Characterization,Pathogenicity and Chemical Control of <Emphasis Type="Italic">Streptomyces acidiscabies</Emphasis> Associated to Potato Common Scab

The pathogenicity of 10 bacterial isolates was investigated on potato, radish, carrot and beet, including sensitivity and pathogen control efficacy. The isolates were identified by morphological, biochemical and molecular methods. All isolates were pathogenic on radish, carrot, and beet, and were highly virulent on potato. Although the isolates were obtained from different locations in the El Fuerte Valley (Sinaloa, Mexico), they were similar in their morphological, physiological and biochemical characteristics. Sequences of the 16S rRNA gene obtained by PCR were identical for all isolates. These results indicate that the bacterial isolates from potato scabby tissue belong to S. acidiscabies. Furthermore, the effectiveness of fluazinam, both in vitro and under greenhouse and field conditions, represents a possibleoption for chemical control of potato common scab disease. While our results suggest that spraying at seeding is effective in controlling common scab, future studies to combine this treatment with seed dressing before planting will be conducted to determine if there is an increase in disease control.     

Common potato disease symptoms: ambiguity of symptom-based identification of causal pathogens and value of on-site molecular diagnostics

Journal of General Plant Pathology - Because symptoms of plant diseases are often ambiguous for identifying the causal pathogen, chemical applications and cultural managements are occasionally...     

Curvularia brachyspora causing leaf spot on Cucurbita argyrosperma in Mexico

Journal of General Plant Pathology - In September 2021, severe leaf spots were observed on Cucurbita argyrosperma plants in nine commercial fields in Cocula, Guerrero, Mexico. Conidia were similar...     

Evaluation of Bacillus spp. isolates as potential biocontrol agents against charcoal rot caused by Macrophomina phaseolina on common bean

The fungus Macrophomina phaseolina, the causal agent of charcoal rot of common beans, damages the roots, stems, and leaves of seedlings and plants and forms resistant structures, so that chemicals are not sufficient for disease control. Integrated management systems associated with the use of biological control techniques are a sustainable alternative. Here we collected 37 native bacterial isolates from the common bean rhizosphere and screened them for antagonistic activity against M. phaseolina. Four isolates (BA97, BN17, BN20, and BR20) identified as Bacillus spp. showed antagonism in vitro against M. phaseolina, inhibiting its growth by 62.5–85%. In an in planta antagonistic assay, isolate BN20 reduced disease severity the most. Isolates BA97, BN17, BN20, and BR20 produced volatile compounds as a mechanism of antagonism. They also produced indole acetic acid in vitro (1.98–3.87 μg/ml). These results suggest that seed bacterization with the rhizobacterial isolates for field planting may be an effective means to reduce crop damage by M. phaseolina.

     

First report of Leveillula clavata causing powdery mildew on Euphorbia leucocephala from India

In December 2020, Euphorbia leucocephala plants exhibiting symptoms of powdery mildew were observed in the Botanical Garden of Tuljaram Chaturchand College, Baramati, Maharashtra, India. Based on morphological identification, DNA sequence analysis, and pathogenicity, the fungal pathogen of the disease was identified as Leveillula clavata. This is the first report of L. clavata on Euphorbia leucocephala from India and in general.     

First report of Bipolaris yamadae causing leaf blight on giant reed (Arundo donax L.) in Mexico and its pathogenicity on sorghum and maize

Journal of Plant Diseases and Protection - In August 2020, leaf blight was observed on Arundo donax L. plants in the municipalities of Ahome and El Fuerte, Sinaloa, Mexico. Molecular analysis of...