Caracterizacion morfologica y molecular de hongos fitopatogenos de suelo e identificacion de bacterias foliares en el cultivo de cebolla (Spanish text).

摘要

The objectives of the present investigation were to characterize morphological and molecularly some soilborne phytopathogenic fungi and identify bacteria associated to onion foliage in southern Puerto Rico. Thirteen representative isolates of Fusarium, 4 of Alternaria and 4 of Phoma were selected and classified at species level. ITS (Internal Transcribed Spacer) of the ribosomal DNA (rADN) was amplified. Fungal isolates were identified as Fusarium solani, F. equiseti, Alternaria tenuissima, a non-taxonomically described group of Alternaria spp. (semi-arborescent), Phoma putaminun and P. macrostoma var. incolorata . Pathogenicity tests performed in-vitro showed that Fusarium solani and F. equiseti caused damage to onion's roots but not under field conditions. Phoma spp. isolates showed erratic behavior in both tests.; Thirty nine bacterial isolates were found associated with onion foliage. Nineteen of them have phytopathogenic potential and belong to the genera Acidovorax, Burkholderia, Clavibacter, Curtobacterium, Pseudomonas and Xanthomonas. Pathogenicity tests showed that six out of eight isolates produced symptoms in onion plants (Pseudomonas sp, Xanthomonas sp, Acidovorax avenae supsp. citrulli and Burkholderia glumae species).