Effects of infection with the viral complex alfalfa dwarf disease on productivity traits and coumestrol production in alfalfa plants

Abstract

Context. Viral infections generate yield losses in alfalfa due to the impact on growth, seed production, impaired nitrogen fixation and fungal disease susceptibility, but also stimulate production of coumestrol, which can exhibit oestrogenic activity in livestock and human. Aims. We investigated the change in coumestrol content and its relationship with morphological and productivity traits in alfalfa plants infected with alfalfa viral complex. Methods. Seven genotypes from cultivar Monarca SP-INTA and six of Traful PV-INTA were used. Plants were cloned and treated as non-infected and infected with alfalfa viral complex (alfalfa dwarf disease). Productivity and morphological traits were assessed. Disease symptoms were used to estimate the genotype severity index (GSI, %), coumestrol content was determined by high pressure liquid chromatography. Key results. Viral infection reduced internode distance (iD) for the majority of Monarca genotypes, whereas in Traful one was affected, generating dwarfism. The iD reduction positively correlated with GSI only in Monarca genotypes. Coumestrol content varied between genotypes of each of the two cultivars. Monarca genotypes ranged between 350 and 1140 (infected and non-infected) ppm, and Traful genotypes ranged between 0 and 942 (infected and non-infected) ppm. However, viral infection promoted coumestrol increase in three genotypes only. Conclusions. All Monarca genotypes studied seem to be more sensitive to viral infections than those of Traful, as GSI demonstrated. Independently of cultivar, coumestrol content increased for three genotypes. High coumestrol content was correlated with low GSI. Implications. The knowledge of genotype response to viral infections would be useful for breeders to select superior genotypes as well as to originate new cultivars either as forage or as natural sources of phytoestrogens.