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.
Local seed systems that are developed, managed and maintained by farmers are a fundamental practice in smallholder crop production, supporting more than 80% of farmers in sub-Saharan Africa and feeding more than 70% of its population. The resilience of such systems is under threat from poverty, climate change, drought, increased pests and diseases, over-promotion of modern crop varieties, change of lifestyles and restrictive seed policies. The system continues to be maligned as having inferior quality, yet few studies support this assertion. This study aims to fill this research gap by evaluating 60 sorghum seed samples collected from smallholder farmers in Uzumba-MarambaPfungwe and Chimanimani districts of Zimbabwe. We investigated the effect of farmer-led seed management practices (e.g. seed acquisition and seed storage practices) on farm-derived sorghum seed quality (moisture, germination and fungal incidences). We found farmers using diverse seed sources and seed storage practices. Seeds were typically of good quality in that their storage moisture content was low, their germination was high, and fungal incidences were low. Seed sourced from local markets, non-governmental organizations and other farmers had germination and moisture standards that met the sorghum certification standards in Zimbabwe. However, few samples obtained from the relatives and government failed to meet the germination and/or moisture certification standards. We detected low incidences of fungi (Aspergillus flavus, Aspergillus niger, Curvularia lunata, Fusarium sp. and Penicillium sp.) in sorghum seed samples tested and in particular Fusarium sp., which is the most economic important fungus in sorghum production. We conclude that farmer-led seed systems have the capacity to supply seeds of good quality and recommend that such systems should be recognized and promoted to meet the ever-evolving needs of smallholder farmers in sub-Saharan Africa.
The aim of this study was to apply some of the vegetative and fruit traits which are easily recognised to identify the variation and the diversity level of the most famous Sudanese date palm cultivars grown on farm in the northern region of Sudan. Sixteen phenotypic traits consisting of ten quantitative and six qualitative characteristics were used for describing the vegetative and fruit characteristics. The principal components analysis (PCA) and UPGMA clustering were used to analyse the data set. The results revealed high variability among the cultivars according to PCA. Fourteen out of the sixteen quantitative and qualitative traits investigated showed a strong discriminating factor suggesting their possible uses in the initiation of Sudanese date palm morphological descriptor list. UPGMA clustering exhibited strong relationship between some cultivars according to their fruit and vegetative characteristics similarity. Based on morphological traits, cultivars Wad-laggi (Lag) and Wad-khateeb (Kha) formed a distinct group suggesting their close relatedness. Similarly, the cultivars sharing the dry fruit texture such as Gondaila (Gon), Tamoda (Tam), Kolmah (Kol), and Barkawi (Bar) were grouped together according to their vegetative traits. Further investigations on Sudanese date palm using more phenotypic characteristics are recommended in order to shape and complete the set of the morphological descriptor list.
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