ISHS Acta Horticulturae 538: Eucarpia symposium on Fruit Breeding and Genetics
SCREENING OF PLUM, PEACH AND APRICOT CULTIVARS FOR RESISTANCE TO PLUM POX POTYVIRUS |
| Authors: | H. Kegler, S. Schwarz, E. Fuchs, M. Grüntzig |
| Keywords: | Plum pox potyvirus, resistance, screening |
| Abstract:
Various methods of screening genotypes for PPV resistance have been applied. The most common one is the determination and registration of natural infections and varietal reactions in the field under high infection pressure. This method is essential for confirming the state of resistance detected by experimental investigation. Apart from field testing, PPV resistance should be examined by artificial inoculation, too, because both procedures complement each other. The procedure of artificial inoculation can be divided into two steps: pre-screening and main-screening. Pre-screening is carried out by double grafting in the glass house and after a few months it results in preliminary selection of genotypes immune, hypersensitive and highly resistant, respectively, to PPV. Genotypes selected in this way, should afterwards be tested in the field for several years by inoculation methods of chip budding, top grafting and aphid application, respectively (main screening). Evaluation of PPV resistance is closely connected with the type of resistance which is dependent on the genetic constellation and interaction of host genotype and virus strain. In view of the diversity of PPV strains, different PPV strains and sources should be included in the screening procedures. The most important traits of PPV resistance that have to be evaluated are the symptoms on leaves and fruits, damage to the shoots, as well as virus accumulation and systemic distribution in the host plant. A genotype is immune or absolutely resistant if it is not or only locally infected and if it does not become diseased (qualitative resistance). A genotype is highly resistant if it becomes infected but shows no or only very mild symptoms, if the virus does not become fully systemic and its concentration in the host plant is rather low (quantitative resistance). Moreover, an immune or absolutely resistant genotype remains healthy in the field, and a highly resistant genotype shows only a low rate of natural infection over a long period of time. | |
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