Development of simple sequence repeat markers in hazelnut (Corylus avellana L.) by next-generation sequencing and discrimination of Turkish hazelnut cultivars

Abstract

European hazelnut (Corylus avellana) is a diploid tree species and is widely used in confections. Hazelnuts are, to a large part, produced in Turkey with the cultivar "Tombul" widely grown in the Black Sea region. In this work, the "Tombul" genome was partially sequenced by next-generation sequencing technology yielding 29.2% (111.85 Mb) of the similar to 385 Mb (1C). This sequence information was used to develop genetic markers in order to enable differentiation of material before the long maturation process and to facilitate future breeding strategies. A total of 90,142 simple sequence repeats (SSRs) were identified in the contigs giving a frequency of 1 SSR per 1240 nt in the assembly. Mononucleotides were the most abundant SSR marker type (60.9%) followed by di- and trinucleotides. Primer pairs were designed for 75,139 (83.3%) of the SSRs. Fifty SSR primers were applied to 47 hazelnut accessions from nine countries to test their effectiveness and polymorphism. The markers amplified an average of 3.2 fragments. The highest polymorphism information content value was for cavSSR11062 (0.97) and the lowest (0.04) was for cavSSR13386. Two markers were monomorphic: cavSSR12855 and cavSSR13267. Single-copy SSR primers were also assessed for their ability to discriminate 19 Turkish cultivars, and it was found that seven primer pairs (Cav4217, Cav14875, Cav14418, Cav2704, Cav12862, Cav3909, Cav1361) were sufficient for this task. Thus, this study developed new SSR markers for use in hazelnut breeding and genetic studies and also provide a method to distinguish and identify true-type Turkish cultivars.