RGA) and 162 simple sequence repeat (SSR) markers identified three markers which are linked to the resistance gene LpPg1. Two flanking markers were mapped 2.6 and 6.7 cM to the resistance gene and may be used for marker assisted selection (MAS) in backcrossing and pyramiding programs. Besides that, the correlated markers give a first indication for the position of LpPg1 on linkage group 4 (Hirta et al. 2006).