Estefanía Trapiello

Gnomoniopsis castaneae Tamietti (syn. G. smithogilvyi L.A. Shuttleworth, E.C.Y. Liew and D.I. Guest) is the causal agent of chestnut rot disease (Visentin et al. 2012). It has recently become known for being responsible for wood cankers on sweet chestnut, similar those caused by Cryphonectria parasitica on twigs and scions of sweet chestnut (Seddaiu et al. 2017). In November 2016, three samples of hybrid plants C. sativa x C. crenata showing chestnut blight symptoms such as bark coloration, were collected in a nursery in Asturias, northern Spain. Symptomatic branches were surface-sterilized in 98% ethanol for 30 s and dried on sterilized tissue paper, plated on potato dextrose agar (PDA) and incubated at room temperature with amnatural photoperiod (about 11 h light, 13 h dark). Fungal colonies different from C. parasitica were consistently isolated from affected bark after 5 days of incubation in two of the samples. Colonies were transferred on PDA and next incubated at 25º C with a natural photoperiod (1...

Angular leaf spot (ALS) symptoms were observed in 2015 in common bean fields at four locations in Asturias, NW Spain. This disease is frequent in tropical areas and we have no record of its presence in our region, at least in the last 30 years. However, since its detection its presence in the crops has been increasing. Symptoms were necrotic spots on leaves and reddish-brown to black circular spots on pods, stems, branches and petioles. The damage observed in the mentioned crops was highly variable (between 60% and 100% affected leaves), being most severe in crops where no agrochemical treatment were applied. Three strains were selected and identified based in morphological features as Pseudocercospora griseola. The ITS region was amplified by PCR obtaining a sequence that was identical for the three isolates (Acc. No. LT222499). This sequence showed 99-100% similarity with those deposited in databases corresponding to P. griseola. To fulfill Koch's postulates, a pathogenicity test was carried out in two common bean cultivars (‘Andecha’ and ‘Maruxina’). P. griseola was re-isolated from inoculated plants and not from control plants. In cv. ‘Andecha’, chlorosis was observed in all the inoculated plants, before the appearance of spots. Consequently this is the first confirmed report of this pathogen in our region.

A yellow Gram-reaction-positive bacterium isolated from bean seeds (Phaseolus vulgaris L.) was identified as Clavibacter michiganensis by 16S rRNA gene sequencing. Molecular methods were employed in order to identify the subspecies. Such methods included the amplification of specific sequences by PCR, 16S amplified rDNA restriction analysis (ARDRA), RFLP and multilocus sequence analysis as well as the analysis of biochemical and phenotypic traits including API 50CH and API ZYM results. The results showed that strain LPPA 982^T did not represent any known subspecies of C. michiganensis . Pathogenicity tests revealed that the strain is a bean pathogen causing a newly identified bacterial disease that we name bacterial bean leaf yellowing. On the basis of these results, strain LPPA 982^T is regarded as representing a novel subspecies for which the name Clavibacter michiganensis subsp. phaseoli subsp. nov. is proposed. The type strain is LPPA 982^T ( = CECT 8144^T = LMG 27667^T).