Characterization of Brazilian Cordyceps fumosorosea isolates: Conidial production, tolerance to ultraviolet-B radiation, and elevated temperature.

Cordyceps fumosorosea is an entomopathogenic fungus with a global distribution and is used for the biological control of agricultural pests. High conidial productivity and tolerance to abiotic stresses such as elevated temperature and ultraviolet radiation (UV-B) are desired characteristics in candidate isolates for commercial products. Our goal in this study was to characterize promising isolates of C. fumosorosea from five Brazilian biomes regarding conidial production, tolerance to UV-B, and elevated temperature (45°). Seventy-two isolates out of 172 were chosen visually, based on growth and sporulation in culture medium, and grown on parboiled rice. Next, fourteen isolates were selected, based on productivity on rice and origin of isolation, for production in polypropylene bags and submitted to UV-B for 2, 4, 6, and 8 h or to 45 °C for 30, 60, and 90 min. High variations in conidial production were observed among isolates, and a positive correlation was observed between UV-B and heat tolerance. The isolates ESALQ4556 and ESALQ4778 showed the highest yields of conidial production in polypropylene bags (3.51 × 109 conidia/g dry rice), while ESALQ1296, an isolate recovered from insects, was the most tolerant to UV-B and 45 °C. Exposure to radiation for more than 4 h and placed directly at 45 °C for more than 30 min significantly reduced conidial germination for all C. fumosorosea isolates. These results contribute to a better understanding of the tolerance to abiotic factors of Brazilian isolates of C. fumosorosea.

Red propolis effect analysis of dairy calves health based on Weibull regression model with long-term survivors.

Diarrhea is the most common cause of mortality and morbidity in dairy calves during the first weeks of life. It is responsible for the majority of costs related to animal death and treatments, as well as lower productivity due to reduced weight gain. Therefore, studies that focus on strategies to reduce diarrhea incidence and to improve animal welfare are very important for the dairy industry. For that reason, the beneficial effects of red propolis on the health status of preweaned dairy calves was studied. Animal disease data usually present incomplete observations of interest time, so-called censored observations and one of the statistical techniques for this modeling type is the survival analysis, hence it is a set of methods for analyzing data where the response variable is the time until the occurrence of an event of interest. We propose among some methods of survival data analysis, the long-term models. The motivation to study these models is the fact that part of the population is not susceptible to the event of interest during the period of the study, considered as immune or cured. In this paper, we studied the Weibull distribution in a structure of long-term model, including the covariates in the proportion of cured through the logistic link function. Besides, we used the residual analysis to check the assumptions of the model. The reason for the choice of the Weibull distribution was that this model is very flexibility to model a variety of data sets, among them animal science and long-term survival data. We illustrate its application with a case study from an animal experiment, which examined the time till the occurrence of diarrhea in Holstein calves, where a proportion of the animals were not susceptible to this health condition. This experiment aimed to verify the efficiency of red propolis in disease prevention and the influence of that on the proportion of animals that are not susceptible to diarrhea.

UV-B Radiation Tolerance and Temperature-Dependent Activity Within the Entomopathogenic Fungal Genus Metarhizium in Brazil.

Metarhizium comprises a phylogenetically diverse genus of entomopathogenic fungi. In Brazil, Metarhizium anisopliae s.str. subclade Mani 2 is predominantly isolated from insects, while M. robertsii and M. brunneum mostly occur in the soil environment. Solar radiation and high temperatures are important abiotic factors that can be detrimental to fungal propagules. We hypothesized that among 12 Brazilian isolates of Metarhizium spp., M. anisopliae Mani 2 (n = 6), being adapted to abiotic conditions of the phylloplane, is more tolerant to UV light and high temperatures than M. robertsii (n = 3) and M. brunneum (n = 3). Inoculum of each isolate was exposed to UV-B for up to 8 h and viability evaluated 48 h later. After 8 h under UV-B, most of the isolates had germination rates below 5%. Discs of mycelia were incubated at different temperatures, and diameter of colonies were recorded for 12 days. Mycelia of M. robertsii isolates grew faster at 33 °C, while M. anisopliae and M. brunneum grew most at 25 °C. Dry conidia were incubated at 20, 25 or 40 °C for 12 days, and then viabilities were examined. At 40 °C, conidia of five M. anisopliae isolates were the most tolerant. In the three experiments, considerable intra- and inter-specific variability was detected. The results indicate that conclusions about tolerance to these abiotic factors should be made only at the isolate level.