Moneim Fatih

Genetic diversity in watermelon (Citrullus lanatus) landraces from Zimbabwe revealed by RAPD and SSR markers.

Low polymorphism in cultivated watermelon has been reported in previous studies, based mainly on US Plant Introductions and watermelon cultivars, most of which were linked to breeding programmes associated with disease resistance. Since germplasm sampled in a putative centre of origin in southern Africa may harbour considerably higher variability, DNA marker-based diversity was estimated among 81 seedlings from eight accessions of watermelon collected in Zimbabwe; five accessions of cow-melons (Citrullus lanatus var. citroides) and three of sweet watermelons (C. lanatus var. lanatus). Two molecular marker methods were used, random amplified polymorphic DNA (RAPD) and simple sequence repeats (SSR) also known as microsatellite DNA. Ten RAPD primers produced 138 markers of which 122 were polymorphic. Nine SSR primer pairs detected a total of 43 alleles with an average of 4.8 alleles per locus. The polymorphic information content (PIC) ranged from 0.47 to 0.77 for the RAPD primers and from 0.39 to 0.97 for the SSR loci. Similarity matrices obtained with SSR and RAPD, respectively, were highly correlated but only RAPD was able to provide each sample with an individual-specific DNA profile. Dendrograms and multidimensional scaling (MDS) produced two major clusters; one with the five cow-melon accessions and the other with the three sweet watermelon accessions. One of the most variable cow-melon accessions took an intermediate position in the MDS analysis, indicating the occurrence of gene flow between the two subspecies. Analysis of molecular variation (AMOVA) attributed most of the variability to within-accessions, and contrary to previous reports, sweet watermelon accessions apparently contain diversity of the same magnitude as the cow-melons.

Phylogenetic analysis of the genus Sorghum based on combined sequence data from cpDNA regions and ITS generate well-supported trees with two major lineages

BACKGROUND AND AIMS Wild Sorghum species provide novel traits for both biotic and abiotic stress resistance and yield for the improvement of cultivated sorghum. A better understanding of the phylogeny in the genus Sorghum will enhance use of the valuable agronomic traits found in wild sorghum. METHODS Four regions of chloroplast DNA (cpDNA; psbZ-trnG, trnY-trnD, trnY-psbM and trnT-trnL) and the internal transcribed spacer (ITS) of nuclear ribosomal DNA were used to analyse the phylogeny of sorghum based on maximum-parsimony analyses. KEY RESULTS Parsimony analyses of the ITS and cpDNA regions as separate or combined sequence datasets formed trees with strong bootstrap support with two lineages: the Eu-sorghum species S. laxiflorum and S. macrospermum in one and Stiposorghum and Para-sorghum in the other. Within Eu-sorghum, S. bicolor-3, -11 and -14 originating from southern Africa form a distinct clade. S. bicolor-2, originally from Yemen, is distantly related to other S. bicolor accessions. CONCLUSIONS Eu-sorghum species are more closely related to S. macrospermum and S. laxiflorum than to any other Australian wild Sorghum species. S. macrospermum and S. laxiflorum are so closely related that it is inappropriate to classify them in separate sections. S. almum is closely associated with S. bicolor, suggesting that the latter is the maternal parent of the former given that cpDNA is maternally inherited in angiosperms. S. bicolor-3, -11 and -14, from southern Africa, are closely related to each other but distantly related to S. bicolor-2.

Elucidating the genetic diversity of farmer cultivars of female date palms (Phoenix dactylifera L.) from Sudan by microsatellite markers

Genetic diversity in female date palms for a total of 89 tree samples, representing 18 cultivar groups, was investigated using 10 loci of microsatellite (SSR) primers. The microsatellites examined showed high polymorphism, a total of 126 for the 10 microsatellite loci, giving an average of 12.6. Low FST values were observed among different fruit classification groups of Sudanese date palms (soft, semi-soft and dry) suggesting that the observed high genetic variability is maintained locally within cultivars. Across all genetic parameters, in comparison among the cultivar groups, the Jaw group was consistently highly variable followed by Korsha, Gondela and Barakawi, respectively. Multivariate analysis of the 89 date palms showed some strong relationships with some mixed grouping, showing a tendency of relate fruit classification and related genotypes. Dry dates almost grouped together while the soft and semi-soft were mixed and somewhat related to genotypes. The effect of genotype was highly supported by the relationship of 14 cultivar groups, in which similar cultivars were associated regardless of the state to which they belong. Further detailed analyses of female date palm populations from different geographic locations represented by a minimum of five plants per cultivar is necessary to provide the basis for understanding of the date palm genomes, revealing the true extent of gene flow between farmer cultivars.