LAUSR

Early (ELS) and late leaf spots (LLS) are two of the most destructive diseases in peanut (Arachis hypogaea). They can cause severe plant defoliation and tremendous yield loss in the absence of fungicide applications. The high costs of fungicides, their potential for deleterious effects on the environment, the tightening of regulations and the development of fungicide resistance call for additional management strategies to mitigate both diseases. The use of resistant cultivars is an economical way to manage these diseases, but there are limited sources of leaf spot resistance available in cultivated peanuts. Wild peanut species are excellent sources of resistance but, because of the ploidy level, when crossed with peanut they do not produce fertile progeny. To circumvent this, induced allotetraploids were developed so that resistance traits can be introgressed from wild species into peanut. Here we screened 13 induced allotetraploids (BatDur1, BatDur2, BatSten1, GregSten1, IpaCor1, IpaCor2, IpaDur1, IpaDur2, IpaDur3, IpaVillo1, MagDur1, MagSten1, and ValSten1) against ELS and LLS using a detached leaf bioassay to characterize various components of resistance and identify genotypes that can be used for breeding. Strong associations were detected between the measured components of disease resistance (r=0.91 to 1.0; p<0.001) and between ELS and LLS bioassays (r=0.81 to 0.91; p<0.001). Induced allotetraploids, particularly those derived from Arachis stenosperma, exhibited fewer and smaller lesions with limited sporulation and reductions in disease progression in both bioassays. Interestingly, allotetraploids derived from the B-genome peanut progenitor A. ipaënsis were almost as susceptible as cultivated genotypes. The overall results reveal several sources of foliar disease resistance that can be used in breeding programs for ELS and LLS resistance.