title: Evidence of Genomic Exchanges between Homeologous Chromosomes in a Cross of Peanut with Newly Synthetized Allotetraploid Hybrids.
abstract: Cultivated peanut and synthetics are allotetraploids (2n= 4x= 40) with two homeologous sets of chromosomes. Meiosis in allotetraploid peanut is generally thought to show diploid-like behavior. However, a recent study pointed out the occurrence of recombination between homeologous chromosomes, especially when synthetic allotetraploids are used, challenging the view of disomic inheritance in peanut. In this study, we investigated the meiotic behavior of allotetraploid peanut using 380 SSR markers and 90 F2progeny derived from the cross betweenArachis hypogaeacv Fleur 11 (AABB) and ISATGR278-18 (AAKK), a synthetic allotetraploid that harbors a K-genome that was reported to pair with the cultivated B-genome during meiosis. Segregation analysis of SSR markers showed 42 codominant SSRs with unexpected null bands among some progeny. Chi-square tests for these loci deviate from the expected 1:2:1 Mendelian ratio under disomic inheritance. A linkage map of 357 codominant loci aligned on 20 linkage groups (LGs) with a total length of 1728 cM, averaging 5.1 cM between markers, was developed. Among the 10 homeologous sets of LGs, one set consisted of markers that all segregated in a polysomic-like pattern, six in a likely disomic pattern and the three remaining in a mixed pattern with disomic and polysomic loci clustered on the same LG. Moreover, we reported a substitution of homeologous chromosomes in some progeny. Our results suggest that the homeologous recombination events occurred between the A and K genomes in the newly synthesized allotetraploid and have been highlighted in the progeny. Homeologous exchanges are rarely observed in tetraploid peanut and have not yet been reported for AAKK and AABB genomes. The implications of these results on peanut breeding are discussed.
authors.affiliation: Centre d'Etudes Régional pour I'Amélioration de I'Adaptation à la Sécheresse Thies, Senegal.
authors.forename: Joel R
authors.initials: JR
authors.lastname: Nguepjop
authors.affiliation: Centre d'Etudes Régional pour I'Amélioration de I'Adaptation à la Sécheresse Thies, Senegal.
authors.forename: Hodo-Abalo
authors.initials: HA
authors.lastname: Tossim
authors.affiliation: Département de Biologie et Physiologie Végétales, Université de Yaoundé I Yaoundé, Cameroon.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Bell
authors.affiliation: UMR AGAP, Centre de Coopération Internationale en Recherche Agronomique pour le Développement Montpellier, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Rami
authors.affiliation: International Crops Research Institute for the Semi-Arid Tropics Patancheru, India.
authors.forename: Shivali
authors.initials: S
authors.lastname: Sharma
authors.affiliation: Centre d'Etudes Régional pour I'Amélioration de I'Adaptation à la Sécheresse Thies, Senegal.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Courtois
authors.affiliation: International Crops Research Institute for the Semi-Arid Tropics Patancheru, India.
authors.forename: Nalini
authors.initials: N
authors.lastname: Mallikarjuna
authors.affiliation: Département de Biologie Végétale, Université Cheikh Anta Diop Dakar, Senegal.
authors.forename: Djibril
authors.initials: D
authors.lastname: Sane
authors.affiliation: Centre d'Etudes Régional pour I'Amélioration de I'Adaptation à la SécheresseThies, Senegal; UMR AGAP, Centre de Coopération Internationale en Recherche Agronomique pour le DéveloppementMontpellier, France.
authors.forename: Daniel
authors.initials: D
authors.lastname: Fonceka
keywords: allotetraploid; breeding; disomic; genetic map; inheritance; peanut; polysomic