Evaluation of apple cultivars to four pome fruit viruses in Iranian National Collection of Kamalshahr Horticulture Research Station, Karaj

Abstract

Abstract The National Iranian Apple Collection comprises a wide range of native and imported commercial cultivars used for breeding researches. Successful phenotyping requires healthy plants capable of expressing the existing genetic potential. The time-consuming and expensive process of producing healthy primary nucleus may be avoided by a primitive screening of the plant material. Indeed, the new young shoots grown next to heavy pruning under high regional solar radiation may act as in vivo thermotherapy. A total of 98 samples collected from 48 apple cultivars were assessed to detect the occurrence and prevalence of lethal viruses such as Apple stem pitting virus, Apple chlorotic leaf spot virus, Apple stem grooving virus and Tomato ring spot virus. The presence of ASPV, ACLSV, ASGV and ToRSV was tested by DAS ELISA using specific antibodies. To confirm ELISA results, all virus-free samples, or ones suspected of being infected by a sole virus, were consequently subjected to reverse transcription polymerase chain reaction (RT-PCR). This was achieved by the use of specific primers for a region of the ACLSV and ASPV genomes which encode part of the coat protein (CP), specific primers for full length CP of ASGV, and specific primers for a region of the ToRSV genome which encodes part of the replicase. The ELISA results demonstrated that 71.4%, 47.5% and 18.5% of the samples in total were infected by ACLSV, ASPV, and ASGV respectively. No infection by ToRSV was observed within the tested cultivars. The integration of ELISA results with RT-PCR proved that McIntosh1, Starking1, Red spur cooper2, Yellow transparent1, and Glockenapfel were recognized virus-free material, and therefore could be used and maintained as primary nucleus and healthy mother orchards.