Pre-breeding and breeding of potatoes for quantitative resistance to Phytophthora infestans on foliage and tubers and for different utilization - problems, solutions and results

Pre-breeding and breeding of potatoes for quantitative resistance to Phytophthora infestans on foliageand tubers and for different utilization - problems, solutions and results. During the long history of breeding for late blight resistance of the potato the quantitative type of resistance became apparent to be very difficult not only concerning the assessment of the both traits but also concerning breeding progress because of polygenic inheritance and the very long breeding way from wild species as source of resistance. Compared with R-genes this type has the advantage of lastingness. However methodical and economical arguments were opposed to breeding effort and progress in long-day conditions; chemical plant protection was the alternative; its application could be reduced by one third by breeding for resistance. Pre-breeding for more than 40 years at ZL Gross Luesewitz resulted in development of methods and breeding material which requires revision as well of value of quantitative type of blight resistance as chance of success to combine resistance with other quantitative traits, and of most interpretations of molecular genetic results. 74 tables, 157 fi gures and 33 pedigrees inform about methodical details and results of breeding in 68 traits. Solution of problems in assessment of resistance and in breeding are explained. Slow breeding progress was stated in combining resistance with other quantitative traits. Necessary changing in selection system of variety breeding is recommended to improve efficiency of introduction of quantitative blight resistance. State of research of pathogenicity of P. infestans and of resistance is analysed, also global state of quantitative resistance in varieties, reasons of insufficient resistance level and current chances of success. A comprehensive overview is given about methods of assessment of blight resistance on foliage and tubers, on inheritance of mentioned traits, on assessment and use of wild species. The very extensive number of references includes elder and usually ignored literature. Pre-breeding material handed over to variety breeding is characterized in important traits and shows breeding progress during 30 years. Conclusions for utilization of quantitative late blight resistance in future and recommendations are given for concentrated organization of this pre-breeding in EU.