In vivo and in vitro screening for resistance against Penicillium allii in garlic accessions María C. Salinas & Pablo F. Cavagnaro Accepted: 17 October 2019 # Koninklijke Nederlandse Planteziektenkundige Vereniging 2019 Abstract Garlic blue mold disease, caused by Penicil- lium allii, is responsible for important economic losses produced yearly in garlic field crops and in postharvest storage. The identification of genetic resistance sources may help in the management of this disease. The present study investigated in vivo and in vitro antifungal effects of a genetically-diverse garlic collection against P. allii in two growing seasons. Cloves of garlic accessions were inoculated with P. allii conidia, and lesion area and sporulation of the fungus in the clove were estimat- ed as a means to characterize the accessions response to the infection. Significant and continuous variation was found among the accessions (p < 0.001), suggesting a quantitative mode of resistance against P. allii in this garlic collection. ‘Castaño’ and ‘Peteco’ were consis- tently the most resistant and susceptible genotypes, respectively. Culture media of the fungus supplemented with crude garlic extracts (CGEs) revealed significant inhibition of P. allii growth in vitro by all the garlic accessions, with fungal-growth inhibition being dose- dependent up to a concentration of 20–26% (v/v), be- yond which the CGEs became fungicidal. These data indicate that garlic bulbs have antifungal compounds, which at high concentration can be fungicidal for P. allii. CGEs of ‘Castaño’ and a few other accessions were consistently the more inhibitory extracts. Total pheno- lics and pyruvate (an estimator of the total thiosulfinates content) concentration in the garlic bulbs was not asso- ciated with P. allii resistance in vivo, but their content in the CGEs correlated significantly and negatively with the fungal growth in vitro (r = -0.38 to -0.72), suggest- ing that these compounds have antifungal effect, but their content is not the main factor conditioning P. allii resistance in vivo. Keywords Allium sativum . Blue mold . Penicillium allii . Disease resistance . Thiosulfinates . Phenolic compounds Introduction Garlic (Allium sativum L.) is one of the most important and widespread horticultural crops. Blue mold disease, caused by Penicillium allii Vincent & Pitt [P. allii Vincent & Pitt is a synonymous denomination of “Pen- icillium hirsutum Dierckx ” and “ Penicillium corymbiferum Westling”, as used in earlier publications Eur J Plant Pathol https://doi.org/10.1007/s10658-019-01875-z Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10658-019-01875-z) contains supplementary material, which is available to authorized users. M. C. Salinas : P. F. Cavagnaro National Council of Scientific and Technical Research (CONICET), Mendoza, Argentina M. C. Salinas : P. F. Cavagnaro National Institute of Agricultural Technology (INTA) – E.E.A. La Consulta, La Consulta CC8, San Carlos, 5567 Mendoza, Argentina P. F. Cavagnaro (*) Faculty of Agricultural Sciences, National University of Cuyo, Almirante Brown 500, Luján de Cuyo, 5505 Mendoza, Argentina e-mail: cavagnaro.pablo@inta.gob.ar