Abstract
Two exotic Valencia groundnut ( Arachis hypogaea L.) breeding lines (NuMex-M 3 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 F 1 , F 2 , BC 1 P 1 and BC 1 P 2 populations, together with their parents (P 1 and P 2 ) of each of the six crosses, namely Valencia C (P 1 ) × ICGV-SM 90704 (P 2 ), Valencia C (P 1 ) × ICGV-SM 96801(P 2 ), Valencia C (P 1 ) × ICGV-SM 99566 (P 2 ), NuMex-M 3 (P 1 ) × ICGV-SM 90704 (P 2 ), NuMex-M 3 × ICGV-SM 96801 (P 2 ), and NuMex-M 3 (P 1 ) × ICGVSM 99566 (P 2 ), 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 × additive [i], additive × dominance [j] and dominance × dominance [l],were exhibited tocontrol GRD resistance. The component dominance × dominance [l] was more predominant in Valencia C × ICGV-SM 96801, NuMex-M 3 × ICGV-SM 96801, NuMex- M 3 × ICGV-SM 90704, NuMex-M 3 × ICGV-SM 99566 and Valencia C × ICGV-SM 99566 crosses. Opposite and significant signs of dominance [d] and dominance × 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. Keywords: Arachis hypogaea , gene effects, GRD resistance
Highlights
Development of improved cultivars requires understanding of the nature of gene action governing key traits, such as groundnut rosette disease (GRD) resistance in the germplasm used for breeding
Results on gene effects are presented in (Table 3).There was a significant contribution of additive gene effects [a] in controlling resistance to GRD in all the crosses, except for NuMex-M × ICGV-SM 96801 (Table 3)
Dominance × dominance (l) gene effects were siginficant in Valencia C × ICGV-SM 96801,NuMex-M3 × ICGV-SM 96801,NuMex-M3 × ICGV-SM 90704 and NuMex-M × ICGV-SM
Summary
Development of improved cultivars requires understanding of the nature of gene action governing key traits, such as groundnut rosette disease (GRD) resistance in the germplasm used for breeding. There is limited information on the nature and type of gene interactions exististing in groundnuts (Arachis hypogaea L.), for GRD resistance. This information is necessary for planning appropriate breeding and selection strategies (Zhang et al, 2005; Wambi et al, 2014). The process of emasculation and pollination to generate BC P and BC P seeds, was done as ICGV-SM 99566 ICGV-SM 90704 ICGV-SM 96801 Valencia C NuMex- M3 Acholi white a Genotype described for generation F1s above. The parents were crossed to generate more F1 seeds as described above
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