Abstract
The objective of this work was to evaluate the processes of selection in a citrus hybrid population using segregation analysis of RAPD markers. The segregation of 123 RAPD markers between 'Cravo' mandarin (Citrus reticulata Blanco) and 'Pêra' sweet orange (C. sinensis (L.) Osbeck) was analysed in a F1 progeny of 94 hybrids. Genetic composition, diversity, heterozygosity, differences in chromosomal structure and the presence of deleterious recessive genes are discussed based on the segregation ratios obtained. A high percentage of markers had a skeweness of the 1:1 expected segregation ratio in the F1 population. Many markers showed a 3:1 segregation ratio in both varieties and 1:3 in 'Pêra' sweet orange, probably due to directional selection processes. The distribution analysis of the frequencies of the segregant markers in a hybrid population is a simple method which allows a better understanding of the genetics of citrus group.
Highlights
IntroductionDifferent types of molecular markers have been used in genetic analyses of citrus with the purpose of selecting hybrids and nucellar plants (Oliveira et al, 2000), evaluating the cultivar
The objective of this work was to study the processes of selection that occurred in a citrus hybrid population using segregation analysis of RAPD markers
Plant material Through morphologic and RAPD markers, it was possible to select 94 zygotic seedlings obtained from the crossing between ‘Cravo’ mandarin (Citrus reticulata Blanco), female parental, and ‘Pêra’ sweet orange (C. sinensis (L.) Osbeck)
Summary
Different types of molecular markers have been used in genetic analyses of citrus with the purpose of selecting hybrids and nucellar plants (Oliveira et al, 2000), evaluating the cultivar. The loci analyses of molecular markers with expected or skewed Mendelian segregation for a hybrid population is an important tool for genetic studies. Studies carried out by Gmitter Junior et al (1994) and Luro et al (1996) showed that structural alterations in the genome of the parental species occurred during the speciation with a consequential failure in the pairing and, especially, the existence of recessive deleterious genes in the Citrus due to its highly heterozygous make-up have been the causes of the processes of selection. The objective of this work was to study the processes of selection that occurred in a citrus hybrid population using segregation analysis of RAPD markers
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