Survival of Spray-Dried Rhodotorula mucilaginosa Isolated from Natural Microbiota of Murta Berries and AntagonisticEffect on Botrytis cinerea.

The aim of this study is to evaluate the survival rate and effective antagonistic activity against Botrytis cinerea, responsible for grey mould on harvested fruits and vegetables, of yeast Rhodotorula mucilaginosa, isolated and identified from the natural microbiota of murta (Chilean guava) berries, after spray drying at different inlet air temperatures, mass per volume ratio of encapsulating agent (maltodextrin) and feed flow rates. The 100% survival of the yeast was obtained after spray drying with 18% maltodextrin at 130 °C inlet temperature and a feed flow rate of 9.25 mL/min. The dried yeast obtained under such conditions had the highest antagonistic activity in vitro and in vivo on apples, which showed that spray drying is a valid method to produce active dried cells of R. mucilaginosa that can be used for biocontrol of grey mould spoilage. It was also found that the encapsulating agent maltodextrin improved the in vitro antagonistic activity of R. mucilaginosa.

In vivo administration of LPS and ß-glucan generates the expression of a serum lectin and its cellular receptor in Cherax quadricarinatus.

In crustaceans, it has been suggested that specific protection against pathogens could be triggered by vaccines and biological response modifiers; although the specific mechanisms of this protection have not been clarified yet. In the crayfish Cherax quadricarinatus, a humoral lectin (CqL) binds its own granular hemocytes through a specific receptor (CqLR) and increases the production of reactive oxygen species (ROS). In the present study, we challenged in vivo crayfishes with immunostimulants, ß-glucan (200 µg/kg) or LPS (20 µg/kg), and identified the participation of cellular and humoral mechanisms. The stimulants generated a complex modification in the total hemocytes count (THC), as well as in the proportion of hemocyte subsets. At 2 h after the challenge, the largest value in THC was observed in either challenged crayfishes. Furthermore, at the same time, hyaline hemocytes were the most abundant subset in the hemolymph; after 6 h, granular hemocytes (GH) were the most abundant hemocyte subset. It has been observed that a specific subset of GH possesses a CqLR that has been related to ROS production. After 2 and 6 h of the ß-glucan challenge, a significant increase in CqLR expression was observed in the three circulating hemocyte subsets; also, an increased expression of CqL was detected in a granular hemocytes sub-population. After 2 and 6 h of stimulation, the specific activity of the serum lectin challenged with ß-glucan was 250% and 160% higher than in the LPS-treated-group, respectively (P < 0.05). Hemocytes from challenged crayfishes were stimulated ex vivo with CqL, ROS production was 180% higher in hemocytes treated with ß-glucan + CqL than in hemocytes treated with LPS + CqL (P < 0.05). The results evidence the effectivity of immune stimulators to activate specific crayfish defense mechanisms, the participation of CqL and its receptor (CqLR) could play an important role in the regulation of immune cellular functions, like ROS production, in Cherax quadricarinatus.

Characterization of Cladosporium Rot in Grapevines, a Problem of Growing Importance in Chile.

Cladosporium rot (Cladosporium spp.) of grapevine (Vitis vinifera) is a common disease in Chile, particularly in Cabernet Sauvignon and other red wine grape cultivars. It is favored by delayed harvest to obtain the phenolic maturity necessary for high-quality red wine. This study expands on previous investigations of the specific causal agents, the histopathological host:pathogen relationship, and the population dynamics of Cladosporium spp. during the seasonal development of grape clusters. Over 100 isolates were obtained and identified as C. cladosporioides and C. herbarum, confirming previous results. The identity of a subset of isolates was confirmed by molecular analysis. Isolates of both C. cladosporioides and C. herbarum from grapevines were pathogenic on inoculated table grapes and wine grapes. These pathogens were reisolated, fulfilling Koch's postulates. Berry injuries and total soluble solids content above 15% were necessary for Cladosporium spp. to infect wine grapes. The mycelia of C. cladosporioides and C. herbarum grew between 0 and 30°C, but no growth was obtained at 35°C in vitro. The histological studies showed that Cladosporium spp. superficially colonize mature V. vinifera berries, invading the epidermis but scarcely penetrating the hypodermis. The Cladosporium populations obtained on apparently healthy berries of V. vinifera cvs. Cabernet Sauvignon and Chardonnay were significantly larger (P = 0.05) than the populations obtained under similar conditions on berries of V. champini cv. Ramsey and hybrids Kober 5BB and Couderc 1613. Considering the importance of Cladosporium rot in Chile compared with other grape production areas, the development of control strategies is needed to prevent high disease severity, which affects both yield and wine quality.

Canker and Twig Dieback of Blueberry Caused by Pestalotiopsis spp. and a Truncatella sp. in Chile.

Blueberry (Vaccinium spp.) has great economic importance in Chile, which currently has about 8,500 ha being cultivated. Recently, the presence of canker and dieback symptoms has been observed along the productive blueberry zone of Chile. Species of Pestalotiopsis and Truncatella were consistently isolated from diseased samples in 22 different locations. Therefore, the objective of this study was to identify and characterize the species of Pestalotiopsis and Truncatella associated with canker and twig dieback symptoms on blueberry. Forty-nine isolates were obtained on acidified potato dextrose agar in 2006 and 2007. These isolates were identified as Pestalotiopsis clavispora, P. neglecta, and Truncatella (=Pestalotia) angustata on the basis of colony characteristics and conidial morphology. This identification was verified by internal transcribed spacer analysis of DNA. Isolates of P. clavispora, P. neglecta, and T. angustata were pathogenic on apple, kiwifruit, and blueberry fruit. Similarly, isolates of P. clavispora were pathogenic on detached blueberry twigs of cv. O'Neal. Additionally, three selected isolates of P. clavispora induced light-brown canker lesions, surrounded by a reddish halo, and shoot dieback after twig inoculations on 2-year-old twigs of blueberry cvs. O'Neal, Bluecrop, Brightwell, Brigitta, Duke, Elliot, and Misty. Among blueberry cultivars, Brightwell and O'Neal were the most susceptible and Bluecrop and Misty the least susceptible, while Elliot, Brigitta, and Duke were moderately susceptible to P. clavispora. These pathogens were isolated consistently from inoculated plants, confirming Koch's postulates. P. clavispora was highly sensitive to fludioxonil and pyraclostrobin with a median effective concentration of 0.06 to 0.08 and 0.04 to 0.8 µg/ml, respectively. Therefore, the results of this study indicate that P. clavispora, P. neglecta, and T. angustata are primary pathogens that can cause canker lesions and dieback symptoms on blueberry not previously described in Chile. However, these results do not exclude that other species of these genera or other plant-pathogenic fungi (e.g., Botryosphaeria, Pestalotia, and Phomopsis spp.) may eventually be involved in this syndrome of blueberry.