RFLP analysis of chromosomal segregation in progeny from an interspecific hexaploid somatic hybrid between Solanum brevidens and Solanum tuberosum.

Abstract

Segregation of restriction fragment length polymorphism (RFLP) loci was monitored to determine the degree of homeologous pairing and recombination in a hexaploid somatic hybrid, A206, the result of protoplast fusion between Solanum tuberosum (PI 203900, a tetraploid cultivated potato) and Solanum brevidens (PI 218228), a diploid, sexually incompatible, distant relative harboring several traits for disease resistance. Somatic hybrid A206 was crossed to Katahdin, a tetraploid potato cultivar, to generate a segregating population of pentaploid progeny. Although the clones of the tetraploid S. tuberosum lines PI 203900 and Katahdin were highly polymorphic, the diploid S. brevidens clone was homozygous at all but two of the tested RFLP loci. Thus, homeologous recombination could be detected only when S. tuberosum and S. brevidens chromosomes paired and the S. brevidens homologs then segregated into separate gametes. A bias toward homologous pairing was observed for all 12 chromosomes. At least four and perhaps six chromosomes participated in homologous pairing only; each of 24 progeny contained all S. brevidens-derived RFLP markers for chromosomes 4, 8, 9 and 10. The remaining six chromosomes paired with their homolog(s) about twice as often as expected if hexaploid pairings were completely random. Where detectable with RFLPs, homeologous recombination (both single and double) occurred at a frequency of 1.31 per chromosome. Cytological observations of meiosis I in the somatic hybrid indicated that homeologous pairing had occurred. Enhanced recombinational activity was observed for chromosome 2. A specific small deletion from chromosome 4 was detected in A206 and 11 other somatic hybrids out of 14 screened.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic Diversity, QTL Mapping, and Marker-Assisted Selection Technology in Cotton (Gossypium spp.)

“…Marker-assisted selection (MAS) technology refers to any form of molecular selection that uses genetic markers to crop improvement ( Choudhary et al, 2008 ; Sebastian et al, 2012 ). Basically, depending on the goal of the research, MAS is used for the following tasks: (i) Evaluation of the purity and identity of the varietal material and the assessment of the genetic diversity of modern varieties ( Williams et al, 1993 ; Sonah et al, 2011 ), (ii) Introgression of genes/QTL loci in various MAS schemes ( Mackay, 2001 ; Hospital, 2009 ), and (iii) Combining several genes/loci of QTL donor lines into one genotype and, thus, the creation of new lines that have several useful traits ( Visscher et al, 1996 ; Hospital, 2009 ).…”