Simple sequence repeats in watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai).
Simple sequence repeat length polymorphisms were utilized to examine genetic relatedness among accessions of watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai). A size-fractionated TaqI genomic library was screened for the occurrence of dimer and trimer simple sequence repeats (SSRs). A total of 96 (0.53%) SSR-bearing clones were identified and the inserts from 50 of these were sequenced. The dinucleotide repeats (CT)n and (GA)n accounted for 82% of the SSRs sequenced. PCR primer pairs flanking seven SSR loci were used to amplify SSRs from 32 morphologically variable watermelon genotypes from Africa, Europe, Asia, and Mexico and a single accession of Citrullus colocynthis from Chad. Cluster analysis of SSR length polymorphisms delineated 4 groups at the 25% level of genetic similarity. The largest group contained C. lanatus var. lanatus accessions. The second largest group contained only wild and cultivated "citron"-type or C. lanatus var. citroides accessions. The third group contained an accession tentatively identified as C. lanatus var. lanatus but which perhaps is a hybrid between C. lanatus var. lanatus and C. lanatus var. citroides. The fourth group consisted of a single accession identified as C. colocynthis. "Egusi"-type watermelons from Nigeria grouped with C. lanatus var. lanatus. The use of SSRs for watermelon germplasm characterization and genetic diversity studies is discussed.
Jarret
R L
RL
United States Department of Agriculture, Agricultural Research Service, Plant Genetic Resources, Griffin, GA 30223, USA.
Merrick
L C
LC
Holms
T
T
Evans
J
J
Aradhya
M K
MK
D018744:DNA, Plant / Q000235:genetics*; D010945:Plants, Edible / Q000235:genetics*; D012150:Polymorphism, Restriction Fragment Length; D012091:Repetitive Sequences, Nucleic Acid
D018744:DNA, Plant