Resistance to triazole fungicides in Pyricularia species associated with invasive plants from wheat fields in Brazil

Triazole fungicides have not been effective for managing the wheat blast disease in Brazil. A broad analysis across six geographical populations of Pyricularia graminis-tritici in central-southern Brazil indicated a high level of resistance to triazole fungicides. Since P. graminis-tritici is also associated with others poaceous species, here, we analyzed whether triazole-resistant isolates of the blast pathogen could be recovered from other poaceous hosts that are invasive of sprayed wheat fields. In addition to P. graminis-tritici (Pygt), we also evaluated the levels of sensitivity of three other grass-associated blast pathogens, which included P. grisea (Pg), P. pennisetigena (Pp), and P. urashimae (Pu). Resistance to the triazole fungicides tebuconazole and epoxiconazole was assessed phenotypically based on EC50 values and molecularly by analysis of the presence of mutations in the CYP51A gene, which encodes for the target enzyme 14-alpha-demethylase. We detected triazole-resistant Pyricularia spp. (Pg, Pp, Pu and Pygt) that is associated with Avena sativa, Cenchrus echinatus, Chloris distichophylla, Cynodon sp., Digitaria horizontalis, D. sanguinalis, Panicum maximum or Urochloa spp. The major outcome from our study was the evidence that invasive poaceous species from wheat fields could be an important source of triazole resistant fungal inoculum for the initial phases of the wheat blast epidemics

Effect of light spectra on in vitro multiplication, elongation and adventitious rooting stages of Bambusa vulgaris Schrad. ex J. C. Wendl.

Bamboos occur throughout much of the temperate and tropical world, have rapid growth, and have various commercial and environmental applications. Clonal production of selected plants on a industrial scale is an important strategy for the bamboo sector. This study aimed to evaluate the effects of the light spectrum on in vitro multiplication, elongation, adventitious rooting, and anatomical features of the leaf surface of Bambusa vulgaris. In the multiplication and elongation stages, in vitro–established explants were transferred to a culture medium supplemented with 8.88 µmol of 6-benzylaminopurine (BAP) and 2.69 µmol of α-naphthalene acetic acid (NAA), and subjected to four light spectra (i.e., white, blue, green, and red). At the adventitious rooting stage, the culture medium was supplemented with 9.84 µmol of indole-3-butyric acid (IBA), 5.37 µmol NAA, and 2.22 µmol BAP under identical light spectra. Explant survival was not influenced by light spectra in the multiplication and elongation stages. White (2.2 shoots) and blue (1.8 shoots) light spectra were the most suitable for the number of shoots per explant. The white spectrum was associated with the highest average length of shoots (7.4 cm) and number of leaves per explant (3.0 leaves). The white light spectrum resulted in the highest average chlorophyll a contents (12.60 µg mg−1), total chlorophyll (16.60 µg mg−1), and carotenoids (10.10 µg mg−1). White and blue light spectra resulted in the best responses for vigor, and least senescence and tissue oxidation. White and blue light spectra favored the chlorophyll b content, resulting in 4.60 and 3.60 µg mg−1, respectively. Survival (80.0 %), adventitious rooting (50.0 %), vigor, senescence, and tissue oxidation were favored in the white light spectrum in the adventitious rooting stage. Scanning electron microscopy of leaves exposed to the white light spectrum revealed microtrichomes and spines on the adaxial surface of the leaf blade, papillae and stomata; on the abaxial surface, there were many unicellular trichomes arranged in rows, denoting normal growth and development. These results may help the production of micropropagated plants of Bambusa vulgaris on an industrial scale