Margarita Rodríguez

Serratia marcescens associated with bell pepper (Capsicum annuum L.) soft-rot disease under greenhouse conditions

Soft-rotting bacteria affecting bell peppers crops represent an economically destructive disease of growing importance worldwide. In Venezuela since 2006, soft-rot symptoms have been occasionally observed in bell pepper fruits grown under greenhouse conditions. Affected fruits presented water-soaked lesions that progressed to complete fruit maceration. Bacteria were isolated from water-soaked lesions in order to identify the causal agent of this disease. Of 13 bacterial isolates recovered from affected fruits, only isolate AGPim1A was able to produce a hypersensitive reaction in tobacco plants and to reproduce soft-rot symptoms in bell peppers fruits. Several methods, including classical bacteriological tests and carbon utilization profiling, alongside with sequence analysis of 16S rRNA and housekeeping genes gyrB and groES-groEL, allowed identification of the soft-rotting bacterium as Serratia marcescens. To our knowledge, this is the first report showing a S. marcescens strain associated with soft-rot disease in bell pepper fruits.

First Report of Bell Pepper Soft-Rot Caused by Pectobacterium carotovorum subsp. brasiliense in Venezuela

Soft rot symptoms were observed during the rainy season, particularly in July, in 2008 on bell pepper (Capsicum annuum L., Hybrid RPP 1216, Syngenta) cultivated under greenhouse conditions (25/18°C, 85% RH) in Sartenejas, Miranda State, Venezuela. Initial symptoms on plants consisted of watery lesions at the basal part of the stem. As the lesions progressed, the whole stem presented water-soaked and necrotic tissue, with detached cortical tissues. Infected plants showed general wilt with defoliation. Fruits showed watery lesions that progressed until complete maceration. Plant samples displaying soft rot symptoms were collected to isolate the causal agent of the disease. Tissue from the lesions was surface-disinfected by standard protocols and ground to prepare serial-dilutions that were plated on Luria Bertani-agar medium. After 48 h of incubation at 28°C, a predominant bacterium was isolated from all samples. Five strains from independent samples were subjected to biochemical and pathogenicity tests. Al...