No abstract

Approximately 75% of the worldwide production of hard natural fibers originates from sisal, an industrial crop from arid and semiarid tropical regions. Brazil is the world's largest producer of sisal fiber, accounting for more than 40% of the worldwide production, and sisal bole rot disease has been the main phytosanitary problem of this crop. All previous studies reporting Aspergillus niger as the causal agent of the disease were based on the morphological features of fungal isolates from infected plant tissues in pure cultures. Black aspergilli are one of the most complex and difficult groups to classify and identify. Therefore, we performed an integrative analysis of this disease based on the isolation of black aspergilli from the endospheres and soils in the root zones of symptomatic adult plants, in vivo pathogenicity tests, histopathology of symptomatic plants, and molecular phylogeny and worldwide genetic variability of the causal agent. All sisal isolates were pathogenic and unequivocally produced symptoms of bole rot disease in healthy plants. In all tree-based phylogenetic methods used, a monophyletic group formed by A. welwitschiae along with all sisal isolates was retrieved. Ten A. welwitschiae haplotypes have been identified in the world, and three occur in the largest sisal-producing area. Most of the isolates are from a unique haplotype, present in only the sisal-producing region. A. welwitschiae destroyed parenchymatic and vascular cylinder cells and induced the necrosis of internal stem tissues. Therefore, sisal bole disease is probably the consequence of a saprotrophic fungus that opportunistically invades sisal plants and behaves as a typical necrotrophic pathogen.

The aim of this paper was to investigate the physicochemical characteristics and rheological behavior of some floral honeys from species of wild plants found in the Caatinga biome, as well as, correlate honey viscosities with its chemical composition.

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The forest species are frequent targets of diseases. In this context, the plant-parasitic algae comprise a separate group in this process, including the algae genus Cephaleuros, which attacks mahogany cultivars. The objective of this work was to accomplish the molecular and morphological characterization of the causal agent of algae spots occurring in Brazilian mahogany (Swietenia macrophylla). Somatic and reproductive algae structures contained in lesions on the leaves had the DNA extracted and amplified by primers 18SHf and 18SLr of the rRNA nuclear gene 18S. Then, the amplicons were purified and sequenced. The algae structures too were characterized under light microscope. In addition, a total of 12 injured leaves located in the lower third of each attacked tree were randomly extracted for lesion characterization according to its size and number. After algae structures measurements, sporangiophores and sporangia had 260.2 x 12.9 μm and 25 x 18.8 μm. These measurements, combined with the molecular identification, indicated that the algae found in Brazilian mahogany leaves is C. virescens. Attacked leaves showed an average of 33 lesions, 60% of which were smaller than 2 mm in diameter, which shows great capacity of the pathogen to reach different parts of the foliar limb. These measurements, combined with molecular identification, confirmed the algae found in Brazilian mahogany leaves to be C. virescens.