HERITABILITY FOR RESISTANCE TO ROSETTE DISEASE IN EXOTIC VALENCIA GROUNDNUTS

Groundnut rosette disease (GRD) is the most destructive virus disease of Valencia groundnuts ( Arachis hypogaea L.) in sub-Saharan Africa. Cultural, biological and chemical control measures have received limited success due to small scale farmers\u2019 inability to use them. Use of host plant resistance provides the most effective and economically viable management option for the resource poor farmers. This study was conducted to determine heritability for resistance to GRD in Valencia groundnuts. Six crosses; 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 made to generate F1, F2, BC1P1 and BC1P2 populations. Data on GRD severity were collected on a 1-9 score scale. Genetic Advance as a percentage of the mean (GAM) and heritability were estimated using variance components. Phenotypic Coefficient of Variation (PCV) and Genotypic Coefficient of Variation (GCV) estimates were high (20.04-70.1%) in the six crosses, except for Valencia C 7 ICGV-SM 96801(18.1%) and NuMex-M3 7 ICGV-SM 96801(17.1%), which exhibited moderate GCV values. Broad and narrow sense heritability estimates for GRD disease score ranged from 64.1 to 73.7% and 31 to 41.9%, respectively, in all the crosses. GAM was high in all the crosses (21-50.7%), except for Valencia C x ICGV-SM 96801 (14.67), M3 x ICGV-SM 99566 (18%) and NuMex-M3 x ICGV-SM 96801 (13.5%) crosses that exhibited moderate GAM. The study revealed the presence of variability of GRD resistance, implying that genetic improvement of these exotic materials is possible.La maladie de rosette chez l\u2019arachide ( Arachis hypogaea L.) est la plus destructive des maladies virales chez les vari\ue9t\ue9s Valencia en Afrique au sud du Sahara. Les moyens de lutte culturale, biologique et chimique pr\ue9sentent des limitations surtout li\ue9es \ue0 l\u2019inhabilit\ue9 des petits producteurs \ue0 les mettre en pratique. L\u2019utilisation de vari\ue9t\ue9s resistantes repr\ue9sente le moyen le plus efficace et \ue9conomiquement viable pour les petits producteurs. La pr\ue9sente \ue9tude a \ue9t\ue9 conduite afin de d\ue9terminer l\u2019h\ue9ritabilit\ue9 de la r\ue9sistance \ue0 la maladie de rosette chez les vari\ue9t\ue9s d\u2019arachide Valencia. Six croisements; 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 effectu\ue9s afin de g\ue9n\ue9rer F1, F2, BC1P1 et BC1P2 populations. Des donn\ue9es ont \ue9t\ue9 collect\ue9es sur le degr\ue9 s\ue9v\ue9rit\ue9 de GRD en se servant d\u2019une \ue9chelle de 1-9. Les param\ue8tres d\u2019avanc\ue9e g\ue9n\ue9tique exprim\ue9e en pourcentage de la moyenne (GAM) et h\ue9ritabilit\ue9 ont \ue9t\ue9 estim\ue9s \ue0 partir de composantes de variance. Le coefficient de variation ph\ue9notypique (PCV) et g\ue9notypique (GCV) estim\ue9s \ue9taient \ue9lev\ue9s (20,04-70,1%) dans les six croisements, sauf pour Valencia C 7 ICGV-SM 96801(18,1%) et NuMex-M3 7 ICGV-SM 96801(17,1%), o\uf9 les valeurs de GCV \ue9taient mod\ue9r\ue9es. Les valeurs de l\u2019h\ue9ritabilit\ue9 au sens large et au sens strict pour la r\ue9sistance \ue0 GRD variaient respectivement de 64,1 \ue0 73,7% et de 31 \ue0 41,9%, au niveau de tous les croisements. Les valeurs de GAM \ue9taient \ue9lev\ue9es au niveau de tous les croisements (21-50,7%), sauf pour les croisements Valencia C x ICGV-SM 96801 (14,67), M3 x ICGV-SM 99566 (18%) et NuMex-M3 x ICGV-SM 96801 (13,5%) o\uf9 les valeurs de GAM \ue9taient mod\ue9r\ue9es. L\u2019\ue9tude a r\ue9v\ue9l\ue9 l\u2019existence dans la r\ue9sistance au GRD, ceci implique qu\u2019il est possible d\u2019entreprendre l\u2019am\ue9lioration g\ue9n\ue9tique de ces mat\ue9riels