Influence of Non-Saccharomyces Strains on Chemical Characteristics and Sensory Quality of Fruit Spirit

The use of non-Saccharomyces yeasts for alcoholic beverage improvement and diversification has gained considerable attention in recent years. The effect of pure and mixed inocula (of Torulaspora delbrueckii, Lachancea thermotolerans, and Saccharomyces cerevisiae) on apple mash fermentation has been determined for the production of Hungarian fruit spirit (Pálinka), with a special emphasis on the chemical, volatile, and sensory attributes. The enological parameters were followed during the fermentation process. Sugar consumption and organic acid production were determined by HPLC, whereas the aromatic profile of the distillates was characterized by GC-FID. According to the results, single and mixed cultures showed similar characteristics during mash fermentation. The identified volatile compounds included aldehydes, esters, and higher alcohols. Mixed culture fermentation trials revealed a significantly higher concentration of volatile compounds and better sensorial attributes compared to those exhibited by the pure culture of S. cerevisiae.

Mit Tropfenmikrofluidik zu Hochgeschwindigkeits-Biotechnologie

In recent years, microfluidic technologies were introduced for massively parallel cultivation and screening approaches. Individual cells can easily be singularized, compartmentalized, and cultivated from mixed inocula using droplet microfluidics. The generation of millions of droplets in a high-throughput manner enables studying diverse samples and combining the evaluation of genetic and phenotypic variants. It is a powerful tool to explore and exploit natural metabolic diversity.

Effect of Single and Combined Inoculations of Potato Plants with Four Fusarium Species on Wilt Severity, Plant Growth, and Production

Potato (Solanum tuberosum L.) Fusarium wilt is an increasingly serious disease in many potato-growing regions worldwide and notably in Tunisia. Fusarium sambucinum, F. oxysporum, F. solani, and F. graminearum are the main causal agents with F. oxysporum being the most aggressive on plants. Co-infection with this Fusarium species complex is frequently observed. Cultivar responses to different pathogen mixtures can give additional information on the relative aggressiveness of the different complexes. This study may lead to a better understanding of how interactions between the four Fusarium species may affect disease incidence and severity. Interactions between these Fusarium species was evaluated using single and combined inoculations (15 different Fusraium inocula) onto potato the two cultivars Spunta and Oceania. The tested inocula were evaluated for their effects on leaf yellowing and necrosis, vascular discoloration severity, potato growth and production. Necrosis severity noted 75 days post-planting induced by three different inocula C2-1 (F. sambucinum + F. solani), C2-2 (F. solani + F. oxysporum), and C3-3 (F. sambuinum+F. oxysporum +F. graminearum) were found to be the highly aggressive inoculation treatments. Overall, all mixed inocula including F. sambucinum showed increased aggressiveness levels. The two cultivars exhibited differential response to the different tested Fusarium mixtures and behaved in the majority as sensitive to moderately sensitive to C1-1, C1- 4, C2-1, C2-2, C2-3, C2-4, C2-5, C2-6, C3-1, C3-3, C3-4 and C4 treatments. This study clearly demonstrated that Fusarium wilt of potato is expected to be more severe when more than one Fusarium species is present. The relative predominance of F. sambucinum may reflect its competitive potential in mixture and its significant involvement in potato Fusarium wilt severity.

Co-infection with a wheat rhabdovirus causes a reduction inMal de Río Cuarto virustiter in its planthopper vector

Mal de Río Cuarto virus(MRCV,Fijivirus,Reoviridae) causes one of the most important diseases in maize (Zea maysL.) in Argentina and has been detected in mixed infections with a rhabdovirus closely related to Maize yellow striate virus. In nature both viruses are able to infect maize and several grasses including wheat, and are transmitted in a persistent propagative manner byDelphacodes kuscheliFennah (Hemiptera: Delphacidae). This work describes the interactions between MRCV and rhabdovirus within their natural vector and the consequences of such co-infection regarding virus transmission and symptom expression. First- and third-instarD. kuschelinymphs were fed on MRCV-infected wheat plants or MRCV-rhabdovirus-infected oat plants, and two latency periods were considered. Transmission efficiency and viral load of MRCV-transmitting and non-transmitting planthoppers were determined by real-time quantitative polymerase chain reaction analysis (RTqPCR). Vector transmission efficiency was related to treatments (life stages at acquisition and latency periods). Nevertheless, no correlation between transmission efficiency and type of inoculum used to infect insects with MRCV was found. Treatment by third-instar nymphs 17 days after Acquisition Access Period was the most efficient for MRCV transmission, regardless of the type of inoculum. Plants co-infected with MRCV and rhabdovirus showed the typical MRCV symptoms earlier than plants singly infected with MRCV. The transmitting planthoppers showed significantly higher MRCV titers than non-transmitting insects fed on single or mixed inocula, confirming that successful MRCV transmission is positively associated with viral accumulation in the insect. Furthermore, MRCV viral titers were higher in transmitting planthoppers that acquired this virus from a single inoculum than in those that acquired the virus from a mixed inoculum, indicating that the presence of the rhabdovirus somehow impaired MRCV replication and/or acquisition. This is the first study about interactions between MRCV and a rhabdovirus closely related to Maize yellow striate virus in this insect vector (D. kuscheli), and contributes to a better understanding of planthopper–virus interactions and their epidemiological implications.

Control of Fire Blight by Pseudomonas fluorescens A506 and Pantoea vagans C9-1 Applied as Single Strains and Mixed Inocula

The biological control agents Pseudomonas fluorescens A506 and Pantoea vagans C9-1 were evaluated individually and in combination for the suppression of fire blight of pear or apple in 10 field trials inoculated with the pathogen Erwinia amylovora. The formulation of pathogen inoculum applied to blossoms influenced establishment of the pathogen and the efficacy of biological control. Pantoea vagans C9-1 suppressed fire blight in all five trials in which the pathogen was applied as lyophilized cells but in none of the trials in which the pathogen was applied as freshly harvested cells. In contrast, Pseudomonas fluorescens A506 reduced disease significantly in only one trial. A mixture of the two strains also suppressed fire blight, but the magnitude of disease suppression over all field trials (averaging 32%) was less than that attained by C9-1 alone (42%). The two biological control agents did not antagonize one another on blossom surfaces, and application of the mixture of A506 and C9-1 to blossoms resulted in a greater proportion of flowers having detectable populations of at least one bacterial antagonist than the application of individual strains. Therefore, the mixture of A506 and C9-1 provided less disease control than expected based upon the epiphytic population sizes of the antagonists on blossom surfaces. We speculate that the biocontrol mixture was less effective than anticipated due to incompatibility between the mechanisms by which A506 and C9-1 suppress disease.