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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 Sho- bak (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. [ABSTRACT FROM AUTHOR]

The results of the first detailed screening of a resistance to Bremia lactucae in naturally growing populations of Lactuca saligna are presented here. In total, 146 accessions from 25 populations of L. saligna originating in Israel ( N = 136), France ( N = 8), Jordan ( N = 1) and Turkey ( N = 1) were tested at seedling stage for their resistance to 10 highly virulent isolates (races) of B. lactucae from Lactuca sativa (DEG2, Bl:5, Bl:15, Bl:16, Bl:17, Bl:18, Bl:21, Bl:22, Bl:24 and Bl:25). Our study strongly supports the suggestion that L. saligna is indeed generally highly resistant to B. lactucae. However, our results provide evidence that at least at a seedling stage L. saligna may not be a non-host plant for B. lactucae, as was hypothesised for approximately the last 30 years. Some accessions expressed a differential (i.e. race-specific) response, which accords with other recently published data for this Lactuca species. Furthermore, some geographical differences in race-specific resistance were observed, too. Tests performed at an adult-plant stage, however, did not prove race-specificity of the respective accessions. To summarise, what is behind the race-specific character of the responses observed at a seedling stage is still uncertain, as is its comparability with the race-specific resistance of some other Lactuca species such as L. sativa or L. serriola. The presence of plant stage-dependent resistance, governed by a combined effect of different quantitative trait loci in young and adult plants of L. saligna, is discussed. [ABSTRACT FROM AUTHOR]