MALUS SP. - V. INAEQUALIS INTERACTION CHARACTERISTICS AMONG LOCAL APPLE CULTIVARS IN LITHUANIA

Apple fruit production is a leading horticultural practice in Lithuania. Apple scab is one of the most damaging apple tree diseases that incurs additional costs and ecological risks due to plant protection practices. Identification of apple scab resistance genes and efficient introduction of the genes to apple cultivars is therefore crucial for apple breeding. Apple trees have been grown in northern Europe for centuries and a number of traditional cultivars carrying genes for qualitative and quantitative resistance are spread throughout the region. However, the pedigree of many of the traditional cultivars is unknown and information on genetic background of resistance of the cultivars is scarce. Over 40 accessions of traditional cultivars and cultivars derived from traditional cultivars are deposited at the genetic resources collection of the Institute of Horticulture, LRCAF. In this study, we classified morphological traits of apple scab resistance of 37 traditional cultivars and cultivars released by the Institute during the last century and four known progenitor cultivars. Six cultivars carrying Rvi6 (Vf) or Rvi10 (Va) resistance genes or polygenic resistance traits showed no scab symptoms (class 0). In addition, no scab was observed on ‘Puikis’ and ‘Katja’. Two cultivars were susceptible and demonstrated extensive sporulation symptoms (class 4-3b). Nine cultivars exhibited resistance with chlorosis and/or necrosis symptoms without sporulation (class 2) or scarce sporulation levels (class 2-3a). The remaining cultivars displayed low levels of resistance with varying degrees of sporulation (class 3a, 3a-3b and 3b). Analysis of genetic polymorphism of microsatellite loci established genetic relationships among the traditional cultivars and reference cultivars used in this analysis.