Polyphenoloxidase isozyme and Vfa1 sequence specific markers in apple cultivars differing in scab resistance

Abstract

The objective of the study was to elucidate the isozyme markers related to scab resistance. Polymorphism in the polyphenoloxidase (PPO, EC 1.14.18.1) enzyme system was investigated and DNA analysis using a Vfa1 sequence specific marker was performed to identify the presence of Vfa1 gene like sequences in apple cultivars having the above-mentioned isoforms. The number of PPO bands was found to change during the vegetation period. The PPO enzyme systems showed considerable variation among the apple cultivars. Some specific bands or their combination were determined for scab-susceptible and scab-immune apple cultivars. Our results showed that the cultivars ‘Prima’, ‘Aldas’, ‘Skaistis’ and ‘Rudenis’, which are immune to 1–5 Venturia ineaqualis races, have a DNA fragment of 500bp specific for the Vfa1 gene. The immune cultivar ‘Štaris’ doesn’t have this fragment. However, this fragment was detected in the genome of the cultivar ‘Tellissare’ having a polygenic scab resistance mechanism. The above-mentioned DNA fragment was not obtained for the susceptible cultivars ‘Noris’ and ‘Papirovka’ and the cultivars ‘Katja’ and ‘Auksis’ resistant to polygenic scab. The possible genetic background of such results is discussed. Keywords: apple cultivars, isozymes, scab resistance, DNA, Vfa1, PPO