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Brown spot of pear (BSP), a fungal disease, was recently detected in the Alto Valle of Río Negro region in Patagonia, Argentina. BSP is caused by Stemphylium vesicarium (teleomorph: Pleospora herbarum, syn. P. allii) in its sexual and asexual stages, and its main symptoms are lesions in fruit and leaves. The aim of the present study was to characterize the susceptibility of four main pear cultivars grown in the Alto Valle of Río Negro to infection by S. vesicarium. Over four recent growing seasons, BSP incidence and severity were monitored in an orchard with 'Williams', 'Packham's', 'D'Anjou', and 'Abate Fetel' pear cultivars. In addition, inoculations of a pathogenic S. vesicarium strain were performed on detached fruit and leaves of the four cultivars. Both in-field observations and in vitro inoculation experiments indicated that fruit and leaf susceptibility to BSP was markedly higher in 'D'Anjou' and 'Abate Fetel' compared to 'Packham's' and 'Williams'. These findings provide valuable information for the correct allocation of resources to efficiently monitor and control BSP. [ABSTRACT FROM AUTHOR]

Brown spot of pear (BSP), a fungal disease of importance in Europe, has been recently detected for the first time in pear orchards in the Alto Valle of Río Negro (Patagonia), Argentina, South America. The disease is caused by Stemphylium vesicarium and its main symptoms are lesions in fruits and leaves. To assess counteracting measures against BSP, we tested the efficacy of fungicides by means of in vitro assessment of mycelial growth and spore germination of native S. vesicarium strains, and in vivo preventive and curative treatments in pear fruit 'D'Anjou' var. The fungicides were chosen according to their commercial availability and registration in pear crops and included: pyraclostrobin + boscalid (Bellis®); ziram (Ziram®); captan (Merpan®); and Melaleuca alternifolia extract (Timorex®). In addition, the efficacy of Bellis® and Ziram® was determined through in-field assays. Bellis® presented the lowest EC50 values in germination and mycelial growth tests. Ziram® and Merpan® were also very effective in inhibiting germination. Timorex® did not achieve satisfactory effectiveness in in vitro trials, nor in bioassays after preventive and curative treatments. Bioassay results showed that preventive measures using Bellis®, Ziram®, or Merpan® were effective in reducing disease severity and suggested that BSP could be controlled by adequate selection of spraying time. [Display omitted] • S. vesicarium native north-patagonia strains were very sensible at Bellis® in vitro. • Bellis®, Ziram®, and Merpan® applications reduce disease severity of brown spot of pear. • Preventive treatments reduced the incidence and severity of S. vesicarium infection. • Curative treatments were not effective on brown spot of pear control. [ABSTRACT FROM AUTHOR]

In the present work, we evaluated the effects of a mixture of biocontrol agents against two toxigenic strains of Penicillium expansum isolated in Argentine Patagonia from pome fruits. The two strains, INTA-5 and INTA-10, were previusly selected among ten strains coming from the Alto Valle (Rio Negro-Argentina) for their high production of patulin. For the biocontrol, Kosakonia radicincitans , Cryptococcus laurentii , and Rhodosporidium fluviale were tested in vitro experiments on Potato Dextrose Agar (PDA) dishes against the INTA-5 and INTA-10 strains. The bacterium K. radicincitans and the yeast C. laurentii were selected to be used in a mixture due to their capacity to control the fungus and reduce the mycotoxin severely. In vitro assays with the mixture showed a high antagonism against P. expansum INTA-5 and INTA-10, at 21 d of incubation at 25 °C and a patulin reduction of 98%. The mixture of microorganisms was also effective in apples stored at 25 °C for 10 d and 4 °C for 30 d. At cold storage, the mixture controlled moderately the development of rot and decreased patulin concentration. At 25 °C, the pathogen's optimal growth temperature, the mixture of Biological Control Agent (BCAs) assured both the control of rot and decrease of patulin concentration. The combination of two microorganisms, with different requirements and abilities, resulted in a mix with a strong antagonism against P. expansum with the capability to decrease the patulin concentration. Treatment with the selected mixture could be a good option for controlling strains with different behaviours and in different environmental conditions. [Display omitted] • P. expansum strains producer of patulin were controlled by a microorganism mixture. • The yeast C. laurentii and the bacterium K. radicincitans were used in the mixture. • The mixture of microorganisms was effective in apples stored at 4 °C and 25 °C. • Mixture controlled P. expansum rot and was able to decrease patulin at both temperatures. [ABSTRACT FROM AUTHOR]

• B. velezensis SL-6 antagonized the main fungal pathogens of pome fruits in Argentina. • Strain SL-6 has and expresses gene clusters for non-ribosomal lipopeptide synthesis. • Lipopeptide-enriched extract reduced A. alternata and B. cinerea rots in postharvest. • Six fengycin variants were the lipopeptides responsible of antifungal antagonism. • Lipopeptides preserved fruit quality and could extend shelf-life in the fruit market. Considering the economic losses in the fruit processing industry caused by phytopathogenic diseases , Bacillus sp. SL-6 was isolated from freshwater samples of the Cruz de Piedra Reservoir (San Luis, Argentina) and selected for its antifungal activity against Penicillium expansum, Botrytis cinerea and Alternaria alternata. These fungi are recognized as the main causal agents of postharvest diseases of pome fruits in Argentina. Pears are an important export product while apples are one of the fruits that lead internal commercialization throughout the country. Morphological, biochemical and phylogenetic analyses clustered strain SL-6 with Bacillus velezensis. To unveil the antimicrobial activity of this strain, gene fragments from the biosynthetic pathway of three lipopeptide families, surfactin, iturin and fengycin, were amplified by PCR and its expression assessed by RT-PCR. Cell-free supernatant from batch culture displayed inhibition only against A. alternata and B. cinerea. Partial purification of lipopeptides in the methanolic extract retained all antagonistic activities and fengycin was detected as responsible for the antifungal activity by TLC-bioautography assay. During short storage at room temperature, disease incidence and severity reduction in apples provided values of 59 and 67% against B. cinerea , respectively. The appearance of rot symptoms caused by A. alternata challenge was delayed in comparison with non-treated control, yielding total protection after 21 days of storage. Medium-term storage under cold conditions significantly reduced infection rates by B. cinerea in pears, with values higher than 80%. Four fengycin A and two fengycin B homologues were identified as active compounds by MALDI TOF and LC-ESI-MS/MS analyses. Successful curative protection by lipopeptides-enriched extract is a promising result for the further development of a biocontrol by-product as an alternative method for prevention of these pome fruit postharvest diseases. [ABSTRACT FROM AUTHOR]