The Journal of Heredity 2000:91(4)
© 2000 The American Genetic Association 91:322-325
Distorted segregation resulting from pea chromosome reconstructions with alien segments from Pisum fulvum
1Department of Agronomy and Plant Genetics, University of Naples 'Federico II', Portici, Italy 2CNR-IMOF, Research Institute for Vegetable and Ornamental Plant Breeding, Via Università 133, 80055 Portici, Italy *Corresponding author E-mail: conicell@unina.it
Pea (Pisum sativum L.) satellited chromosome reconstructions were analyzed by cytologic markers to identify segregation distortion events. The presence of modified chromosomes was evaluated on the basis of additional rDNA genes, an extra and a longer satellite, all derived from chromosome 5 and chromosome 7 from P. fulvum Sibth. & Sm. The segregation of modified satellited chromosome 5 was monitored through fluorescent in situ hybridization with rDNA probe; it fitted the expected 1:2:1 ratio after self-pollination of a heterozygous genotype for modified chromosome 5. In different genotypes, which were heterozygous for both modified chromosomes 5 and 7, the combined segregation of these chromosomes showed the occurrence of seven karyotype classes instead of the expected nine. The classes with modified chromosome 7 and without modified chromosome 5, whether heterozygous or homozygous, were absent. The hypothesis of gamete selection was rejected since the expected segregation ratio of 5:3:1 was significant by chi-square test. Based on the other hypothesis of postzygotic selection, the segregation ratio did not show a significant deviation from the expected 9:3:1 ratio, thereby indicating that embryo abortion caused the segregation distortion (SD). The hypothesis of the SD system involving two loci carried by the alien satellites of modified chromosomes 5 and 7 is discussed in relation to the evolution of the P. fulvum genome.
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