Genetic analysis of Citrus aurantium L. (Rutaceae) cultivars by ISSR molecular markers

Abstract

Eight cultivars of Citrus aurantium L., showing peculiar morphological traits of the fruits and leaves, were analyzed genetically. Inter simple sequence repeat (ISSR) was chosen as molecular markers because they represent a highly efficient system for investigating variability at intraspecific level. The particular morphological traits were discussed, the genetic identity and distance matrix based on Nei index was calculated, and the unweighted pair group method with arithmetic mean (UPGMA) dendrogram was generated. A total of 53 clearly distinguished DNA bands were considered for the ISSR analysis of which 24 were polymorphic. A basic C. aurantium fingerprinting pattern was obtained. The ISSR profiles allowed to discriminate only two cultivars, while the other six ones did not show polymorphisms, although their phenotypes were notably different, indicating that mutations must have occurred without significantly modifying the DNA length between the simple sequence repeats. The results showed a very low level of genetic variability among the cultivars; ‘‘Canaliculata’’ formed a separated cluster with C. sinensis Osbeck, suggesting a probable hybrid origin derived from crossing between sour and sweet orange. This study confirmed the reliability and reproducibly of ISSR markers for Citrus fingerprinting purposes, although some morphological differences could not be detected; therefore, both morphological and genetic characters must be considered for cultivar or variety identification.