The antifungal activity of polygodial, a secondary metabolite extracted from Canelo, on mycelial growth of different Botrytis cinerea isolates has been evaluated. The results show that polygodial affects growth of normal and resistant isolates of B. cinerea with EC₅₀ values ranging between 117 and 175 ppm. In addition, polygodial markedly decreases the germination of B. cinerea, i.e., after six hours of incubation the percentage of germination decreases from 92% (control) to 25% and 5% in the presence of 20 ppm and 80 ppm of polygodial, respectively. Morphological studies indicate that conidia treated with polygodial are smaller, with irregular membrane border, and a lot of cell debris, as compared to conidia in the control. The existence of polygodial-induced membrane damage was confirmed by SYTOX^® Green uptake assay. Gene expression studies confirm that the effect of polygodial on B. cinerea is mainly attributed to inhibition of germination and appears at early stages of B. cinerea development. On the other hand, drimenol, a drimane with chemical structure quite similar to polygodial, inhibits the mycelial growth efficiently. Thus, both compounds inhibit mycelial growth by different mechanisms. The different antifungal activities of these compounds are discussed in terms of the electronic density on the double bond.

Background: In plants, host factors encoded by susceptibility (S) genes are indispensable for viral infection. Resistance is achieved through the impairment or the absence of those susceptibility factors. ManySgenes have been cloned from model and crop species and a majority of them are coding for members of the eukaryotic translation initiation complex, mainly eIF4E, eIF4G and their isoforms. The aim of this study was to investigate the role of those translation initiation factors in susceptibility of stone fruit species to sharka, a viral disease due toPlum pox virus(PPV).Results: For this purpose, hairpin-inducing silencing constructs based onPrunus persicaorthologs were used to generatePrunus salicina(Japanese plum) 4E and 4G silenced plants byAgrobacterium tumefaciens-mediated transformation and challenged with PPV. While down-regulatedeIFiso4Etransgenic Japanese plums were not regenerated in our conditions,eIFiso4G11-, but not theeIFiso4G10-, silenced plants displayed durable and stable resistance to PPV. We also investigated the alteration of the si- and mi-RNA profiles in transgenic and wild-type Japanese plums upon PPV infection and confirmed that the newly generated small interfering (si) RNAs, which are derived from the engineered inverted repeat construct, are the major contributor of resistance to sharka.Conclusions: Our results indicate thatSgene function of the translation initiation complex isoform is conserved inPrunusspecies. We discuss the possibilities of using RNAi silencing or loss-of-function mutations of the different isoforms of proteins involved in this complex to breed for resistance to sharka in fruit trees.