Utilization of Wild Relatives in Genetic Improvement of Arachis hypogaea L. VI. Fertility in Triploids: Cytological Basis and Breeding Implications¹

The triploid hybrids between Arachis hypogaea L. and diploid species of section Arachis nom. nud. which had been observed to be sterile at Reading, England, produced pegs and pods at the ICRISAT Center. Cytological investigations of these and other triploid hybrids revealed (1) spindle abnormalities resulting in restitution nuclei and unreduced gametes, and (2) unequal segregation of chromosomes resulting in haploid to hyperdiploid gametes. Of the 225 F₂ plants derived from triploids, 82% were hexaploid, 8% were tetraploid, and 10% had chromosome numbers from 20–59. This indicates that the above processes occurred both at micro- and mega-sporogenesis and that unreduced gametes were more effective in fertilization resulting in a higher percentage of hexaploid progenies. The implications of these results are that triploids can be used in Arachis interspecific breeding for increased recombination between chromosomes and quick recovery of Arachis hypogaea like tetraploid lines.