GENE EFFECTS FOR RESISTANCE TO GROUNDNUT ROSSETTE DISEASE IN EXOTIC VALENCIA GROUNDNUTS

Two exotic Valencia groundnut ( Arachis hypogaea L.) breeding lines (NuMex-M3 and Valencia C) with superior characteristics were introduced by National Legume Improvement Program at the National Semi-Arid Resources Research Institute (NaSARRI), from the United States of America, to broaden the Valencia germplasm base in Uganda. The materials were evaluated for biotic and abiotic stresses, but succumbed to groundnut rosette disease (GRD). For these superior lines to find utility in Uganda, they need further improvement by introducing resistance genes to GRD. A study was conducted at NaSARRI to determine nature of gene action controlling resistance to GRD, using the Exotic Valencia groundnut breeding materials.Six generations that included F1, F2, BC1P1 and BC1P2 populations, together with their parents (P1and P2) of each of the six crosses, namely Valencia C (P1) 7 ICGV-SM 90704 (P2), Valencia C (P1) 7 ICGV-SM 96801(P2), Valencia C (P1) 7 ICGV-SM 99566 (P2), NuMex-M3 (P1) 7 ICGV-SM 90704 (P2), NuMex-M3 7 ICGV-SM 96801 (P2), and NuMex-M3 (P1) 7 ICGV-SM 99566 (P2), were evaluated for GRD resistance.The study reaveled additive and non-additive gene effects in the control of GRD resistance.Three types of epistatic gene effects, viz. additive 7 additive [i], additive 7 dominance [j] and dominance 7 dominance [l],were exhibited tocontrol GRD resistance. The component dominance 7 dominance [l] was more predominant in Valencia C 7 ICGV-SM 96801, NuMex-M3 7 ICGV-SM 96801, NuMex- M3 7 ICGV-SM 90704, NuMex-M3 7 ICGV-SM 99566 and Valencia C 7 ICGV-SM 99566 crosses. Opposite and significant signs of dominance [d] and dominance 7 dominance [l] components indicated the importance of duplicate epitasis in the latter crosses in the control of GRD resistance, which revealed a complex nature of inheritance of GRD resistance.Deux nouvelles vari\ue9t\ue9s d\u2019arachide ( Arachis hypogaea L.) de la lign\ue9e Valencia (NuMex-M3 et Valencia C) ayant des traits sup\ue9rieurs, ont \ue9t\ue9 import\ue9es des Etats Unis d\u2019Am\ue9riques par le Programme National d\u2019am\ue9lioration des l\ue9gumineuses et introduites \ue0 l\u2019Institut Nationale de Recherche sur les Ressources Semi-Arides (NaSARRI), dans le but d\u2019\ue9largir la base g\ue9n\ue9tique de la lign\ue9e Valencia en Ouganda. Ce mat\ue9riel g\ue9n\ue9tique a \ue9t\ue9 \ue9valu\ue9 pour les stress biotiques et abiotiques, mais a succomb\ue9 \ue0 l\u2019attaque par la rosette d\u2019arachide (GRD). Afin que ces lign\ue9es sup\ue9rieures trouvent leur utilit\ue9 en Ouganda, il faudra les am\ue9liorer d\u2019avantage, en y introduisant des genes de r\ue9sistance au GRD. Une exp\ue9rimentation a \ue9t\ue9 conduite \ue0 NaSARRI afin de determiner l\u2019action des genes controllant la r\ue9sistance au GRD, en se servant des lign\ue9es exotiques du type d\u2019arachide Valencia. Six g\ue9n\ue9rations form\ue9es de F1, F2, BC1P1 et BC1P2 populations, et des parents (P1 and P2) de chacun des six croisements, plus pr\ue9cis\ue9ment, Valencia C (P1) 7 ICGV-SM 90704 (P2), Valencia C (P1) 7 ICGV-SM 96801(P2), Valencia C (P1) 7 ICGV-SM 99566 (P2), NuMex-M3 (P1) 7 ICGV-SM 90704 (P2), NuMex-M3 7 ICGV-SM 96801 (P2), et NuMex-M3 (P1) 7 ICGV-SM 99566 (P2), ont \ue9t\ue9 \ue9valu\ue9 pour leur r\ue9sistance au GRD. L\u2019\ue9tude a r\ue9v\ue9l\ue9 des effets additifs et non-additifs des g\ue8nes controllant la r\ue9sistance au GRD. Trois types d\u2019effets epistatiques des g\ue8nes, viz. additif 7 additif [i], additif 7 dominance [j] and dominance 7 dominance [l], ont \ue9t\ue9 observ\ue9s. La composante dominance 7 dominance [l] \ue9tait la plus pr\ue9dominante chez les croisements Valencia C 7 ICGV-SM 96801, NuMex-M3 7 ICGV-SM 96801, NuMex- M3 7 ICGV-SM 90704, NuMex-M3 7 ICGV-SM 99566 et Valencia C 7 ICGV-SM 99566. Des signes oppos\ue9s et significatives des composantes dominance [d] et dominance 7 dominance [l] ont montr\ue9 l\u2019importance de la double \ue9pistasie dans les derniers croisements pour la r\ue9sistance au GRD, indiquant ainsi la nature complexe du mode de transmission de la r\ue9sistance au GRD