Arachis Assemble: Recruiting New Heroes for Peanut Leaf Spot Resistance

Early leaf spot, caused by the fungal pathogen Passalora arachidicola, threatens peanut (Arachis hypogea) production, leading to severe defoliation and substantial yield losses. Fungicide applications are commonly used to manage this disease, but this practice increases production costs, the risk of fungicide resistance, and environmental concerns. Only moderate levels of early leaf spot resistance have been identified within the cultivated peanut germplasm, but disease resistance has been identified in the peanut crop wild relatives, Arachis species. Due to ploidy differences, these species can be introgressed into cultivated lines when hybridized and tetraploidized, generating new allotetraploids. This study evaluates early leaf spot resistance in thirteen wild peanut genotypes and thirteen new wild allotetraploids. Resistance was assessed through in-vitrodetached leaf bioassays measuring six components, most were highly correlated (r = 0.37-0.92; P<0.001). Four allotetraploids (MagDio1, MagnaKuhlmannii, MagnaHoehnei1, and ValMicro1) and one wild diploid (A. hoenhnei) developed fewer lesions with no sporulation and had reduced disease progression compared to the controls. Between genotypes varying levels of resistance in each component were observed, mainly lesion development and sporulation, demonstrating the diversity of alleles in wild species. These results underscore the potential of wild Arachis species as valuable sources of resistance for multiple epidemiological aspects of early leaf spot.