A polymerase chain reaction and single-strand conformation polymorphism determination (PCR-SSCP) was used to detect deoxyribonucleic acid sequence polymorphisms in the transcribed non-coding regions between the small and large sub-unit ribosomal ribonucleic acid (rRNA) genes in Leishmania donovani from 63 clinical samples collected in eastern Sudan, between April 1997 and October 1998. Specific Leishmania primers were used to amplify the internal transcribed spacer (ITS) regions of L. donovani isolates directly from clinical samples spotted on filter papers. Amplification products were subsequently analysed by SSCP. Eleven polymorphic patterns were detected in the first part of the spacer, the ITS1 region, and were sequenced. Most of the changes were due to deletions of adenine bases and AT pairs within the first 192 nucleotides of the ITS region. This is the first application of PCR-linked SSCP analysis for the detection of population variation with direct display of sequence variation in parasitologically positive clinical samples spotted on filter paper. Culturing the parasite is thus not required, which is beneficial particularly in epidemiological studies based on field work where obtaining cultures can be extremely difficult.

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Interspecific hybridization and accompanying backcross between crops and relatives have been recognized as a powerful method to broaden genetic diversity and transfer desirable adaptive traits. Crosses between radish (Raphanus sativus, RR, 2n = 18) and Brassica oleracea (CC, 2n = 18), which formed allotetraploid Raphanobrassica (RRCC, 2n = 36), initiated the construction of resynthetic allopolyploids. However, these progenies from the backcrosses between Raphanobrassica and the two diploid parents have not been well deciphered. Herein, thousands of backcrosses using both Raphanobrassica and the two diploid parents as pollen donors were employed. Several hybrids with expected (2n = 27) and unexpected chromosome numbers (2n = 26 and 2n = 36) were obtained. Fluorescence in situ hybridization (FISH) analysis with R-genome-specific sequences as probes demonstrated that the genome structures of the two expected hybrids were RRC and CCR, and the genome structures of the three unexpected hybrids were RRRC, CCCR, and RRC’ (harbouring an incomplete C genome). The unexpected hybrids with extra R or C genomes showed similar phenotypic characteristics to their expected hybrids. FISH analysis with C-genome-specific sequences as probes demonstrated that the unexpected allotetraploid hybrids exhibited significantly more intergenomic chromosome pairings than the expected hybrids. The expected and unexpected hybrids provide not only novel germplasm resources for the breeding of radish and B. oleracea but also very important genetic material for genome dosage analysis.