Leveillula lactucae-serriolae on Lactuca serriola in Jordan

Abstract

Jordan contributes significantly to the Near East plant biodiversity with numerous primitive forms and species of crops and their wild relatives. Prickly lettuce (Lactuca serriola) is a common species in Jordan, where it grows in various habitats. During a survey of wild Lactuca distribution in Jordan in August 2007, plants of L. serriola with natural infections of powdery mildew were observed at a site near Shobak (Ma’an Governorate). Lactuca serriola leaf samples with powdery mildew infections were collected from two plants and the pathogen was analyzed morphologically. Characteristics of the asexual and sexual forms were obtained. Sequence analyses of the rDNA ITS region and D1/D2 domains of the 28S rDNA were used to obtain phylogenetic data, and to reach taxonomic conclusions about these specimens. Molecular determination, performed by sequencing of the ITS region, proved its identity with the type material of Leveillula lactucae-serriolae. Sequencing of the 28S rDNA region provided the first verified GenBank record of Leveillula lactucae-serriolae deposited in this public nucleotide repository. This is the first taxonomically verified record of L. lactucae-serriolae on L. serriola growing wild in Jordan, and one of the first records of the fungus in the Near East.

Keywords

• Lettuce powdery mildew
• morphology
• Near East
• prickly lettuce
• ITS and and 28S rDNA region