Low Genetic Diversity Indicates the Need to Broaden the Genetic Base of Cultivated Watermelon

Levi, Amnon; Thomas, C. A.; Wehner, Todd C.; Zhang, Xingping

doi:10.21273/hortsci.36.6.1096

Cited by 125 publications

(106 citation statements)

References 21 publications

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“…In contrast, germplasm collections of watermelon (Levi and Thomas 2001) and peanut (Kochert et al 1991;Lanham et al 1992;He and Prakash 2001) typically report levels of genetic diversity that are as low, or lower than those found in castor bean (but also see Hopkins et al 1999). These results suggest that genetic diversity in germplasm collections may in fact differ substantially and that the differences observed in genetic variation may simply be taxon specific.…”

Section: Worldwide Genetic Diversity In Castor Bean Germplasmmentioning

confidence: 97%

Worldwide genotyping of castor bean germplasm (Ricinus communis L.) using AFLPs and SSRs

Allan

Williams

Rabinowicz³

et al. 2007

Genet Resour Crop Evol

102

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Worldwide genetic diversity in 200 individuals comprising 41 castor bean accessions was assessed using amplified fragment polymorphisms (AFLPs) and simple sequence repeats (SSRs). We found that, despite surveying five continents and 35 countries, genetic diversity in castor bean germplasm is relatively low (overall H e = 0.126 for AFLPs and 0.188 for SSRs) compared to estimates of genetic diversity in other plant species. Our data also show no geographic structuring of genotypes across continents or countries within continents. An assessment of the congruence between AFLP and SSRs indicates a low correlation (R 2 = 0.19) between the two data sets, but each marker class nonetheless shows similar patterns of low-genetic diversity and a lack of geographic structure. Our data do suggest that SSRs yield a higher percentage of polymorphic loci, higher heterozyosity and a greater range of genetic distances, and are therefore more informative than are AFLPs on a locus-by-locus basis. Based on comparisons with numerous other plant species, we suggest that the lower genetic variation in this worldwide collection may be due to one or more factors including: sampling strategies that have not captured the full extent of genetic variation in the species; artifactual variation due to long-term germplasm storage and seed regeneration; or intense selection followed by domestic cultivation of a limited number of castor bean genotypes, which are widely propagated for their horticultural and agro-economic value.

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Section: Worldwide Genetic Diversity In Castor Bean Germplasmmentioning

confidence: 97%

Worldwide genotyping of castor bean germplasm (Ricinus communis L.) using AFLPs and SSRs

Allan

Williams

Rabinowicz³

et al. 2007

Genet Resour Crop Evol

102

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“…Seeds from C. ecirrhosus and C. rehmii C. lanatus were obtained through B&T World Seeds. Cultivars and accessions were selected based on dendrograms using simple sequence repeat (SSR) polymorphism (Jarret et al 1997) or random amplified polymorphic DNA (RAPD) marker polymorphisms (Levi et al 2001). More than 55 C. lanatus accessions from widely different geographical areas were selected (Table 1).…”

Section: Plant Materialsmentioning

confidence: 99%

Comparative analysis of chloroplast DNA variability in wild and cultivated Citrullus species

2003

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PCR amplification and restriction site analysis of chloroplast (cp) DNA regions was used to detect inter- and intraspecific differences in the genus Citrullus. More than 55 C. lanatus and 15 C. colocynthis accessions collected from diverse geographical areas, C. ecirrhosus and C. rehmii were used. Most of the cpDNA variation within Citrullus was the result of large indels and transitions and transversions. Indels at the ndhA, trnS- trnfM and trnC- trnD regions and several substitutions at restriction enzyme sites can be used to separate C. colocynthis from the other Citrullus species. A nucleotide substitution at a restriction enzyme site at the 3' flanking region of ndhF provided a diagnostic haplotype for C. lanatus var. lanatus, the cultivated watermelon. Similarly, a nucleotide substitution at an intergenic spacer region of the trnC- trnD region resulted in a diagnostic haplotype for citron, C. lanatus var. citroides. Several C. lanatus var. citroides accessions showed the var. lanatus haplotype. C. rehmii showed almost the same haplotype as C. lanatus var. citroides with the exception of a unique insertion at a cpSSR site. Since C. ecirrhosus lacks the derived diagnostic nucleotide substitutions of C. lanatus, it is probably the progenitor of the cultivated watermelon. Intraspecific haplotypes detected within C. colocynthis were associated with geographic origin.

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“…However, genetic diversity within watermelon cultivars is low. For example, Levi et al (2001b) found high genetic similarity values (92-99%) among watermelon cultivars, which make them especially vulnerable to attacks by the large numbers of diseases of insect pests of watermelon. Therefore, in China, there are increasing interests from both growers and watermelon breeders in introducing new germplasm from different geographical regions to enhance watermelon genetic diversity.…”

Section: Introductionmentioning

confidence: 99%

Identification and validation of a core set of microsatellite markers for genetic diversity analysis in watermelon, Citrullus lanatus Thunb. Matsum. & Nakai

et al. 2011

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Watermelon, Citrullus lanatus Thunb. Matsum. & Nakai is an important vegetable crop worldwide. Due to its narrow genetic base, detection and utilization of the genetic variations, cultivar identification and increasing genetic diversity are some important tasks for watermelon breeders. Molecular markers, especially microsatellites or simple sequence repeats (SSRs) are playing increasingly important roles for these purposes. In the present study, a core set of 23 highly informative SSR markers was developed for watermelon genetic diversity analysis. Based on whole genome sequencing of 17 watermelon inbred lines, we identified 3.9 million single nucleotide polymorphisms (SNPs) which were used to construct a SNP-based dendrogram for the 17 lines. Meanwhile, from the sequenced genome, 13,744 SSRs were developed, of which 704 were placed on a high-resolution watermelon linkage map. To develop the core set SSR markers, 78 of the 704 mapped SSRs were selected as the candidate markers. Using the SNPbased dendrogram as calibration, 23 SSR markers evenly distributed across the genome were identified as the core marker set for watermelon genetic diversity analysis. Each marker was able to detect 2-7 alleles with polymorphism information content values ranging from 0.45 to 0.82. The dendrograms of 17 watermelon lines based on SNPs, the base set of 78 SSRs and the core set of 23 SSRs were highly consistent. The utility of this core set SSRs was demonstrated in 100 commercial watermelon cultivars and elite lines, which could be placed into six clusters that were largely consistent with previous classification based on morphology and parentage data. This core set of SSR markers should be very useful for genotyping and genetic variation analysis in watermelon.

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Low Genetic Diversity Indicates the Need to Broaden the Genetic Base of Cultivated Watermelon

Cited by 125 publications

References 21 publications

Worldwide genotyping of castor bean germplasm (Ricinus communis L.) using AFLPs and SSRs

Worldwide genotyping of castor bean germplasm (Ricinus communis L.) using AFLPs and SSRs

Comparative analysis of chloroplast DNA variability in wild and cultivated Citrullus species

Identification and validation of a core set of microsatellite markers for genetic diversity analysis in watermelon, Citrullus lanatus Thunb. Matsum. & Nakai

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